Visual Imperative Stimulus Research Articles

Neural gain induced by startling acoustic stimuli is additive to preparatory activation.

Loud acoustic stimuli presented during movement preparation can shorten reaction time and increase response forcefulness. We examined how efferent connectivity of an agonist muscle to reticulospinal and corticospinal pathways, and the level of prepared movement force, affect reaction time and movement execution when the motor response is triggered by an intense acoustic stimulus. In Experiment 1, participants executed ballistic wrist flexion and extension movements of low and high force in response to visual stimuli. A loud acoustic stimulus (LAS; 105dBa) was presented simultaneously with the visual imperative stimulus in probe trials. In Experiment 2, participants executed ballistic wrist flexion movements ranging from 10%-50% of maximum voluntary contraction with a LAS presented in probe trials. The shortening of response initiation was not affected by movement type (flexion or extension) or prepared movement force. Enhancement of response magnitude, however, was proportionally greater for low force movements and for the flexor muscle. Changes in peak force induced by the intense acoustic stimulus indicated that the neural activity introduced to motor program circuits by acoustic stimulation is additive to the voluntary neural activity that occurs due to movement preparation, rather than multiplicative.

Effect of auditory stimulus on executive function and execution time during cognitively demanding stepping task in patients with Parkinson’s disease

Start hesitation in patients with Parkinson’s disease (PD) occurs predominantly during distractive and conflictual situations. The aim of this study was to investigate how differently an auditory stimulus (AS) influences execution function and execution time during a cognitively demanding stepping task in PD patients as compared to healthy controls. PD patients and healthy controls stepped forward in response to a visual imperative stimulus of an arrow. We applied a Simon task that comprised congruent and incongruent conditions. Direction and location of the arrow matched in the congruent condition, while they didn’t in the incongruent condition. AS were randomly and simultaneously presented with the visual stimulus. An error in the direction of an anticipatory postural adjustment (APA), termed an APA error, and temporal parameters (reaction onset of APA and APA duration) were analyzed. As a result, the AS increased the APA error rate in the control group regardless of the condition, but they did not influence it in the PD group. The AS also speeded the reaction onset in both groups regardless of the condition. The APA duration was prolonged by the AS for the control group, while it was unaffected by the AS for the PD group in both conditions. These findings indicate that AS could facilitate a step initiation, conceivably by facilitating a stimulus identification process and increasing attentional control of stepping behavior, without influencing a decision-making process even in a cognitively demanding condition in patients with PD.

Modulation of EMG-EMG Coherence in a Choice Stepping Task.

The voluntary step execution task is a popular measure for identifying fall risks among elderly individuals in the community setting because most falls have been reported to occur during movement. However, the neurophysiological functions during this movement are not entirely understood. Here, we used electromyography (EMG) to explore the relationship between EMG-EMG coherence, which reflects common oscillatory drive to motoneurons, and motor performance associated with stepping tasks: simple reaction time (SRT) and choice reaction time (CRT) tasks. Ten healthy elderly adults participated in the study. Participants took a single step forward in response to a visual imperative stimulus. EMG-EMG coherence was analyzed for 1000 ms before the presentation of the stimulus (stationary standing position) from proximal and distal tibialis anterior (TA) and soleus (SOL) muscles. The main result showed that all paired EMG-EMG coherences in the alpha and beta frequency bands were greater in the SRT than the CRT task. This finding suggests that the common oscillatory drive to the motoneurons during the SRT task occurred prior to taking a step, whereas the lower value of corticospinal activity during the CRT task prior to taking a step may indicate an involvement of inhibitory activity, which is consistent with observations from our previous study (Watanabe et al., 2016). Furthermore, the beta band coherence in intramuscular TA tended to positively correlate with the number of performance errors that are associated with fall risks in the CRT task, suggesting that a reduction in the inhibitory activity may result in a decrease of stepping performance. These findings could advance the understanding of the neurophysiological features of postural adjustments in elderly individuals.

Auditory stimulus has a larger effect on anticipatory postural adjustments in older than young adults during choice step reaction.

