Acute Modulation of Cortical Glutamate and GABA Content by Physical Activity

MRS-assessed brain GABA modulation in response to task performance and learning

Gamma-aminobutyric acid (GABA), the most important inhibitory neurotransmitter in the human brain, has long been considered essential in human behavior in general and learning in particular. GABA concentration can be quantified using magnetic resonance spectroscopy (MRS). Using this technique, numerous studies have reported associations between baseline GABA levels and various human behaviors. However, regional GABA concentration is not fixed and may exhibit rapid modulation as a function of environmental factors. Hence, quantification of GABA levels at several time points during the performance of tasks can provide insights into the dynamics of GABA levels in distinct brain regions. This review reports on findings from studies using repeated measures (n = 41) examining the dynamic modulation of GABA levels in humans in response to various interventions in the perceptual, motor, and cognitive domains to explore associations between GABA modulation and human behavior. GABA levels in a specific brain area may increase or decrease during task performance or as a function of learning, depending on its precise involvement in the process under investigation. Here, we summarize the available evidence and derive two overarching hypotheses regarding the role of GABA modulation in performance and learning. Firstly, training-induced increases in GABA levels appear to be associated with an improved ability to differentiate minor perceptual differences during perceptual learning. This observation gives rise to the 'GABA increase for better neural distinctiveness hypothesis'. Secondly, converging evidence suggests that reducing GABA levels may play a beneficial role in effectively filtering perceptual noise, enhancing motor learning, and improving performance in visuomotor tasks. Additionally, some studies suggest that the reduction of GABA levels is related to better working memory and successful reinforcement learning. These observations inspire the 'GABA decrease to boost learning hypothesis', which states that decreasing neural inhibition through a reduction of GABA in dedicated brain areas facilitates human learning. Additionally, modulation of GABA levels is also observed after short-term physical exercise. Future work should elucidate which specific circumstances induce robust GABA modulation to enhance neuroplasticity and boost performance.

Intracerebroventricular administration of the exercise hormone irisin or acute strenuous exercise alleviates epileptic seizure-induced neuroinflammation and improves memory dysfunction in rats

BACKGROUND

Status epilepticus is a common and potentially life-threatening neurological emergency with a high risk for cognitive and neurobiological impairment. Our aim was to evaluate the neuroprotective effects of centrally administered irisin and acute exhausting exercise against oxidative brain injury and memory dysfunction due to a pentylenetetrazole (PTZ)-induced single seizure. Male Sprague Dawley rats with intracerebroventricular (icv) cannulas were randomly divided into intraperitoneally (ip) saline-injected control and PTZ-injected (45 mg/kg) seizure groups. Both the control and PTZ groups were then treated with irisin (7.5 µg/kg, 2 µl, icv), saline (2 µl, icv) or were forced to an acute bout of strenuous exercise before the ip injection of saline (control) or PTZ. Seizures were evaluated using the Racine score. To evaluate memory performance, a passive avoidance test was performed before and after PTZ injection. Following euthanasia at the 24th hour of seizure induction, brain tissues were removed for histopathological examination and for evaluating oxidative damage, antioxidant capacity, and neurotransmitter levels.

RESULTS

Glutamate/GABA imbalance observed in PTZ rats was corrected by irisin administration (p < 0.001/p < 0.01), while irisin prevented the generation of reactive oxygen species and lipid peroxidation (p < 0.05 - 0.001) and replenished the antioxidant catalase and glutathione levels (p < 0.01-0.01) in the cerebral tissue, and reduced the histologically evident neuronal injury due to a single seizure (p < 0.05 - 0.01). Irisin also delayed the onset of seizures (p < 0.05) and improved memory dysfunction (p < 0.05), but did not affect the severity of seizures. The acute exhaustive swimming exercise completed before PTZ-seizure depressed glutamate level (p < 0.001), maintained the oxidant/antioxidant balance, alleviated neuronal injury (p < 0.05 - 0.01) and upregulated cerebral BDNF expression (p < 0.05).

CONCLUSION

In conclusion, acute high-intensity exercise or exogenously administered irisin provides neuroprotection by maintaining the balance of excitatory/inhibitory neurotransmitters and oxidant/antioxidant systems.

Acute effects of aerobic exercise on corticomotor plasticity in individuals with and without depression

BACKGROUND

Although complex in nature, the pathophysiology of depression involves reduced or impaired neuroplastic capabilities. Restoring or enhancing neuroplasticity may serve as a treatment target for developing therapies for depression. Aerobic exercise (AEx) has antidepressant benefits and may enhance neuroplasticity in depression although the latter has yet to be substantiated. Therefore, we sought to examine the acute effect of AEx on neuroplasticity in depression.

METHODS

Sixteen individuals with (DEP; 13 female; age = 28.5 ± 7.3; Montgomery-Äsberg Depression Rating Scale [MADRS] = 21.3 ± 5.2) and without depression (HC; 13 female; age 27.2 ± 7.5; MADRS = 0.8 ± 1.2) completed three experimental visits consisting of 15 min of low intensity AEx (LO) at 35% heart rate reserve (HRR), high intensity AEx (HI) at 70% HRR, or sitting (CON). Following AEx, excitatory paired associative stimulation (PAS25ms) was employed to probe neuroplasticity. Motor evoked potentials (MEP) were assessed via transcranial magnetic stimulation before and after PAS25ms to indicate acute changes in neuroplasticity.

RESULTS

PAS25ms primed with HI AEx led to significant increases in MEP amplitude compared to LO and CON. HI AEx elicited enhanced PAS25ms-induced neuroplasticity for up to 1-h post-PAS. There were no significant between-group differences.

CONCLUSION

HI AEx enhances PAS measured neuroplasticity in individuals with and without depression. HI AEx may have a potent influence on the brain and serve as an effective primer, or adjunct, to therapies that seek to harness neuroplasticity.

Physical activity is predictive of conditioned pain modulation in healthy individuals: a cross-sectional study

Even in healthy populations, conditioned pain modulation (CPM) magnitude varies. This may be accounted for by (non-)modifiable factors, including physical activity. Yet, little research has thoroughly examined physical activity and its relation with CPM magnitude in a representative sample. Therefore, the present study investigated the predictive effect of physical activity on CPM magnitude in 105 healthy adults. Physical activity was assessed during seven consecutive days by self-report using the International Physical Activity Questionnaire and by monitored-based accelerometry. CPM was examined using a heterotopic noxious conditioning stimulation protocol during which the effect of a hot water conditioning stimulus on pressure pain thresholds was evaluated. Comparative, correlation, and hierarchical linear regression analyses were performed. Report-based walking predicts 4.8% of variance in pain modulatory capacity, moderate physical activity predicts 10.2% of variance in pain modulatory capacity, and report-based time spent on total physical activity predicts 7.0% of variance in pain modulatory capacity. More MET-minutes/week spent on total physical activity, including walking and moderate physical activity is associated with greater pain modulatory capacity. The findings of this study add to the limited evidence on the predictive effect of physical activity on CPM. It urges to consider physical activity a confounding factor when examining CPM. The current study provides evidence that a physically active lifestyle benefits endogenous pain modulation in healthy adults. Given its potential, walking and moderate-intensity physical activity might be achievable treatment strategies for pain patients known to have impaired CPM. PERSPECTIVE: The results of this article show that a physically active lifestyle including larger amounts of walking and moderate activity predict greater pain modulatory capacity. TRIAL REGISTRATION: This study has not been preregistered.

Examination of acute spin exercise on GABA levels in aging and stroke: The EASE study protocol

BACKGROUND

Changes in regional levels of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) may indicate the potential for favorable responses to the treatment of stroke affecting the upper extremity. By selectively altering GABA levels during training, we may induce long-term potentiation and adjust excitatory/inhibitory balance (E/I balance). However, the impact of this alteration may be limited by neural damage or aging. Aerobic exercise has been shown to increase GABA levels in the sensorimotor cortex and improve motor learning by widening the dynamic range of E/I balance. The cross-sectional project, Effects of Acute Exercise on Functional Magnetic Resonance Spectroscopy Measures of GABA in Aging and Chronic Stroke (EASE), is designed to assess the functional relevance of changes in GABA concentration within the sensorimotor cortex before and after an acute aerobic exercise session.

