Relational memory in psychotic bipolar disorder

Recent research has highlighted the phenotypic and genetic overlap of bipolar disorder and schizophrenia. Cognitive deficits in bipolar disorder parallel those seen in schizophrenia, particularly for bipolar disorder patients with a history of psychotic features. Here we explored whether relational memory deficits, which are prominent in schizophrenia, are also present in patients with psychotic bipolar disorder.

We tested 25 patients with psychotic bipolar disorder on a relational memory paradigm previously employed to quantify deficits in schizophrenia. During the training, participants learned to associate a set of faces and background scenes. During the testing, participants viewed a single background overlaid by three trained faces and were asked to recall the matching face, which was either present (Match trials) or absent (Non-Match trials). Explicit recognition and eye-movement data were collected and compared to those for 28 schizophrenia patients and 27 healthy subjects from a previously published dataset.

Contrary to our prediction, we found psychotic bipolar disorder patients were less impaired in relational memory than schizophrenia subjects. Bipolar disorder subjects showed eye-movement behavior similar to healthy controls, whereas schizophrenia subjects were impaired relative to both groups. However, bipolar disorder patients with current delusions and/or hallucinations were more impaired than bipolar disorder patients not currently experiencing these symptoms.

We found that patients with psychotic bipolar disorder had better relational memory performance than schizophrenia patients, indicating that a history of psychotic symptoms does not lead to a significant relational memory deficit.