The Neuromodulatory Role of the Noradrenergic and Cholinergic Systems and Their Interplay in Cognitive Functions: A Focused Review

Cross-species real-time detection of trends in pupil size fluctuation

Pupillometry is a popular method because pupil size is easily measured and sensitive to central neural activity linked to behavior, cognition, emotion, and perception. Currently, there is no method for online monitoring phases of pupil size fluctuation. We introduce rtPupilPhase-an open-source software that automatically detects trends in pupil size in real time. This tool enables novel applications of real-time pupillometry for achieving numerous research and translational goals. We validated the performance of rtPupilPhase on human, rodent, and monkey pupil data, and we propose future implementations of real-time pupillometry.

The effect of listening to music and drawing on coping with dysmenorrhea complaints in nursing students: randomized controlled trial

AIM

To examine the effect of listening to music and drawing on coping with dysmenorrhea complaints of nursing students.

METHODS

The study was a double-blind, three parallel-group randomized controlled trial conducted between August 2023 and May 2024 at Bartın University, Faculty of Health Sciences, Department of Nursing. Ninety-six dysmenorrheic nursing students with regular menstrual cycles were included in the study and randomly assigned to three groups as drawing, music and control groups. Visual Analog Scale (100mmVAS of pain), Perceived Stress Scale (PSS) and Menstrual Symptoms Scale (MSS) were applied to the students at baseline, 1st and 2nd months. The interventions were as follows: the music group listened to a 29-minute and 32-second song three days before menstruation and on the first day of menstruation in the third month composed by Juan Sebastian Martin-Saavedra, while the drawing group created art for the same duration. The pain scores, perceived stress, and menstrual symptoms were measured in all groups after the interventions.

RESULTS

Pretest, 1st and 2nd months 100mmVAS of pain score averages were 7.16 ± 1.99, 7.16 ± 1.99 and 7.50 ± 1.98 for the control group, 7.22 ± 1.64, 4.84 ± 1.80 and 2.13 ± 1.45 for the music group and 6.69 ± 1.80, 5.09 ± 1.55 and 2.91 ± 1.33 for the drawing group, respectively. Pretest, 1st and 2nd months PSS score averages were 28.75 ± 3.71, 29.09 ± 3.87 and 30.03 ± 4.16 for the control group, 29.91 ± 3.98, 14.06 ± 4.06 and 3.59 ± 3.82 for the music group and 27.38 ± 3.63, 18.13 ± 5.60 and 8.34 ± 5.46 for the drawing group, respectively. Pretest, 1st and 2nd months MSS score averages were 79.25 ± 15.41, 88.00 ± 20.08 and 90.66 ± 19.13 for the control group, 85.41 ± 10.77, 62.41 ± 15.23 and 34.00 ± 12.62 for the music group and 80.69 ± 11.07, 65.53 ± 15.37 and 47.31 ± 15.11 for the drawing group, respectively. Mean menstrual pain intensity, mean perceived stress level, and mean menstrual symptoms level in the art and music group decreased significantly at 1st and 2nd months post-intervention (p < .001). A significant increase in score levels was observed in the control group.

CONCLUSIONS

Both art and music practices are effective in significantly reducing menstrual pain, perceived stress, and menstrual symptoms in nursing students with dysmenorrhea. It is important to include listening to music and drawing on women's health and disease nursing practices to control menstrual pain, perceived stress, and menstrual symptoms in dysmenorrhea.

CLINICAL TRIALS REGISTRATION NUMBER

https://clinicaltrials.gov identifier NCT06027489; registered August 30, 2023.

