Acute Effects of Aerobic Exercise on Executive Function and Attention in Adult Patients With ADHD

Aerobic exercise can improve cognitive functions in healthy individuals and in various clinical groups, which might be particularly relevant for patients with ADHD. This study investigated the effects of a single bout of aerobic exercise on attention and executive functions in adult patients with ADHD, including functional MRI to examine the underlying neural mechanisms. On two different days, 23 adult patients with ADHD and 23 matched healthy controls performed in a flanker task, while functional MR images were collected, following 30 min of continuous stationary cycling with moderate intensity as well as after a control condition (watching a movie). Behavioral performance and brain activation were tested for differences between groups and conditions and for interactions to investigate whether exercise improves executive function to a greater extent in patients compared to healthy controls. Exercise significantly improved reaction times in congruent and incongruent trials of the flanker task in patients with ADHD but not in healthy controls. We found no changes in brain activation between the two conditions for either group. However, a subgroup analysis of ADHD patients with a higher degree of cardiorespiratory fitness revealed decreased activation in premotor areas during congruent trials and in premotor and medial frontal cortex during incongruent trials in the exercise compared to the control condition. Our results indicate exercise-induced improvements in attention and processing speed in patients with ADHD, demonstrating that adult patients with ADHD may benefit from an acute bout of exercise. These findings could be of high relevance for developing alternative treatment approaches for ADHD. In addition, results of the current study contribute to elucidate the neurophysiological mechanisms underlying the beneficial effects of exercise on cognition and to better understand the role of cardiorespiratory fitness on these effects.

Relationships between dietary nutrients intake and lipid levels with functional MRI dorsolateral prefrontal cortex activation

Background

Dorsolateral prefrontal cortex (DLPFC) is a key node in the cognitive control network that supports working memory. DLPFC dysfunction is related to cognitive impairment. It has been suggested that dietary components and high-density lipoprotein cholesterol (HDL-C) play a vital role in brain health and cognitive function.

Purpose

This study aimed to investigate the relationships between dietary nutrient intake and lipid levels with functional MRI (fMRI) brain activation in DLPFC among older adults with mild cognitive impairment.

Participants and methods

A total of 15 community-dwelling older adults with mild cognitive impairment, aged ≥60 years, participated in this cross-sectional study at selected senior citizen clubs in Klang Valley, Malaysia. The 7-day recall Diet History Questionnaire was used to assess participants’ dietary nutrient intake. Fasting blood samples were also collected for lipid profile assessment. All participants performed N-back (0- and 1-back) working memory tasks during fMRI scanning. DLPFC (Brodmann’s areas 9 and 46, and inferior, middle, and superior frontal gyrus) was identified as a region of interest for analysis.

Results

Positive associations were observed between dietary intake of energy, protein, cholesterol, vitamins B6 and B12, potassium, iron, phosphorus, magnesium, and HDL-C with DLPFC activation (P<0.05). Multivariate analysis showed that vitamin B6 intake, β=0.505, t (14)=3.29, P=0.023, and Digit Symbol score, β=0.413, t (14)=2.89, P=0.045; R²=0.748, were positively related to DLPFC activation.

Conclusion

Increased vitamin B6 intake and cognitive processing speed were related to greater activation in the DLPFC region, which was responsible for working memory, executive function, attention, planning, and decision making. Further studies are needed to elucidate the mechanisms underlying the association.

Neural Correlates of Orthographic Access in Mandarin Chinese Writing: An fMRI Study of the Word-Frequency Effect

Writing is an essential tool for human communication and involves multiple linguistic, cognitive, and motor processes. Chinese, a logographic writing system, differs remarkably from the writing systems of alphabetic languages. The neural substrates of Chinese writing are largely unknown. Using functional magnetic resonance imaging (fMRI) in a copying task, this study probed the neural underpinnings of orthographic access during Mandarin Chinese writing by employing the word-frequency effect. The results showed that writing low-frequency characters evoked greater activation in the bilateral superior/middle/inferior frontal gyrus, superior/inferior parietal lobule, and fusiform gyrus than writing high-frequency characters. Moreover, psychophysiological interaction (PPI) analysis demonstrated that the word-frequency effect modulated functional connectivity within the frontal-occipital networks and the parietal-occipital networks. Together, these findings illustrate the neural correlates of orthographic access for Mandarin Chinese writing, shedding new light on the cognitive architecture of writing across various writing systems.