The study aim was to compare the influence of an auditory stimulus (AS) on anticipatory postural adjustments (APAs) between young and older adults during a choice step reaction. Sixteen young and 19 older adults stepped forward in response to a visual imperative stimulus of an arrow. We used a choice reaction time (CRT) task and a Simon task which consisted of congruent and incongruent conditions. The direction of the presented arrow and its spatial location matched in the congruent condition while they did not in the incongruent condition. The AS was presented randomly and simultaneously with the visual stimulus. Incorrect weight shifts before lifting off the foot, termed APA errors, stepping errors, temporal parameters, and APA amplitudes were analyzed. The APA error rate was higher in trials with than without AS in all task conditions for the older group, while this increase occurred only in the incongruent condition for the young group. The stepping error rate was also increased in the presence of AS in the incongruent condition for the older group. Reaction times were faster with AS in both groups. The APA amplitude of erroneous APA trials became larger with AS in the incongruent condition for both groups, and this effect appeared greater for the older group. The effect of AS on APAs is larger in the elderly during a choice step reaction. In the presence of incongruent visual information, this effect becomes even greater, potentially inducing not only APA errors but also stepping errors.

Performance monitoring and response conflict resolution associated with choice stepping reaction tasks

Choice reaction requires response conflict resolution, and the resolution processes that occur during a choice stepping reaction task undertaken in a standing position, which requires maintenance of balance, may be different to those processes occurring during a choice reaction task performed in a seated position. The study purpose was to investigate the resolution processes during a choice stepping reaction task at the cortical level using electroencephalography and compare the results with a control task involving ankle dorsiflexion responses. Twelve young adults either stepped forward or dorsiflexed the ankle in response to a visual imperative stimulus presented on a computer screen. We used the Simon task and examined the error-related negativity (ERN) that follows an incorrect response and the correct-response negativity (CRN) that follows a correct response. Error was defined as an incorrect initial weight transfer for the stepping task and as an incorrect initial tibialis anterior activation for the control task. Results revealed that ERN and CRN amplitudes were similar in size for the stepping task, whereas the amplitude of ERN was larger than that of CRN for the control task. The ERN amplitude was also larger in the stepping task than the control task. These observations suggest that a choice stepping reaction task involves a strategy emphasizing post-response conflict and general performance monitoring of actual and required responses and also requires greater cognitive load than a choice dorsiflexion reaction. The response conflict resolution processes appear to be different for stepping tasks and reaction tasks performed in a seated position.

Preparatory state and postural adjustment strategies for choice reaction step initiation

A loud auditory stimulus (LAS) presented simultaneously with a visual imperative stimulus can reduce reaction time (RT) by automatically triggering a movement prepared in the brain and has been used to investigate a movement preparation. It is still under debate whether or not a response is prepared in advance in RT tasks involving choice responses. The purpose of the present study was to investigate the preparatory state of anticipatory postural adjustments (APAs) during a choice reaction step initiation. Thirteen young adults were asked to step forward in response to a visual imperative stimulus in two choice stepping conditions: (i) the responding side is not known and must be selected and (ii) the responding side is known but whether to initiate or inhibit a step response must be selected. LAS was presented randomly and simultaneously with the visual imperative stimulus. LAS significantly increased the occurrence rates of inappropriately initiated APAs while reducing the RTs of correct and incorrect trials in both task conditions, demonstrating that LAS triggered the prepared APA automatically. This observation suggests that APAs are prepared in advance and withheld from release until the appropriate timing during a choice reaction step initiation. The preparatory activity of APAs might be modulated by the inhibitory activity required by the choice tasks. The preparation strategy may be chosen for fast responses and is judged most suitable to comply with the tasks because inappropriately initiated APAs can be corrected without making complete stepping errors.

Accessory stimulus modulates executive function during stepping task.