METHODS/DESIGN

EASE will enroll 30 participants comprised of healthy younger adults (18-35 years; n = 10), older adults (60+ years; n = 10), and persons with chronic stroke (n = 10) affecting distal upper extremity function. We will use resting magnetic resonance spectroscopy to measure all participants' GABA levels at rest before and after aerobic exercise. In addition, we will employ functional magnetic resonance spectroscopy using motor skill acquisition and recall tasks in healthy adults. We hypothesize that acute aerobic exercise will increase resting sensorimotor GABA concentration and that higher GABA resting levels will predict better motor learning performance on measures taken both inside and outside the magnet. We also hypothesize that a higher dynamic range of GABA during task-based spectroscopy in healthy adults will predict better motor skill acquisition and recall.

DISCUSSION

The EASE project will evaluate the effect of acute exercise on GABA levels as a biomarker of upper extremity motor skill learning with two populations (aging adults and those with chronic stroke). We predict that acute exercise, higher sensorimotor GABA levels, and broader dynamic range will be related to better motor skill acquisition.

The relationship between neurotransmission-related amino acid blood concentrations and neuropsychological performance following acute exercise

Amino acid neurotransmitters, including glutamate, phenylalanine, tyrosine, alanine, and glycine, underlie the majority of the excitatory and inhibitory neurotransmission in the nervous system, and acute exercise has been shown to modulate their concentrations. We aimed to determine whether any correlation exists between the above-mentioned amino acid blood concentrations and the neuropsychological performance after an acute exercise intervention. Sixty basketball players were randomly assigned to one of two experimental conditions: exercise or inactive resting. All participants underwent a comprehensive neuropsychological assessment and blood samples were taken on a Guthrie card before and after the end of the experimental conditions. Amino acid blood concentrations were significantly elevated and cognitive performance significantly improved post-exercise on specific neuropsychological assessments. Significant intervention × group interaction effects were apparent for Trail Making Test part-B [F(1,58) = 20.46, p < .0001, η2 = .26] and Digit Span Backwards [F(1,58) = 15.47, p < .0001, η2 = .21] neuropsychological assessments. Additionally, regression analysis indicated that tyrosine accounted for 38.0% of the variance in the Trail Making Test part-A test. These results suggest that elevated blood concentrations of neurotransmission-related amino acids are associated with improved neuropsychological performance after a single bout of high-intensity exercise.

Mechanisms and benefits of cardiac rehabilitation in individuals with stroke: emerging role of its impact on improving cardiovascular and neurovascular health

Human and animal studies have demonstrated the mechanisms and benefits of aerobic exercise for both cardiovascular and neurovascular health. Aerobic exercise induces neuroplasticity and neurophysiologic reorganization of brain networks, improves cerebral blood flow, and increases whole-body VO2peak (peak oxygen consumption). The effectiveness of a structured cardiac rehabilitation (CR) program is well established and a vital part of the continuum of care for people with cardiovascular disease. Individuals post stroke exhibit decreased cardiovascular capacity which impacts their neurologic recovery and extends disability. Stroke survivors share the same risk factors as patients with cardiac disease and can therefore benefit significantly from a comprehensive CR program in addition to neurorehabilitation to address their cardiovascular health. The inclusion of individuals with stroke into a CR program, with appropriate adaptations, can significantly improve their cardiovascular health, promote functional recovery, and reduce future cardiovascular and cerebrovascular events thereby reducing the economic burden of stroke.

Fat loss and muscle gain: The possible role of cortical glutamate in determining the efficacy of physical exercise

BACKGROUND

Physical exercise is widely acknowledged for its health benefits, but its effectiveness in treating obesity remains contentious due to variability in response. Owing to the roles of glutamate in appetite regulation, food addiction, and impulsivity, this observational cohort-study evaluated medial prefrontal cortex (mPFC) glutamate as a predictor of variability in exercise response, specifically in terms of fat loss and muscle gain.

METHODS

Healthy non-exercising adult men (n = 21) underwent an 8-week supervised exercise program. Baseline glutamate levels in the mPFC were measured through magnetic resonance spectroscopy. For exercise-dependent changes in body composition (fat and muscle mass), basal metabolic rate (BMR), and blood metabolic biomarkers related to lipid and glucose metabolism, measurements were obtained through bioelectrical impedance and blood sample analyses, respectively.

RESULTS

The exercise program resulted in significant improvements in body composition, including reductions in percentage body fat mass, body fat mass, and waist-to-hip ratio and an increase in mean muscle mass. Furthermore, BMR and metabolic indicators linked to glucose and lipids exhibited significant changes. Notably, lower baseline glutamate levels were associated with greater loss in percentage body fat mass (r = 0.482, p = 0.027), body fat mass (r = 0.441, p = 0.045), and increase in muscle mass (r = -0.409, p = 0.066, marginal) following the exercise program.

CONCLUSION

These preliminary findings contribute to our understanding of the neurobiology of obesity and emphasize the significance of glutamate in regulating body composition. The results also highlight cortical glutamate as a potential predictor of exercise-induced fat loss and muscle gain.

Aerobic Exercise Improves Cortical Inhibitory Function After Stroke: A Preliminary Investigation

BACKGROUND AND PURPOSE

Aerobic exercise can elicit positive effects on neuroplasticity and cognitive executive function but is poorly understood after stroke. We tested the effect of 4 weeks of aerobic exercise training on inhibitory and facilitatory elements of cognitive executive function and electroencephalography markers of cortical inhibition and facilitation. We investigated relationships between stimulus-evoked cortical responses, blood lactate levels during training, and aerobic fitness postintervention.

METHODS

Twelve individuals with chronic (>6 months) stroke completed an aerobic exercise intervention (40 minutes, 3×/wk). Electroencephalography and motor response times were assessed during congruent (response facilitation) and incongruent (response inhibition) stimuli of a Flanker task. Aerobic fitness capacity was assessed as o2peak during a treadmill test pre- and postintervention. Blood lactate was assessed acutely (<1 minute) after exercise each week. Cortical inhibition (N2) and facilitation (frontal P3) were quantified as peak amplitudes and latencies of stimulus-evoked electroencephalographic activity over the frontal cortical region.

RESULTS

Following exercise training, the response inhibition speed increased while response facilitation remained unchanged. A relationship between earlier cortical N2 response and faster response inhibition emerged postintervention. Individuals who produced higher lactate during exercise training achieved faster response inhibition and tended to show earlier cortical N2 responses postintervention. There were no associations between o2peak and metrics of behavioral or neurophysiologic function.

DISCUSSION AND CONCLUSIONS

These preliminary findings provide novel evidence for selective benefits of aerobic exercise on inhibitory control during the initial 4-week period after initiation of exercise training and implicate a potential therapeutic effect of lactate on poststroke inhibitory control.

A preliminary study of dynamic neurochemical changes in the dorsolateral prefrontal cortex during working memory

Working memory (WM) is one of the fundamental cognitive functions associated with the dorsolateral prefrontal cortex (DLPFC). However, the neurochemical mechanisms of WM, including the dynamic changes in neurometabolites such as glutamate and GABA in the DLPFC, remain unclear. Here, we investigated WM-related glutamate and GABA changes, alongside hemodynamic responses in the DLPFC, using a combination of functional magnetic resonance spectroscopy (fMRS) and functional magnetic resonance imaging (fMRI). During a WM task, we measured Glx (glutamate + glutamine) and GABA levels using GABA editing MEscher-GArwood Point REsolved Spectroscopy (MEGA-PRESS) sequence and blood-oxygen-level-dependent (BOLD) signal changes. In the DLPFC, we observed elevated Glx levels and increased BOLD signal changes during a 2-back task. Specifically, the Glx levels in the DLPFC were significantly higher during the 2-back task compared with fixation, although this difference was not significant when compared with a 0-back task. However, Glx levels during the 0-back task were higher than during fixation. Furthermore, there was a positive correlation between Glx levels in the DLPFC during the 2-back task and the corresponding BOLD signal changes. Notably, higher Glx increases were associated with increased DLPFC activation and lower WM task performance in individuals. No notable changes in DLPFC GABA levels were observed during WM processing. These findings suggest that the modulation of glutamatergic activity in the DLPFC may play a crucial role in both working memory processing and its associated performance outcomes.