Correspondence Between Resting-State and Episodic Memory-Task Related Networks in Elderly Subjects

Resting-state fMRI studies demonstrated temporally synchronous fluctuations in brain activity among ensembles of brain regions, suggesting the existence of intrinsic functional networks. A spatial match between some of the resting-state networks and regional brain activation during cognitive tasks has been noted, suggesting that resting-state networks support particular cognitive abilities. However, the spatial match and predictive value of any resting-state network and regional brain activation during episodic memory is only poorly understood. In order to address this research gap, we obtained fMRI acquired both during rest and a face-name association task in 38 healthy elderly subjects. In separate independent component analyses, networks of correlated brain activity during rest or the episodic memory task were identified. For the independent components identified for task-based fMRI, the design matrix of successful encoding or retrieval trials was regressed against the time course of each of the component to identify significantly activated networks. Spatial regression was used to assess the match of resting-state networks against those related to successful memory encoding or retrieval. We found that resting-state networks covering the medial temporal, middle temporal, and frontal areas showed increased activity during successful encoding. Resting-state networks located within posterior brain regions showed increased activity during successful recognition. However, the level of resting-state network connectivity was not predictive of the task-related activity in these networks. These results suggest that a circumscribed number of functional networks detectable during rest become engaged during successful episodic memory. However, higher intrinsic connectivity at rest may not translate into higher network expression during episodic memory.

Increased Corticomuscular Coherence and Brain Activation Immediately After Short-Term Neuromuscular Electrical Stimulation

Neuromuscular Electrical Stimulation (NMES) is commonly used in motor rehabilitation for stroke patients. It has been verified that NMES can improve muscle strength and activate the brain, but the studies on how NMES affects the corticomuscular connection are limited. Some studies found an increased corticomuscular coherence (CMC) after a long-term NMES. However, it is still unknown about CMC during NMES, as relatively pure EMG is very difficult to obtain with the contamination of NMES current pulses. In order to approach the condition during NMES, we designed an experiment with short-term NMES and immediately captured data within 100 s. The repetition of wrist flexion was used to realize static muscle contractions for CMC calculation and dynamic contractions for event-related desynchronization (ERD). The result of 13 healthy participants showed that maximal values (p = 0.0020) and areas (p = 0.0098) of CMC and beta ERD were significantly increased immediately after NMES. It was concluded that a short-term NMES can still reinforce corticomuscular functional connection and brain activation related to motor task. This study verified the immediate strengthen of corticomuscular changes after NMES, which was expected to be the basis of long-term neural plasticity induced by NMES.

Adult brain activation during visual learning and memory tasks. An experimental approach to translational neuroscience

RATIONALE, AIMS, AND OBJECTIVES

Human brain connectome is a new and rapidly developing field in neuroscience. The pattern of structural and functional connectivity in the brain is not fixed but is continuously changing in response to experiences. Exploring these phenomena opens a powerful arsenal of analyses and computational approaches that could provide important new insights into clinical and cognitive neuroscience. The aim of the present study was to investigate the activations of adult brain cortical areas during a memory task performance by using functional MRI with a specific focus on gender differences.

METHODS

Twenty-nine right-handed subjects (15 men and 14 women) were scanned. The memory paradigm consisted of 4 consecutive sets of "on" and "off" blocks with a total duration of 4 minutes. The subjects were first presented with 4 pictures (fixation F-part) of the same theme-landscapes, portraits, anatomical images of internal organs, and geometric figures denoted by specific mismatching nouns (seasons, personal names, internal organs, and figures), followed by 3 of the presented pictures and questions for memory evaluation (recall R-part). For the active conditions, the participants were instructed to read the statements carefully and answer with a button press.

RESULTS

We found reliable occipital and temporal signal responses across the block design contrasts with statistical significant differences within the groups in both genders. Statistical significance in brain cortical activation was not found between men and women.

CONCLUSION

The results highlighted several detailed distinctions between the genders and potential future directions in brain activation studies as part of the multidisciplinary approach in translational neuroscience.

The sweet taste signalling pathways in the oral cavity and the gastrointestinal tract affect human appetite and food intake: a review

Sweet taste is associated with food reward and energy source in the form of carbohydrate. Excessive sweet consumption is blamed for the prevalence of obesity. However, evidence for the potential of sweet taste to influence food intake and bodyweight regulation in humans remains unclear. The purpose of this review was to examine the physiological responses relevant to sweet taste mechanisms and the impact on appetite control. The literature was examined for studies that assessed the effects of non-nutritive sweeteners and natural sugars on hormonal secretions and neural activations via oral and gastrointestinal pathways. The findings indicated that a network of sweet taste signalling pathways in the oral cavity and the gut seem to mediate hormonal responses and some metabolism differences in neural circus that orchestrating the hunger-satiety cycle. Individual variations of sweet taste perception which is modulated by hormonal and genetic factors have been associated with dietary nutrient and sugar consumption.

Best core stabilization exercise to facilitate subcortical neuroplasticity: A functional MRI neuroimaging study

OBJECTIVE

To investigate the effects of conscious (ADIM) and subconscious (DNS) core stabilization exercises on cortical changes in adults with core instability.

