Functional Neuroanatomy of Human Rapid-Eye-Movement

Sleep and DreamingPierre Maquet, Jean-Marie Peters , Joel Aerts , Guy

Delfiore, Christian Degueldre, Andre Luxen , & Georges Franck

Sharon Dhaliwal

Introduction

What is the purpose of this study? To use positron emission topography & statistical parametric mapping to study the brain state associated with REM sleep in humans

What is REM sleep? it is associated with intense neuronal activity, ocular saccades, muscular atonia & dreaming

MethodSubjects: 30 right-handed male subjects Mean age: 22.5 years old (range 20-25 years

old)

Subjects were monitored polygraphically over 3 nights spent on a scanner couch, at one-week intervals

Subjects were selected based on those who could maintain two periods of slow wave sleep & 20 minutes of REM sleep during the first two test nights

On the third night, regional cerebral blood flow (rCBF) distribution was recorded during sleep

Scans were done when polysomnography showed characteristic sleep patterns (slow-wave & REM sleep)

After each sleep scan, the subjects were woken up & asked to describe what was in their minds

Experimental Task

ResultsPositive correlations: Pontine tegmentum Left thalamus Left & right amygdaloid complexes Anterior cingulate cortex Right parietal operculum

ResultsNegative Correlations: Dorsofrontal prefrontal cortex Parietal cortex Posterior cingulate cortex Precuneus

Discussion Amygdaloid complexes are involved in the

formation & consolidation of memories paired with emotional stimuli

Previous neuroimaging studies suggest that dorsolateral prefrontal areas & precuneus involved in the encoding & retrieval of episodic memory- this study showed that these memory processes are not prominent during REM sleep

Discussion cont’d Coactivation of anterior cingulate cortex

& amygdaloid complexes could account for the emotional & affective aspects of dreams

Other formal characteristics of dreams (temporal distortions, weakening of self-reflective control, amnesia or awakening) might be related to the relative prefrontal deactivation

STRENGTHS Results from the rCBF distribution agree with previous research that suggests there is a functional link between the amygdala, the hippocampal formations & cortical areas during REM sleep

These results shed light on the idea that amygdalocortical activation could account for the perceptual components of dreaming

This study looked at both positive and negative correlations of PET data

NEXT STEP … Test subjects that vary in age group, gender, handedness - will the same brain regions become activated?

Conduct the experiment during the morning or afternoon – will we obtain the same results?

Perform the same procedure except this time do not ask participants to stay awake during the preceding second and third night test nights since that obviously produced some fatigue effects in this current study

LIMITATIONS Only used male subjects – could there be a genetic bias?

Subjects were all right-handed – why not test left-handed subjects?

Subjects were all roughly part of the same age group – could there be an effect of age?

Previous neuroimaging studies have suggested occiptal & temporal areas are activated during REM sleep but that was not shown in this study – WHY? Because group analysis averaged out cortical activations specific to each individual subject or even to each scanned REM sleep episode

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Questions…?