Somato-motor inhibitory processing in humans: evidence from neurophysiology and neuroimaging

Behavioral and Neurophysiological Aspects of Inhibition-The Effects of Acute Cardiovascular Exercise

This review summarizes behavioral and neurophysiological aspects of inhibitory control affected by a single bout of cardiovascular exercise. The review also examines the effect of a single bout of cardiovascular exercise on these processes in young adults with a focus on the functioning of prefrontal pathways (including the left dorsolateral prefrontal cortex (DLPFC) and elements of the prefrontal-basal ganglia pathways). Finally, the review offers an overview on the potential effects of cardiovascular exercise on GABA-ergic and glutamatergic neurotransmission in the adult brain and propose mechanisms or processes that may mediate these effects. The main findings show that a single bout of cardiovascular exercise can enhance inhibitory control. In addition, acute exercise appears to facilitate activation of prefrontal brain regions that regulate excitatory and inhibitory pathways (specifically but not exclusively the prefrontal-basal-ganglia pathways) which appear to be impaired in older age. Based on the reviewed studies, we suggest that future work examine the beneficial effects of exercise on the inhibitory networks in the aging brain.

Effects of whole body skin cooling on human cognitive processing: a study using SEPs and ERPs

The present study investigated the effect of whole body skin cooling on somatosensory ascending processing by utilizing somatosensory-evoked potentials (SEPs) and motor execution, as well as inhibitory processing by event-related potentials (ERPs). Fourteen healthy participants wearing a water-perfused suit performed two sessions (sessions 1 and 2) consisting of SEPs and ERPs with somatosensory Go/No-go paradigms under two conditions (cold stress and control) on different days. In session 2, under the cold stress condition, whole body skin cooling was achieved by circulating 20°C water through the suit for 40 min, whereas 34°C water was perfused in the other sessions. The mean skin temperature decreased from 35.0 ± 0.5°C (session 1) to 30.4 ± 0.9°C (session 2) during whole body skin cooling, but the internal temperature was maintained. Whole body skin cooling delayed the peak latencies of N20, P25, and P45 components at C4' of SEPs (all: P < 0.05). Moreover, the peak latencies of P14, N18, and P22 components at Fz of SEPs and the Go-P300 component of ERPs were delayed (all: P < 0.05). In contrast, the peak amplitudes of all individual components of SEPs as well as N140 and P300 of ERPs remained unchanged. These results suggest that passive whole body skin cooling delays neural activities on somatosensory processing and higher cognitive function.

The difference in hemodynamic responses between dominant and non-dominant hands during muscle contraction and relaxation: An fNIRS study

The present study used functional near-infrared spectroscopy (fNIRS), and investigated the differences in neural activation of ipsi- or contralateral hemispheres between right dominant and left non-dominant hands among right-handed subjects using consecutive motor tasks with muscle contraction and relaxation. The subjects performed tasks under four conditions: (1) right hand up (R-Up), (2) left hand up (L-Up), (3) right hand down (R-Down), and (4) left hand down (L-Down). The peak amplitude of oxy-Hb was significantly larger at the contralateral than ipsilateral hemisphere in the premotor area (PM) under the R-Up condition, and no significant differences were observed between contra- and ipsilateral hemispheres under the L-Up condition. In addition, the peak amplitude was more negative at the contra- than ipsilateral hemisphere in the PM under the R-Down condition, while the peak amplitude was significantly more negative at the ipsi- than contralateral hemisphere in the PM under the L-Down condition. These results suggest that the PM of the left hemisphere among right-handed subjects plays an important role in muscle contraction and relaxation with force control.