PARTICIPANTS

Five non-symptomatic participants with core instability.

METHODS

A novel core stabilization task switching paradigm was designed to separate cortical or subcortical neural substrates during a series of DNS or ADIM core stabilization tasks.

RESULTS

fMRI blood BOLD analysis revealed a distinctive subcortical activation pattern during the performance of the DNS, whereas the cortical motor network was primarily activated during an ADIM. Peak voxel volume values showed significantly greater DNS (11.08 ± 1.51) compared with the ADIM (8.81 ± 0.21) (p= 0.043).

CONCLUSION

The ADIM exercise activated the cortical PMC-SMC-SMA motor network, whereas the DNS exercise activated both these same cortical areas and the subcortical cerebellum-BG-thalamus-cingulate cortex network.

Cue-Induced Brain Activation in Chronic Ketamine-Dependent Subjects, Cigarette Smokers, and Healthy Controls: A Task Functional Magnetic Resonance Imaging Study

BACKGROUND

Observations of drug-related cues may induce craving in drug-dependent patients, prompting compulsive drug-seeking behavior. Sexual dysfunction is common in drug users. The aim of the study was to examine regional brain activation to drug (ketamine, cigarette smoking) associated cues and natural (sexual) rewards.

METHODS

A sample of 129 [40 ketamine use smokers (KUS), 45 non-ketamine use smokers (NKUS) and 44 non-ketamine use non-smoking healthy controls (HC)] participants underwent functional magnetic resonance imaging (fMRI) while viewing ketamine use related, smoking and sexual films.

RESULTS

We found that KUS showed significant increased activation in anterior cingulate cortex and precuneus in response to ketamine cues. Ketamine users (KUS) showed lower activation in cerebellum and middle temporal cortex compared with non-ketamine users (NKUS and HC) in response to sexual cues. Smokers (KUS and NKUS) showed higher activation in the right precentral frontal cortex in response to smoking cues. Non-ketamine users (NKUS and HC) showed significantly increased activation of cerebellum and middle temporal cortex while viewing sexual cues.

CONCLUSION

These findings clearly show the engagement of distinct neural circuitry for drug-related stimuli in chronic ketamine users. While smokers (both KUS and NKUS) showed overlapping differences in activation for smoking cues, the former group showed a specific neural response to relevant (i.e., ketamine-related) cues. In particular, the heightened response in anterior cingulate cortex may have important implications for how attentionally salient such cues are in this group. Ketamine users (KUS) showed lower activation in response to sexual cues may partly reflect the neural basis of sexual dysfunction.

Integration between Glycolysis and Glutamate-Glutamine Cycle Flux May Explain Preferential Glycolytic Increase during Brain Activation, Requiring Glutamate

The 1988 observation by Fox et al. (1988) that brief intense brain activation increases glycolysis (pyruvate formation from glucose) much more than oxidative metabolism has been abundantly confirmed. Specifically glycolytic increase was unexpected because the amount of ATP it generates is much smaller than that formed by subsequent oxidative metabolism of pyruvate. The present article shows that preferential glycolysis can be explained by metabolic processes associated with activation of the glutamate-glutamine cycle. The flux in this cycle, which is essential for production of transmitter glutamate and GABA, equals 75% of brain glucose utilization and each turn is associated with utilization of ~1 glucose molecule. About one half of the association between cycle flux and glucose metabolism occurs during neuronal conversion of glutamine to glutamate in a process similar to the malate-aspartate shuttle (MAS) except that glutamate is supplied from glutamine, not formed from α-ketoglutarate (αKG) as during operation of conventional MAS. Regular MAS function is triggered by one oxidative process in the cytosol during glycolysis causing NAD⁺ reduction to NADH. Since NADH cannot cross the mitochondrial membrane (MEM) for oxidation NAD⁺ is re-generated by conversion of cytosolic oxaloacetate (OAA) to malate, which enters the mitochondria for oxidation and in a cyclic process regenerates cytosolic OAA. Therefore MAS as well as the "pseudo-MAS" necessary for neuronal glutamate formation can only operate together with cytosolic reduction of NAD⁺ to NADH. The major process causing NAD⁺ reduction is glycolysis which therefore also must occur during neuronal conversion of glutamine to glutamate and may energize vesicular glutamate uptake which preferentially uses glycolytically derived energy. Another major contributor to the association between glutamate-glutamine cycle and glucose utilization is the need for astrocytic pyruvate to generate glutamate. Although some oxidative metabolism occurs during glutamate formation it is only one half of that during normal tricarboxylic acid (TCA) cycle function. Glutamate's receptor stimulation leads to potassium ion (K⁺) release and astrocytic uptake, preferentially fueled by glycolysis and followed by release and neuronal re-accumulation. The activation-induced preferential glycolysis diminishes with continued activation and is followed by an increased ratio between oxidative metabolism and glycolysis, reflecting oxidation of generated glutamate and accumulated lactate.