When multiple sensory modalities are simultaneously presented, reaction time can be reduced while interference enlarges. The purpose of this research was to examine the effects of task-irrelevant acoustic accessory stimuli simultaneously presented with visual imperative stimuli on executive function during stepping. Executive functions were assessed by analyzing temporal events and errors in the initial weight transfer of the postural responses prior to a step (anticipatory postural adjustment errors). Eleven healthy young adults stepped forward in response to a visual stimulus. We applied a choice reaction time task and the Simon task, which consisted of congruent and incongruent conditions. Accessory stimuli were randomly presented with the visual stimuli. Compared with trials without accessory stimuli, the anticipatory postural adjustment error rates were higher in trials with accessory stimuli in the incongruent condition and the reaction times were shorter in trials with accessory stimuli in all the task conditions. Analyses after division of trials according to whether anticipatory postural adjustment error occurred or not revealed that the reaction times of trials with anticipatory postural adjustment errors were reduced more than those of trials without anticipatory postural adjustment errors in the incongruent condition. These results suggest that accessory stimuli modulate the initial motor programming of stepping by lowering decision threshold and exclusively under spatial incompatibility facilitate automatic response activation. The present findings advance the knowledge of intersensory judgment processes during stepping and may aid in the development of intervention and evaluation tools for individuals at risk of falls.

Noradrenergic and cholinergic effects on speed and sensitivity measures of phasic alerting.

An intense but task-irrelevant auditory accessory stimulus that is presented almost simultaneously with a visual imperative stimulus can reduce reaction times (RTs) to that stimulus. The information-processing locus and neural underpinnings underlying this phasic alerting effect are still poorly understood. The authors investigated a possible noradrenergic or cholinergic basis of the accessory stimulus effect in a double-blind pharmacological study (N = 18), in which healthy participants received a single dose of clonidine (an α2-adrenergic agonist), scopolamine (a muscarinic antagonist), and placebo in separate test sessions. A backward-masking procedure was used to examine, for the first time, the effect of accessory stimuli on perceptual sensitivity. The authors found that accessory stimuli enhanced perceptual sensitivity and decreased RTs to target stimuli, consistent with a recent hypothesis that phasic alerting speeds up stimulus encoding. In contrast to the authors' expectations, clonidine increased the accessory stimulus effect, a finding that seems at odds with earlier proposals that phasic alerting effects are mediated by a phasic noradrenergic response. Furthermore, the accessory stimulus effect was modulated to a similar extent by clonidine and scopolamine, suggesting that the effect of clonidine was not specific to the noradrenergic system. The results instead suggest that clonidine and scopolamine decrease general alertness and that these drug-related reductions in alertness yield room for compensatory performance improvements by phasic alerting.

StartReact Restores Reaction Time in HSP: Evidence for Subcortical Release of a Motor Program

Startling acoustic stimuli (SAS) can accelerate reaction times ("StartReact" effect), but the underlying mechanism remains unclear. Both direct release of a subcortically stored motor program and a subcortically mediated trigger for a cortically stored motor program have been hypothesized. To distinguish between these hypotheses, we examined the StartReact effect in humans with pure hereditary spastic paraplegia (HSP). Delayed reaction times in HSP patients in trials both with and without a SAS would argue in favor of a cortically stored response. We instructed 12 HSP patients and 12 matched controls to respond as rapidly as possible to a visual imperative stimulus, in two different conditions: dorsiflexion of the dominant ankle; or flexion of the dominant wrist. In 25% of trials, a SAS was delivered simultaneously with the imperative stimulus. Before these tests, subjects received five SAS while standing to verify normal function of the reticulospinal tract in HSP. Latencies of startle responses in sternocleidomastoid and tibialis anterior muscles were comparable between patients and controls. During the ankle dorsiflexion task, HSP patients had an average 19 ms delay in reaction times compared with controls. Administration of a SAS accelerated ankle dorsiflexion in both groups, but more so in the patients, which completely normalized their latencies. The wrist flexion task yielded no differences in onset latencies between HSP patients and controls. The reticulospinal tract seems unaffected in HSP patients, because startle reflex onsets were normal. The corticospinal tract was affected, as reflected by delayed ankle dorsiflexion reaction times. These delayed onsets in HSP were normalized when the imperative stimulus was combined with a SAS, presumably through release of a subcortically stored motor program conveyed by the preserved reticulospinal tract.