Effects of acute hypoxia on human cognitive processing: a study using ERPs and SEPs

Although hypoxia has the potential to impair the cognitive function, the effects of acute hypoxia on the high-order brain function (executive and/or inhibitory processing) and somatosensory ascending processing remain unknown. We tested the hypothesis that acute hypoxia impairs both motor executive and inhibitory processing and somatosensory ascending processing. Fifteen healthy subjects performed two sessions (sessions 1 and 2), consisting of electroencephalographic event-related potentials with somatosensory Go/No-go paradigms and somatosensory-evoked potentials (SEPs) under two conditions (hypoxia and normoxia) on different days. On 1 day, participants breathed room air in the first and second sessions of the experiment; on the other day, participants breathed room air in the first session, and 12% O₂ in the second session. Acute hypoxia reduced the peak amplitudes of Go-P300 and No-go-P300, and delayed the peak latency of Go-P300. However, no significant differences were observed in the peak amplitude or latency of N140, behavioral data, or the amplitudes and latencies of individual SEP components between the two conditions. These results suggest that acute hypoxia impaired neural activity in motor executive and inhibitory processing, and delayed higher cognitive processing for motor execution, whereas neural activity in somatosensory processing was not affected by acute hypoxia.NEW & NOTEWORTHY Hypoxia has the potential to impair the cognitive function, but the effects of acute hypoxia on the cognitive function remain debatable. We investigated the effects of acute hypoxia on human cognitive processing using electroencephalographic event-related potentials and somatosensory-evoked potentials. Acute normobaric hypoxia impaired neural activity in motor executive and inhibitory processing, but no significant differences were observed in neural activity in somatosensory processing.

Skill-Specific Changes in Somatosensory Nogo Potentials in Baseball Players

Athletic training is known to induce neuroplastic alterations in specific somatosensory circuits, which are reflected by changes in somatosensory evoked potentials and event-related potentials. The aim of this study was to clarify whether specific athletic training also affects somatosensory Nogo potentials related to the inhibition of movements. The Nogo potentials were recorded at nine cortical electrode positions (Fz, Cz, Pz, F3, F4, C3, C4, P3 and P4) in 12 baseball players (baseball group) and in 12 athletes in sports, such as track and field events and swimming, that do not require response inhibition, such as batting for training or performance (sports group). The Nogo potentials and Go/Nogo reaction times (Go/Nogo RTs) were measured under a somatosensory Go/Nogo paradigm in which subjects were instructed to rapidly push a button in response to stimulus presentation. The Nogo potentials were obtained by subtracting the Go trial from the Nogo trial. The peak Nogo-N2 was significantly shorter in the baseball group than that in the sports group. In addition, the amplitude of Nogo-N2 in the frontal area was significantly larger in the baseball group than that in the sports group. There was a significant positive correlation between the latency of Nogo-N2 and Go/Nogo RT. Moreover, there were significant correlations between the Go/Nogo RT and both the amplitude of Nogo-N2 and Nogo-P3 (i.e., amplitude of the Nogo-potentials increases with shorter RT). Specific athletic training regimens may induce neuroplastic alterations in sensorimotor inhibitory processes.

Changes in Cerebral Hemodynamics during Complex Motor Learning by Character Entry into Touch-Screen Terminals

Introduction

Studies of cerebral hemodynamics during motor learning have mostly focused on neurorehabilitation interventions and their effectiveness. However, only a few imaging studies of motor learning and the underlying complex cognitive processes have been performed.

Methods

We measured cerebral hemodynamics using near-infrared spectroscopy (NIRS) in relation to acquisition patterns of motor skills in healthy subjects using character entry into a touch-screen terminal. Twenty healthy, right-handed subjects who had no previous experience with character entry using a touch-screen terminal participated in this study. They were asked to enter the characters of a randomly formed Japanese syllabary into the touch-screen terminal. All subjects performed the task with their right thumb for 15 s alternating with 25 s of rest for 30 repetitions. Performance was calculated by subtracting the number of incorrect answers from the number of correct answers, and gains in motor skills were evaluated according to the changes in performance across cycles. Behavioral and oxygenated hemoglobin concentration changes across task cycles were analyzed using Spearman’s rank correlations.

Results

Performance correlated positively with task cycle, thus confirming motor learning. Hemodynamic activation over the left sensorimotor cortex (SMC) showed a positive correlation with task cycle, whereas activations over the right prefrontal cortex (PFC) and supplementary motor area (SMA) showed negative correlations.

Conclusions

We suggest that increases in finger momentum with motor learning are reflected in the activity of the left SMC. We further speculate that the right PFC and SMA were activated during the early phases of motor learning, and that this activity was attenuated with learning progress.