Charles A. Warren

Movement-related potentials during development: a replication and extension of relationships to age, motor control, mental status and IQ.

Three age groups of normals (children, preadolescents, and adults) and a group of mentally retarded adults performed a noncued button press task from which averaged movement-related potentials (MRPs) were derived. MRP wave shapes replicated our previously reported modal waveform types, except for the preadolescents, who showed no modal MRP. The normal groups showed a developmental shift in the prevalence of waveforms with the retarded differing from normal adults. The modal child waveform had a large amplitude positive-negative-positive form; the retarded had a uniphasic positive form; while normal adults showed the usual negative form. Major MRP types among children could not be attributed to differences in sampling or number of the trials averaged, or to trial-to-trial MRP variability. Background EEG activity did not differ in different modal MRP types. Modal child MRPs showed an initial peak positivity at Fz, and a late peak at Cz. The retarded had a sustaining central positivity developed by midepoch. MRP positivity and negativity were related to age, inhibition of extraneous eye movement (EM), and IQ. In children, greater cognitive proficiency is associated with adult-like MRP. The results suggest that positivity, in part, reflects a subjects efforts at inhibiting movement extraneous to the instructed task.

CNV during memory retrieval by normal and retarded adults.

Publisher Summary This chapter discusses contingent negative variation (CNV) during memory retrieval by normal and retarded adults. The moderately and mildly retarded with no apparent organic or medical involvement are known to do poorly on short term memory tasks. They are also known to perform slower memory scans than normals of the same age, at least for alphanumeric stimuli. On the other hand, these memory scan studies have shown no qualitative difference between the retarded and normals scan stage of processing. The present chapter is of initial findings of memory scan and event-related potentials in the retarded and during development. It is expected that event-related potentials (CNV and P300) could provide additional information on the processes responsible for the slower scans of the retarded. Any interpretation of the retarded data must be considered tentative because of the small sample relative to the large variability. There are, however, a few points that are suggestive of the results of previous studies. As with other memory scanning studies the retarded had slower scans.

Developmental Changes in ERP Preceding Movement are not Affected by Temporal Aspects of the Response

Publisher Summary This chapter discusses the developmental changes in event-related potentials (ERPs) preceding movement are not affected by temporal aspects of the response. Waveforms preceding right thumb flexion have been found to vary with development and mental retardation. Adults had typical negative-going waveforms. In contrast, young children had a biphasic waveform with positive components at 600 and 150 msec prior to movement. Mentally retarded young adults often had uniphasic positive-going waveforms. Pre-adolescents are variable, exhibiting waveforms similar to all 3 other groups. Subjects are instructed to press and release a hand-held button every few seconds but not to count or try to pace their presses. A demonstration is given and a few practice presses are allowed to assure proper performance. There are no explicit instructions as to how long to press or interval among presses except those implied by the demonstration. If during the task, however, the subject began pressing too rapidly (less than about 2 sec among presses) or appeared too rhythmical in responses is stopped and reinstructed. For each subject press durations and interresponse intervals are determined for each trial.

P3B and Positive Slow Wave following Real and Dummy Feedback on Arithmetic Rule-Learning and Perceptuomotor Tasks

Event-related Potentials (ERPs) were recorded to feedback during a cognitively demanding, arithmetic rule-learning task and a relatively simple, skill-oriented, perceptuomotor task. For both tasks, a compound feedback display was employed. It consisted of numeric feedback information presented simultaneously with a red or green light (50% each) which indicated whether the numeric information was real (valid) or dummy (invalid). The task and feedback-validity manipulations showed a functional dissociation between the P3b (350–450 msec.) and a Positive Slow Wave (600–900 msec.). P3b was larger for real than for dummy feedback; Positive Slow Wave was larger for rule-learning than for perceptuomotor tasks.