MRI Study Reveals Inner Workings of Brain During Imagery

Subjects were 10 people with high degrees of alexithymia (HDA) and 10 subjects with low degrees of alexithymia (LDA), who were selected according to their scores on the 20-item Toronto Alexithymia Scale (TAS-20). The two groups' regional cerebral activation was compared during various imagery conditions - imagining a past happy (PH) event, a past sad (PS) event, a past neutral (PN) event, a future happy (FH) event, a future sad (FS) event, and a future neutral (FN) event. The activation levels during these conditions were compared with those during a rest condition (REST).

T tests showed that the mean subjective ratings of both the vividness of the imagery and the intensity of emotion during the imagery were higher in the subjects with LDA than in those with HDA for the PS and FS imagery conditions. On the other hand, relative to the LDA group, the HDA group showed significantly less activation in the posterior cingulate cortex (this is the part of the brain that puts the brakes on alarm activation and settles the system down after a threat) during the PH and FH imagery conditions compared with REST and during the FH imagery condition compared with the FN imagery condition.

The pilot study findings suggest an association between a high degree of alexithymia and reduced activation of the posterior cingulate during happy imagery. Given the function of this brain region, these results might be related to a dysfunction of episodic memory retrieval during happy imagery in subjects with HDA.

Citation: Mantani T, Okamoto Y, Shirao N, Okada G, Yamawaki S. Reduced activation of posterior cingulate cortex during imagery in subjects with high degrees of alexithymia: a functional magnetic resonance imaging study. Biological Psychiatry. 2005 May 1; 57(9): pages 982-90.