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Physiological and behavioral data reported here show an involvement of the primate frontal eye field (FEF) cortex in smooth-pursuit eye movements, in addition to its well-established role in saccadic eye movements. Microstimulation just ventral to the small saccade representation of the FEF elicits eye movements that, in contrast to elicited saccades, have(More)
1. We electrically stimulated the macaque monkey's frontal eye field (FEF) region to localize and to analyze the smooth pursuit eye movement representation. Rhesus monkeys were trained to fixate stationary spots of light, and trains of stimulation (usually 250-500 ms at 10-100 microA) were applied while the fixation targets remained lit and stationary. This(More)
1. Intracortical microstimulation of a portion of the monkey frontal eye field (FEF) lying in the floor and posterior bank of the arcuate sulcus evokes smooth, rather than saccadic eye movements. To further explore this region's involvement in pursuit, we recorded from FEF neurons in the vicinity of sites from which smooth eye movements (SEMs) were elicited(More)
The decline in motor performance that accompanies advanced age has unclear neurobiological substrates but may relate, in part, to degeneration of the nigrostriatal dopamine system. This research tested the hypothesis that striatal dopamine transporter (DAT) availability in healthy elderly individuals was related to measures of motor performance. Thirty-six(More)
UNLABELLED Postmortem binding studies have established that the concentration of alpha(4)beta(2)-nicotinic acetylcholine receptors (alpha(4)beta(2)-nAChR) is reduced in advanced Alzheimer disease (AD). However, the status of this receptor in mild or prodromal AD has remained the subject of controversy. METHODS We compared alpha(4)beta(2)-nAChR(More)
Magnetic resonance imaging (MRI) is showing increased utility in examining medial temporal lobe atrophy and its relationship to memory performance in Alzheimer's disease (AD). We studied 56 AD patients and 42 older healthy subjects with neuropsychological assessment and MRI. Hippocampal and amygdaloid volumes (normalized to intracranial volume) were(More)
The effect of delta 9-tetrahydrocannabinol (delta 9-THC) and alcohol, singly and in combination, on divided attention performance was investigated in cannabis users and non-users who were matched for alcohol use. Both cannabis and alcohol produced decrements in central and peripheral signal detections. Drug and alcohol effects were greater for signal(More)
OBJECTIVE The apolipoprotein E (ApoE) epsilon4 allele is a well-documented genetic risk factor for Alzheimer's disease (AD). Its role, if any, in the progression of cognitive and functional impairment in AD has been the subject of discrepant reports in the literature. This study aimed to determine whether ApoE epsilon4 dose is related to the progression of(More)
Interhemispheric connections were studied in tree shrews (Tupaia belangeri) after multiple injections of horseradish peroxidase or horseradish peroxidase conjugated to wheat germ agglutinin into the cortex of one cerebral hemisphere. After an appropriate survival period, the areal pattern of connections was revealed by flattening the other hemisphere,(More)
The effects of delta9-tetrahydrocannabinol (delta9-THC) and alcohol, and their combination, on divided attention performance were compared for cannabis users and non-users of both sexes. Performance by all subjects was significantly impaired following 2.6 and 5.2 mg delta9-THC but not at blood alcohol concentrations of 48 and 96 mg/100 ml. The combined(More)