Hippocampal volume linked to verbal memory performance in BD patients
MedWire News: Results from a US study show that reduced hippocampal volume is associated with increased verbal memory impairment in patients with bipolar disorder (BD).
"Findings from both postmortem histochemical studies and neuroimaging research demonstrate structural hippocampal abnormalities in BD, including decreased cell density, abnormal markers of neuronal function and plasticity, and decreases in hippocampus volume," explain Hilary Blumberg (Yale University School of Medicine, New Haven, Connecticut) and team.
They add: "Consistent with these neurobiological findings, deficits in verbal memory functions that are subserved by the hippocampus are the cognitive abnormalities most consistently identified in individuals with BD."
To investigate whether hippocampal volume is associated with verbal memory impairments in BD patients, the team studied 31 individuals, aged 20-58 years, with the mood disorder and 32 mentally healthy controls, aged 19-58 years.
There were no significant between-group differences regarding mean age, education level, gender distribution, or IQ, the team notes in Biological Psychiatry.
The researchers used magnetic resonance imaging (MRI) to assess the participants for hippocampal volume, and the California Verbal Learning Test-Second Edition (CVLT) was used to assess total immediate recall, short and long delay free recall, and short and long delay cued recall.
Results from the MRI scans revealed that BD patients had significantly reduced hippocampus volumes compared with controls, at a mean of 2588 mm3 versus 2748 mm3.
BD patients also had significantly poorer CVLT scores than controls for total immediate recall (50.0 vs 57.2), short delay cued recall (-0.32 vs 0.49), short delay free recall (-0.25 vs 0.52), and long delay cued recall (-0.30 vs 0.26), and a trend towards poorer scores for long delay free recall.
In BD patients, hippocampus volume was positively associated with CVLT scores for total immediate recall, short delay cued recall, long delay free recall, and long delay cued recall, after accounting for total brain volume.
There were no significant associations between hippocampal volume and CVLT performance measures in controls, the researchers note.
Blumberg and team conclude: "This work demonstrates a positive correlation between smaller hippocampus volume and performance deficits on the CVLT in individuals with BD."
They add: "Future research that includes systematic study of medication and clinical course, as well as exploration of the genetic mechanisms that underlie the hippocampus morphological changes in BD, are needed."
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By Mark Cowen