Verbal memory impairment in new onset bipolar disorder: Relationship with frontal and medial temporal morphology

Abstract

Objectives. Verbal memory (VM) impairment is a trait feature of bipolar I disorder (BDI) that is present at illness onset and associated with functional outcome. However, little is known about the morphological abnormalities underlying this deficit early in the disease course. This study examined the neurobiological correlates of VM impairment in euthymic newly diagnosed patients, with attention to frontal and medial temporal (MT) structures known to contribute to VM. Methods. Euthymic patients with BDI recently recovered from their first episode of mania (n = 42) were compared with healthy subjects (n = 37) using measures of the California Verbal Learning Test (CVLT-II) associated with frontal and MT functioning. A subset of participants had 3T MRI scan (n = 31 patient group, n = 30 healthy subject group). Hippocampal and prefrontal volumes were analyzed using FreeSurfer 5.1 and correlated with their corresponding CVLT-II subscores. Results. Patients showed decreased performance in total learning as well as short and long delay verbal recall. Consistent with MT dysfunction, they also showed deficits in recognition discriminability and learning slope. In the patient group only, left hippocampal volumes were negatively correlated with these measures. Conclusions. These results suggest that anomalous MT functioning is involved with VM impairment early in the course of BDI.

Key Words::

• bipolar I disorder
• hippocampus
• verbal memory
• neuropsychological tests
• MRI

Acknowledgements

The data for this manuscript was generated from the Systematic Treatment Optimization Program for Early Mania (STOP-EM), which was supported by an unrestricted grant funding from Astrazeneca Canada.

Statement of interest

Dr Lam has received research funds from or is on ad-hoc speaker/advisory boards for AstraZeneca, Bristol-Myers Squibb, Canadian Institutes of Health Research, Canadian Network for Mood and Anxiety Treatments, Canadian Psychiatric Association Foundation, Eli Lilly, Litebook Company, Lundbeck, Lundbeck Institute, Mochida, Pfizer, Servier, St. Jude Medical, Takeda, and UBC Institute of Mental Health/Coast Capital Savings. Dr Yatham has received research grants from or is on speaker/advisory boards for AstraZeneca, Bristol-Myers Squibb, Canadian Institutes of Health Research, Canadian Network for Mood and Anxiety Treatments, Eli Lilly & Co., Forest, GlaxoSmithKline, Janssen, Lundbeck, Michael Smith Foundation for Health Research, Novartis, Otsuka, Pfizer, Ranbaxy, Servier, and the Stanley Foundation. Dr. Torres has been a consultant with Lundbeck. Dr. Chakrabarty and Jan-Marie Kozicky report no disclaimers.

Supplementary material available online

Supplementary Table I and II