Unraveling the complexity of human brain: Structure, function in healthy and disease states

The human brain stands as an intricate organ, embodying a nexus of structure, function, development, and diversity. This review delves into the multifaceted landscape of the brain, spanning its anatomical intricacies, diverse functional capacities, dynamic developmental trajectories, and inherent variability across individuals. The dynamic process of brain development, from early embryonic stages to adulthood, highlights the nuanced changes that occur throughout the lifespan. The brain, a remarkably complex organ, is composed of various anatomical regions, each contributing uniquely to its overall functionality. Through an exploration of neuroanatomy, neurophysiology, and electrophysiology, this review elucidates how different brain structures interact to support a wide array of cognitive processes, sensory perception, motor control, and emotional regulation. Moreover, it addresses the impact of age, sex, and ethnic background on brain structure and function, and gender differences profoundly influence the onset, progression, and manifestation of brain disorders shaped by genetic, hormonal, environmental, and social factors. Delving into the complexities of the human brain, it investigates how variations in anatomical configuration correspond to diverse functional capacities across individuals. Furthermore, it examines the impact of neurodegenerative diseases on the structural and functional integrity of the brain. Specifically, our article explores the pathological processes underlying neurodegenerative diseases, such as Alzheimer's, Parkinson's, and Huntington's diseases, shedding light on the structural alterations and functional impairments that accompany these conditions. We will also explore the current research trends in neurodegenerative diseases and identify the existing gaps in the literature. Overall, this article deepens our understanding of the fundamental principles governing brain structure and function and paves the way for a deeper understanding of individual differences and tailored approaches in neuroscience and clinical practice-additionally, a comprehensive understanding of structural and functional changes that manifest in neurodegenerative diseases.

Vagus nerve stimulation during training fails to improve learning in healthy rats

Learning new skills requires neuroplasticity. Vagus nerve stimulation (VNS) during sensory and motor events can increase neuroplasticity in networks related to these events and might therefore serve to facilitate learning on sensory and motor tasks. We tested if VNS could broadly improve learning on a wide variety of tasks across different skill domains in healthy, female adult rats. VNS was paired with presentation of stimuli or on successful trials during training, strategies known to facilitate plasticity and improve recovery in models of neurological disorders. VNS failed to improve either rate of learning or performance for any of the tested tasks, which included skilled forelimb motor control, speech sound discrimination, and paired-associates learning. These results contrast recent findings from multiple labs which found VNS pairing during training produced learning enhancements across motor, auditory, and cognitive domains. We speculate that these contrasting results may be explained by key differences in task designs, training timelines and animal handling approaches, and that while VNS may be able to facilitate rapid and early learning processes in healthy subjects, it does not broadly enhance learning for difficult tasks.

Cross-species real time detection of trends in pupil size fluctuation

Pupillometry is a popular method because pupil size is easily measured, sensitive to central neural activity, and associated with behavior, cognition, emotion, and perception. Currently, there is no method for online monitoring phases of pupil size fluctuation. We introduce rtPupilPhase - an open source software that automatically detects trends in pupil size in real time, enabling novel implementations of real time pupillometry towards achieving numerous research and translational goals. We validated the performance of rtPupilPhase on human, rodent, and monkey pupil data and propose future applications of real time pupillometry.

Galanin receptor 1 expressing neurons in hippocampal-prefrontal circuitry modulate goal directed attention and impulse control

While amino acid neurotransmitters are the main chemical messengers in the brain, they are co-expressed with neuropeptides which are increasingly recognized as modulators of cognitive pathways. For example, the neuropeptide galanin has been implicated in a wide range of pathological conditions in which frontal and temporal structures are compromised. In a recent study in rats, we discovered that direct pharmacological stimulation of galanin receptor type 1 (GalR1) in the ventral prefrontal cortex (vPFC) and ventral hippocampus (vHC) led to opposing effects on attention and impulse control behavior. In the present study, we investigate how subtypes of neurons expressing GalR1 in these two areas differentially contribute to these behaviors. We first establish that GalR1 is predominantly expressed in glutamatergic neurons in both the vPFC and HC. We develop a novel viral approach to gain genetic access to GalR1-expressing neurons and demonstrate that optogenetic excitation of GalR1 expressing neurons in the vPFC, but not vHC, selectively disrupts attention in a complex behavioral task. Finally, using fiber photometry, we measure the bulk calcium dynamics in GalR1-expressing neurons during the same task to demonstrate opposing activity in vPFC and vHC. These results are consistent with our previous work demonstrating differential behavioral effects induced by GalR1 activating in vPFC and vHC. These results indicate the distinct neuromodulatory and behavioral contributions of galanin mediated by subclasses of neurons in the hippocampal and prefrontal circuitry.