First trial and StartReact effects induced by balance perturbations to upright stance

Postural responses (PR) to a balance perturbation differ between the first and subsequent perturbations. One explanation for this first trial effect is that perturbations act as startling stimuli that initiate a generalized startle response (GSR) as well as the PR. Startling stimuli, such as startling acoustic stimuli (SAS), are known to elicit GSRs, as well as a StartReact effect, in which prepared movements are initiated earlier by a startling stimulus. In this study, a StartReact effect paradigm was used to determine if balance perturbations can also act as startle stimuli. Subjects completed two blocks of simple reaction time trials involving wrist extension to a visual imperative stimulus (IS). Each block included 15 CONTROL trials that involved a warning cue and subsequent IS, followed by 10 repeated TEST trials, where either a SAS (TESTSAS) or a toes-up support-surface rotation (TESTPERT) was presented coincident with the IS. StartReact effects were observed during the first trial in both TESTSAS and TESTPERT conditions as evidenced by significantly earlier wrist movement and muscle onsets compared with CONTROL. Likewise, StartReact effects were observed in all repeated TESTSAS and TESTPERT trials. In contrast, GSRs in sternocleidomastoid and PRs were large in the first trial, but significantly attenuated over repeated presentation of the TESTPERT trials. Results suggest that balance perturbations can act as startling stimuli. Thus first trial effects are likely PRs which are superimposed with a GSR that is initially large, but habituates over time with repeated exposure to the startling influence of the balance perturbation.

The effects of startle and non-startle auditory stimuli on wrist flexion movement in Parkinson's disease

Startle stimuli lead to shorter reaction times in control subjects and Parkinson's disease (PD) patients. However, non-startle stimuli also enhance movement initiation in PD. We wanted to examine whether a startle-triggered movement would retain similar kinematic and EMG-related characteristics compared to one induced by a non-startle external cue in PD patients. In this study we investigated the electromyography pattern and the reaction time during a wrist flexion movement in response to three different stimuli: a visual imperative stimulus; visual stimulus simultaneous with a non-startle auditory stimulus and with a startle auditory stimulus. Ten PD patients and ten aged matched controls participated in this study. The reaction times were faster for startle and non-startle stimuli in comparison with the visual imperative stimulus, in both patients and control subjects. The startle cue induced a faster reaction than the non-startle cue. The electromyography pattern remained unchanged across the conditions. The results suggest that the startle reaction effect for upper limb movements are unimpaired in PD patients and has different characteristics than the effect of non-startle stimuli.

The effects of auditory startle and nonstartle stimuli on step initiation in Parkinson's disease

Auditory external cues enhance step initiation in Parkinson's disease (PD) patients. We wanted to explore whether a startle reaction has a comparable effect on step initiation in PD. Thirteen PD patients and 13 aged-matched controls participated in this study. Electromyography pattern and onset toe-off time during a step initiation task were recorded in response to three different stimuli: a visual imperative stimulus; visual stimulus simultaneous with a nonstartle auditory stimulus and with a startle auditory stimulus. In all subjects, onset of tibialis anterior was faster in the startle auditory condition, compared with the nonstartle auditory condition. However, in the patient group, there was no difference in onset of soleus and toe-off between the startle and nonstartle conditions. Startle reaction in PD patients demonstrates a disordered coupling between the anticipatory postural adjustments that initiate the weight shift and the movement to initiate toe-off during step initiation.

Effects of anticipation certainty on preparatory brain activity and anticipatory postural adjustments associated with voluntary unilateral arm movement while standing

We examined the effects of anticipation certainty concerning which voluntary movement is required in response to a stimulus while standing on preparatory brain activity and anticipatory postural adjustments (APAs). Ten right-handed adults abducted their left or right arm rapidly in response to a visual imperative stimulus, based on the type of stimulus. A warning cue, which did or did not contain information about the side of arm abduction, was presented 2000ms before the imperative stimulus. Preparatory brain activity before arm abduction was quantified by the mean amplitude of the contingent negative variation 100ms before the imperative stimulus (late CNV amplitude). Compared with the low anticipation condition, in the high anticipation condition the following results were obtained only in the case of right arm abduction: (1) larger late CNV amplitude, (2) earlier postural muscle activities with respect to the focal muscle of arm abduction, and (3) smaller peak displacement of center of pressure during the abduction. These findings suggest that high anticipation of voluntary movement of dominant arm to a stimulus while standing influences preparatory brain activity before the movement, resulting in earlier APAs and thus smaller disturbance of postural equilibrium during the movement.