Possible role of exercise therapy on depression: Effector neurotransmitters as key players

About 280 million people suffer from depression as the most common neurological disorder and the most common cause of death worldwide. Exercise with serotonin released in the brain by the 5-HT3-IGF-1 mechanism can lead to antidepressant effects. Swimming exercise has antidepressant effects by increasing the sensitivity of serotonin 5-HT2 receptors and postsynaptic 5-HT1A receptors, increasing 5-HT and 5HIAA levels, increasing TPH and serotonin, and decreasing inflammatory levels of IFN-γ and TNF-α. Anaerobic and aerobic exercises increase beta-endorphin, enkephalin, and dynorphin and have antidepressant effects. Exercise by increasing dopamine, D1R, and D2R leads to the expression of BDNF and activation of TrkB and has antidepressant behavior. Exercise leads to a significant increase in GABAAR (γ2 and α2 subunits) and reduces neurodegenerative disorders caused by GABA imbalance through anti-inflammatory pathways. By increasing glutamate and PGC1α and reducing glutamatergic neurotoxicity, exercise enhances neurogenesis and synaptogenesis and prevents neurodegeneration and the onset of depression. Irisin release during exercise shows an important role in depression by increasing dopamine, BDNF, NGF, and IGF-1 and decreasing inflammatory mediators such as IL-6 and IL-1β. In addition, exercise-induced orexin and NPY can increase hippocampal neurogenesis and relieve depression. After exercise, the tryptophan to large neutral amino acids (TRP/LNAA) ratio and the tryptophan to branched-chain amino acids (BCAA) ratio increase, which may have antidepressant effects. The expression of M5 receptor and nAChR α7 increases after exercise and significantly increases dopamine and acetylcholine and ameliorates depression. It appears that during exercise, muscarinic receptors can reduce depression through dopamine in the absence of acetylcholine. Therefore, exercise can be used to reduce depression by affecting neurotransmitters, neuromodulators, cytokines, and/or neurotrophins.

Associations between physical exercise type, fluid intelligence, executive function, and processing speed in the oldest-old (85 +)

BACKGROUND

While much is known about the effects of physical exercise in adult humans, literature on the oldest-old (≥ 85 years old) is sparse. The present study explored the relationship between self-reported engagement in physical exercise and cognition in the oldest-old.

METHODS

The sample included 184 cognitively healthy participants (98 females, MoCA mean score = 24.81) aged 85 to 99 years old (mean = 88.49 years). Participants completed the Community Healthy Activities Model Program for Seniors (CHAMPS) questionnaire and a cognitive battery including NIH-TB, Coding, Symbol Search, Letter Fluency, and Stroop task. Three groups of participants - sedentary (n = 58; MoCA mean score = 24; 36 females; mean age = 89.03), cardio (n = 60; MoCA mean score = 25.08; 29 females; mean age = 88.62), and cardio + strength training (n = 66; MoCA mean score = 25.28; 33 females; mean age = 87.91) - were derived from responses on CHAMPS.

RESULTS

Analyses controlled for years of education, NIH-TB Crystallized Composite, and metabolic equivalent of tasks. The cardio + strength training group had the highest cognitive performances overall and scored significantly better on Coding (p < 0.001) and Symbol Search (p < 0.05) compared to the sedentary group. The cardio + strength training group scored significantly better on Symbol Search, Letter Fluency, and Stroop Color-Word compared to the cardio group (p < 0.05).

CONCLUSIONS

Our findings suggest self-reported exercise in the oldest-old is linked to better performance on cognitive measures of processing speed and executive functioning, and that there may be a synergistic effect of combining aerobic and resistance training on cognition.

Lithium and exercise ameliorate insulin-deficient hyperglycemia by independently attenuating pancreatic α-cell mass and hepatic gluconeogenesis

As in type 1 diabetes, the loss of pancreatic β-cells leads to insulin deficiency and the subsequent development of hyperglycemia. Exercise has been proposed as a viable remedy for hyperglycemia. Lithium, which has been used as a treatment for bipolar disorder, has also been shown to improve glucose homeostasis under the conditions of obesity and type 2 diabetes by enhancing the effects of exercise on the skeletal muscles. In this study, we demonstrated that unlike in obesity and type 2 diabetic conditions, under the condition of insulin-deficient type 1 diabetes, lithium administration attenuated pancreatic a-cell mass without altering insulin-secreting β-cell mass, implying a selective impact on glucagon production. Additionally, we also documented that lithium downregulated the hepatic gluconeogenic program by decreasing G6Pase protein levels and upregulating AMPK activity. These findings suggest that lithium's effect on glucose metabolism in type 1 diabetes is mediated through a different mechanism than those associated with exerciseinduced metabolic changes in the muscle. Therefore, our research presents the novel therapeutic potential of lithium in the treatment of type 1 diabetes, which can be utilized along with insulin and independently of exercise.

The different cell-specific mechanisms of voluntary exercise and forced exercise in the nucleus accumbens

Physical inactivity is a global epidemic. People who take the initiative to exercise will feel pleasure during the exercise process and stick with it for a long time, while people who passively ask for exercise will feel pain and cannot stick with it. However, the neural mechanisms underlying voluntary and forced exercise remain unclear. Here, we report that voluntary running increased the frequency and amplitude of miniature excitatory postsynaptic currents (mEPSC) but decreased membrane excitability in D1R-MSNs, whereas D2R-MSNs did not change in mEPSC and membrane excitability. Forced running increased the frequency of mEPSC and membrane excitability in D2R-MSNs, but D1R-MSNs did not change, which may be the mechanism by which forced exercise has a non-rewarding effect. These findings provide new insights into how voluntary and forced exercise mediate reward and non-reward effects.

Increased neural differentiation after a single session of aerobic exercise in older adults

Aging is associated with decreased cognitive function. One theory posits that this decline is in part due to multiple neural systems becoming dedifferentiated in older adults. Exercise is known to improve cognition in older adults, even after only a single session. We hypothesized that one mechanism of improvement is a redifferentiation of neural systems. We used a within-participant, cross-over design involving 2 sessions: either 30 minutes of aerobic exercise or 30 minutes of seated rest (n = 32; ages 55-81 years). Both functional Magnetic Resonance Imaging (fMRI) and Stroop performance were acquired soon after exercise and rest. We quantified neural differentiation via general heterogeneity regression. There were 3 prominent findings following the exercise. First, participants were better at reducing Stroop interference. Second, while there was greater neural differentiation within the hippocampal formation and cerebellum, there was lower neural differentiation within frontal cortices. Third, this greater neural differentiation in the cerebellum and temporal lobe was more pronounced in the older ages. These data suggest that exercise can induce greater neural differentiation in healthy aging.

Virtual reality as a tool to explore multisensory processing before and after engagement in physical activity

Introduction

This pilot study employed a non-randomized control trial design to explore the impact of physical activity within a virtual reality (VR) environment on multisensory processing among community-dwelling older adults.

Methods

The investigation compared both chronic (over 6 weeks) and acute effects of VR-based physical activity to a reading control group. The evaluation metrics for multisensory processing included audiovisual response time (RT), simultaneity judgments (SJ), sound-induced flash illusion (SIFI), and temporal order judgments (TOJ). A total of 13 older adults were provided with VR headsets featuring custom-designed games, while another 14 older adults were assigned to a reading-based control group.

Results

Results indicated that acute engagement in physical activity led to higher accuracy in the SIFI task (experimental group: 85.6%; control group: 78.2%; p = 0.037). Additionally, both chronic and acute physical activity resulted in quicker response times (chronic: experimental group = 336.92; control group = 381.31; p = 0.012; acute: experimental group = 333.38; control group = 383.09; p = 0.006). Although the reading group showed a non-significant trend for greater improvement in mean RT, covariate analyses revealed that this discrepancy was due to the older age of the reading group.

Discussion

The findings suggest that immersive VR has potential utility for enhancing multisensory processing in older adults. However, future studies must rigorously control for participant variables like age and sex to ensure more accurate comparisons between experimental and control conditions.

Smoking, tobacco dependence, and neurometabolites in the dorsal anterior cingulate cortex

Cigarette smoking has a major impact on global health and morbidity, and positron emission tomographic research has provided evidence for reduced inflammation in the human brain associated with cigarette smoking. Given the consequences of inflammatory dysfunction for health, the question of whether cigarette smoking affects neuroinflammation warrants further investigation. The goal of this project therefore was to validate and extend evidence of hypoinflammation related to smoking, and to examine the potential contribution of inflammation to clinical features of smoking. Using magnetic resonance spectroscopy, we measured levels of neurometabolites that are putative neuroinflammatory markers. N-acetyl compounds (N-acetylaspartate + N-acetylaspartylglutamate), glutamate, creatine, choline-compounds (phosphocholine + glycerophosphocholine), and myo-inositol, have all been linked to neuroinflammation, but they have not been examined as such with respect to smoking. We tested whether people who smoke cigarettes have brain levels of these metabolites consistent with decreased neuroinflammation, and whether clinical features of smoking are associated with levels of these metabolites. The dorsal anterior cingulate cortex was chosen as the region-of-interest because of previous evidence linking it to smoking and related states. Fifty-four adults who smoked daily maintained overnight smoking abstinence before testing and were compared with 37 nonsmoking participants. Among the smoking participants, we tested for associations of metabolite levels with tobacco dependence, smoking history, craving, and withdrawal. Levels of N-acetyl compounds and glutamate were higher, whereas levels of creatine and choline compounds were lower in the smoking group as compared with the nonsmoking group. In the smoking group, glutamate and creatine levels correlated negatively with tobacco dependence, and creatine correlated negatively with lifetime smoking, but none of the metabolite levels correlated with craving or withdrawal. The findings indicate a link between smoking and a hypoinflammatory state in the brain, specifically in the dorsal anterior cingulate cortex. Smoking may thereby increase vulnerability to infection and brain injury.