Phase synchrony between prefrontal noradrenergic and cholinergic signals indexes inhibitory control

Inhibitory control is a critical executive function that allows animals to suppress their impulsive behavior in order to achieve certain goals or avoid punishment. We investigated norepinephrine (NE) and acetylcholine (ACh) dynamics and population neuronal activity in the prefrontal cortex during inhibitory control. Using fluorescent sensors to measure extracellular levels of NE and ACh, we simultaneously recorded the dynamics of prefrontal NE and ACh in mice performing an inhibitory control task. The prefrontal NE and ACh signals exhibited strong coherence at 0.4-0.8 Hz. Chemogenetic inhibition of locus coeruleus (LC) neurons that project to the basal forebrain region reduced inhibitory control performance to chance levels. However, this manipulation did not diminish the difference in NE/ACh signals between successful and failed trials; instead, it abolished the difference in NE-ACh phase synchrony between the successful and failed trials, indicating that NE-ACh phase synchrony is a task-relevant neuromodulatory feature. Chemogenetic inhibition of cholinergic neurons that project to the LC region did not impair the inhibitory control performance, nor did it abolish the difference in NE-ACh phase synchrony between successful or failed trials, further confirming the relevance of NE-ACh phase synchrony to inhibitory control. To understand the possible effect of NE-ACh synchrony on prefrontal population activity, we employed Neuropixels to record from the prefrontal cortex with and without inhibiting LC neurons that project to the basal forebrain during inhibitory control. The LC inhibition reduced the number of prefrontal neurons encoding inhibitory control. Demixed principal component analysis (dPCA) further revealed that population firing patterns representing inhibitory control were impaired by the LC inhibition. Disparities in NE-ACh phase synchrony relevant to inhibitory control occurred only in the prefrontal cortex, but not in the parietal cortex, somatosensory cortex, and the somatosensory thalamus. Taken together, these findings suggest that the LC modulates inhibitory control through its collective effect with cholinergic systems on population activity in the prefrontal cortex. Our results further revealed that NE-ACh phase synchrony is a critical neuromodulatory feature with important implications for cognitive control.

Transcutaneous auricular vagus nerve stimulation enhances short-latency afferent inhibition via central cholinergic system activation

The present study examined the effects of transcutaneous auricular vagus nerve stimulation (taVNS) on short-latency afferent inhibition (SAI), as indirect biomarker of cholinergic system activation. 24 healthy adults underwent intermittent taVNS (30 s on/30 s off, 30 min) or continuous taVNS at a frequency of 25 Hz (15 min) along with earlobe temporary stimulation (15 min or 30 min) were performed in random order. The efficiency with which the motor evoked potential from the abductor pollicis brevis muscle by transcranial magnetic stimulation was attenuated by the preceding median nerve conditioning stimulus was compared before taVNS, immediately after taVNS, and 15 min after taVNS. Continuous taVNS significantly increased SAI at 15 min post-stimulation compared to baseline. A positive correlation (Pearson coefficient = 0.563, p = 0.004) was observed between baseline SAI and changes after continuous taVNS. These results suggest that 15 min of continuous taVNS increases the activity of the cholinergic nervous system, as evidenced by the increase in SAI. In particular, the increase after taVNS was more pronounced in those with lower initial SAI. This study provides fundamental insight into the clinical potential of taVNS for cholinergic dysfunction.

Combined in vivo MRI assessment of locus coeruleus and nucleus basalis of Meynert integrity in amnestic Alzheimer's disease, suspected-LATE and frontotemporal dementia

BACKGROUND

The locus coeruleus (LC) and the nucleus basalis of Meynert (NBM) are altered in early stages of Alzheimer's disease (AD). Little is known about LC and NBM alteration in limbic-predominant age-related TDP-43 encephalopathy (LATE) and frontotemporal dementia (FTD). The aim of the present study is to investigate in vivo LC and NBM integrity in patients with suspected-LATE, early-amnestic AD and FTD in comparison with controls.

