C.H.M. Brunia

Wait and see.

Anticipatory behavior is aimed at goals that can be reached in the near future. Underlying this behavior are neurophysiological processes, which realize a setting of brain structures involved in the future perception, information processing and action. Anticipatory behavior is accompanied by slow brain potentials, which are generated in the cerebral cortex. They are known as the readiness potential (RP), the contingent negative variation (CNV) and the stimulus preceding negativity (SPN). The RP reflects the timing of a future voluntary movement. The CNV reflects the preparation of a signaled movement and the simultaneous anticipatory attention for the imperative stimulus. The SPN reflects partly the anticipatory attention for the upcoming stimulus. Although these slow potentials are generated in the cortex, the paper shows that a subcortical input from basal ganglia, and in the case of the RP also from the cerebellum, is a necessary condition for their emergence. Slow cortical potentials are the result of concerted activity in a number of cerebral networks, in which the thalamus forms a crucial node. It is suggested that the reticular nucleus of the thalamus plays a pivotal role in anticipatory attention.

A psychophysiological analysis of inhibitory motor control in the stop-signal paradigm

We examined two potential inhibitory mechanisms for stopping a motor response. Participants performed a standard visual two-choice task in which visual stop signals and no-go signals were presented on a small proportion of the trials. Psychophysiological measures were taken during task performance to examine the time course of response activation and inhibition. The results were consistent with a horse race model previously proposed to account for data obtained using a stop-signal paradigm. The pattern of psychophysiological responses was similar on stop-signal and no-go trials suggesting that the same mechanism may initiate inhibitory control in both situations. We found a distinct frontal brain wave suggesting that inhibitory motor control is instigated from the frontal cortex. The results are best explained in terms of a single, centrally located inhibition mechanism. Results are discussed in terms of current neurophysiological knowledge.

Stimulation of the Subthalamic Region Facilitates the Selection and Inhibition of Motor Responses in Parkinson's Disease

The aim of the present study was to specify the involvement of the basal ganglia in motor response selection and response inhibition. Two samples were studied. The first sample consisted of patients diagnosed with Parkinsons disease (PD) who received deep-brain stimulation (DBS) of the subthalamic nucleus (STN). The second sample consisted of patients who received DBS for the treatment of PD or essential tremor (ET) in the ventral intermediate nucleus of the thalamus (Vim). Stop-signal task and go/no-go task performances were studied in both groups. Both groups performed these tasks with (on stimulation) and without (off stimulation) DBS to address the question of whether stimulation is effective in improving choice reaction time (RT) and stop-signal RT. The results show that DBS of the STN was associated with significantly enhanced inhibitory control, as indicated by shorter stop-signal RTs. An additional finding is that DBS of the STN led to significantly shorter choice RT. The effects of DBS on responding and response inhibition were functionally independent. Although DBS of the Vim did not systematically affect task performance in patients with ET, a subgroup of Vim-stimulated PD patients showed enhanced stop-signal RTs in on stimulation versus off stimulation. This result suggests that the change in performance to stop signals may not be directly related to STN function, but rather results from a change in PD function due to DBS in general. The findings are discussed in terms of current functional and neurobiological models that relate basal ganglia function to the selection and inhibition of motor responses.

Movement and stimulus preceding negativity

After a short description of the different premovement potentials it is suggested that readiness potentials (RPs) recorded over different cortical motor areas reflect different functions. Then it is proposed that the late wave of the contingent negative variation (CNV) is a composite of a RP and a stimulus preceding negativity (SPN). Arguments for the existence of a non-motoric SPN are given, based upon our recent experiments. Next, it is suggested that a SPN is found preceding at least three different kinds of stimuli. Finally, it is stated that motor preparation and stimulus anticipation are different processes, reflected in a different distribution of the accompanying Slow Waves and an all or none accompanying change in reflex amplitudes.

Anticipatory attention: an event-related desynchronization approach

This paper addresses the question of whether anticipatory attention--i.e. attention directed towards an upcoming stimulus in order to facilitate its processing--is realized at the neurophysiological level by a pre-stimulus desynchronization of the sensory cortex corresponding to the modality of the anticipated stimulus, reflecting the opening of a thalamocortical gate in the relevant sensory modality. It is argued that a technique called Event-Related Desynchronization (ERD) of rhythmic 10-Hz activity is well suited to study the thalamocortical processes that are thought to mediate anticipatory attention. In a series of experiments, ERD was computed on EEG and MEG data, recorded while subjects performed a time estimation task and were informed about the quality of their time estimation by stimuli providing Knowledge of Results (KR). The modality of the KR stimuli (auditory, visual, or somatosensory) was manipulated both within and between experiments. The results indicate to varying degrees that preceding the presentation of the KR stimuli, ERD is present over the sensory cortex, which corresponds to the modality of the KR stimulus. The general pattern of results supports the notion that a thalamocortical gating mechanism forms the neurophysiological basis of anticipatory attention. Furthermore, the results support the notion that Event-Related Potential (ERP) and ERD measures reflect fundamentally different neurophysiological processes.