Integration between Glycolysis and Glutamate-Glutamine Cycle Flux May Explain Preferential Glycolytic Increase during Brain Activation, Requiring Glutamate

The 1988 observation by Fox et al. (1988) that brief intense brain activation increases glycolysis (pyruvate formation from glucose) much more than oxidative metabolism has been abundantly confirmed. Specifically glycolytic increase was unexpected because the amount of ATP it generates is much smaller than that formed by subsequent oxidative metabolism of pyruvate. The present article shows that preferential glycolysis can be explained by metabolic processes associated with activation of the glutamate-glutamine cycle. The flux in this cycle, which is essential for production of transmitter glutamate and GABA, equals 75% of brain glucose utilization and each turn is associated with utilization of ~1 glucose molecule. About one half of the association between cycle flux and glucose metabolism occurs during neuronal conversion of glutamine to glutamate in a process similar to the malate-aspartate shuttle (MAS) except that glutamate is supplied from glutamine, not formed from α-ketoglutarate (αKG) as during operation of conventional MAS. Regular MAS function is triggered by one oxidative process in the cytosol during glycolysis causing NAD+ reduction to NADH. Since NADH cannot cross the mitochondrial membrane (MEM) for oxidation NAD+ is re-generated by conversion of cytosolic oxaloacetate (OAA) to malate, which enters the mitochondria for oxidation and in a cyclic process regenerates cytosolic OAA. Therefore MAS as well as the "pseudo-MAS" necessary for neuronal glutamate formation can only operate together with cytosolic reduction of NAD+ to NADH. The major process causing NAD+ reduction is glycolysis which therefore also must occur during neuronal conversion of glutamine to glutamate and may energize vesicular glutamate uptake which preferentially uses glycolytically derived energy. Another major contributor to the association between glutamate-glutamine cycle and glucose utilization is the need for astrocytic pyruvate to generate glutamate. Although some oxidative metabolism occurs during glutamate formation it is only one half of that during normal tricarboxylic acid (TCA) cycle function. Glutamate's receptor stimulation leads to potassium ion (K+) release and astrocytic uptake, preferentially fueled by glycolysis and followed by release and neuronal re-accumulation. The activation-induced preferential glycolysis diminishes with continued activation and is followed by an increased ratio between oxidative metabolism and glycolysis, reflecting oxidation of generated glutamate and accumulated lactate.

Integration between Glycolysis and Glutamate-Glutamine Cycle Flux May Explain Preferential Glycolytic Increase during Brain Activation, Requiring Glutamate

The 1988 observation by Fox et al. (1988) that brief intense brain activation increases glycolysis (pyruvate formation from glucose) much more than oxidative metabolism has been abundantly confirmed. Specifically glycolytic increase was unexpected because the amount of ATP it generates is much smaller than that formed by subsequent oxidative metabolism of pyruvate. The present article shows that preferential glycolysis can be explained by metabolic processes associated with activation of the glutamate-glutamine cycle. The flux in this cycle, which is essential for production of transmitter glutamate and GABA, equals 75% of brain glucose utilization and each turn is associated with utilization of ~1 glucose molecule. About one half of the association between cycle flux and glucose metabolism occurs during neuronal conversion of glutamine to glutamate in a process similar to the malate-aspartate shuttle (MAS) except that glutamate is supplied from glutamine, not formed from α-ketoglutarate (αKG) as during operation of conventional MAS. Regular MAS function is triggered by one oxidative process in the cytosol during glycolysis causing NAD⁺ reduction to NADH. Since NADH cannot cross the mitochondrial membrane (MEM) for oxidation NAD⁺ is re-generated by conversion of cytosolic oxaloacetate (OAA) to malate, which enters the mitochondria for oxidation and in a cyclic process regenerates cytosolic OAA. Therefore MAS as well as the "pseudo-MAS" necessary for neuronal glutamate formation can only operate together with cytosolic reduction of NAD⁺ to NADH. The major process causing NAD⁺ reduction is glycolysis which therefore also must occur during neuronal conversion of glutamine to glutamate and may energize vesicular glutamate uptake which preferentially uses glycolytically derived energy. Another major contributor to the association between glutamate-glutamine cycle and glucose utilization is the need for astrocytic pyruvate to generate glutamate. Although some oxidative metabolism occurs during glutamate formation it is only one half of that during normal tricarboxylic acid (TCA) cycle function. Glutamate's receptor stimulation leads to potassium ion (K⁺) release and astrocytic uptake, preferentially fueled by glycolysis and followed by release and neuronal re-accumulation. The activation-induced preferential glycolysis diminishes with continued activation and is followed by an increased ratio between oxidative metabolism and glycolysis, reflecting oxidation of generated glutamate and accumulated lactate.