METHODS

Seventy-two participants (23 early amnestic-AD patients, 17 suspected-LATE, 17 FTD patients, defined by a clinical-biological diagnosis reinforced by amyloid and tau PET imaging, and 15 controls) underwent neuropsychological assessment and 3T brain MRI. We analyzed the locus coeruleus signal intensity (LC-I) and the NBM volume as well as their relation with cognition and with medial temporal/cortical atrophy.

RESULTS

We found significantly lower LC-I and NBM volume in amnestic-AD and suspected-LATE in comparison with controls. In FTD, we also observed lower NBM volume but a slightly less marked alteration of the LC-I, independently of the temporal or frontal phenotype. NBM volume was correlated with the global cognitive efficiency in AD patients. Strong correlations were found between NBM volume and that of medial temporal structures, particularly the amygdala in both AD and FTD patients.

CONCLUSIONS

The alteration of LC and NBM in amnestic-AD, presumed-LATE and FTD suggests a common vulnerability of these structures to different proteinopathies. Targeting the noradrenergic and cholinergic systems could be effective therapeutic strategies in LATE and FTD.

Modulation of metastable ensemble dynamics explains optimal coding at moderate arousal in auditory cortex

Performance during perceptual decision-making exhibits an inverted-U relationship with arousal, but the underlying network mechanisms remain unclear. Here, we recorded from auditory cortex (A1) of behaving mice during passive tone presentation, while tracking arousal via pupillometry. We found that tone discriminability in A1 ensembles was optimal at intermediate arousal, revealing a population-level neural correlate of the inverted-U relationship. We explained this arousal-dependent coding using a spiking network model with a clustered architecture. Specifically, we show that optimal stimulus discriminability is achieved near a transition between a multi-attractor phase with metastable cluster dynamics (low arousal) and a single-attractor phase (high arousal). Additional signatures of this transition include arousal-induced reductions of overall neural variability and the extent of stimulus-induced variability quenching, which we observed in the empirical data. Altogether, this study elucidates computational principles underlying interactions between pupil-linked arousal, sensory processing, and neural variability, and suggests a role for phase transitions in explaining nonlinear modulations of cortical computations.

Transcutaneous cervical vagus nerve stimulation improves sensory performance in humans: a randomized controlled crossover pilot study

Accurate senses depend on high-fidelity encoding by sensory receptors and error-free processing in the brain. Progress has been made towards restoring damaged sensory receptors. However, methods for on-demand treatment of impaired central sensory processing are scarce. Prior invasive studies demonstrated that continuous vagus nerve stimulation (VNS) in rodents can activate the locus coeruleus-norepinephrine system to rapidly improve central sensory processing. Here, we investigated whether transcutaneous VNS improves sensory performance in humans. We conducted three sham-controlled experiments, each with 12 neurotypical adults, that measured the effects of transcutaneous VNS on metrics of auditory and visual performance, and heart rate variability (HRV). Continuous stimulation was delivered to cervical (tcVNS) or auricular (taVNS) branches of the vagus nerve while participants performed psychophysics tasks or passively viewed a display. Relative to sham stimulation, tcVNS improved auditory performance by 37% (p = 0.00052) and visual performance by 23% (p = 0.038). Participants with lower performance during sham conditions experienced larger tcVNS-evoked improvements (p = 0.0040). Lastly, tcVNS increased HRV during passive viewing, corroborating vagal engagement. No evidence for an effect of taVNS was observed. These findings validate the effectiveness of tcVNS in humans and position it as a method for on-demand interventions of impairments associated with central sensory processing dysfunction.

