Dopaminergic system and dream recall: An MRI study in Parkinson's disease patients.

Patients with Parkinson's Disease (PD) show no substantial differences from healthy controls in sleep, dream, or neuroanatomical measures. Higher dopamine agonist dosages in PD patients are associated with qualitatively impoverished dreams—lower bizarreness and emotional load. Visual vividness of dream reports positively correlates with amygdala volume and left medial prefrontal cortex thickness, while emotional load correlates with hippocampal volume. These findings support the hypothesis that a dopamine network involving the amygdala and medial prefrontal cortex plays a key role in dream generation, though causal relations cannot be established due to limitations in using dopamine agonist dosage as a proxy for hypodopaminergic state.

Study at a glance

Abstract

We investigated the role of the dopamine system [i.e., subcortical-medial prefrontal cortex (mPFC) network] in dreaming, by studying patients with Parkinson's Disease (PD) as a model of altered dopaminergic transmission. Subcortical volumes and cortical thickness were extracted by 3T-MR images of 27 PD patients and 27 age-matched controls, who were asked to fill out a dream diary upon morning awakening for one week. PD patients do not substantially differ from healthy controls with respect to the sleep, dream, and neuroanatomical measures. Multivariate correlational analyses in PD patients show that dopamine agonist dosage is associated to qualitatively impoverished dreams, as expressed by lower bizarreness and lower emotional load values. Visual vividness (VV) of their dream reports positively correlates with volumes of both the amygdalae and with thickness of the left mPFC. Emotional load also positively correlates with hippocampal volume. Beside the replication of our previous finding on the role of subcortical nuclei in dreaming experience of healthy subjects, this represents the first evidence of a specific role of the amygdala-mPFC dopaminergic network system in dream recall. The association in PD patients between higher dopamine agonist dosages and impoverished dream reports, however, and the significant correlations between VV and mesolimbic regions, however, provide an empirical support to the hypothesis that a dopamine network plays a key role in dream generation. The causal relation is however precluded by the intrinsic limitation of assuming the dopamine agonist dosage as a measure of the hypodopaminergic state in PD. Periodicals, Inc.