ABSTRACT
OBJECTIVE: The role of visual cortex in modulation of the human eye blink reflex was assessed. METHODS: Participants were 13 patients with unilateral striate cortex damage. Nonreflexogenic gratings were presented in their intact or blind hemifield prior to white noise or air puff blink-eliciting stimuli. RESULTS: Inhibition of reflex amplitude was observed at asynchronies ranging from about 120 to 600ms for visible but not invisible prepulses. Facilitation by intact-hemifield gratings was observed for (1) the latency of the acoustic blink reflex, (2) the amplitude of the disynaptic cutaneous blink reflex, R1, and (3) the latency of voluntary hand-grip reactions to the reflexogenic stimuli. These facilitatory effects were absent on trials with blind-hemifield prepulses. CONCLUSIONS: An intact V1 is required for prepulse facilitation as well as inhibition. SIGNIFICANCE: These results extend a popular model of sensorimotor gating deficits in schizophrenia.
Subject(s)
Blinking/physiology , Brain Injuries/physiopathology , Neural Inhibition/physiology , Visual Cortex/physiology , Adolescent , Adult , Aged , Electromyography , Electrooculography , Female , Humans , Male , Middle Aged , Reaction TimeABSTRACT
The effect of a visual warning signal (1.0-6.5 s random foreperiod, FP) on the latency of voluntary (hand-grip) and reflexive (startle-eyeblink) reactions was investigated in Parkinson's disease (PD) patients and in young and aged control subjects. Equivalent FP effects on blink were observed across groups. By contrast, FP effects diverged for voluntary responses across groups with no effect of foreperiod duration for PD patients. The convergence of these results with findings from animal research suggests that interval-timing processes associated with higher level voluntary behaviors are dependent upon intact dopaminergic pathways, while those associated with lower level reflexive behaviors are spared in PD.
Subject(s)
Association Learning/physiology , Parkinson Disease/physiopathology , Psychomotor Performance/physiology , Reaction Time/physiology , Time Perception/physiology , Acoustic Stimulation , Adult , Aged , Aging/physiology , Arousal/physiology , Blinking/physiology , Cues , Female , Hand Strength/physiology , Humans , Male , Middle Aged , Muscle, Skeletal/physiology , Reflex, Startle/physiologyABSTRACT
Executive cognitive functions have been postulated to include both dynamic behavioral selection and strategic goal-setting or response preparation. To investigate the relation between these aspects of executive processing, we embedded an event-related oddball paradigm within a blocked design. Subjects responded to infrequent targets presented within a series of standard stimuli that required no response; this task alternated with a visually similar nontask condition. Using functional magnetic resonance imaging (fMRI), we found that a set of brain regions including dorsolateral prefrontal cortex (dlPFC), insular cortex, cingular cortex, and the basal ganglia demonstrated transient activation both to target stimuli and to the onset of task blocks. Within the parietal cortex, there was a dissociation such that the supramarginal gyrus exhibited greater activity to the target stimuli than to block onsets, while the converse pattern was observed in the intraparietal sulcus. Sustained positive activity during task blocks was present in the caudate and supplementary motor area, while sustained negative activity was present in the precuneus and medial parietal cortex. We conclude that dlPFC and related brain regions mediate both dynamic and strategic processing, through the preparation and selection of rules for behavior.