Anatomical Modularity of Verbal Working Memory? Functional Anatomical Evidence from a Famous Patient with Short-Term Memory Deficits

Cognitive skills are the emergent property of distributed neural networks. The distributed nature of these networks does not necessarily imply a lack of specialization of the individual brain structures involved. However, it remains questionable whether discrete aspects of high-level behavior might be the result of localized brain activity of individual nodes within such networks. The phonological loop of working memory, with its simplicity, seems ideally suited for testing this possibility. Central to the development of the phonological loop model has been the description of patients with focal lesions and specific deficits. As much as the detailed description of their behavior has served to refine the phonological loop model, a classical anatomoclinical correlation approach with such cases falls short in telling whether the observed behavior is based on the functions of a neural system resembling that seen in normal subjects challenged with phonological loop tasks or whether different systems have taken over. This is a crucial issue for the cross correlation of normal cognition, normal physiology, and cognitive neuropsychology. Here we describe the functional anatomical patterns of JB, a historical patient originally described by Warrington et al. (1971), a patient with a left temporo-parietal lesion and selective short phonological store deficit. JB was studied with the H₂¹⁵O PET activation technique during a rhyming task, which primarily depends on the rehearsal system of the phonological loop. No residual function was observed in the left temporo-parietal junction, a region previously associated with the phonological buffer of working memory. However, Broca's area, the major counterpart of the rehearsal system, was the major site of activation during the rhyming task. Specific and autonomous activation of Broca's area in the absence of afferent inputs from the other major anatomical component of the phonological loop shows that a certain degree of functional independence or modularity exists in this distributed anatomical-cognitive system.

Influence of Pre-reproductive Maternal Enrichment on Coping Response to Stress and Expression of c-Fos and Glucocorticoid Receptors in Adolescent Offspring

Environmental enrichment (EE) is an experimental setting broadly used for investigating the effects of complex social, cognitive, and sensorimotor stimulations on brain structure and function. Recent studies point out that parental EE experience, even occurring in the pre-reproductive phase, affects neural development and behavioral trajectories of the offspring. In the present study we investigated the influences of pre-reproductive EE of female rats on maternal behavior and adolescent male offspring's coping response to an inescapable stressful situation after chronic social isolation. For this purpose female Wistar rats were housed from weaning to breeding age in enriched or standard environments. Subsequently, all females were mated and housed in standard conditions until offspring weaning. On the first post partum day (ppd 1), mother-pup interactions in undisturbed conditions were recorded. Further, after weaning the male pups were reared for 2 weeks under social isolation or in standard conditions, and then submitted or not to a single-session Forced Swim Test (FST). Offspring's neuronal activation and plastic changes were identified by immunohistochemistry for c-Fos and glucocorticoid receptors (GRs), and assessed by using stereological analysis. The biochemical correlates were measured in the hippocampus, amygdala and cingulate cortex, structures involved in hypothalamic-pituitary-adrenocortical axis regulation. Enriched dams exhibited increased Crouching levels in comparison to standard reared dams. In the offspring of both kinds of dams, social isolation reduced body weight, decreased Immobility, and increased Swimming during FST. Moreover, isolated offspring of enriched dams exhibited higher levels of Climbing in comparison to controls. Interestingly, in the amygdala of both isolated and control offspring of enriched dams we found a lower number of c-Fos immunopositive cells in response to FST and a higher number of GRs in comparison to the offspring of standard dams. These results highlight the profound influence of a stressful condition, such as the social isolation, on the brain of adolescent rats, and underline intergenerational effects of maternal experiences in regulating the offspring response to stress.

"Neural Efficiency" of Athletes' Brain during Visuo-Spatial Task: An fMRI Study on Table Tennis Players

Long-term training leads experts to develop a focused and efficient organization of task-related neural networks. “Neural efficiency” hypothesis posits that neural activity is reduced in experts. Here we tested the following working hypotheses: compared to non-athletes, athletes showed lower cortical activation in task-sensitive brain areas during the processing of sports related and sports unrelated visuo-spatial tasks. To address this issue, cortical activation was examined with fMRI in 14 table tennis athletes and 14 non-athletes while performing the visuo-spatial tasks. Behavioral results showed that athletes reacted faster than non-athletes during both types of the tasks, and no accuracy difference was found between athletes and non-athletes. fMRI data showed that, athletes exhibited less brain activation than non-athletes in the bilateral middle frontal gyrus, right middle orbitofrontal area, right supplementary motor area, right paracentral lobule, right precuneus, left supramarginal gyrus, right angular gyrus, left inferior temporal gyrus, left middle temporal gyrus, bilateral lingual gyrus and left cerebellum crus. No region was significantly more activated in the athletes than in the non-athletes. These findings possibly suggest that long-standing training prompt athletes develop a focused and efficient organization of task-related neural networks, as a possible index of “neural efficiency” in athletes engaged in visuo-spatial tasks, and this functional reorganization is possibly task-specific.

