Motor Preparation for Action Inhibition: A Review of Single Pulse TMS Studies Using the Go/NoGo Paradigm

Stop-signal delay reflects response selection duration in stop-signal task

The stop-signal task (SST) is widely used for studying the speed of the latent process of response inhibition. The SST patterns are typically explained by a horse-race model (HRM) with supposed Go and Stop processes. However, HRM does not agree with the sequential-stage model of response control. As a result, the exact relationship between the response selection, the response execution stages, and the Stop process remains unclear. We propose that response selection occurs within the stop-signal delay (SSD) period, and that the competition between the Go and Stop processes occurs within the response execution period. To confirm this, we conducted two experiments. In Experiment 1, participants carried out a modified SST task with an additional stimulus category - Cued-Go. In the Cued-Go trials, cues were followed by imperative Go signals. The Cue-Go period duration was dynamically adjusted by an adaptive algorithm based on the response times reflecting the individual response selection duration. In Experiment 2, Cued-Go stimuli were followed by Stop Signals in half of the trials and response inhibition efficiency was calculated. The results of Experiment 1 indicate that SSD reflects the duration of the response selection process. The results of Experiment 2 show that this process has an independent and small effect on the effectiveness of controlled inhibition of the target response. Based on our findings, we propose a two-stage model of response inhibition in SST, with the first stage including response selection process and the second stage response inhibition following the SS presentation.

Multi-scale and cross-dimensional TMS mapping: A proof of principle in patients with Parkinson's disease and deep brain stimulation

Introduction

Transcranial magnetic stimulation (TMS) mapping has become a critical tool for exploratory studies of the human corticomotor (M1) organization. Here, we propose to gather existing cutting-edge TMS-EMG and TMS-EEG approaches into a combined multi-dimensional TMS mapping that considers local and whole-brain excitability changes as well as state and time-specific changes in cortical activity. We applied this multi-dimensional TMS mapping approach to patients with Parkinson's disease (PD) with Deep brain stimulation (DBS) of the sub-thalamic nucleus (STN) ON and OFF. Our goal was to identifying one or several TMS mapping-derived markers that could provide unprecedent new insights onto the mechanisms of DBS in movement disorders.

Methods

Six PD patients (1 female, mean age: 62.5 yo [59-65]) implanted with DBS-STN for 1 year, underwent a robotized sulcus-shaped TMS motor mapping to measure changes in muscle-specific corticomotor representations and a movement initiation task to probe state-dependent modulations of corticospinal excitability in the ON (using clinically relevant DBS parameters) and OFF DBS states. Cortical excitability and evoked dynamics of three cortical areas involved in the neural control of voluntary movements (M1, pre-supplementary motor area - preSMA and inferior frontal gyrus - IFG) were then mapped using TMS-EEG coupling in the ON and OFF state. Lastly, we investigated the timing and nature of the STN-to-M1 inputs using a paired pulse DBS-TMS-EEG protocol.

Results

In our sample of patients, DBS appeared to induce fast within-area somatotopic re-arrangements of motor finger representations in M1, as revealed by mediolateral shifts of corticomuscle representations. STN-DBS improved reaction times while up-regulating corticospinal excitability, especially during endogenous motor preparation. Evoked dynamics revealed marked increases in inhibitory circuits in the IFG and M1 with DBS ON. Finally, inhibitory conditioning effects of STN single pulses on corticomotor activity were found at timings relevant for the activation of inhibitory GABAergic receptors (4 and 20 ms).

Conclusion

Taken together, these results suggest a predominant role of some markers in explaining beneficial DBS effects, such as a context-dependent modulation of corticospinal excitability and the recruitment of distinct inhibitory circuits, involving long-range projections from higher level motor centers and local GABAergic neuronal populations. These combined measures might help to identify discriminative features of DBS mechanisms towards deep clinical phenotyping of DBS effects in Parkinson's Disease and in other pathological conditions.

Does neck flexion improve performance? Effects on reaction time depend on whether responses are expected

This research investigates the limitations of the apparent paradox in which neck flexion, which is associated with poor inhibition and neck pain, seems to facilitate performance in some tasks. We compared the effect of a flexed neck on performance in a reaction time and go-nogo task using a novel method of fixing neck posture. We hypothesize that using a flexed neck posture speeds response time for tasks with high prepotency (when participants are biased toward responding), but not for tasks with low prepotency (when participants are more likely to withhold a response). Previous findings demonstrated the effect of neck flexion on reaction time with a harness. In this study, participants complete both simple reaction time and go-nogo tasks with neck angles fixed in neutral or forward positions with tape. We found that simple reaction times were 10 ms faster in the forward neck position than in neutral; this facilitation was not seen in the go-nogo task. We conclude that using tape to induce a flexed neck posture facilitates reaction time during tasks that always require a response and does not affect reaction time on a task which may require withholding a response.

