G.J.M. van Boxtel

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.

Motor and non-motor aspects of slow brain potentials

In order to study motor and non-motor aspects of the contingent negative variation (CNV), fifteen right-handed subjects were asked to perform tightly controlled responses in a WS-S1-S2 paradigm. WS was a non-informative warning signal; S1 and S2 provided information about the response required at S2. This information was either delivered before a block of trials (Simple), at S1 (Precued), or at S2 (Choice). Negativity was larger prior to the informative than to the non-informative stimulus, suggesting the presence of a component called stimulus-preceding negativity (SPN). This finding supported the hypothesis that the late CNV consists of a readiness potential and an SPN. The scalp distribution of the SPN was different before S1 and before S2. The significance of these components is discussed in terms of motor preparation, stimulus anticipation and energetical processes.

Motor and non-motor components of the contingent negative variation

To study the contribution of the Stimulus-Preceding Negativity (SPN) to the late wave of the Contingent Negative Variation (CNV), negativity was recorded preceding an instruction stimulus (S1), an instruction stimulus to which a motor response was required (S2) and a stimulus that transmitted Knowledge of Results (KR). All recorded negativities showed a centro-parietal maximum. The pre-instruction negativities tended to be larger over the left hemisphere, while a right hemisphere preponderance was found for the pre-KR negativity. Unlike the pre-S1 negativity, the pre-KR negativity may depend on affective-motivational processes. The pre-S1 negativity was small and influenced by factors other than the instruction at S1. It is concluded that the SPN contributes to the late CNV, but that this contribution was relatively small.

Lifespan changes in motor activation and inhibition during choice reactions: A Laplacian ERP study

Response speed improves from childhood to early adulthood and declines steadily with advancing age. The present event-related brain potential (ERP) study explored the contribution of the primary motor cortex (M1) to lifespan changes in response speed and accuracy using a choice reaction time (RT) task. Two groups of children (8 and 12 years) and two groups of adults (21 and 76 years) responded to left- or right-pointing arrows. RTs showed a typical U-shaped lifespan pattern. RT was segmented into pre-selection time, pre-motor time, and motor time by using the onset of the central motor command (i.e., LRP, and the negative Laplacian potential) and the onset of response-related EMG. Pre-motor time was most sensitive to age-related change. In addition, the positive Laplacian potential, assumed to be associated with inhibition of the incorrect response alternative, was absent in children. In adults, the onset of the ipsilateral positivity started before the onset of the contralateral negativity but in elderly the onsets occurred approximately at the same time. This pattern of findings is consistent with the observed differences in choice error rates between age groups. Taken together, the lifespan changes in motor potentials point to suboptimal motor response control in children and the elderly compared to young adults.

Development of response activation and inhibition in a selective stop-signal task.

To gain more insight into the development of action control, the current brain potential study examined response selection, activation, and selective inhibition during choice- and stop-signal processing in three age groups (8-, 12-, and 21-year-olds). Results revealed that age groups differed in the implementation of proactive control; children slowed their go response and showed reduced cortical motor output compared to adults. On failed inhibition trials, children were less able than adults to suppress muscle output resulting in increased partial-inhibition rates. On invalid stop trials, all age groups initially activated, subsequently inhibited, and then reactivated the go response. Yet, children were less efficient in implementing this strategy. Then, older children recruit motor responses to a greater extent than younger children and adults, which reduced the efficiency of implementing response inhibition and proactive control. The results are discussed in relation to current notions of developmental change in proactive and reactive action control.To gain more insight into the development of action control, the current brain potential study examined response selection, activation, and selective inhibition during choice- and stop-signal processing in three age groups (8-, 12-, and 21-year-olds). Results revealed that age groups differed in the implementation of proactive control; children slowed their go response and showed reduced cortical motor output compared to adults. On failed inhibition trials, children were less able than adults to suppress muscle output resulting in increased partial-inhibition rates. On invalid stop trials, all age groups initially activated, subsequently inhibited, and then reactivated the go response. Yet, children were less efficient in implementing this strategy. Then, older children recruit motor responses to a greater extent than younger children and adults, which reduced the efficiency of implementing response inhibition and proactive control. The results are discussed in relation to current notions of developmental change in proactive and reactive action control.

The thalamic contribution to the emergence of the readiness potential.

Publisher Summary This chapter discusses the reasons behind a unilateral movement being preceded by a bilateral readiness potential (RP). Unilateral self-paced movements and warned stimulus-triggered movements are preceded by bilateral slow brain waves, RP, and the contingent negative variation. The chapter proposes two possibilities. The first possibility is that the RP is the consequence of a unilateral cortical activation contra-lateral to the movement side. The bilateral emergence could be because of volume conduction or to a mirror activation via the corpus callosum. The second possibility is that there is a bilateral activation of cortical motor areas. This might be because of a bilateral corticocortical activation, for example, from the prefrontal cortex to the motor cortex or to a bilateral subcortico-cortical activation via a cerebello-thalamocortical circuit or via a basal ganglia-thalamocortical circuit.