Bruce E. McDonough

Altered transfer of visual motion information to parietal association cortex in untreated first-episode psychosis: Implications for pursuit eye tracking

Visual motion processing and its use for pursuit eye movement control represent a valuable model for studying the use of sensory input for action planning. In psychotic disorders, alterations of visual motion perception have been suggested to cause pursuit eye tracking deficits. We evaluated this system in functional neuroimaging studies of untreated first-episode schizophrenia (N=24), psychotic bipolar disorder patients (N=13) and healthy controls (N=20). During a passive visual motion processing task, both patient groups showed reduced activation in the posterior parietal projection fields of motion-sensitive extrastriate area V5, but not in V5 itself. This suggests reduced bottom-up transfer of visual motion information from extrastriate cortex to perceptual systems in parietal association cortex. During active pursuit, activation was enhanced in anterior intraparietal sulcus and insula in both patient groups, and in dorsolateral prefrontal cortex and dorsomedial thalamus in schizophrenia patients. This may result from increased demands on sensorimotor systems for pursuit control due to the limited availability of perceptual motion information about target speed and tracking error. Visual motion information transfer deficits to higher-level association cortex may contribute to well-established pursuit tracking abnormalities, and perhaps to a wider array of alterations in perception and action planning in psychotic disorders.

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.

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.