A spatiotemporal dipole model of the stimulus preceding negativity (spn) prior to feedback stimuli

SummaryTen subjects performed a time production task, in which they were instructed to press a button four seconds after the presentation of an auditory stimulus. Two seconds after the button press they received either auditory or visual feedback on the temporal accuracy of their response. In such a paradigm negative slow brain potentials can be recorded preceding the response (Movement Preceding Negativity, MPN) as well as preceding the feedback stimulus (Stimulus Preceding Negativity, SPN). Spatiotemporal dipole modelling is used to gain insight in the possible generators of MPN and SPN. From the models it follows that the MPN can be described by one contralateral radial dipole and a bilateral pair of tangential dipoles. All three dipoles are located near central electrode positions, so the generators of the MPN probably reside within the motor cortex. The SPN is modelled by a bilateral frontotemporal pair of dipoles, hypothetically representing activation of the Insulae Reili. The insular cortex is involved in the processing of affective-motivational input, such as carried by the feedback in the present paradigm. However, processing of the information content of the feedback stimulus might by itself also activate the frontal cortex. Both the response and the feedback stimulus are followed by a positive peak, which can be described by the same deep posterior dipole. Both peaks probably represent a P3, which is related to context updating.

A spatio-temporal dipole model of the readiness potential in humans. I. Finger movement

Readiness potentials (RP) have been recorded in 9 subjects who performed voluntary unilateral plantar flexions with the right or left foot. These show a paradoxical ipsilateral dominance. Spatio-temporal dipole models were obtained for these data, by iterative parameter estimation. The non-uniqueness of the inverse problem leads to several models which describe the data almost equally well, and which all pass orthogonality tests for the individual residuals and source waves. In these dipole models the ipsilateral preponderance is attributed to generators in the contralateral hemisphere, which agrees with results from MEG recording. According to these models the main generators of the RP are in the primary motor cortex, one bilaterally in its posterior wall and the other in the contralateral crown. This agrees with earlier results for finger RPs. However, for foot RPs, it was difficult to distinguish individual sub-components in both the observed scalp potentials and the estimated temporal activation patterns of the dipoles. Some of the presented models include a fronto-central dipole which possibly represents activity of the supplementary motor area. It is concluded that this finding is at best suggestive and needs further investigation.

CNV and EMG preceding a plantar flexion of the foot

In 25 subjects CNV and EMG were recorded during a reaction time experiment with a fixed 4 sec foreperiod. The response was plantar flexion of the right foot. EEGs were recorded with four electrodes from the central area, two over each hemisphere. CNV amplitudes were larger over the ipsilateral than over the contralateral hemisphere. Amplitudes were smaller in the more lateral derivations. The late component of the CNV showed larger amplitudes when preceding relatively fast responses. EMG activity was recorded from the calf muscles of both legs. In the left leg it was not different during the intertrial interval and the foreperiod. A small but systematic increase in EMG activity was found during the foreperiod in the right leg. The increase was larger preceding fast responses, parallel to the amplitude changes in CNV late waves.

Movement related slow potentials. II. A contrast between finger and foot movements in left-handed subjects

Finger and foot movement related potentials (MRPs) were recorded over the frontal, central and parietal areas of both hemispheres in 20 left-handed subjects. A unilateral flexion of the index finger and a plantar flexion of the foot were studied on either side. MRPs were larger preceding foot movements than preceding finger movements, their onset being earlier also. Prior to a finger flexion amplitudes were larger over the hemisphere contralateral to the movement than over the ipsilateral hemisphere. Preceding a foot movement, however, amplitudes were larger over the ipsilateral hemisphere. These results indicate differently localized sources of the MRPs in the two kinds of movement, in accordance with data obtained in right-handed subjects. No indication of a hemisphere effect, possibly related to motor dominance, was found in left-handers. This is in contrast to a slight hemisphere effect found with foot movements in right-handed subjects in the former study.

Movement‐Associated Potentials and Motor Control Report of the EPIC VI Motor Panel

The entirety of human behavior is based on motor acts. Without some kind of motor expression no reasoning or tradition could be retained in the culture. Mans capacity for acting on and interacting with the environment is dependent on his voluntary movements. Although investigations into human sensory information processing are numerous and have a long history, comparably fewer studies have been devoted to the analysis of human cortical motor functions. Previous views of human cortical motor control, determined by the sequelae of cerebral stroke and cortical stimulation experiments, envisaged an exclusively contralateral organization. However, the processes underlying early preparation for voluntary movement are different. Readiness for movement is accompanied by a widespread slow negativity over both hemispheres, the Bereitschaftspotential (BP, Kornhuber and Deecke, 1964, 1965). There are basically two major categories of movements, the distinction being made by how the movements are initiated. Movements can occur in response to an external stimulus. Movements of this kind are reactions to our environment. But we can also move spontaneously, i.e. of our own volition. Movements of this kind are our free actions on the environment. Although we also need motivation to react to an external