MedWire News: The retrieval of emotionally charged memories is impaired in patients with bipolar disorder, say researchers who believe that defects in amygdala brain circuitry may be the root cause of this impairment.
The results appear to be consistent with those of previous studies showing that bipolar patients are less able to accurately recognize emotions in people's faces than mentally healthy controls.
Cognitive impairments have been well documented in bipolar disorder and are associated with problems in social and occupational functioning, note Lakshmi Yatham (University of British Columbia, Vancouver, Canada) and colleagues in the British Journal of Psychiatry.
While verbal and nonverbal episodic memory have been intensively studied, emotional memory has yet to be examined in patients with bipolar disorder.
In the present study, Yatham and co-workers investigated emotional memory in 20 euthymic patients with bipolar I or II disorder and 20 mentally healthy controls.
The researchers presented 10 patients and 10 controls with slide-show stories that had emotionally arousing content, and presented 10 patients and 10 controls with stories that were considered emotionally neutral.
Participants were asked to recall information from these stories 1 week later with multiple-choice questions, and were also asked to rate the emotional impact of stories.
Overall, mentally healthy controls were able to recall more information about the stories than patients with bipolar disorder, with 38% of correct answers versus 30%. This result is reflective of general cognitive memory impairments seen in patients with bipolar disorder, say Yatham et al.
Mentally healthy controls who listened to emotionally arousing stories were better able to recall information than controls who listened to emotionally neutral stories. Yatham et al say that this is an expected adaptive response since emotional stimuli are "more important for survival."
By contrast, bipolar patients who were read emotionally arousing stories did not show greater retrieval of information than bipolar patients who were read emotionally neutral stories.
Interestingly, bipolar patients scored both emotionally arousing and emotionally neutral stories with high emotional impact scores.
Yatham et al comment: "This may suggest that people with bipolar disorder may have an oversensitive emotional reaction to facts, which is not functional because it can be restrictive for the ability to focus on the real emotional content."
They add: "One can speculate that this altered perception may lead individuals to remember neutral stimuli as emotional, thus making them more susceptible to interpreting life events as traumatic."
Yatham and colleagues also note that patients with bilateral amygdala damage who have had a temporal lobectomy show a compromised ability to form enhanced emotional memories, implicating this brain region in emotional memory.
Free abstract
