Rapid Eye Movements in Sleep Furnish a Unique Probe Into Consciousness

Abstract

The neural correlates of rapid eye movements (REMs) in sleep are extraordinarily robust; including REM-locked multisensory-motor integration and accompanying activation in the retrosplenial cortex, the supplementary eye field and areas encompassing cholinergic basal nucleus (Hong et al., 2009). The phenomenology of REMs speaks to the notion that perceptual experience in both sleep and wakefulness is a constructive process – in which we generate predictions of sensory inputs and then test those predictions through actively sampling the sensorium with eye movements. On this view, REMs during sleep may index an internalized active sampling or ‘scanning’ of self-generated visual constructs that are released from the constraints of visual input. If this view is correct, it renders REMs an ideal probe to study consciousness as “an exclusively internal affair” (Metzinger, 2009). In other words, REMs offer a probe of active inference – in the sense of predictive coding – when the brain is isolated from the sensorium in virtue of the natural blockade of sensory afferents during REM sleep. Crucially, REMs are temporally precise events that enable powerful inferences based on time series analyses. As a natural, task-free probe, (REMs) could be used in non-compliant subjects, including infants and animals. In short, REMs constitute a promising probe to study the ontogenetic and phylogenetic development of consciousness and perhaps the psychopathology of schizophrenia and autism, which have been considered in terms of aberrant predictive coding.

fMRI Evidence for Default Mode Network Deactivation Associated with Rapid Eye Movements in Sleep

“…Crucially, within the widespread activation, robust (corrected p < 0.0005) peak responses are seen in the primary and secondary visual cortices and the multisensory binding system [ 13 ]. These findings speak to REM-locked hierarchical processing of visual information, where each sensory modality is processed in its respective primary sensory cortex, with ensuing multisensory integration at higher hierarchical levels [ 13 , 16 , 17 , 18 ]. REM-locked responses in the visual hierarchy have led to the notion that REM sleep dreams may be accompanied by internally scanning a virtual sensorium: please see [ 19 ], and [ 16 , 20 ] for review and discussion of this ‘scanning hypothesis’, in relation to empirical evidence and dream reports.…”

Sleepers Selectively Suppress Informative Inputs during Rapid Eye Movements

“…Such selective suppression may reflect the presence of ongoing high-order internal activity, such as dreaming. Indeed, substantial literature investigating neural processes during eye movements indicates a link between EMs and dreams (see [26] for a recent review) [10,[26][27][28][29][30][31][32]]. Yet, dreaming has also been reported outside EMs, during both REM and NREM sleep [33,34].…”

Sleepers Selectively Suppress Informative Inputs During Rapid Eye Movements

“…Such selective suppression may reflect the presence of ongoing high-order internal activity, such as dreaming. Indeed, substantial literature investigating neural processes during eye movements indicates a link between EMs and dreams (see [26] for a recent review) [10,[26][27][28][29][30][31][32]]. Yet, dreaming has also been reported outside EMs, during both REM and NREM sleep [33,34].…”