Migraine as an allostatic reset triggered by unresolved interoceptive prediction errors

Until now, a satisfying account of the cause and purpose of migraine has remained elusive. We explain migraine within the frameworks of allostasis (the situationally-flexible, forward-looking equivalent of homeostasis) and active inference (interacting with the environment via internally-generated predictions). Due to its multimodality, and long timescales between cause and effect, allostasis is inherently prone to catastrophic error, which might be impossible to correct once fully manifest, an early indicator which is elevated prediction error (discrepancy between prediction and sensory input) associated with internal sensations (interoception). Errors can usually be resolved in a targeted manner by action (correcting the physiological state) or perception (updating predictions in light of sensory input); persistent errors are amplified broadly and multimodally, to prioritise their resolution (the migraine premonitory phase); finally, if still unresolved, progressive amplification renders further changes to internal or external sensory inputs intolerably intense, enforcing physiological stability, and facilitating accurate allostatic prediction updating. As such, migraine is an effective 'failsafe' for allostasis, however it has potential to become excessively triggered, therefore maladaptive.

Optimization of Temporal Coding of Tactile Information in Rat Thalamus by Locus Coeruleus Activation

The brainstem noradrenergic nucleus, the locus coeruleus (LC), exerts heavy influences on sensory processing, perception, and cognition through its diffuse projections throughout the brain. Previous studies have demonstrated that LC activation modulates the response and feature selectivity of thalamic relay neurons. However, the extent to which LC modulates the temporal coding of sensory information in the thalamus remains mostly unknown. Here, we found that LC stimulation significantly altered the temporal structure of the responses of the thalamic relay neurons to repeated whisker stimulation. A substantial portion of events (i.e., time points where the stimulus reliably evoked spikes as evidenced by dramatic elevations in the firing rate of the spike density function) were removed during LC stimulation, but many new events emerged. Interestingly, spikes within the emerged events have a higher feature selectivity, and therefore transmit more information about a tactile stimulus, than spikes within the removed events. This suggests that LC stimulation optimized the temporal coding of tactile information to improve information transmission. We further reconstructed the original whisker stimulus from a population of thalamic relay neurons' responses and corresponding feature selectivity. As expected, we found that reconstruction from thalamic responses was more accurate using spike trains of thalamic neurons recorded during LC stimulation than without LC stimulation, functionally confirming LC optimization of the thalamic temporal code. Together, our results demonstrated that activation of the LC-NE system optimizes temporal coding of sensory stimulus in the thalamus, presumably allowing for more accurate decoding of the stimulus in the downstream brain structures.

Transcutaneous cervical vagus nerve stimulation improves sensory performance in humans

Accurate senses depend on high-fidelity encoding by sensory receptors and error-free processing in the brain. Progress has been made towards restoring damaged sensory receptors. However, methods for on-demand treatment of impaired central sensory processing are scarce. Prior invasive studies demonstrated that continuous vagus nerve stimulation (VNS) in rodents can activate the locus coeruleus-norepinephrine system to rapidly improve central sensory processing. Here, we investigated whether transcutaneous VNS improves sensory performance in humans. We conducted three sham-controlled experiments, each with 12 neurotypical adults, that measured the effects of transcutaneous VNS on metrics of auditory and visual performance, and heart rate variability (HRV). Continuous stimulation was delivered to cervical (tcVNS) or auricular (taVNS) branches of the vagus nerve while participants performed psychophysics tasks or passively viewed a display. Relative to sham stimulation, tcVNS improved auditory performance by 37% (p=0.00052) and visual performance by 23% (p=0.038). Participants with lower performance during sham conditions experienced larger tcVNS-evoked improvements (p=0.0040). Lastly, tcVNS increased HRV during passive viewing, corroborating vagal engagement. No evidence for an effect of taVNS was observed. These findings validate the effectiveness of tcVNS in humans and position it as a method for on-demand interventions of impairments associated with central sensory processing dysfunction.

Neuro-protective Effect of Acetyl-11-keto-β-boswellic Acid in a Rat Model of Scopolamine-induced Cholinergic Dysfunction

BACKGROUND

Acetyl-11-keto-β-boswellic acid (AKBA) is a major component of the oleo-gum resin of B. serrata with multiple pharmacological activities. The objective of this study was to explore the underlying mechanisms of neuroprotective potential of AKBA against scopolamine-mediated cholinergic dysfunction and memory deficits in rats.

