The role of the amygdala in dreaming

Abstract

Neuro-imaging studies have strongly implicated the basolateral amygdala in dreaming (e.g. Maquet et al., 1996). Various neuropsychological dream theorists (Domhoff, 2001; Hobson, Pace-Schott & Stickgold, 2000; Revonsuo, 2000) propose central roles for the amygdala in dreaming (particularly in the generation of dream affect); however, little empirical research on its function in dreaming exists. Urbach-Wiethe Disease (UWD) is a very rare genetic condition that can lead to calcifications in the medial temporal lobes. This study analysed 26 dream reports collected from eight adult UWD patients with fully calcified basolateral amygdalae bilaterally, and compared them to 58 dream reports collected from 17 matched controls. Dream affect and various other dream characteristics were examined. A number of significant results of small to moderate effect size were found. Notably, UWD patients’ dream reports had a significantly higher mean intensity of positive affect than controls’ dream reports, a significantly lower mean intensity of negative affect, a significantly higher mean intensity of PLAY, and a significantly lower mean intensity of RAGE. The UWD patients’ dream reports were also significantly more wish-fulfilling than the controls’ dream reports, were significantly less likely to be classified as nightmares, and had a significantly lower word count and narrative item count. These results are consistent with an extensive literature that implicates the basolateral amygdala in fear conditioning, emotional appraisal and in similar affective processes in waking life (e.g. LeDoux, 2003; Pessoa, 2010). The dream reports were also analysed for instances of threat and escape, as well as for approach and avoidance behaviour, in order to test some of the hypotheses central to Revonsuo’s (2000) threat simulation theory (TST) of dreaming. These analyses produced no significant results. Given that the amygdala is essential to Revonsuo’s (2000) conceptualisation of dreaming as an evolutionarily adaptive mechanism to safely simulate threat avoidance, these findings contradict some of TST’s central predictions. In general, these findings suggest that the average dream of persons with bilateral basolateral amygdalae damage is significantly simpler, more pleasant, less unpleasant, more wish-fulfilling and less likely to be a nightmare than the average control dream. As such, the dream reports of the UWD patients seem strikingly similar to the dreams of young children.