Elevated susceptibility to exogenous seizure triggers and impaired interneuron excitability in a mouse model of Leigh syndrome epilepsy

Mutations in the NADH dehydrogenase (ubiquinone reductase) iron‑sulfur protein 4 (NDUFS4) gene, which encodes for a key structural subunit of the OXFOS complex I (CI), lead to the most common form of mitochondrial disease in children known as Leigh syndrome (LS). As in other mitochondrial diseases, epileptic seizures constitute one of the most significant clinical features of LS. These seizures are often very difficult to treat and are a sign of poor disease prognosis. Mice with whole-body Ndufs4 KO are a well-validated model of LS; they exhibit epilepsy and several other clinical features of LS. We have previously shown that mice with Ndufs4 KO in only GABAergic interneurons (Gad2-Ndufs4-KO) reproduce the severe epilepsy phenotype observed in the global KO mice. This observation indicated that these mice represent an excellent model of LS epilepsy isolated from other clinical manifestations of the disease. To further characterize this epilepsy phenotype, we investigated seizure susceptibility to selected exogenous seizure triggers in Gad2-Ndufs4-KO mice. Then, using electrophysiology, imaging, and immunohistochemistry, we studied the cellular, physiological, and neuroanatomical consequences of Ndufs4 KO in GABAergic interneurons. Homozygous KO of Ndufs4 in GABAergic interneurons leads to a prominent susceptibility to exogenous seizure triggers, impaired interneuron excitability and interneuron loss. Finally, we found that the hippocampus and cortex participate in the generation of seizure activity in Gad2-Ndufs4-KO mice. These findings further define the LS epilepsy phenotype and provide important insights into the cellular mechanisms underlying epilepsy in LS and other mitochondrial diseases.

γ-Aminobutyric acids (GABA) and serum GABA/AABA (G/A) ratio as potential biomarkers of physical performance and aging

Declining physical performance with age and disease is an important indicator of declining health. Biomarkers that identify declining physical performance would be useful in predicting treatment outcomes and identifying potential therapeutics. γ-aminobutyric acid (GABA), a muscle autocrine factor, is a potent inhibitor of muscle function and works as a muscle relaxant. L-α-aminobutyric acid (L-AABA) is a biomarker for malnutrition, liver damage, and depression. We sought to determine if GABA and L-AABA may be useful for predicting physical performance. Serum levels of GABA and L-AABA were quantified in 120 individuals divided by age, sex, and physical capacity into low, average, and high performer groups. Analyses explored correlations between serum levels and physical performance. Both GABA and the ratio of GABA/AABA (G/A), but not AABA, were highly positively associated with age (Pearson correlations r = 0.35, p = 0.0001 for GABA, r = 0.31, p = 0.0007 for G/A, n = 120). GABA showed negative associations in the whole cohort with physical performance [fast gait speed, 6 min walk test (6MWT), PROMIS score, and SF36PFS raw score] and with subtotal and femoral neck bone mineral density. L-AABA was positively associated with usual gait speed, 6MWT, total SPPB score, and SF36PFS raw score in the total cohort of 120 human subjects, also with 6MWT and SF36PFS raw score in the 60 male subjects, but no associations were observed in the 60 females. As both GABA and L-AABA appear to be indicative of physical performance, but in opposite directions, we examined the G/A ratio. Unlike GABA, the G/A ratio showed a more distinct association with mobility tests such as total SPPB score, usual and fast gait speed, 6MWT, and SF36PFS raw score in the males, regardless of age and metabolic status. Serum G/A ratio could be potentially linked to physical performance in the male population. Our findings strongly suggest that GABA, L-AABA, and the G/A ratio in human serum may be useful markers for both age and physical function. These new biomarkers may significantly enhance the goal of identifying universal biomarkers to accurately predict physical performance and the beneficial effects of exercise training for older adults.

Effects of acute physical activity on brain metabolites as measured by magnetic resonance spectroscopy (1H-MRS) in humans: A systematic review

Physical activity (PA) promotes brain health in a variety of domains including cognition, mood, and neuroplasticity. At the neurochemical level, the mechanisms underlying these effects in the brain are not fully understood. With proton Magnetic Resonance Spectroscopy (1H-MRS), it is possible to non-invasively quantify metabolite concentrations, enabling studies to obtain measures of exercise-induced neurochemical changes. This systematic review aimed to examine the existing literature on acute effects of PA on brain metabolites as measured by 1H-MRS. Four databases (Cochrane Central Register of Controlled Trials, PubMed, Embase, and PsycINFO) were searched, identifying 2965 studies, of which 9 met the inclusion criteria. Across studies, Gamma-AminoButyric Acid (GABA) and lactate tended to increase after exercise, while no significant changes in choline were reported. For glutamine/glutamate (Glx), studies were inconclusive. Conclusions were limited by the lack of consensus on 1H-MRS data processing and exercise protocols. To reduce inter-study differences, future studies are recommended to (1): apply a standardized exercise index (2), consider the onset time of MRS scans, and (3) follow standardized MRS quantification methods.

Synergistic effects of aerobic exercise and transcranial direct current stimulation on executive function and biomarkers in healthy young adults

OBJECTIVE

This research explored the combined effects of transcranial direct current stimulation (tDCS) and aerobic exercise (AE) on executive function and specific serum biomarkers in healthy adults.

METHODS

Sixty healthy young adults were randomly assigned into tDCS+AE, tDCS only, or AE only groups. Interventions were carried out for 20 days. Executive functions were evaluated using tasks such as the 2,3-back task, the spatial working memory task, the Stroop test, T test, and hexagonal obstacle jump task. Serum biomarkers, including brain-derived neurotrophic factor (BDNF), malondialdehyde (MDA), superoxide dismutase (SOD), glutamate, glutathione peroxidase 4 (GPX4) and iron ion, were analyzed pre- and post-intervention.

RESULTS

The tDCS+AE group showed superior enhancements in executive function, evidenced by improved accuracy rates in 2,3-back tasks, better performance in the staircase task, and reduced reaction times in the incongruent reaction time of the Stroop task compared to other groups. Importantly, we found substantial changes in serum biomarkers: increased levels of BDNF and SOD, and decreased levels of MDA and glutamate in the tDCS+AE group. These changes were significantly different when compared with the tDCS and AE only groups. Notably, these alterations in serum biomarkers were correlated with improvements in executive function tasks, thus offering a potential physiological basis for the cognitive improvements witnessed.

CONCLUSION

The combined tDCS and AE intervention effectively improved executive function in healthy young adults, with the improvements linked to changes in key serum biomarkers. The results emphasize the potential of combined tDCS and AE interventions in engaging multiple physiological pathways to enhance executive function.

The benefits of rehabilitation exercise in improving chronic traumatic encephalopathy: recent advances and future perspectives

Traumatic encephalopathy syndrome (TES) is used to describe the clinical manifestations of chronic traumatic encephalopathy (CTE). However, effective treatment and prevention strategies are lacking. Increasing evidence has shown that rehabilitation training could prevent cognitive decline, enhance brain plasticity, and effectively improve neurological function in neurodegenerative diseases. Therefore, the mechanisms involved in the effects of rehabilitation exercise therapy on the prognosis of CTE are worth exploring. The aim of this article is to review the pathogenesis of CTE and provide a potential clinical intervention strategy for CTE.

Myokines as mediators of exercise-induced cognitive changes in older adults: protocol for a comprehensive living systematic review and meta-analysis

Background

The world's population is aging, but life expectancy has risen more than healthy life expectancy (HALE). With respect to brain and cognition, the prevalence of neurodegenerative disorders increases with age, affecting health and quality of life, and imposing significant healthcare costs. Although the effects of physical exercise on cognition in advanced age have been widely explored, in-depth fundamental knowledge of the underlying mechanisms of the exercise-induced cognitive improvements is lacking. Recent research suggests that myokines, factors released into the blood circulation by contracting skeletal muscle, may play a role in mediating the beneficial effect of exercise on cognition. Our goal in this ongoing (living) review is to continuously map the rapidly accumulating knowledge on pathways between acute or chronic exercise-induced myokines and cognitive domains enhanced by exercise.

