Auditory attention independent of mood, medication, psychosis in BD
MedWire News: Study findings suggest that disrupted auditory attention is observed in bipolar disorder (BD) patients independent of their mood state, medication status, or history of psychotic features, but may be influenced by the presence of a comorbid anxiety disorder.
Previous studies have shown that BD patients show aberrations of event-related potential (ERP) measures of auditory processing elicited during “oddball” discrimination tasks, in which infrequent target tones presented within a series of frequent distracter tones must be identified.
“Aberrations in auditory ERPs may reflect a neurophysiologic marker, or endophenotype, for BD, but the effect of patients’ mood state, current medication usage, or history of other psychiatric disorders on these measures are not well understood,” explain Daniel Fridberg (Indiana University, Bloomington, USA) and co-authors.
The team therefore administered an auditory "oddball” discrimination task to elicit ERPs in 69 patients with type I BD, of whom 14 were unmedicated, and 52 healthy individuals with no history of psychiatric disorders. Patients were placed into subgroups based on whether they were euthymic or symptomatic, and amplitude and peak latency measures from N100, P200, N200, and P300 ERP components were compared across subgroups.
The P300 ERP component is believed to provide an index of selective attention and general cognitive efficiency, with the peak latency believed to represent stimulus evaluation speed independent of reaction time, and its amplitude representing neural activity underlying attention and memory process involved in updating stimulus representations.
N100, P200, and N200 ERP components precede the P300 in time and reflect earlier stages of information processing, the authors explain.
P300 amplitude to target tones was reduced in both the symptomatic and euthymic BD patient groups compared with controls. BD patients also had a prolongation in P300 latency compared with controls, at 408.3 versus 380.4 ms.
Furthermore, symptomatic and euthymic BD patient groups did not differ on P300 amplitude or latency, and also showed reduced P200 amplitude to frequent tones compared with controls.
Regression analysis showed that history of comorbid anxiety disorder diagnosis was associated with reduced N200 peak latency but increased P300 peak latency. No effects of medication status, history of psychotic features, or mood state on ERP measures in BD patients were observed.
Writing in the journal Bipolar Disorders, the team says that “the present study provides further support for auditory P300 amplitude as a candidate endophenotype for BD,” and “indicates that P300 latency may be sensitive to the presence of a comorbid anxiety disorder in BD patients.”
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By Ingrid Grasmo