Biomedical subjects

Jessica Irwin

Publications and source records attributed to Jessica Irwin.

4 recordsLinked to original sources

PubMed2005

M50 sensory gating predicts negative symptoms in schizophrenia.

Impaired auditory sensory gating is considered characteristic of schizophrenia and a marker of the information processing deficit inherent to that disorder. Predominance of negative symptoms also reflects the degree of deficit in schizophrenia and is associated with poorer pre-morbid functioning, lower IQ, and poorer outcomes. However, a consistent relationship between auditory sensory gating and negative symptoms in schizophrenia has yet to be demonstrated. The absence of such a finding is surprising, since both impaired auditory gating and negative symptoms have been linked with impaired fronto-temporal cortical function. The present study measured auditory gating using the P50 event related potential (ERP) in a paired-click paradigm and capitalized on the relative localization advantage of magnetoencephalography (MEG) to assess auditory sensory gating in terms of the event related field (ERF) M50 source dipoles on bilateral superior temporal gyrus (STG). The primary hypothesis was that there would be a positive correlation between lateralized M50 auditory sensory gating measures and negative symptoms in patients with schizophrenia. A standard paired-click paradigm was used during simultaneous EEG and MEG data collection to determine S2/S1 sensory gating ratios in a group of 20 patients for both neuroimaging techniques. Participants were administered the Schedule for the Assessment of Negative Symptoms (SANS), the Positive and Negative Symptom Scale (PANSS), and the Calgary Depression Scale for Schizophrenia. Consistent with previous reports, there was no relationship between ERP P50 sensory gating and negative symptoms. However, right (not left) hemisphere ERF M50 sensory gating ratio was significantly and positively correlated with negative symptoms. This finding is compatible with information processing theories of negative symptoms and with more recent findings of fronto-temporal abnormality in patients with predominantly negative symptoms.

Adolescent↗

PubMed2005

Distinct M50 and M100 auditory gating deficits in schizophrenia.

The time course of the schizophrenia auditory gating deficit may provide clues to mechanisms of impaired cognition. Magnetoencephalography was recorded during a standard paired-click paradigm. Using source strength of the M50 and M100 components for each click, calculated from dipole locations identified as underlying each component for the first click, a ratio of the second divided by the first was used to measure gating. Patients showed a left-hemisphere gating deficit in M50 and a bilateral gating deficit in M100. Hypothesizing that an early deficit may affect later processing, hierarchical regression was used to examine variance shared between the components. A left-hemisphere M100 gating deficit was coupled with the left M50 gating deficit. In contrast, a right-hemisphere M100 gating deficit was unrelated to M50 gating in either hemisphere. Investigations of interhemisphere gating relations may clarify group differences in regional connectivity and their role in gating.

Adult↗

PubMed2003

Visual processing of facial affect.

To evaluate the role of the fusiform gyrus in identifying and processing facial emotional expression in humans, MEG data were collected while six healthy subjects judged whether photographs of faces displayed emotion (happiness or disgust) compared to neutral faces and equiluminant scrambled faces. For all six subjects, a magnetic source localizing to right fusiform gyrus was evident approximately 150 ms following presentation of face stimuli, but not following non-face stimuli. MEG source strength for this component was greatest for happy, intermediate for disgust, and lowest for neutral facial expressions, suggesting that activity in fusiform gyrus is sensitive to both face-specific stimuli and to the affective content of the face. These findings are considered in the context of a specialized neural face-dependent information system.

Adult↗

PubMed2003

Lateralization of auditory sensory gating and neuropsychological dysfunction in schizophrenia.

OBJECTIVE: Sensory gating assessed via EEG in a paired-click paradigm has often served as a neurophysiological metric of attentional function in schizophrenia. However, the standard EEG measure of sensory gating using the P50 component at electrode Cz does not foster differential assessment of left and right hemisphere contributions. Magnetoencephalography (MEG) is complementary to EEG, and its analogous M50 component may be better suited for localization and analysis of such lateralized cortical generators. The authors hypothesized that 1) auditory gating would be evident in M50 sources in superior temporal gyrus, demonstrating ratios similar to P50; 2) M50 would resemble P50 in distinguishing gating in comparison subjects and patients with schizophrenia, but M50 would show lateralization of the gating deficit; and 3) P50 and M50 sensory gating ratios would predict neuropsychological measures in patients and comparison subjects, with the MEG identification of left and right hemisphere sources allowing for the evaluation of lateralization in brain-behavior relationships. METHOD: Event-related EEG and MEG recordings were simultaneously obtained from 20 patients with schizophrenia and 15 comparison subjects. P50 amplitudes, M50 dipole source strengths, and P50 and M50 gating ratios were compared and assessed with respect to scores on neuropsychological performance measures. RESULTS: M50 dipoles localizing to superior temporal gyrus demonstrated gating similar to that of P50. As expected, patients demonstrated less P50 gating than did comparison subjects. Left (but not right) hemisphere M50 gating 1) correlated with EEG gating, 2) differentiated patients and comparison subjects, and 3) correlated with neuropsychological measures of sustained attention and working memory. CONCLUSIONS: Converging evidence from EEG, MEG, and neuropsychological measures points to left hemisphere dysfunction as strongly related to the well-established sensory gating deficit in schizophrenia.

Acoustic Stimulation↗