Method

Randomized controlled studies will be systematically collected at baseline and every 6 months for at least 5 years. Literature search will be performed online in PubMed, EMBASE, PsycINFO, Web of Science, SportDiscus, LILACS, IBECS, CINAHL, SCOPUS, ICTRP, and ClinicalTrials.gov. Risk of bias will be assessed using the Revised Cochrane Risk of Bias tool (ROB 2). A random effects meta-analysis with mediation analysis using meta-analytic structural equation modeling (MASEM) will be performed. The primary research question is to what extent exercise-induced myokines serve as mediators of cognitive function. Secondarily, the pooled effect size of specific exercise characteristics (e.g., mode of exercise) or specific older adults' populations (e.g., cognitively impaired) on the relationship between exercise, myokines, and cognition will be assessed. The review protocol was registered in PROSPERO (CRD42023416996).

Discussion

Understanding the triad relationship between exercise, myokines and cognition will expand the knowledge on multiple integrated network systems communicating between skeletal muscles and other organs such as the brain, thus mediating the beneficial effects of exercise on health and performance. It may also have practical implications, e.g., if a certain myokine is found to be a mediator between exercise and cognition, the optimal exercise characteristics for inducing this myokine can be prescribed. The living review is expected to improve our state of knowledge and refine exercise regimes for enhancing cognitive functioning in diverse older adults' populations.

Registration

Systematic review and meta-analysis protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO) on the 24th of April 2023 (registration number CRD42023416996).

Increased brain 1H-MRS glutamate and lactate signals following maximal aerobic capacity exercise in young healthy males: an exploratory study

Physical exercise involves increased neuronal activity of many brain structures, but 1H-MRS investigations on the effects of human brain glutamate (Glu) concentrations on acute exercise have been sparse. Previous studies consistently found increases in brain lactate (Lac) concentrations following graded exercise up to 85% of the predicted maximal heart rate. However, the reported effects on brain concentrations of glutamine and glutamate were not consistent. This study aimed to determine the effect of acute intense graded maximal exercise on 1H-MRS signals related to concentrations of Glu, glutamate+glutamine (Glx), and Lac. Young adult males were randomly divided into two groups and subjected to 1H-MRS when resting (NE) or shortly after cessation of the intense graded exercise intended to pass the anaerobic threshold (E). 1H-MRS spectra were acquired from the large voxel encompassing the occipito-parietal cortex only once. Estimates of Glu, Glx, and Lac concentrations were calculated in institutional units by normalizing to a spectroscopic signal originating from creatine-containing compounds (Cr). Concentrations of Glu, Glx, and Lac were respectively 11%, 12.6%, and 48.5% higher in E than in NE (p < 0.001). The increased brain Lac signal in the exercising group indicated that in our experiment, vigorous exercise resulted in passing the anaerobic threshold and lactate apparently entered the brain. Concomitantly glutamate-related resonance signals from the vicinity of the occipito-parietal cortex were significantly increased; physiological mechanisms underlying these phenomena require further study. Future studies should evaluate whether the normalization rate of these concentrations is a marker of general physical fitness.

Acute exercise as a modifier of neocortical plasticity and aperiodic activity in the visual cortex

Long-term potentiation (LTP) is a form of neuroplasticity commonly implicated in mechanistic models of learning and memory. Acute exercise can boost LTP in the motor cortex, and is associated with a shift in excitation/inhibition (E:I) balance, but whether this extends to other regions such as the visual cortex is unknown. We investigated the effect of a preceding bout of exercise on LTP induction and the E:I balance in the visual cortex using electroencephalography (EEG). Young adults (N = 20, mean age = 24.20) engaged in 20 min of high-intensity interval training (HIIT) exercise and rest across two counterbalanced sessions. LTP was induced using a high frequency presentation of a visual stimulus; a "visual tetanus". Established EEG markers of visual LTP, the N1b and P2 component of the visual evoked potential, and an EEG-derived measure of the E:I balance, the aperiodic exponent, were measured before and after the visual tetanus. As expected, there was a potentiation of the N1b following the visual tetanus, with specificity to the tetanised stimulus, and a non-specific potentiation of the P2. These effects were not sensitive to a preceding bout of exercise. However, the E:I balance showed a late shift towards inhibition following the visual tetanus. A preceding bout of exercise resulted in specificity of this E:I balance shift to the tetanised stimulus, that was not seen following rest. This novel finding suggests a possible exercise-induced tuning of the visual cortex to stimulus details following LTP induction.

Physical activity for cognitive health promotion: An overview of the underlying neurobiological mechanisms

Physical activity is one of the modifiable factors of cognitive decline and dementia with the strongest evidence. Although many influential reviews have illustrated the neurobiological mechanisms of the cognitive benefits of physical activity, none of them have linked the neurobiological mechanisms to normal exercise physiology to help the readers gain a more advanced, comprehensive understanding of the phenomenon. In this review, we address this issue and provide a synthesis of the literature by focusing on five most studied neurobiological mechanisms. We show that the body's adaptations to enhance exercise performance also benefit the brain and contribute to improved cognition. Specifically, these adaptations include, 1), the release of growth factors that are essential for the development and growth of neurons and for neurogenesis and angiogenesis, 2), the production of lactate that provides energy to the brain and is involved in the synthesis of glutamate and the maintenance of long-term potentiation, 3), the release of anti-inflammatory cytokines that reduce neuroinflammation, 4), the increase in mitochondrial biogenesis and antioxidant enzyme activity that reduce oxidative stress, and 5), the release of neurotransmitters such as dopamine and 5-HT that regulate neurogenesis and modulate cognition. We also discussed several issues relevant for prescribing physical activity, including what intensity and mode of physical activity brings the most cognitive benefits, based on their influence on the above five neurobiological mechanisms. We hope this review helps readers gain a general understanding of the state-of-the-art knowledge on the neurobiological mechanisms of the cognitive benefits of physical activity and guide them in designing new studies to further advance the field.

Physiological, Anatomical and Metabolic Correlates of Aerobic Fitness in Human Primary Motor Cortex: A Multimodal Study

Physical activity (PA) has been shown to benefit various cognitive functions and promote neuroplasticity. Whereas the effects of PA on brain anatomy and function have been well documented in older individuals, data are scarce in young adults. Whether high levels of cardiorespiratory fitness (CRF) achieved through regular PA are associated with significant structural and functional changes in this age group remains largely unknown. In the present study, twenty young adults that engaged in at least 8 hours per week of aerobic exercise during the last 5 years were compared to twenty sedentary controls on measures of cortical excitability, white matter microstructure, cortical thickness and metabolite concentration. All measures were taken in the left primary motor cortex and CRF was assessed with VO_2max. Transcranial magnetic stimulation (TMS) revealed higher corticospinal excitability in high- compared to low-fit individuals reflected by greater input/output curve amplitude and slope. No group differences were found for other TMS (short-interval intracortical inhibition and intracortical facilitation), diffusion MRI (fractional anisotropy and apparent fiber density), structural MRI (cortical thickness) and magnetic resonance spectroscopy (NAA, GABA, Glx) measures. Taken together, the present data suggest that brain changes associated with increased CRF are relatively limited, at least in primary motor cortex, in contrast to what has been observed in older adults.

Strength gains after 12 weeks of resistance training correlate with neurochemical markers of brain health in older adults: a randomized control 1H-MRS study

Physical exercise is considered a potent countermeasure against various age-associated physiological deterioration processes. We therefore assessed the effect of 12 weeks of resistance training on brain metabolism in older adults (age range: 60-80 years). Participants either underwent two times weekly resistance training program which consisted of four lower body exercises performed for 3 sets of 6-10 repetitions at 70-85% of 1 repetition maximum (n = 20) or served as the passive control group (n = 21). The study used proton magnetic resonance spectroscopy to quantify the ratio of total N-acetyl aspartate, total choline, glutamate-glutamine complex, and myo-inositol relative to total creatine (tNAA/tCr, tCho/tCr, Glx/tCr, and mIns/tCr respectively) in the hippocampus (HPC), sensorimotor (SM1), and prefrontal (dlPFC) cortices. The peak torque (PT at 60°/s) of knee extension and flexion was assessed using an isokinetic dynamometer. We used repeated measures time × group ANOVA to assess time and group differences and correlation coefficient analyses to examine the pre-to-post change (∆) associations between PT and neurometabolite variables. The control group showed significant declines in tNAA/tCr and Glx/tCr of SM1, and tNAA/tCr of dlPFC after 12 weeks, which were not seen in the experimental group. A significant positive correlation was found between ∆PT knee extension and ∆SM1 Glx/tCr, ∆dlPFC Glx/tCr and between ∆PT knee flexion and ∆dlPFC mIns/tCr in the experimental group. Overall, findings suggest that resistance training seems to elicit alterations in various neurometabolites that correspond to exercise-induced "preservation" of brain health, while simultaneously having its beneficial effect on augmenting muscle functional characteristics in older adults.