METHODS

The rats received AKBA (2.5, 5, and 10 mg/kg, oral) for 21 days. In the third week, scopolamine was administered 30 min before the Morris water maze and passive avoidance tests. In order to perform biochemical assessments, the hippocampus and prefrontal cortex were extracted from the rats euthanized under deep anesthesia.

RESULTS

In the MWM test, treatment with AKBA (5 and 10 mg/kg) decreased the latency and distance to find the platform. Moreover, in the PA test, AKBA remarkably increased latency to darkness and stayed time in lightness while decreasing the frequency of entry and time in the darkness. According to the biochemical assessments, AKBA decreased acetylcholinesterase activity and malondialdehyde levels while increasing antioxidant enzymes and total thiol content. Furthermore, AKBA administration restored the hippocampal mRNA and protein levels of brain-derived neurotrophic factor (BDNF) and mRNA expression of B-cell lymphoma (Bcl)- 2 and Bcl-2- associated X genes in brain tissue of scopolamine-injured rats.

CONCLUSION

The results suggested the effectiveness of AKBA in preventing learning and memory dysfunction induced by scopolamine. Accordingly, these protective effects might be produced by modulating BDNF, cholinergic system function, oxidative stress, and apoptotic markers.

Adaptive decision-making depends on pupil-linked arousal in rats performing tactile discrimination tasks

Perceptual decision-making is a dynamic cognitive process and is shaped by many factors, including behavioral state, reward contingency, and sensory environment. To understand the extent to which adaptive behavior in decision-making is dependent on pupil-linked arousal, we trained head-fixed rats to perform perceptual decision-making tasks and systematically manipulated the probability of Go and No-go stimuli while simultaneously measuring their pupil size in the tasks. Our data demonstrated that the animals adaptively modified their behavior in response to the changes in the sensory environment. The response probability to both Go and No-go stimuli decreased as the probability of the Go stimulus being presented decreased. Analyses within the signal detection theory framework showed that while the animals' perceptual sensitivity was invariant, their decision criterion increased as the probability of the Go stimulus decreased. Simulation results indicated that the adaptive increase in the decision criterion will increase possible water rewards during the task. Moreover, the adaptive decision-making is dependent on pupil-linked arousal as the increase in the decision criterion was the largest during low pupil-linked arousal periods. Taken together, our results demonstrated that the rats were able to adjust their decision-making to maximize rewards in the tasks, and that adaptive behavior in perceptual decision-making is dependent on pupil-linked arousal.NEW & NOTEWORTHY Perceptual decision-making is a dynamic cognitive process and is shaped by many factors. However, the extent to which changes in sensory environment result in adaptive decision-making remains poorly understood. Our data provided new experimental evidence demonstrating that the rats were able to adaptively modify their decision criterion to maximize water reward in response to changes in the statistics of the sensory environment. Furthermore, the adaptive decision-making is dependent on pupil-linked arousal.

Noradrenergic neuromodulation in ageing and disease

The locus coeruleus (LC) is a small brainstem structure located in the lower pons and is the main source of noradrenaline (NA) in the brain. Via its phasic and tonic firing, it modulates cognition and autonomic functions and is involved in the brain's immune response. The extent of degeneration to the LC in healthy ageing remains unclear, however, noradrenergic dysfunction may contribute to the pathogenesis of Alzheimer's (AD) and Parkinson's disease (PD). Despite their differences in progression at later disease stages, the early involvement of the LC may lead to comparable behavioural symptoms such as preclinical sleep problems and neuropsychiatric symptoms as a result of AD and PD pathology. In this review, we draw attention to the mechanisms that underlie LC degeneration in ageing, AD and PD. We aim to motivate future research to investigate how early degeneration of the noradrenergic system may play a pivotal role in the pathogenesis of AD and PD which may also be relevant to other neurodegenerative diseases.

Effects of indoor exposure to low level toluene on neural network alterations during working memory encoding

OBJECTIVE

While high concentrations of toluene are known to affect multiple human organ systems, research concerning the influence of immediate, short-term exposure to toluene indoors and at low concentrations is scarce. Here, we studied effects of indoor toluene exposure on neural network alterations during working memory (WM) encoding.

