Tamara Hershey

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N-methyl-D-aspartate (NMDA) glutamate receptor antagonists are reported to induce schizophrenia-like symptoms in humans, including cognitive impairments. Shortcomings of most previous investigations include failure to maintain steady-state infusion conditions, test multiple doses and/or measure antagonist plasma concentrations. This double-blind,(More)
This study is the first report on the effects of total sleep deprivation (about 32 h) on regional cerebral glucose metabolism during wakefulness in man, using positron emission tomography (PET) with F-18 deoxyglucose (FDG). Sleep deprivation leads to a significant reorganization of regional cerebral metabolic activity, with relative decreases in the(More)
BACKGROUND Glucocorticoids (GCs) can regulate hippocampal metabolism, physiologic functions, and memory. Despite evidence of memory decreases during pharmacological GC treatment, and correlations between memory and cortisol levels in certain disease conditions, it remains unclear whether exposure to the endogenous GC cortisol at levels seen during physical(More)
OBJECTIVE To test the hypothesis that subthalamic nucleus (STN) stimulation in Parkinson disease (PD) patients affects working memory and response inhibition performance, particularly under conditions of high demand on cognitive control. METHODS To test this hypothesis, spatial working memory (spatial delayed response [SDR]) and response inhibition(More)
OBJECTIVE To assess whether subthalamic nuclei (STN) stimulation's primary mechanism of action is to drive or inhibit output neurons. METHODS Cerebral blood flow responses to STN stimulation were measured using PET in 13 patients with Parkinson disease. Patients were scanned with stimulators off and on (six scans each condition). Clinical ratings, EMG,(More)
Dopamine can induce fascinating, complex human behavioral states, including disinhibition, euphoria, or elaborate stereotypies, whereas dopamine deficiency can cause anxiety or sadness. Limited data suggest that these phenomena may involve dysfunction of orbital frontal cortex, cingulate cortex, or ventral striatum. The dopamine D3 receptor (D3R) has an(More)
The basal ganglia are thought to be important in the selection of wanted and the suppression of unwanted motor patterns according to explicit rules (i.e. response inhibition). The subthalamic nucleus has been hypothesized to play a particularly critical role in this function. Deep brain stimulation of the subthalamic nucleus in individuals with Parkinson's(More)
BACKGROUND AND OBJECTIVE Deep brain stimulation (DBS) of the ventral intermediate nucleus of the thalamus (VIM) provides remarkable relief of tremor in the limbs contralateral to the side of the brain stimulated. The benefits have been sufficiently dramatic that this is now an accepted clinical treatment of essential as well as other forms of tremor.(More)
Glucocorticoids (GCs) have a variety of effects on the brain including site-preferential, inhibitory effects on hippocampal neurons. In the case of dexamethasone (DEX), extended rather than single-dose treatment in vivo may be required for binding to brain rather than peripheral (e.g., pituitary) GC receptors and for maximizing other biologic effects in(More)
Dopamine has been hypothesized to modulate response inhibition. To test this hypothesis, we used functional magnetic resonance imaging (fMRI) to measure the effects of the dopamine prodrug levodopa on the brain responses to a well-validated response inhibition task (go/no-go, or GNG). Since abnormalities of response inhibition and dopamine have been thought(More)