Increased performance uncertainty in children with ADHD? - Elevated post-imperative negative variation (PINV) over the ventrolateral prefrontal cortex

BackgroundWe aimed to investigate the influences of attention deficit/hyperactivity disorder (ADHD) on response evaluation, as reflected by the postimperative negative variation (PINV), a slow event-related potential.MethodsWe investigated PINV as an indicator of performance uncertainty in an audio-visual contingent negative variation (CNV) paradigm with an interstimulus interval of 3 seconds. A constant, unilateral, quick motor reaction with either the right or the left thumb was required after an auditory forewarned (S1) visual imperative stimulus (S2). We examined 18 ADHD patients (combined or hyperactive-impulsive subtype) aged between 8 and 14 years and an age-, sex and IQ-matched control group of 19 healthy subjects using 64-channel high-density EEG. A first run was recorded drug-free, a second one under methylphenidate (MPH) medication in the ADHD group.ResultsWe found a significantly increased negativity of the PINV-component over the ventrolateral prefrontal cortex in ADHD children compared to the healthy control group. PINV amplitude was influenced by movement side, most likely due to the slightly more difficult task when left hand responses were required. After the intake of MPH, PINV amplitudes of ADHD children normalized.ConclusionsWe conclude that children with ADHD are likely to be more uncertain about the correctness of their performance and interpret the increased PINV as a hint towards compensatory mechanisms for a deficit in the evaluation of contingencies. Further studies are needed to assess the exact extent to which remainders of eye-movement related potentials contribute to PINV amplitude despite the correction for eye-artifacts.

Choice reaction times for human head rotations are shortened by startling acoustic stimuli, irrespective of stimulus direction

Auditory startle reflexes can accelerate simple voluntary reaction times (StartReact effect). To investigate the role of startle reflexes on more complex motor behaviour we formulated two questions: (1) can auditory startle reflexes shorten choice reaction times?; (2) is the StartReact effect differentially modulated when startling auditory stimuli are delivered ipsilaterally or contralaterally to an imperative 'go' signal? We instructed 16 healthy subjects to rotate their head as rapidly as possible to the left or to right in response to a guiding visual imperative stimulus (IS), in both a simple and choice reaction protocol. Startling acoustic stimuli (113 dB) were delivered simultaneously with the IS (from either the same or opposite side) to induce the StartReact effect. We recorded kinematics of head rotations and electromyographic responses. The StartReact effect was present during choice reaction tasks (56 ms onset reduction; P < 0.001). The presentation side of the startling stimulus (left/right) did not influence the effect in choice reaction tasks. We observed a directional effect in simple reaction tasks, but this probably occurred due to a flooring effect of reaction times. Onsets of EMG responses in neck muscles were not influenced by the direction of the acoustic startling stimulus. Startling acoustic stimuli decrease reaction times not only in simple but also in choice reaction time tasks, suggesting that startle reflexes can accelerate adequate human motor responses. The absence of a clear directional sensitivity of reaction times to startling acoustic stimuli suggests that the acceleration is not highly specific, but seems to provide a global preparatory effect upon which further tailored action can be undertaken more quickly.

Reaction time facilitation by acoustic task-irrelevant stimuli is not related to startle

Previous research has been interpreted to suggest that the startle reflex mediates the RT facilitation observed if intense, accessory acoustic stimuli are presented coinciding with the onset of a visual imperative stimulus in a forewarned simple RT task. The present research replicated this finding as well as the facilitation of startle observed during the imperative stimulus. It failed, however, to find any relationship between the size of the blink startle reflex elicited by the accessory acoustic stimuli, which differed in intensity and rise time, and RT or RT facilitation observed on trials with accessory acoustic stimuli. This finding suggests that the RT facilitation is not mediated by the startle reflex elicited by the accessory acoustic stimuli.

