Dopamine and Dreams
Research suggests that dopamine has a large influence on our dreams.
Posted Jan 08, 2016
The role of dopamine in REM sleep, dream recall, and dream content has come under increasingly stronger scrutiny in recent years. This is theoretically important for understanding sleep and dreams because dopamine is a very well characterized neurotransmitter that is central to fundamental motivational and cognitive activities of human beings. Its role in REM sleep and dreams was for many years obscure given the general view that catecholaminergic activity during REM sleep was reduced. Noradrenergic activity appears to be clearly reduced in REM but the picture is more complex for dopamine.
Early indicators that dopaminergic activity in the limbic emotional brain and in the frontal lobes might be enhanced during REM sleep was that dream recall was reduced or dramatically altered in conditions with aberrant dopamine activity playing a causally central role.
For example, REM intrusion in narcolepsy and in schizophrenia seem to be associated with hallucinatory experiences that could be revered with anti-dopamine agents. People with frontal lobectomies (the frontal lobes are a primary projection site of dopamine fibers) reported reduced dream recall. Mark Solms in his landmark work on brain lesions and dream recall supported the association between dream recall and frontal lobes. He proposed that dreaming was at least in part a wish fulfillment process (as proposed by Freud) with dopamine fueling the hallucinatory wish fulfillment dream content. He also argued that dreams occur both within and outside REM which is clearly the case.
The recent data on dopaminergic influences on REM sleep, dream recall and dream content suggests that Solms did not need to appeal to NREM dreaming to support the role of dopamine in dreams. A number of animal studies and studies in human populations strongly supports the idea that dopamine is central to REM physiology, dream recall and dream content. Lampros Perogamvrosa and Sophie Schwartz, of the University of Geneva, Switzerland in their recent paper “The roles of the reward system in sleep and dreaming.” published in Neuroscience and Biobehavioral Reviews (volume 36, 2012, pages 1934–1951) reviews a lot of this recent literature. Perogamvrosa and Schwartz present what they call their ‘Reward Activation Model’ (RAM) of sleep and dreams.
The authors integrate recent neurophysiological, neuroimaging, and clinical findings that point to significant activation of the mesolimbic dopaminergic (ML-DA) reward system during both NREM (N2 in humans, SWS in rats) and REM sleep. With regard to REM dopamine bursting activity within the ventral tegmental area is elevated. This is significant because this is precisely what occurs in the waking brain when it is processing stimuli that is surprising or of special significance.
These data on dopamine activity in REM are consistent with the long standing finding concerning theta rhythm activity during REM in many animals including to some extent in humans. Both phasic bursting of dopamine neurons in VTA in REM and theta activity suggest that REM is processing information of special significance to the organism. But we need more information on the role of dopamine in REM in humans. One way to look at dopamine’s role in REM in humans is to study REM, dream recall and content in people with altered levels of dopamine in their central nervous systems.
De Gennaro and associates have recently reported (De Gennaro L, Lanteri O, Piras F, Scarpelli S, Assogna F, Ferrara M, Caltagirone C, Spalletta G Dopaminergic system and dream recall: An MRI study in Parkinson's disease patients. Hum Brain Mapp. 2015 Dec 24. doi: 10.1002/hbm.23095. [Epub ahead of print]) an interesting set of associations between indirect measures of dopaminergic activity and dream recall in a group of patients with Parkinson’s Disease (PD).
They studied sleep parameters, dream recall, dream content and MRI scans of various brain regions in 27 patients with Parkinson’s Disease (PD) and 27 age-matched controls. People with PD suffer a loss of central dopamine and the disease is treated with dopamine replacement therapy. Multivariate correlational analyses in PD patients revealed that dopamine agonist dosage was associated to lower bizarreness and lower emotional load values in dreams. Visual vividness (VV) of their dream reports positively correlated with volumes of both the amygdalae and with thickness of the left medial prefrontal cortex (mPFC).
The authors argue in the abstract to the paper that “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.”
Given that the amygdala is a highly activated site during REM it is not surprising that vividness of dream reports correlated with volume of the amygdala. The relation of agonist dosage level with lower emotional values in dreams is counter-intuitive for me. Agonist generally stimulate the ventral striatum or the nucleus accumbens circuit which is crucial for emotional processing. Perhaps higher dosage indicate more efficient processing of emotional information and therefore less emotional information in overt dream content?
In any case the Gennaro et al paper adds the growing literature supporting a central role of dopamine in the dream generation process and a more general role of REM in the process of selection and consolidation of significant emotional memories.