A Systematic Review on the Effects of Acute Aerobic Exercise on Neurophysiological, Molecular, and Behavioral Measures in Chronic Stroke

BACKGROUND

A single bout of aerobic exercise (AE) can produce changes in neurophysiological and behavioral measures in healthy individuals and those with stroke. However, the effects of AE-priming effects on neuroplasticity markers and behavioral measures are unclear.

OBJECTIVES

This systematic review aimed to examine the effects of AE on neuroplasticity measures, such as corticomotor excitability (CME), molecular markers, cortical activation, motor learning, and performance in stroke.

METHODS

A literature search was performed in MEDLINE, CINAHL, Scopus, and PsycINFO databases. Randomized and non-randomized studies incorporating acute AE in stroke were selected. Two reviewers independently assessed the risk of bias and methodological rigor of the studies and extracted data on participant characteristics, exercise interventions, and neuroplasticity related outcomes. The quality of transcranial magnetic stimulation reported methods was assessed using a standardized checklist.

RESULTS

A total of 16 studies were found suitable for inclusion. Our findings suggest mixed evidence for the effects of AE on CME, limited to no effects on intracortical inhibition and facilitation and some evidence for modulating brain derived neurotrophic factor levels, motor learning, and cortical activation. Exercise intensities in the moderate to vigorous range showed a trend towards better effects on neuroplasticity measures.

CONCLUSION

It appears that choosing a moderate to vigorous exercise paradigm for at least 20 to 30 minutes may induce changes in some neuroplasticity parameters in stroke. However, these findings necessitate prudent consideration as the studies were diverse and had moderate methodological quality. There is a need for a consensus on an exercise priming paradigm and for good-quality, larger controlled studies.

Too much is too little: Estimating the optimal physical activity level for a healthy mental state

Introduction

Although physical activity and exercise are generally thought to have favorable effects on mental health, excessive physical activity may have unfavorable effects. In this study, the associations between physical activity and the states of mental health with U-shaped dose-response curves were hypothesized, and the ranges of physical activity resulting in optimal effects on mental health were investigated.

Methods

A cross-sectional survey was conducted on 1,237 adult volunteers in 2017 and 2018. Of these volunteers, 526 participants validly answered the self-administered questionnaires asking about physical activity, depression, anxiety, resilience, insomnia vulnerability, and life events. A comparison of mental health measures by physical activity levels and quadratic equation model regressions were performed.

Results

No significant linear associations between physical activity levels and mental health measurements were observed; however, the U-shaped, quadratic equation models indicated a significance. The following levels of physical activity per week optimized the mental health measurements values of the participants: 6,953 MET-minutes and 25.70 h for depression, 5,277 MET-minutes and 21.60 h for state anxiety, 5,678 MET-minutes and 22.58 h for trait anxiety, 25.41 h for resilience, and 9,152 MET-minutes and 31.17 h for insomnia vulnerability.

Conclusion

Physical activities in the optimal range were associated with more favorable mental health measurements. Physical activities that were too much or too long and outside of the optimal range were associated with less favorable mental health measurements.

Effects of acute exercise on memory: Considerations of exercise intensity, post-exercise recovery period and aerobic endurance

Accumulating research demonstrates that acute exercise can enhance long-term episodic memory. However, it is unclear if there is an intensity-specific effect of acute exercise on long-term episodic memory function and whether this is influenced by the post-exercise recovery period, which was the primary objective of this experiment. Another uncertainty in the literature is whether aerobic endurance influences the interaction between exercise intensity and post-exercise recovery period on long-term episodic memory function, which was a secondary objective of this study. With exercise intensity and post-exercise recovery period occurring as within-subject factors, and fitness as a between-subject factor, 59 participants (M_age = 20 years) completed 12 primary laboratory visits. These visits included a 20-min bout of exercise (Control, Moderate, and Vigorous), followed by a recovery period (1, 5, 10, and 15 min) and then a word-list episodic memory task, involving an encoding phase and two long-term recall assessments (20-min and 24-h delayed recall). The primary finding from this experiment was that moderate and vigorous-intensity exercise improved memory function when compared to a non-exercise control. A secondary finding was that individuals with higher levels of aerobic endurance, compared to their lesser fit counterparts, had greater memory performance after exercise (moderate or vigorous) when compared to after a control condition. Additionally, individuals with higher levels of aerobic endurance, compared to their lesser fit counterparts, generally performed better on the memory task with longer post-exercise recovery periods. Future research should carefully consider these parameters when evaluating the effects of acute exercise on long-term episodic memory.

Visual cortical γ-aminobutyric acid and perceptual suppression in amblyopia

In amblyopia, abnormal visual experience during development leads to an enduring loss of visual acuity in adulthood. Physiological studies in animal models suggest that intracortical GABAergic inhibition may mediate visual deficits in amblyopia. To better understand the relationship between visual cortical γ-aminobutyric acid (GABA) and perceptual suppression in persons with amblyopia (PWA), we employed magnetic resonance spectroscopy (MRS) to quantify GABA levels in both PWA and normally-sighted persons (NSP). In the same individuals, we obtained psychophysical measures of perceptual suppression for a variety of ocular configurations. In PWA, we found a robust negative correlation between the depth of amblyopia (the difference in visual acuity between the amblyopic and non-amblyopic eyes) and GABA concentration that was specific to visual cortex and was not observed in a sensorimotor cortical control region. Moreover, lower levels of visual cortical GABA were associated with weaker perceptual suppression of the fellow eye by the amblyopic eye and stronger suppression of the amblyopic eye by the fellow eye. Taken together, our findings provide evidence that intracortical GABAergic inhibition is an important component of the pathology of human amblyopia and suggest possible therapeutic interventions to restore vision in the amblyopic eye through enhancement of visual cortical GABAergic signaling in PWA.

Aerobic Exercise and Human Visual Cortex Neuroplasticity: A Narrative Review

There is compelling evidence from animal models that physical exercise can enhance visual cortex neuroplasticity. In this narrative review, we explored whether exercise has the same effect in humans. We found that while some studies report evidence consistent with exercise-induced enhancement of human visual cortex neuroplasticity, others report no effect or even reduced neuroplasticity following exercise. Differences in study methodology may partially explain these varying results. Because the prospect of exercise increasing human visual cortex neuroplasticity has important implications for vision rehabilitation, additional research is required to resolve this discrepancy in the literature.

Exerkines and long-term synaptic potentiation: Mechanisms of exercise-induced neuroplasticity

Physical exercise may improve cognitive function by modulating molecular and cellular mechanisms within the brain. We propose that the facilitation of long-term synaptic potentiation (LTP)-related pathways, by products induced by physical exercise (i.e., exerkines), is a crucial aspect of the exercise-effect on the brain. This review summarizes synaptic pathways that are activated by exerkines and may potentiate LTP. For a total of 16 exerkines, we indicated how blood and brain exerkine levels are altered depending on the type of physical exercise (i.e., cardiovascular or resistance exercise) and how they respond to a single bout (i.e., acute exercise) or multiple bouts of physical exercise (i.e., chronic exercise). This information may be used for designing individualized physical exercise programs. Finally, this review may serve to direct future research towards fundamental gaps in our current knowledge regarding the biophysical interactions between muscle activity and the brain at both cellular and system levels.