Effects of acoustic startle stimuli on interceptive action

In reaction time (RT) tasks, presentation of a startling acoustic stimulus (SAS) together with a visual imperative stimulus can dramatically reduce RT while leaving response execution unchanged. It has been suggested that a prepared motor response program is triggered early by the SAS but is not otherwise affected. Movements aimed at intercepting moving targets are usually considered to be similarly governed by a prepared program. This program is triggered when visual stimulus information about the time to arrival of the moving target reaches a specific criterion. We investigated whether a SAS could also trigger such a movement. Human experimental participants were trained to hit moving targets with movements of a specific duration. This permitted an estimate of when movement would begin (expected onset time). Startling and sub-startle threshold acoustic probe stimuli were delivered unexpectedly among control trials: 65, 85, 115 and 135 ms prior to expected onset (10:1 ratio of control to probe trials). Results showed that startling probe stimuli at 85 and 115 ms produced early response onsets but not those at 65 or 135 ms. Sub-threshold stimuli at 115 and 135 ms also produced early onsets. Startle probes led to an increased vigor in the response, but sub-threshold probes had no detectable effects. These data can be explained by a simple model in which preparatory, response-related activation builds up in the circuits responsible for generating motor commands in anticipation of the GO command. If early triggering by the acoustic probes is the mechanism underlying the findings, then the data support the hypothesis that rapid interceptions are governed by a motor program.

Distraction affects frontal alpha rhythms related to expectancy of pain: An EEG study

Previous electroencephalographic (EEG) evidence has shown event-related desynchronization (ERD) of alpha rhythms before predictable painful stimuli, as a possible neural concomitant of attentional preparatory processes (Babiloni, C., Brancucci, A., Babiloni, F., Capotosto, P., Carducci, F., Cincotti, F., Arendt-Nielsen, L., Chen, A.C., Rossini, P.M., 2003. Anticipatory cortical responses during the expectancy of a predictable painful stimulation. A high-resolution electroencephalography study. Eur. J. Neurosci. 18 (6) 1692–700). This study tested the hypothesis that alpha ERD before predictable painful stimuli is reduced as an effect of distraction. A visual warning stimulus preceded a laser painful stimulation, which was strictly followed by visual imperative stimuli. In the Pain (control) condition, no task was required after the imperative stimuli. In the Pain + Movement condition, subjects had to perform a movement of the right index finger. In the Pain + Cognition condition, they had to mentally perform an arithmetical task. EEG data were recorded in 10 subjects from 30 electrodes. Artifact-free recordings were spatially enhanced by surface Laplacian transformation. Alpha ERD was computed at three alpha sub-bands according to subjects' individual alpha frequency peak (i.e., about 6–8 Hz, 8–10 Hz, 10–12 Hz). Compared to the control condition, the subjects reported a significantly lower stimulus intensity perception and unpleasantness in the Pain + Movement and Pain + Cognition conditions. In addition, there was a cancellation of the alpha 3 ERD (i.e., about 10–12 Hz) in Pain + Cognition condition and even a generation of a statistically significant alpha 3 ERS in Pain + Movement condition. These effects were maximum over fronto-central midline. These results suggest that distraction during the expectancy of pain is related to a reduced neural desynchronization of fronto-central midline alpha rhythms (i.e., reduced cortical activation) towards an overt hyper-synchronization (cortical idling).

Cortical and subcortical distribution of middle and long latency auditory and visual evoked potentials in a cognitive (CNV) paradigm.