Reduced frontal activation during verbal fluency task in chronic hepatitis C patients with interferon-based therapy as measured by near-infrared spectroscopy

AIM

Psychiatric side-effects are the main reason for discontinuation of interferon (IFN)-based therapy. Recent developments in near-infrared spectroscopy (NIRS) have enabled non-invasive clarification of brain functions in psychiatric disorders. We prospectively evaluated brain activation in 20 chronic hepatitis C patients with or without IFN-based therapy by using NIRS during a verbal fluency task (VFT).

METHODS

The relative concentrations of oxygenated hemoglobin were measured while patients completed a questionnaire survey at the start of treatment and at 4 and 12 weeks during treatment, using NIRS.

RESULTS

The VFT performance did not change among the two groups. Patients with IFN-based therapy showed significantly lower activation during VFT in frontal channels at 12 weeks than those at the start of treatment and control (P < 0.05). Their Center for Epidemiologic Studies Depression Scale scores were significantly higher at 12 weeks than those at the start of treatment, although major depressive symptoms were not found (8.3 ± 7.9 vs. 13.2 ± 6.0, P < 0.001).

CONCLUSION

The decrease in oxygenated hemoglobin concentrations of the frontal lobe detected using NIRS in this study reflects hypofunction of the frontal lobe. This functional decline that was caused by IFN-based therapy may be associated with the prodromal phase of depression.

Lack of appropriate stoichiometry: Strong evidence against an energetically important astrocyte-neuron lactate shuttle in brain

Glutamate-stimulated aerobic glycolysis in astrocytes coupled with lactate shuttling to neurons where it can be oxidized was proposed as a mechanism to couple excitatory neuronal activity with glucose utilization (CMR_glc ) during brain activation. From the outset, this model was not viable because it did not fulfill critical stoichiometric requirements: (i) Calculated glycolytic rates and measured lactate release rates were discordant in cultured astrocytes. (ii) Lactate oxidation requires oxygen consumption, but the oxygen-glucose index (OGI, calculated as CMR_O2 /CMR_glc ) fell during activation in human brain, and the small rise in CMR_O2 could not fully support oxidation of lactate produced by disproportionate increases in CMR_glc . (iii) Labeled products of glucose metabolism are not retained in activated rat brain, indicating rapid release of a highly labeled, diffusible metabolite identified as lactate, thereby explaining the CMR_glc -CMR_O2 mismatch. Additional independent lines of evidence against lactate shuttling include the following: astrocytic oxidation of glutamate after its uptake can help "pay" for its uptake without stimulating glycolysis; blockade of glutamate receptors during activation in vivo prevents upregulation of metabolism and lactate release without impairing glutamate uptake; blockade of β-adrenergic receptors prevents the fall in OGI in activated human and rat brain while allowing glutamate uptake; and neurons upregulate glucose utilization in vivo and in vitro under many stimulatory conditions. Studies in immature cultured cells are not appropriate models for lactate shuttling in adult brain because of their incomplete development of metabolic capability and astrocyte-neuron interactions. Astrocyte-neuron lactate shuttling does not make large, metabolically significant contributions to energetics of brain activation. © 2017 Wiley Periodicals, Inc.

Evidence of cortical reorganization of language networks after stroke with subacute Broca's aphasia: a blood oxygenation level dependent-functional magnetic resonance imaging study

Aphasia is an acquired language disorder that is a common consequence of stroke. The pathogenesis of the disease is not fully understood, and as a result, current treatment options are not satisfactory. Here, we used blood oxygenation level-dependent functional magnetic resonance imaging to evaluate the activation of bilateral cortices in patients with Broca's aphasia 1 to 3 months after stroke. Our results showed that language expression was associated with multiple brain regions in which the right hemisphere participated in the generation of language. The activation areas in the left hemisphere of aphasia patients were significantly smaller compared with those in healthy adults. The activation frequency, volumes, and intensity in the regions related to language, such as the left inferior frontal gyrus (Broca's area), the left superior temporal gyrus, and the right inferior frontal gyrus (the mirror region of Broca's area), were lower in patients compared with healthy adults. In contrast, activation in the right superior temporal gyrus, the bilateral superior parietal lobule, and the left inferior temporal gyrus was stronger in patients compared with healthy controls. These results suggest that the right inferior frontal gyrus plays a role in the recovery of language function in the subacute stage of stroke-related aphasia by increasing the engagement of related brain areas.

