Impaired allocentric spatial memory in patients with affective disorders.

BACKGROUND: Memory disturbances are frequent in unipolar depression (UD) and bipolar disorder (BD) and may comprise important predisposing and maintaining factors. Previous studies have demonstrated hippocampal abnormalities in UD and BD but there is a lack of studies specifically assessing hippocampus-dependent memory. METHODS: We used a virtual task to assess hippocampus-dependent (allocentric) vs non-hipppocampal (egocentric) spatial memory in remitted and partially remitted patients with UD or BD (N = 22) and a healthy control group (N = 32). Participants also completed a range of standard neuropsychological and functional assessments. RESULTS: Participants in the UD/BD group showed selective impairments on high-load hippocampal (allocentric) memory compared to egocentric memory and this effect was independent of residual mood symptoms. Across both samples, both allocentric and egocentric spatial memory correlated with more general measures of memory and other aspects of cognition measured on standard neuropsychological tests but only high-load allocentric memory showed a significant relationship with functional capacity. CONCLUSION: Results show a selective impairment in high-load allocentric spatial memory compared to egocentric memory in the patient group, suggesting impaired hippocampal functioning in patients with remitted UD/BD.

Virtual reality assessment of daily life executive functions in mood disorders: associations with neuropsychological and functional measures.

BACKGROUND: Mood disorders are often accompanied by cognitive difficulties that impede patients' functional capacity. However, neuropsychological tests provide limited insight into patients' ability to tackle daily life cognitive challenges. To address this challenge, we investigated the sensitivity and validity of the Jansari assessment of Executive Functions (JEF©) virtual reality test in patients with mood disorders and its associations with functional capacity. METHODS: In total, 21 patients with bipolar disorder or unipolar disorder in full or partial remission and 29 healthy control participants were recruited for the study. Participants attended one test session during which they underwent diagnostic assessments, mood ratings and assessments with JEF©, a battery of standard neuropsychological tests (RAVLT, Trial Making A and B, Fluency tests, letter-number sequencing and RBANS digit span and coding tests) and functional capacity measures (UPSA-B and FAST). RESULTS: Patients showed impaired executive functions on JEF© compared to the control group. Relative to the control group, patients were also impaired on neuropsychological sub-composite scores of executive function, verbal memory and processing speed as well as on a global cognition composite score. In addition, JEF© scores predicted performance on a global cognition composite based on neuropsychological tests, and a performance-based measure of functional capacity. LIMITATIONS: This study had a relatively small sample size and included a mixed group of patients with unipolar or bipolar disorder. CONCLUSIONS: JEF© is a sensitive and valid measure of daily life executive impairments in patients with mood disorders that is associated with functional capacity.

Wakeful rest compared to vigilance reduces intrusive but not deliberate memory for traumatic videos.

Intrusive memories are prominent features of post-traumatic stress disorder, but the mechanisms supporting their development, and their relationship to deliberate memories, are subject to competing theories. Are they strengthened examples of a unitary memory system, or fragmented representations lacking aspects of healthy memories? Given the importance of post-encoding processing in memory consolidation, we investigated the effects of a brief wakeful rest compared to a vigilance task immediately after the encoding of traumatic material on subsequent intrusive and deliberate memory. Across two experiments, participants watched emotionally negative film clips immediately followed by a brief wakeful rest or a simple vigilance (0-back) task. Brief wakeful rest had distinct effects on memory compared to the 0-back task, reducing intrusive memory frequency but not changing deliberate memory performance. These differential effects suggest that intrusive memory and deliberate memory reflect dissociable systems, arguing against unitary accounts. Our findings highlight the importance of post-encoding processing in the consolidation of traumatic material and the development of intrusive memories and provide a new perspective for interpreting mechanisms of therapeutic intervention.

Opposing effects of negative emotion on amygdalar and hippocampal memory for items and associations.

Although negative emotion can strengthen memory of an event it can also result in memory disturbances, as in post-traumatic stress disorder (PTSD). We examined the effects of negative item content on amygdalar and hippocampal function in memory for the items themselves and for the associations between them. During fMRI, we examined encoding and retrieval of paired associates made up of all four combinations of neutral and negative images. At test, participants were cued with an image and, if recognised, had to retrieve the associated (target) image. The presence of negative images increased item memory but reduced associative memory. At encoding, subsequent item recognition correlated with amygdala activity, while subsequent associative memory correlated with hippocampal activity. Hippocampal activity was reduced by the presence of negative images, during encoding and correct associative retrieval. In contrast, amygdala activity increased for correctly retrieved negative images, even when cued by a neutral image. Our findings support a dual representation account, whereby negative emotion up-regulates the amygdala to strengthen item memory but down-regulates the hippocampus to weaken associative representations. These results have implications for the development and treatment of clinical disorders in which diminished associations between emotional stimuli and their context contribute to negative symptoms, as in PTSD.