METHODS

A total of 23 healthy college students were recruited. All participants were situated in a closed environmental chamber with a full fresh air system. Each participant was subjected to four exposure experiments with different toluene concentrations (0, 17.5, 35, and 70 ppb, named Group A, B, C and D, respectively), with at least one week between each experiment. WM Behavioral and 19-channel electroencephalogram (EEG) recordings in a pre-set environmental chamber were conducted simultaneously during each toluene exposure experiment. Neural networks relevant to WM encoding were visualized analyzing the obtained data.

RESULTS

1. No significant difference in WM behavioral performance among the four groups was found. However, a significant increase in whole brain neural network functional connectivity was noted, especially in the frontal region. 2. An outflow directional transfer function (DTF_outflow) revealed higher frontal region values among Group D (the 70 ppb group) as compared to Group A, B and C (the0, 17.5 ppb and 35 ppb groups, respectively), although no differences in frontal region DTF_inflow values among the four groups were noted. 3. The DTF_FZ-F7, DTF_FZ-T5, DTF_FZ-P4, DTF_FZ-P3, DTF_FP2-O2, DTF_P3-T4, DTF_P3-F4, DTF_P4-CZ and DTF_P4-T4 values of Group D were found to be higher as compared to those of Group A and B. Furthermore, DTF_FZ-F7 and DTF_P4-T4 values of Group C were higher as compared to those of Group A. The DTF_FZ-F7 values of Group D were higher as compared to those of the Group C.

CONCLUSION

Short-term toluene exposure significantly influences neural networks during cognitive processes such as WM encoding, even at low concentration.

Synergistic effects of transcutaneous vagus nerve stimulation and inhibitory control training on electrophysiological performance in healthy adults

Transcutaneous vagal nerve stimulation (tVNS) is a non-invasive nerve stimulation technique that exerts a positive “exogenous” online neuromodulatory effect on inhibitory control (IC). Additionally, IC training (ICT) is an effective approach for enhancing IC via the “endogenous” activation of brain regions implicated in this process. The aim of the present study was to examine the synergistic effects of tVNS and ICT on IC enhancement. For this, we measured the changes in neural activity in frontal, fronto-central, and central regions in the time domain of the N2 component and the frequency domain of alpha power during the stop signal task. A total of 58 participants were randomly divided into four groups that received five sessions of either ICT or sham ICT with either online tVNS or sham tVNS. No differences in N2 amplitude were detected after any of the interventions. However, N2 latency shortened after tVNS + ICT in frontal, fronto-central, and central regions. N2 latency shortened after the intervention of sham tVNS + ICT in frontal region. Moreover, alpha power after tVNS + ICT intervention was larger than those of the other interventions in frontal, fronto-central, and central regions. The obtained electrophysiological data suggested that combining tVNS with ICT has synergistic ameliorative effects on IC, and provide evidence supporting the IC-enhancing potential of tVNS combined with ICT.

Neuromodulation of Neural Oscillations in Health and Disease

Using EEG and local field potentials (LFPs) as an index of large-scale neural activities, research has been able to associate neural oscillations in different frequency bands with markers of cognitive functions, goal-directed behavior, and various neurological disorders. While this gives us a glimpse into how neurons communicate throughout the brain, the causality of these synchronized network activities remains poorly understood. Moreover, the effect of the major neuromodulatory systems (e.g., noradrenergic, cholinergic, and dopaminergic) on brain oscillations has drawn much attention. More recent studies have suggested that cross-frequency coupling (CFC) is heavily responsible for mediating network-wide communication across subcortical and cortical brain structures, implicating the importance of neurotransmitters in shaping coordinated actions. By bringing to light the role each neuromodulatory system plays in regulating brain-wide neural oscillations, we hope to paint a clearer picture of the pivotal role neural oscillations play in a variety of cognitive functions and neurological disorders, and how neuromodulation techniques can be optimized as a means of controlling neural network dynamics. The aim of this review is to showcase the important role that neuromodulatory systems play in large-scale neural network dynamics, informing future studies to pay close attention to their involvement in specific features of neural oscillations and associated behaviors.