Challenging inhibitory control with high- and low-calorie food: A behavioural and TMS study

Most people are often tempted by their impulses to "indulge" in high-calorie food, even if this behaviour is not consistent with their goal to control weight in the long term and might not be healthy. The outcome of this conflict is strongly dependent on inhibitory control. It has already been reported that individuals with weaker inhibitory control consume more high-calorie food, are more often unsuccessful dieters, overweight or obese compared to people with more effective inhibitory control. In the present study, we aimed at investigating inhibitory control in the context of human eating behaviour. A sample of 20 healthy normal-weight adults performed a 50% probability visual affective Go/NoGo task involving food (high- and low-calorie) and non-food images as stimuli. Single-pulse transcranial magnetic stimulation (TMS) was administered over the right primary motor cortex (M1) either 300 ms after image presentation to measure corticospinal excitability during the different stimulus categories or 300 ms after the appearance of a fixation point, as a control stimulation condition. The experimental session consisted of a food target and a non-food target block. Behavioural outcomes showed a natural implicit inclination towards high-calorie food in that participants were faster and more accurate compared to the other categories. This advantage was selectively deleted by TMS, which slowed down reaction times. MEPs did not differ according to the stimulus category, but, as expected, were bigger for Go compared to NoGo trials. Participants judged high-calorie food also as more appetising than low-calorie food images. Overall, our results point to a differential modulation when targeting inhibitory control, in favour of the more palatable food category (high-calorie). Present data suggest that the activity of the motor system is modulated by food nutritional value, being more engaged by appetising food. Future work should explore to what extent these processes are affected in patients with eating disorders and should aim to better characterise the related dynamics of cortical connectivity within the motor network.

Anodal Transcranial Direct Current Stimulation (tDCS) Over the Primary Motor Cortex (M1) Enhances Motor Response Inhibition and Visual Recognition Memory

BACKGROUND Transcranial direct current stimulation (tDCS) is a non-invasive brain modulatory technique that can boost cognitive processes and alter performance in cognitive tasks. The effect of anodal-tDCS on cognitive functions following a single session has been repeatedly reported. However, results are varied, mixed, and confounded by several factors, including differences in tDCS current intensity and sham conditions used. Therefore, we assessed the effect of a single session of anodal-tDCS over the primary motor cortex (M1) on cognitive functions, particularly response inhibitory control and visual recognition memory, in healthy adults. MATERIAL AND METHODS Thirty healthy male subjects participated in a randomized, double-blind, sham-controlled tDCS study (2 mA, for 20 min). In the sham stimulation, subjects received the same intensity (2 mA, for 30 s, ramped up, then ramped down). We assessed the cognitive functions response inhibitory control and visual recognition memory using the stop signal task (SST) and pattern recognition memory (PRM) task before and after the stimulation. RESULTS There was a statistically significant difference in cognitive function as assessed by the stop signal task go trial (SST) (P=0.019) and SST correct response time on go trials (P=0.04) after real stimulation only. There was no significant effect observed in sham condition. CONCLUSIONS The findings suggest that anodal-tDCS applied over M1 improves inhibitory control and visual recognition memory compared to sham stimulation. Thus, application of anodal-tDCS to the M1, as an integral node in inhibitory motor control, might be a promising adjuvant therapeutic intervention for modulation of motor response inhibition.

Exploring cortico-cortical interactions during action preparation by means of dual-coil transcranial magnetic stimulation: A systematic review

Action preparation is characterized by a set of complex and distributed processes that occur in multiple brain areas. Interestingly, dual-coil transcranial magnetic stimulation (TMS) is a relevant technique to probe effective connectivity between cortical areas, with a high temporal resolution. In the current systematic review, we aimed at providing a detailed picture of the cortico-cortical interactions underlying action preparation focusing on dual-coil TMS studies. We considered four theoretical processes (impulse control, action selection, movement initiation and action reprogramming) and one task modulator (movement complexity). The main findings highlight 1) the interplay between primary motor cortex (M1) and premotor, prefrontal and parietal cortices during action preparation, 2) the varying (facilitatory or inhibitory) cortico-cortical influence depending on the theoretical processes and the TMS timing, and 3) the key role of the supplementary motor area-M1 interactions that shape the preparation of simple and complex movements. These findings are of particular interest for clinical perspectives, with a need to better characterize functional connectivity deficiency in clinical population with altered action preparation.

Effects of Physically Active Lessons on Movement Behaviors, Cognitive, and Academic Performance in Elementary Schoolchildren: ERGUER/Aracaju Project

BACKGROUND

To evaluate the effects of the introduction of physically active lessons on movement behaviors, cognitive, and academic performance in schoolchildren.

METHODS

This was a cluster-controlled trial. A total of 61 students from the second year of elementary school in a public school in Brazil made up 2 intervention classes (n = 34) with the introduction of physically active lessons and 2 control classes (n = 27). Sedentary behavior, physical activity, cognitive, and academic performance were evaluated in 3 moments, which were compared using models of generalized estimating equations.

RESULTS

The intervention was effective for reducing the standing time between the baseline and 3 months while increasing the walking time between baseline and 3 months and baseline and 9 months. There was a reduction in time in stationary activities and increased time in light physical activities between all moments. The intervention group increased their performance in the go/no go test, showing a smaller number of errors between the baseline and 3 months and baseline and 9 months, and a reduction in the test time between baseline and 3 months. No impact on students' academic performance was observed.