Methodology for high-yield acquisition of functional near-infrared spectroscopy data from alert, upright infants

Functional near-infrared spectroscopy (fNIRS) research to date has tended to publish group-averaged rather than individual infant data due to normative basic research goals. Acquisition of individual infant time courses holds interest, however, both for cognitive science and particularly for clinical applications. Infants are more difficult to study than adults as they cannot be instructed to remain still. In addressing this, upright infants pose several associated complications for the researcher. We identified and optimized the factors that affect the quality of fNIRS data from individual 6- to 9-month-old infants exposed to a visual stimulation paradigm. The fNIRS headpiece was reconfigured to reduce inertia, increase comfort, and improve conformity to the head, while preserving fiber density to avoid missing the visual cortex activation. The visual-stimulation protocol was modified to keep the attention of infants throughout the measurement, thus helping to reduce motion artifacts. Adequate optical contact was verified by checking power levels before each measurement. By revising our experimental process and our data rejection criteria to prioritize good optical contact, we report for the first time usable hemodynamic data from 83% of infants and that two-thirds of infants produced a statistically significant fNIRS response.

Prefrontal Cortex Activation Upon a Demanding Virtual Hand-Controlled Task: A New Frontier for Neuroergonomics

Functional near-infrared spectroscopy (fNIRS) is a non-invasive vascular-based functional neuroimaging technology that can assess, simultaneously from multiple cortical areas, concentration changes in oxygenated-deoxygenated hemoglobin at the level of the cortical microcirculation blood vessels. fNIRS, with its high degree of ecological validity and its very limited requirement of physical constraints to subjects, could represent a valid tool for monitoring cortical responses in the research field of neuroergonomics. In virtual reality (VR) real situations can be replicated with greater control than those obtainable in the real world. Therefore, VR is the ideal setting where studies about neuroergonomics applications can be performed. The aim of the present study was to investigate, by a 20-channel fNIRS system, the dorsolateral/ventrolateral prefrontal cortex (DLPFC/VLPFC) in subjects while performing a demanding VR hand-controlled task (HCT). Considering the complexity of the HCT, its execution should require the attentional resources allocation and the integration of different executive functions. The HCT simulates the interaction with a real, remotely-driven, system operating in a critical environment. The hand movements were captured by a high spatial and temporal resolution 3-dimensional (3D) hand-sensing device, the LEAP motion controller, a gesture-based control interface that could be used in VR for tele-operated applications. Fifteen University students were asked to guide, with their right hand/forearm, a virtual ball (VB) over a virtual route (VROU) reproducing a 42 m narrow road including some critical points. The subjects tried to travel as long as possible without making VB fall. The distance traveled by the guided VB was 70.2 ± 37.2 m. The less skilled subjects failed several times in guiding the VB over the VROU. Nevertheless, a bilateral VLPFC activation, in response to the HCT execution, was observed in all the subjects. No correlation was found between the distance traveled by the guided VB and the corresponding cortical activation. These results confirm the suitability of fNIRS technology to objectively evaluate cortical hemodynamic changes occurring in VR environments. Future studies could give a contribution to a better understanding of the cognitive mechanisms underlying human performance either in expert or non-expert operators during the simulation of different demanding/fatiguing activities.

Functional magnetic resonance imaging

Functional magnetic resonance imaging (fMRI) maps the spatiotemporal distribution of neural activity in the brain under varying cognitive conditions. Since its inception in 1991, blood oxygen level-dependent (BOLD) fMRI has rapidly become a vital methodology in basic and applied neuroscience research. In the clinical realm, it has become an established tool for presurgical functional brain mapping. This chapter has three principal aims. First, we review key physiologic, biophysical, and methodologic principles that underlie BOLD fMRI, regardless of its particular area of application. These principles inform a nuanced interpretation of the BOLD fMRI signal, along with its neurophysiologic significance and pitfalls. Second, we illustrate the clinical application of task-based fMRI to presurgical motor, language, and memory mapping in patients with lesions near eloquent brain areas. Integration of BOLD fMRI and diffusion tensor white-matter tractography provides a road map for presurgical planning and intraoperative navigation that helps to maximize the extent of lesion resection while minimizing the risk of postoperative neurologic deficits. Finally, we highlight several basic principles of resting-state fMRI and its emerging translational clinical applications. Resting-state fMRI represents an important paradigm shift, focusing attention on functional connectivity within intrinsic cognitive networks.

