Abstract
Potential abnormalities in the structure and function of the temporal lobes have been studied much less in bipolar disorder than in schizophrenia. This may not be justified because language-related symptoms, such as pressured speech and flight of ideas, and cognitive deficits in the domain of verbal memory are amongst the hallmark of bipolar disorder (BD), and contribution of temporal lobe dysfunction is therefore likely. In the current study, we examined resting-state functional connectivity (FC) between the auditory cortex (Heschl’s gyrus [HG], planum temporale [PT]) and whole brain using seed correlation analysis in n = 21 BD euthymic patients and n = 20 matched healthy controls and associated it with verbal memory performance. In comparison to controls BD patients showed decreased functional connectivity between Heschl’s gyrus and planum temporale and the left superior and middle temporal gyrus. Additionally, fronto-temporal functional connectivity with the right inferior frontal/precentral gyrus and the insula was increased in patients. Verbal episodic memory deficits in the investigated sample of BD patients and language-related symptoms might therefore be associated with a diminished FC within the auditory/temporal gyrus and a compensatory fronto-temporal pathway.
Highlights
The classical Kraepelinian dichotomy of major psychotic disorders into dementia praecox, a disease of relentless progression with prominent cognitive abnormalities, and manic depression, a cyclic disorder without progressive loss of cognitive functions, is increasingly being challenged on clinical and biological grounds [1]
Further tests for group differences showed no significant differences between the groups for the negative affect (NA) of the PANAS
Controls performed significantly better than bipolar disorder (BD) patients in California Verbal Learning Test (CVLT)’s
Summary
The classical Kraepelinian dichotomy of major psychotic disorders into dementia praecox (later termed schizophrenia), a disease of relentless progression with prominent cognitive abnormalities, and manic depression, a cyclic disorder without progressive loss of cognitive functions, is increasingly being challenged on clinical and biological grounds [1]. One of the central questions is whether schizophrenia and manic depressive or bipolar disorder (BD) are parts of a spectrum of disorders with varying cognitive, affective and other psychopathological deficits In both disorders, dysfunctions in language-related memory such as verbal episodic memory have been reported and may be affected during both acute episodes and remitted state (schizophrenia: [2]; bipolar: [3,4,5,6,7]). The superior temporal cortex as main language and speech brain area is known to be functionally and structurally asymmetric, and in most healthy right-handers left Heschl’s Gyrus (HG) and PT are larger than its right hemisphere counterpart [9]. The findings of [15] are of interest, as they suggest that the structural alterations in BD within the superior temporal cortex may be asymmetric
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