The Relationship Between Resting Cerebral Blood Flow, Neurometabolites, Cardio-Respiratory Fitness and Aging-Related Cognitive Decline

Older adults typically experience a decline in cognitive function, but improvements in physical health and lifestyle can be neuroprotective across the human lifespan. The primary objective of this study is to advance our basic understanding of how cardiorespiratory fitness and neurophysiological attributes relate to cognitive decline. While cerebral blood flow (CBF) is critical for the supply of nutrients to the tissue, the brain's major neurotransmitters (i.e., gamma-aminobutyric acid, GABA, and glutamate-glutamine complex, Glx) are closely linked to oxidative metabolism. Within the context of flow-metabolism coupling, the critical question is how these neurophysiological parameters interplay, resulting in cognitive decline. Further, how cardiorespiratory fitness may impact aging neurophysiology and cognition is not well understood. To address these questions, we recruited 10 younger and 12 older cognitively intact participants to collect GABA and Glx using magnetic resonance spectroscopy (MRS), CBF using pseudo-continuous arterial spin labeling Magnetic Resonance Imaging (MRI), VO2max as a measure of cardiorespiratory fitness using the YMCA submax test, and cognitive and motor-cognitive measures using a battery of behavioral assessments. We observed expected differences in GABA+, Glx, and CBF between younger and older participants in pre-SMA, a frontal domain-general region. When GABA+ and Glx were related to CBF via multiple linear regression, Glx was identified as the main contributor to the model. For higher-order executive function (i.e., inhibition versus color naming), GABA*Glx*CBF interaction was critical in younger, while only Glx was involved in older participants. For unimanual motor dexterity, GABA*Glx interaction was the common denominator across both groups, but younger participants' brain also engages CBF. In terms of selective motor inhibition, CBF from younger participants was the only major neurophysiological factor. In terms of fitness, cardiorespiratory fitness was significantly related to GABA, Glx, and motor performance when combining cohorts, but no group-specific relationships were observed. Taken together, our results indicate that Glx and CBF coupling decreases with aging, perhaps due to altered glial oxidative metabolism. Our data suggest that GABA, Glx, and CBF are engaged and weighted differently for different cognitive measures sensitized to aging, and higher fitness allows for a more efficient metabolic shift that facilitates improved performance on cognitive-motor tasks.

Human brain functional MRS reveals interplay of metabolites implicated in neurotransmission and neuroenergetics

While functional MRI (fMRI) localizes brain activation and deactivation, functional MRS (fMRS) provides insights into the underlying metabolic conditions. There is much interest in measuring task-induced and resting levels of metabolites implicated in neuroenergetics (e.g., lactate, glucose, or β-hydroxybutyrate (BHB)) and neurotransmission (e.g., γ-aminobutyric acid (GABA) or pooled glutamate and glutamine (Glx)). Ultra-high magnetic field (e.g., 7T) has boosted the fMRS quantification precision, reliability, and stability of spectroscopic observations using short echo-time (TE) 1H-MRS techniques. While short TE 1H-MRS lacks sensitivity and specificity for fMRS at lower magnetic fields (e.g., 3T or 4T), most of these metabolites can also be detected by J-difference editing (JDE) 1H-MRS with longer TE to filter overlapping resonances. The 1H-MRS studies show that JDE can detect GABA, Glx, lactate, and BHB at 3T, 4T and 7T. Most recently, it has also been demonstrated that JDE 1H-MRS is capable of reliable detection of metabolic changes in different brain areas at various magnetic fields. Combining fMRS measurements with fMRI is important for understanding normal brain function, but also clinically relevant for mechanisms and/or biomarkers of neurological and neuropsychiatric disorders. We provide an up-to-date overview of fMRS research in the last three decades, both in terms of applications and technological advances. Overall the emerging fMRS techniques can be expected to contribute substantially to our understanding of metabolism for brain function and dysfunction.

Alterations in Muscle Force Control With Aging: Is There a Modulatory Effect of Lifelong Physical Activity?

Recent technological developments have enabled significant advances in our understanding of the ability to voluntarily control muscle force output. The fluctuations inherent to muscle force output can be quantified according to both their magnitude and temporal structure (or "complexity"), with such quantification facilitating comparison of force control between distinct populations. In comparison to young adults, older adults exhibit an increase in the magnitude (i.e., decreased steadiness) and a decrease in the complexity (i.e., decreased adaptability) of force fluctuations, both of which are indicative of a loss of force control. There remain, however, key gaps in knowledge that limit our interpretation of this age-related loss of force control. One such gap relates to the effect of lifelong physical activity on force control. To date, research on aging and force control has largely been conducted on inactive or moderately active older adults. However, high levels of lifelong physical activity, such as that exhibited by Masters athletes, have been shown to have protective effects on the function and morphology of the neuromuscular system. Some of these effects (e.g., on impaired inhibitory transmission in the motor cortex and on motor unit discharge rates) have the potential to attenuate the age-related loss of force control, while others (e.g., greater motor unit remodeling capacity) have the potential to worsen it. We therefore propose that, in order to progress our knowledge of the effects of aging on force control, future studies must consider the potential modulatory effect of lifelong physical activity.

Exercise to spot the differences: a framework for the effect of exercise on hippocampal pattern separation in humans

Exercise has a beneficial effect on mental health and cognitive functioning, but the exact underlying mechanisms remain largely unknown. In this review, we focus on the effect of exercise on hippocampal pattern separation, which is a key component of episodic memory. Research has associated exercise with improvements in pattern separation. We propose an integrated framework mechanistically explaining this relationship. The framework is divided into three pathways, describing the pro-neuroplastic, anti-inflammatory and hormonal effects of exercise. The pathways are heavily intertwined and may result in functional and structural changes in the hippocampus. These changes can ultimately affect pattern separation through direct and indirect connections. The proposed framework might guide future research on the effect of exercise on pattern separation in the hippocampus.

Exercise Ameliorates Fluoride-induced Anxiety- and Depression-like Behavior in Mice: Role of GABA

Fluoride exposure caused anxiety- and depression-like behavior in mice. Meanwhile, exercise contributes to relieve anxiety and depression. However, the effects of exercise on anxiety- and depression-like behavior in fluorosis mice remain unclear. In the current study, thirty-six Institute of Cancer Research (ICR) female mice were randomly assigned to four groups: control group (C, gavage with distilled water); exercise group (E, gavage with distilled water and treadmill exercise (speed, 10 m/min; time, 30 min/day)); fluoride group (F, gavage with 24 mg/kg sodium fluoride (NaF)); and exercise plus fluoride group (EF, gavage with 24 mg/kg NaF and treadmill exercise). All treatments lasted for 8 weeks. A number of entries into and time spent in the open zone in the elevated zero maze (EZM), resting time in the tail suspension test (TST) and levels of serotonin (5-HT) and gamma-aminobutyric acid (GABA), were significantly altered in F when compared to C. Meanwhile, the anxiety-like behavior in the EZM and the depression-like behavior in the TST were significantly improved in EF when compared to group F. Exercise significantly enhanced fluoride-induced low GABA level, with less effect on the concentration of 5-HT. Moreover, the mRNA and protein expressions of GABA synthesis and transport-related proteins of glutamic acid decarboxylase (GAD) 65 and GAD67 and vesicular GABA transporter (VGAT) were all strikingly decreased in F, while those in EF were increased. In conclusion, exercise ameliorates anxiety- and depression-like behavior in fluorosis mice through increasing the expressions of GABA synthesis and transport-related proteins, rather than 5-HT system.

Functional Connectivity, Physical Activity, and Neurocognitive Performances in Patients with Vascular Cognitive Impairment, No Dementia

BACKGROUND

Vascular Cognitive Impairment, No Dementia (VCIND) is a key stage at which early intervention will delay or prevent dementia. The pathophysiology of VCIND posits that a lesion in a single location in the brain has the ability to disrupt brain networks, and the subsequent abnormal Functional Connectivity (FC) of brain networks leads to deficits in corresponding neurobehavioral domains. In this study, we tested the hypothesis that disrupted anterior cingulate cortex and striatal networks mediated the effects of Physical Activity (PA) on neurobehavioral function.

METHODS

In 27 patients with VCIND, FC within the brain networks and neurobehavioral dysfunction were assessed. The relationship between the cognitive scores, FC, and PA was studied. The Fitbit Charge 2 was used to measure step counts, distance, and calories burned. In patients with VCIND, a cross-sectional Spearman's correlation to analyze the relationship among patient-level measures of PA, cognitive function scores, and FC strength within the brain networks.

RESULTS

Average step counts and average distance were associated with Trail Making Test B (TM-B) time to completion (seconds) and Instrumental Activities of Daily Living (IADL) score (P <0.05). The average calories burned were associated with IADL score (P = 0.009). The FC within the brain networks anchored by left caudal Anterior Cingulate Cortex (ACC) seeds (x= -5, y= 0, z= 36) and (x= -5, y= -10, z= 47) were positively correlated with average step counts and average distance, were negatively correlated with TMB time to completion (seconds), and were positively correlated with IADL score (P < 0.05). The FC within the brain networks anchored by left subgenual ACC seed (x= -5, y= 25, z= -10) were negatively correlated with average step counts and average distance were positively correlated with TMB time to completion (seconds), and were negatively correlated with IADL score (P < 0.05). The FC within the striatal networks was positively correlated with average calories burned and IADL score (P < 0.05).