CONCLUSION

Physically active lessons improve movement behaviors and cognitive functions among elementary schoolchildren.

Preparing to React: A Behavioral Study on the Interplay between Proactive and Reactive Action Inhibition

Motor preparation, based on one's goals and expectations, allows for prompt reactions to stimulations from the environment. Proactive and reactive inhibitory mechanisms modulate this preparation and interact to allow a flexible control of responses. In this study, we investigate these two control mechanisms with an ad hoc cued Go/NoGo Simon paradigm in a within-subjects design, and by measuring subliminal motor activities through electromyographic recordings. Go cues instructed participants to prepare a response and wait for target onset to execute it (Go target) or inhibit it (NoGo target). Proactive inhibition keeps the prepared response in check, hence preventing false alarms. Preparing the cue-coherent effector in advance speeded up responses, even when it turned out to be the incorrect effector and reactive inhibition was needed to perform the action with the contralateral one. These results suggest that informative cues allow for the investigation of the interaction between proactive and reactive action inhibition. Partial errors' analysis suggests that their appearance in compatible conflict-free trials depends on cue type and prior preparatory motor activity. Motor preparation plays a key role in determining whether proactive inhibition is needed to flexibly control behavior, and it should be considered when investigating proactive/reactive inhibition.

Correlates and clinical implications of tic suppressibility

Purpose of review

Tic disorders are common in the pediatric population and are differentiated from other movement disorders by tic suppressibility. Understanding the mechanism of tic suppression may provide new insights to the pathophysiology of tic disorders. This article highlights clinical phenomenology and neuronal correlates of tic suppressibility.

Recent findings

Recent studies suggest that tic suppressibility exists in children shortly after onset of their tics. Moreover, those who are better able to suppress their tics have better tic outcomes. Interoceptive awareness and automatic action inhibition may be involved in tic suppression.

Summary

We illustrate a possible underlying mechanism of tic suppressibility and its clinical correlations and implications. New concepts such as interoceptive awareness and action inhibition may help explain tic disorders. Further study will be useful to fill remaining knowledge gaps.

The effect of motor engagement on memory: Testing a motor-induced encoding account

The motor system is traditionally thought to reflect the output of cognition. However, the inverse relationship of how the motor system impacts cognitive processes is less known. Work on this interaction has demonstrated that recognition memory for stimuli presented in combination with the inhibition of a prepared action is weaker compared to stimuli associated with the execution of an action (Chiu & Egner, Psychological Science, 26, 27-38, 2015a). This effect has been explained through competition for common neural resources: to the extent that response inhibition processes are recruited, fewer resources are available for memory encoding (Chiu & Egner, Journal of Neuroscience, 35, 11936-11945, 2015b). Alternatively, it has been proposed that action execution enhances memory encoding (Yebra et al., Nature Communications, 10(1), 1-12, 2019). In this report, we examined how recognition memory for stimuli paired with both the preparation and execution of a motor response compare to stimuli absent of any motor processes. We first replicated Chiu and Egner (2015a, 2015b). Next, we added a motor-neutral condition as a baseline comparison. Across three experiments, recognition memory for stimuli associated with action execution was superior to stimuli absent of motor demands. More importantly, we found that recognition memory for stimuli associated with motor preparation, but no subsequent execution, was also superior to stimuli that did not engage the motor system (Experiments 2a and 2b). These results support a motor-induced encoding effect, in which the degree of motor processing (both action preparation and action execution) enhanced memory encoding.

Do sounds near the hand facilitate tactile reaction times? Four experiments and a meta-analysis provide mixed support and suggest a small effect size

The brain represents the space immediately surrounding the body differently to more distant parts of space. Direct evidence for this ‘peripersonal space’ representation comes from neurophysiological studies in monkeys, which show distance-dependent responses to visual stimuli in neurons with spatially coincident tactile responses. Most evidence for peripersonal space in humans is indirect: spatial- and distance-dependent modulations of reaction times and error rates in behavioural tasks. In one task often used to assess peripersonal space, sounds near the body have been argued to speed reactions to tactile stimuli. We conducted four experiments attempting to measure this distance-dependent audiotactile interaction. We found no distance-dependent enhancement of tactile processing in error rates or task performance, but found some evidence for a general speeding of reaction times by 9.5 ms when sounds were presented near the hand. A systematic review revealed an overestimation of reported effect sizes, lack of control conditions, a wide variety of methods, post hoc removal of data, and flexible methods of data analysis. After correcting for the speed of sound, removing biased or inconclusive studies, correcting for temporal expectancy, and using the trim-and-fill method to correct for publication bias, meta-analysis revealed an overall benefit of 15.2 ms when tactile stimuli are accompanied by near sounds compared to sounds further away. While this effect may be due to peripersonal space, response probability and the number of trials per condition explained significant proportions of variance in this near versus far benefit. These confounds need to be addressed, and alternative explanations ruled out by future, ideally pre-registered, studies.