Rathe Karrer

Introversion, attention and the late positive component of event-related potentials

Variation in P3 amplitude across normal individuals under the same experimental conditions has been routinely observed. The possibility that such variation reflects individual differences in the allocation of attention was examined by comparing P3 amplitude in introverts and extraverts, who are thought to differ in the allocation of attention during monotonous tasks. Event-related potentials were recorded while the subjects participated in a lengthy stimulus prediction task. P3 amplitude was determined by principal components analysis and it was found to be significantly larger for the introverts than for the extraverts. This finding is interpreted as evidence that P3 amplitude is sensitive to individual differences in the allocation of attention.

Differential effects of experience on the ERP and behavior of 6‐month‐old infants: Trends during repeated stimulus presentations

Increasing experience with repetitive stimuli may lead to changes in the way the infant processes the information in the stimulus. It has been shown that some components of the event‐related brain potential (ERP) are sensitive to the differential experience provided by two stimuli presented at different probabilities. For example, the negative component (Nc) of the infants ERP is often greater in amplitude to low probability stimuli (oddballs) than to frequent stimuli. Therefore, changes in ERP component amplitudes and latencies may be expected to occur with stimulus repetition. We analyzed the ERP components to the frequent stimulus within an oddball task for 28 six‐month‐old infants. An 80‐trial Benoulli sequence of two female‐face pictures, presented at 80%/20% probabilities, was divided into three blocks. Amplitudes and latencies of Nc and a positive component (Pb) were measured as was the area of a negative slow wave (NSW) at frontal and central scalp sites FZ, CZ, PZ, C3, and C4. Early components w...

Movement-related potentials and control of associated movements

Previous studies have shown a relationship of the readiness potential (RP) preceding a motor act to motor control, as indexed by eye movement (EM). Greater EM and, therefore, less motor control was associated with increased positivity in preresponse RP components. It was hypothesized that these positive components may reflect processes involved in the inhibition of extraneous or associated movement during the performance of a motor act, especially in younger subjects with less motor development. We developed a finger lift task for detecting irrelevant associated movements (AM) from the responding hand and the nonresponding contralateral hand. During each target finger lift, small movements of the other nontarget fingers from the target hand and the contralateral hand were considered movements that should have been inhibited. Trials for each subject were divided into two bins: associated movement (AM) trials which had movement of target plus nontarget fingers, and trials with only target finger movement detected (NAM). Difference waveforms indicated a positive-going shift on trials with discrete target finger movements (NAM). Age and RP positivity at ipsilateral and posterior regions were significantly correlated. We suggest that, on trials on which associated movements are successfully inhibited, the negativity of the RP is confounded by an overlapping slow positivity. The positivity may be related to the effort needed to inhibit associated movements in order to perform a sharper and more discrete response. This relationship is a function of motor control and, indirectly, of age.

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.

Event-Related Potential Correlates of Intelligence and Personality

Event-related potentials (ERPs) have been shown to be sensitive to the manipulation of cognitive processes by instructions to the subject, such as to ignore or to focus attention on a series of events (Naatanen and Michie, 1979). There has been comparatively little work examining the extent to which stable characteristics of the subject as an information processor affect specific ERP components, and their scalp distribution. Studies which have examined relations between ERP features and individual difference variables have generally been encouraging (Callaway, 1975), even though the cognitive demands on the subjects have been minimal, and ERP topography has been typically ignored. The present paper reports on the correlations of ERP measures, obtained during a stimulus guessing task, to measures of intelligence, impulsivity, and free-floating anxiety.

Effects of attention and slow potential shifts on self-regulation of event-related potentials

Research on the effects of self-regulation of slow potentials (SP) and event-related potentials (ERP) has failed to look at the possible interactions of these two kinds of brain potentials. The present study investigated such interactions by recording both ERP and SP potential changes in an operant ERP conditioning paradigm. Ten subjects participated in two conditions that were designed to differentially manipulate attention to the stimuli. In the operant conditioning task, subjects received auditory feedback as they attempted to increase the ERP amplitude at 180 msec poststimulus (P180), which was elicited by a subpainful shock stimulus to the forearm over 250 trials. In the distraction task, subjects were instructed not to attend to stimuli or feedback tones, but rather received and were tested on reading materials. Attention, as manipulated by these tasks, was not a determinant of changes in ERP amplitude since there were no significant differences in the size of P180 between attention conditions. While no significant change in the mean ERP amplitude occurred, subjects were able to produce ERPs above criterion threshold significantly more often during trials in the conditioning task than in the reading task. Thus, there was evidence of some learning. The difference in wave forms between hit and miss trials indicates a latency shift (with misses having a later ERP peak). This may indicate that latency, rather than, or in addition to, amplitude, is shaped during conditioning procedures. In addition, the CNV that developed between the shock stimulus and the feedback signal during conditioning was significantly larger in amplitude than in the distraction condition. This is taken as evidence of increased attention during conditioning. Since hit trials demonstrated larger contingent negative variation (CNV) amplitudes, production of CNVs may be instrumental in mediating hits. Therefore, attentional mechanisms may play a role in successful ERP self-regulation. No correlations were found involving P180, CNVs, or tonic slow potential shifts. Changes in tonic DC levels showed a suggestive trend between conditions. Although both conditions began with a negative shift, during conditioning the negativity increased, while during distraction the tonic level went to positivity. These trends support the hypothesis that attention and arousal increased during conditioning. The possible reasons for the lack of significant correlations between ERP and tonic or phasic slow potential changes in this paradigm are discussed

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.

Input, Central And Motor Segments of Response Time in Mentally Retarded and Normal Children

Paper to: Conference on the Development of Control, Coordination and Skill in the Mentally Handicapped, NICHD, Washington, D.C., September 28-29, 1984. This paper was supported by the NICHD Grant # HD 08365. The work supported here was the result of collaboration with many people over the last ten years. I specifically wish to thank Dr. Charles Warren for his role in the initial implementation of the project and many analyses and discussions; Dr. Jorge Daruna and Bruce McDonough for analysis and discussion of the results; and Randall Cone for keeping our instrumentation functional and for much of the software for computer control and analysis.

Movement-Related Brain Potentials During Hand Squeezing In Children And Adults

Motor readiness potentials (MRPs) during hand squeezing were recorded from scalp leads in a group of right-handed and left-handed children and adults in order to determine: (1) the relationship of the MRP to age and motor control, measured by eye movement, (2) MRP hemispheric differences during both unilateral and bilateral movements and, (3) the relationship between different MRP components. MRP components before the response were independent of those after the squeeze. MRP positivity decreased with age for all squeezes. Motor control, which increased with age, related to MRP polarity in different leads depending on the responding hand. Dominant squeezes showed the greatest MRP positivity followed by non-dominant and bilateral squeezes. Motor control followed an inverse order across tasks; as motor control increased, positivity decreased. There were no asymmetries of the MRP until squeeze onset. Asymmetry occurred only during right hand squeezes regardless of handedness.

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.