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Biomedical subjects

Christine A Carroll

Publications and source records attributed to Christine A Carroll.

5 recordsLinked to original sources
PubMed2005

Steady state visual evoked potential abnormalities in schizophrenia.

OBJECTIVE: The steady state visual evoked potential (SSVEP) can be used to test the frequency response function of neural circuits. Previous studies have shown reduced SSVEPs to alpha and lower frequencies of stimulation in schizophrenia. We investigated SSVEPs in schizophrenia at frequencies spanning the theta (4Hz) to gamma (40Hz) range. METHODS: The SSVEPs to seven different frequencies of stimulation (4, 8, 17, 20, 23, 30 and 40Hz) were obtained from 18 schizophrenia subjects and 33 healthy control subjects. Power at stimulating frequency (signal power) and power at frequencies above and below the stimulating frequency (noise power) were used to quantify the SSVEP responses. RESULTS: Both groups showed an inverse relationship between power and frequency of stimulation. Schizophrenia subjects showed reduced signal power compared to healthy control subjects at higher frequencies (above 17Hz), but not at 4 and 8Hz at occipital region. Noise power was higher in schizophrenia subjects at frequencies between 4 and 20Hz over occipital region and at 4, 17 and 20Hz over frontal region. CONCLUSIONS: SSVEP signal power at beta and gamma frequencies of stimulation were reduced in schizophrenia. Schizophrenia subjects showed higher levels of EEG noise during photic stimulation at beta and lower frequencies. SIGNIFICANCE: Inability to generate or maintain oscillations in neural networks may contribute to deficits in visual processing in schizophrenia.

Adult↗
PubMed2004

Neural synchronization deficits to auditory stimulation in bipolar disorder.

Patients with bipolar disorder show cognitive deficits and disorganized behavior, which may reflect a disturbance in neural synchronization. We tested whether EEG measures of auditory neural synchronization were abnormal in bipolar disorder. Nineteen symptomatic patients with bipolar disorder and 32 non-psychiatric control subjects were evaluated. Click trains (500 ms duration) presented at 20, 30, 40 and 50 Hz were used to evoke EEG synchronization. Patients with bipolar disorder showed reduced power across the frequencies of stimulation. Phase-locking across trials was also disturbed in bipolar disorder, consistent with poor phase synchronization between the stimulus and EEG. Abnormal high frequency neural synchronization may contribute to cognitive deficits in bipolar disorder.

Acoustic Stimulation↗
PubMed2004

P50 and acoustic startle gating are not related in healthy participants.

Although P50 event-related potential (ERP) suppression and acoustic startle prepulse inhibition are conceptualized as measures of sensory and sensorimotor gating, respectively, the relationship between these measures is unclear. In the present study, P50 and prepulse inhibition trials were interleaved in a single testing session to determine their relationship. Thirty-one healthy participants were presented with startle- and P50-eliciting stimuli across six trial blocks. Lead stimuli (i.e., the prepulse to the acoustic startle and the first click in the dual click ERP paradigm) resulted in significant gating, or amplitude attenuation, of responses to the startle probe and second paired click. There were no meaningful correlations between the P50 and prepulse inhibition variables, indicating that P50 suppression and acoustic startle prepulse inhibition measure distinct neural mechanisms. The implications of these findings for operationally defining the psychological construct of gating with these psychophysiological measures are discussed.

Acoustic Stimulation↗
PubMedDate not supplied

Haloperidol impairs learning and error-related negativity in humans.

Humans are able to monitor their actions for behavioral conflicts and performance errors. Growing evidence suggests that the error-related negativity (ERN) of the event-related cortical brain potential (ERP) may index the functioning of this response monitoring system and that the ERN may depend on dopaminergic mechanisms. We examined the role of dopamine in ERN and behavioral indices of learning by administering either 3 mg of the dopamine antagonist (DA) haloperidol (n = 17); 25 mg of diphenhydramine (n = 16), which has a similar CNS profile but without DA properties; or placebo (n = 18) in a randomized, double-blind manner to healthy volunteers. Three hours after drug administration, participants performed a go/no-go Continuous Performance Task, the Eriksen Flanker Task, and a learning-dependent Time Estimation Task. Haloperidol significantly attenuated ERN amplitudes recorded during the flanker task, impaired learning of time intervals, and tended to cause more errors of commission, compared to placebo, which did not significantly differ from diphenhydramine. Drugs had no significant effects on the stimulus-locked P1 and N2 ERPs or on behavioral response latencies, but tended to affect post-error reaction time (RT) latencies in opposite ways (haloperidol decreased and diphenhydramine increased RTs). These findings support the hypothesis that the DA system is involved in learning and the generation of the ERN.

Adult↗