This study concerned sensory processing (post-stimulus late evoked potential components) in different parts of the human brain as related to a motor task (hand movement) in a cognitive paradigm (Contingent Negative Variation). The focus of the study was on the time and space distribution of middle and late post-stimulus evoked potential (EP) components, and on the processing of sensory information in the subcortical-cortical networks. Stereoelectroencephalography (SEEG) recordings of the contingent negative variation (CNV) in an audio-visual paradigm with a motor task were taken from 30 patients (27 patients with drug-resistant epilepsy; 3 patients with chronic thalamic pain). The intracerebral recordings were taken from 337 cortical sites (primary sensorimotor area (SM1); supplementary motor area (SMA); the cingulate gyrus; the orbitofrontal, premotor and dorsolateral prefrontal cortices; the temporal cortex, including the amygdalohippocampal complex; the parietooccipital lobes; and the insula) and from subcortical structures (the basal ganglia and the posterior thalamus). The concurrent scalp recordings were obtained from 3 patients in the thalamic group. In 4 patients in the epilepsy group, scalp recordings were taken separately from the SEEG procedure. The middle and long latency evoked potentials following an auditory warning (S1) and a visual imperative (S2) stimuli were analyzed. The occurrences of EPs were studied in two time windows (200-300 ms; and over 300 ms) following S1 and S2. Following S1, a high frequency of EP with latencies over 200 ms was observed in the primary sensorimotor area, the supplementary motor area, the premotor cortex, the orbitofrontal cortex, the cingulate gyrus, some parts of the temporal lobe, the basal ganglia, the insula, and the posterior thalamus. Following S2, a high frequency of EP in both of the time windows over 200 ms was observed in the SM1, the SMA, the premotor and dorsolateral prefrontal cortex, the orbitofrontal cortex, the cingulate gyrus, the basal ganglia, the posterior thalamus, and in some parts of the temporal cortex. The concurrent scalp recordings in the thalamic group of patients twice revealed potentials peaking approximately at 215 ms following S1. Following S2, EP occurred with latencies of 215 and 310 ms, respectively. Following S1, separate scalp recordings in 4 patients in the epilepsy group displayed EP 3 times in the 'over 300 ms' time window. Following S2, EP were presented once in the '200-300 ms' time window and 3 times in the 'over 300 ms' time window. The SM1, the SMA, multiple sites of the frontal lobe, some parts of the temporal lobe, the cingulate gyrus, the basal ganglia, the insula, and the posterior thalamus all participate in a cortico-subcortical network that is important for the parallel cognitive processing of sensory information in a movement related task.

A SEEG study of ERP in motor and premotor cortices and in the basal ganglia.

Our intention was to study the electrical activity related to the cognitive processing of simple sensory stimuli in the brain structures that participate in motor control. We focused our interest on the 250-600 ms time window, in which cognitive activity most probably provides the basis for the activity recorded. Intracerebral stereoelectroencephalography (SEEG) recordings were made from 15 epilepsy surgery candidates. We studied potentials that were recorded in a time window in which P300 usually could be recorded on the scalp and that were directly recorded from brain structures involved in motor control: the primary motor cortex (MC, Brodmann's area 4); the lateral and mesial (SMA) premotor cortices (Brodmann's area 6); and the basal ganglia. We evaluated the first distinctive potential to occur in the 250-600 ms time window that displayed an amplitude gradient in several adjacent contacts. Four protocols were performed: an auditory oddball (aP3); a visual oddball (vP3); and contingent negative variation (CNV) protocols, in which the potentials evoked by the auditory warning (aCNV) and visual imperative (vCNV) stimuli were evaluated. In the protocols aP3, vP3, and vCNV, the tested person responded by flexing his/her thumb or hand. In the aCNV paradigm, and in a further auditory oddball paradigm (aP3c), no motor response was required. We compared the presence of an event-related potential (ERP) with an amplitude gradient to the absence of a generator. The frequency of P3-like potential components was statistically significantly higher in the basal ganglia when compared with the explored cortical sites. Statistically non-significant latency differences between the basal ganglia and the cortex were displayed. The differences in the distribution of the potentials in the individual cortical areas were insignificant. The mean latency of vP3 was longer than the latencies of aP3, aP3c and vCNV. There was no significant difference between the distribution and latency of aP3 and aP3c. (1) ERPs are generated in cortical as well as in subcortical structures. (2) The cognitive processing of sensory information in all the tested protocols occurred in the basal ganglia; the occurrence in the investigated cortical areas was less frequent and more dependent on the task. The basal ganglia may play an integrative role in cognitive information processing, in motor and non-motor tasks.