Glutamate: The Master Neurotransmitter and Its Implications in Chronic Stress and Mood Disorders

This brief review article makes the argument that glutamate is deserving of its newfound attention within the neuroscience literature and that many directions of important research have yet to be explored. Glutamate is an excitatory neurotransmitter with several types of receptors found throughout the central nervous system, and its metabolism is important to maintaining optimal levels within the extracellular space. As such, it is important to memory, cognition, and mood regulation. The mechanisms by which chronic stress affect the glutamatergic system and neuroplasticity are outlined. Several implications for potential pharmacologic and non-pharmacologic interventions are discussed.

Changes in the urinary proteome in rats with regular swimming exercise

Purpose

Urine can sensitively reflect early pathophysiological changes in the body. The purpose of this study was to explore the changes of urine proteome in rats with regular swimming exercise.

Methods

In this study, experimental rats were subjected to daily moderate-intensity swimming exercise for 7 weeks. Urine samples were collected at weeks 2, 5, and 7 and were analyzed by using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS).

Results

Unsupervised clustering analysis of all urinary proteins identified at week 2 showed that the swimming group was distinctively different from the control group. Compared to the control group, a total of 112, 61 and 44 differential proteins were identified in the swimming group at weeks 2, 5 and 7, respectively. Randomized grouping statistical analysis showed that more than 85% of the differential proteins identified in this study were caused by swimming exercise rather than random allocation. According to the Human Protein Atlas, the differential proteins that have human orthologs were strongly expressed in the liver, kidney and intestine. Functional annotation analysis revealed that these differential proteins were involved in glucose metabolism and immunity-related pathways.

Conclusion

Our results revealed that the urinary proteome could reflect significant changes after regular swimming exercise. These findings may provide an approach to monitor the effects of exercise of the body.

Timing is everything: Exercise therapy and remote ischemic conditioning for acute ischemic stroke patients

Physical exercise is a promising rehabilitative strategy for acute ischemic stroke. Preclinical trials suggest that exercise restores cerebral blood circulation and re-establishes the blood–brain barrier’s integrity with neurological function and motor skill improvement. Clinical trials demonstrated that exercise improves prognosis and decreases complications after ischemic events. Due to these encouraging findings, early exercise rehabilitation has been quickly adopted into stroke rehabilitation guidelines. Unfortunately, preclinical trials have failed to warn us of an adverse effect. Trials with very early exercise rehabilitation (within 24 h of ischemic attack) found an inferior prognosis at 3 months. It was not immediately clear as to why exercise was detrimental when performed very early while it was ameliorative just a few short days later. This review aimed to explore the potential mechanisms of harm seen in very early exercise administered to acute ischemic stroke patients. To begin, the mechanisms of exercise’s benefit were transposed onto the current understanding of acute ischemic stroke’s pathogenesis, specifically during the acute and subacute phases. Then, exercise rehabilitation’s mechanisms were compared to that of remote ischemic conditioning (RIC). This comparison may reveal how RIC may be providing clinical benefit during the acute phase of ischemic stroke when exercise proved to be harmful.

EEG-derived brain graphs are reliable measures for exploring exercise-induced changes in brain networks

The interaction of acute exercise and the central nervous system evokes increasing interest in interdisciplinary research fields of neuroscience. Novel approaches allow to monitor large-scale brain networks from mobile electroencephalography (EEG) applying graph theory, but it is yet uncertain whether brain graphs extracted after exercise are reliable. We therefore aimed to investigate brain graph reliability extracted from resting state EEG data before and after submaximal exercise twice within one week in male participants. To obtain graph measures, we extracted global small-world-index (SWI), clustering coefficient (CC) and characteristic path length (PL) based on weighted phase leg index (wPLI) and spectral coherence (Coh) calculation. For reliability analysis, Intraclass-Correlation-Coefficient (ICC) and Coefficient of Variation (CoV) were computed for graph measures before (REST) and after POST) exercise. Overall results revealed poor to excellent measures at PRE and good to excellent ICCs at POST in the theta, alpha-1 and alpha-2, beta-1 and beta-2 frequency band. Based on bootstrap-analysis, a positive effect of exercise on reliability of wPLI based measures was observed, while exercise induced a negative effect on reliability of Coh-based graph measures. Findings indicate that brain graphs are a reliable tool to analyze brain networks in exercise contexts, which might be related to the neuroregulating effect of exercise inducing functional connections within the connectome. Relative and absolute reliability demonstrated good to excellent reliability after exercise. Chosen graph measures may not only allow analysis of acute, but also longitudinal studies in exercise-scientific contexts.

Exercise alone impacts short-term adult visual neuroplasticity in a monocular deprivation paradigm

Adult homeostatic visual plasticity can be induced by short-term patching, heralded by a shift in ocular dominance in favor of the deprived eye after monocular occlusion. The potential to boost visual neuroplasticity with environmental enrichment such as exercise has also been explored; however, the results are inconsistent, with some studies finding no additive effect of exercise. Studies to date have only considered the effect of patching alone or in combination with exercise. Whether exercise alone affects typical outcome measures of experimental estimates of short-term visual neuroplasticity is unknown. We therefore measured binocular rivalry in 20 healthy young adults (20–34 years old) at baseline and after three 2-hour interventions: patching (of the dominant eye) only, patching with exercise, and exercise only. Consistent with previous work, the patching interventions produced a shift in ocular dominance toward the deprived (dominant) eye. Mild- to moderate-intensity exercise in the absence of patching had several effects on binocular rivalry metrics, including a reduction in the dominant eye percept. The proportion of mixed percept and the time to first switch (onset rivalry) did not change from baseline across all interventions. Thus, we demonstrate that exercise alone can impact binocular rivalry outcomes measures. We did not observe a synergistic effect between patching and exercise in our data.

Timed daily exercise remodels circadian rhythms in mice

Regular exercise is important for physical and mental health. An underexplored and intriguing property of exercise is its actions on the body’s 24 h or circadian rhythms. Molecular clock cells in the brain’s suprachiasmatic nuclei (SCN) use electrical and chemical signals to orchestrate their activity and convey time of day information to the rest of the brain and body. To date, the long-lasting effects of regular physical exercise on SCN clock cell coordination and communication remain unresolved. Utilizing mouse models in which SCN intercellular neuropeptide signaling is impaired as well as those with intact SCN neurochemical signaling, we examined how daily scheduled voluntary exercise (SVE) influenced behavioral rhythms and SCN molecular and neuronal activities. We show that in mice with disrupted neuropeptide signaling, SVE promotes SCN clock cell synchrony and robust 24 h rhythms in behavior. Interestingly, in both intact and neuropeptide signaling deficient animals, SVE reduces SCN neural activity and alters GABAergic signaling. These findings illustrate the potential utility of regular exercise as a long-lasting and effective non-invasive intervention in the elderly or mentally ill where circadian rhythms can be blunted and poorly aligned to the external world.

Using mice with disrupted neuropeptide signaling, Hughes et al. show that daily scheduled voluntary exercise (SVE) promotes suprachiasmatic nuclei (SCN) clock cell synchrony and robust 24 h rhythms in behavior. This study suggests the potential utility of regular exercise as a non-invasive intervention for the elderly or mentally ill, where circadian rhythms can be poorly aligned to the external world.

GABA and glutamate in the preterm neonatal brain: In-vivo measurement by magnetic resonance spectroscopy

Cognitive and behavioral disabilities in preterm infants, even without obvious brain injury on conventional neuroimaging, underscores a critical need to identify the subtle underlying microstructural and biochemical derangements. The gamma-aminobutyric acid (GABA) and glutamatergic neurotransmitter systems undergo rapid maturation during the crucial late gestation and early postnatal life, and are at-risk of disruption after preterm birth. Animal and human autopsy studies provide the bulk of current understanding since non-invasive specialized proton magnetic resonance spectroscopy (¹H-MRS) to measure GABA and glutamate are not routinely available for this vulnerable population due to logistical and technical challenges. We review the specialized ¹H-MRS techniques including MEscher-GArwood Point Resolved Spectroscopy (MEGA-PRESS), special challenges and considerations needed for interpretation of acquired data from the developing brain of preterm infants. We summarize the limited in-vivo preterm data, highlight the gaps in knowledge, and discuss future directions for optimal integration of available in-vivo approaches to understand the influence of GABA and glutamate on neurodevelopmental outcomes after preterm birth.