Functional neuroimaging of normal human sleep by positron emission tomography

Abstract

Functional neuroimaging using positron emission tomography has recently yielded original data on the functional neuroanatomy of human sleep. This paper attempts to describe the possibilities and limitations of the technique and clarify its usefulness in sleep research. A short overview of the methods of acquisition and statistical analysis (statistical parametric mapping, SPM) is presented before the results of PET sleep studies are reviewed. The discussion attempts to integrate the functional neuroimaging data into the body of knowledge already acquired on sleep in animals and humans using various other techniques (intracellular recordings, in situ neurophysiology, lesional and pharmacological trials, scalp EEG recordings, behavioural or psychological description). The published PET data describe a very reproducible functional neuroanatomy in sleep. The core characteristics of this ‘canonical’ sleep may be summarized as follows. In slow‐wave sleep, most deactivated areas are located in the dorsal pons and mesencephalon, cerebellum, thalami, basal ganglia, basal forebrain/hypothalamus, prefrontal cortex, anterior cingulate cortex, precuneus and in the mesial aspect of the temporal lobe. During rapid‐eye movement sleep, significant activations were found in the pontine tegmentum, thalamic nuclei, limbic areas (amygdaloid complexes, hippocampal formation, anterior cingulate cortex) and in the posterior cortices (temporo‐occipital areas). In contrast, the dorso‐lateral prefrontal cortex, parietal cortex, as well as the posterior cingulate cortex and precuneus, were the least active brain regions. These preliminary studies open up a whole field in sleep research. More detailed explorations of sleep in humans are now accessible to experimental challenges using PET and other neuroimaging techniques. These new methods will contribute to a better understanding of sleep functions.

What subjective experiences determine the perception of falling asleep during sleep onset period?

“…Generally speaking though, light sleep was associated with decreased activity in the frontal and parietal areas of the cortex and in the thalamus. Deep sleep is characterized by a further decrease in activity in these areas, as well as within the basal ganglia (e.g., Balkin et al, 2002;Braun et al, 1997Braun et al, , 1998Finelli, Baumann, Borbély, & Achermann, 2000;Kjaer, Nowak, & Lou, 2002;Maquet, 2000;Nofzinger, Mintun, Wiseman, Kupfer, & Moore, 1997;Nofzinger et al, 2002;Peigneux et al, 2001). As for stage 1 sleep, Czisch and his colleagues reported fMRI indications of reduced activation in both the auditory and visual cortex in response to auditory stimuli, as demonstrated by a decrease in the blood-oxygenation (Czisch et al, 2002).…”

Cognitive and emotional processes during dreaming: A neuroimaging view

“…Several regions are significantly hypoactive during REM sleep when compared to wakefulness, in particular in the dorsolateral prefrontal cortex (DLPFC), orbitofrontal cortex, posterior cingulate gyrus, precuneus, and the inferior parietal cortex (Braun et al, 1997;Maquet, 2000Maquet, , 2005Maquet et al, 1996;Nofzinger et al, 1997) (Fig. 1).…”

Ultradian and circadian modulation of dream recall: EEG correlates and age effects

“…Activation in these regions hints to the possibility that memory consolidation processes, particularly emotional memories, may happen during REM sleep (Wagner et al, 2001;Nishida et al, 2009;Sterpenich et al, 2009;Walker, 2009). Conversely, numerous key regions are hypoactive during REM sleep relative to wake state, such as the dorsolateral prefrontal cortex (DLPFC), orbitofrontal cortex, posterior cingulate gyrus, precuneus, and the inferior parietal cortex (Maquet et al, 1996;Nofzinger et al, 1997;Braun et al, 1997;Maquet, 2000). Deactivations in these regions that subserve critical executive and attention functions during wake state point to the fact that the functional neuroanatomy of REM sleep is diametrically apart from that of wake state (Maquet et al, 1996;Nofzinger et al, 1997;Braun et al, 1997;Maquet, 2000).…”