Tutorial on platform for optical topography analysis tools

Optical topography/functional near-infrared spectroscopy (OT/fNIRS) is a functional imaging technique that noninvasively measures cerebral hemoglobin concentration changes caused by neural activities. The fNIRS method has been extensively implemented to understand the brain activity in many applications, such as neurodisorder diagnosis and treatment, cognitive psychology, and psychiatric status evaluation. To assist users in analyzing fNIRS data with various application purposes, we developed a software called platform for optical topography analysis tools (POTATo). We explain how to handle and analyze fNIRS data in the POTATo package and systematically describe domain preparation, temporal preprocessing, functional signal extraction, statistical analysis, and data/result visualization for a practical example of working memory tasks. This example is expected to give clear insight in analyzing data using POTATo. The results specifically show the activated dorsolateral prefrontal cortex is consistent with previous studies. This emphasizes analysis robustness, which is required for validating decent preprocessing and functional signal interpretation. POTATo also provides a self-developed plug-in feature allowing users to create their own functions and incorporate them with established POTATo functions. With this feature, we continuously encourage users to improve fNIRS analysis methods. We also address the complications and resolving opportunities in signal analysis.

Neuronal Nicotinic Receptors Are Crucial for Tuning of E/I Balance in Prelimbic Cortex and for Decision-Making Processes

RATIONALE

Decision-making is an essential component of our everyday life commonly disabled in a myriad of psychiatric conditions, such as bipolar and impulsive control disorders, addiction and pathological gambling, or schizophrenia. A large cerebral network encompassing the prefrontal cortex, the amygdala, and the nucleus accumbens is activated for efficient decision-making.

METHODS

We developed a mouse gambling task well suited to investigate the influence of uncertainty and risk in decision-making and the role of neurobiological circuits and their monoaminergic inputs. Neuronal nicotinic acetylcholine receptors (nAChRs) of the PFC are important for decision-making processes but their presumed roles in risk-taking and uncertainty management, as well as in cellular balance of excitation and inhibition (E/I) need to be investigated.

RESULTS

Using mice lacking nAChRs - β2^-/- mice, we evidence for the first time the crucial role of nAChRs in the fine tuning of prefrontal E/I balance together with the PFC, insular, and hippocampal alterations in gambling behavior likely due to sensitivity to penalties and flexibility alterations. Risky behaviors and perseveration in extinction task were largely increased in β2^-/- mice as compared to control mice, suggesting the important role of nAChRs in the ability to make appropriate choices adapted to the outcome.

Temporal plasticity involved in recovery from manual dexterity deficit after motor cortex lesion in macaque monkeys

The question of how intensive motor training restores motor function after brain damage or stroke remains unresolved. Here we show that the ipsilesional ventral premotor cortex (PMv) and perilesional primary motor cortex (M1) of rhesus macaque monkeys are involved in the recovery of manual dexterity after a lesion of M1. A focal lesion of the hand digit area in M1 was made by means of ibotenic acid injection. This lesion initially caused flaccid paralysis in the contralateral hand but was followed by functional recovery of hand movements, including precision grip, during the course of daily postlesion motor training. Brain imaging of regional cerebral blood flow by means of H2 (15)O-positron emission tomography revealed enhanced activity of the PMv during the early postrecovery period and increased functional connectivity within M1 during the late postrecovery period. The causal role of these areas in motor recovery was confirmed by means of pharmacological inactivation by muscimol during the different recovery periods. These findings indicate that, in both the remaining primary motor and premotor cortical areas, time-dependent plastic changes in neural activity and connectivity are involved in functional recovery from the motor deficit caused by the M1 lesion. Therefore, it is likely that the PMv, an area distant from the core of the lesion, plays an important role during the early postrecovery period, whereas the perilesional M1 contributes to functional recovery especially during the late postrecovery period.

Changes in brain activation in stroke patients after mental practice and physical exercise: a functional MRI study

Mental practice is a new rehabilitation method that refers to the mental rehearsal of motor imagery content with the goal of improving motor performance. However, the relationship between activated regions and motor recovery after mental practice training is not well understood. In this study, 15 patients who suffered a first-ever subcortical stroke with neurological deficits affecting the right hand, but no significant cognitive impairment were recruited. 10 patients underwent mental practice combined with physical practice training, and 5 patients only underwent physical practice training. We observed brain activation regions after 4 weeks of training, and explored the correlation of activation changes with functional recovery of the affected hands. The results showed that, after 4 weeks of mental practice combined with physical training, the Fugl-Meyer assessment score for the affected right hand was significantly increased than that after 4 weeks of practice training alone. Functional MRI showed enhanced activation in the left primary somatosensory cortex, attenuated activation intensity in the right primary motor cortex, and enhanced right cerebellar activation observed during the motor imagery task using the affected right hand after mental practice training. The changes in brain cortical activity were related to functional recovery of the hand. Experimental findings indicate that cortical and cerebellar functional reorganization following mental practice contributed to the improvement of hand function.