Imaging The Human During Sleep Flashcards
Brain imagining of the sleeping brain
By imaging the human brain while in REM sleep, can observe which brain areas are active & not
Can also wake them & ask if dreaming
We already know about area function so can speculate on their role in dreaming
Maqueta et al 1996
7 pp
Remained in steady REM during measurement
Reported dreams afterwards
Started with 30 young people
3 nights in scanner conditions
Must maintain 2 20 min solid periods of REM & nREM
PET scan on 3rd night
19 pp succeeded
Contrasted REM sleep scans with all non-REM sleep data obtained
Brain areas showing a positive correlation with REM
Pons, thalamus, amygdalaoid conplexes, right parietal operculum, anterior Cingulate gyrus
Issues- PET studies give blurry images, not as good as fMRI
Brain areas showing a negative correlation with REM
Pre-frontal cortex, parietal areas, precuneus & adjacent posterior cingulate gyrus
authors interpretation of deactivations- Maquet et al (1996)
Few connections from amygdala to pre-frontal cortex, parietal areas, precuneus & adjacent posterior Cingulate cortex, that’s why they switch off during REM
Pre-frontal cortex controls encoding & retrieval episodic memory so lose that during REM
Parietal areas control working memory so also lose that
In order to dream, have to cut off episodic memory
Braun et al (1997)
37 pp
10 pp with good REM data
PET scan
Decreases during slow wave sleep
Pons Thalamus Hypoathalamus Caudate nucleus Lateral & medial regions of the prefrontal cortex
Comparing nREM to wakefulness
Deactivation of frontal lobe
Cerebellum switched off (because not moving)
Pons switched off
Brain-stem & midline decrease from wake to NREM
Increases during REM sleep compared with nREM baseline
Áreas linked with arousal & sensory activation
Medial forebrain reactivation
Pons reactivation
Midbrain, brainstem, limbic system areas reactivated (midline strictures)
Basal ganglia (arousal system)
Thalamus
Caudal orbital cortex (basal forebrain)
Para limbic regions including anterior ínsula (main thing happening)
Anterior cingulate
Medial temporal cortices
Unimodal sensory cortices- secondary visual & auditory cortex
Medial prefrontal cortex
No difference relative to slow wave sleep & REM sleep
Orbital
Dorsolateral prefrontal
Inferior parietal lobes
All 3 areas decreased
Increases at waking relative to REM
Orbital frontal
Dorsolateral prefrontal
Inferior parietal loves
All 3 areas increase
Authors conclusions
Brainstem, thalamus & basal forebrain= arousal
Changes in striatum are notable in comparisons of wakefulness, nREM & REN sleep
Limbic & para limbic regions
REM appears to represent a generalised activation of the brain workout the participation of regions normally participate in the highest order analysis & integration of neural information
Sensory thalamus & portions of the occipital & temporal may become functionally recouped during REM sleep
REM sleep associated with profound activation of both the para limbic belt & the limbic
In the transition from REM to nREM prominent increases in activity in the sensory thalamus were matched by increases in portions of the occipital & temporal cortices
Did further study on visual cortex, activation of VC but not ordinary VC, sharp distinction between areas
Nofzinger et al (1997)
REM sleep compared to wakefulness
6 women
Compared against lying quietly after sleep
14 min REM episodes
Main activation was area under limbic system
Other small activations, less reliable
Emphasise the potential importance of of the anterior cingulate cortex, which plays a role in attentional states, performance monitoring & error detection in waking thought
Areas of the brain not needed for dreaming
Motor cortex
Pre-frontal cortex
Primary visual cortex
Cerebellum
Effects of dreaming on lesions in various parts of the brain
If medial frontal lobe damaged, lose dreaming
If parietal lobe damaged, excessive or intrusive dreaming
Later studies
Maquet et al (2005)- some areas within the dorsolateral prefrontal cortex are more active in REM than nREM
Ioannides et al (2009)- 4 patients, discovered higher activity in regions within dorsolateral prefrontal cortex than in NREM
The default network
Seen when fMRI brain scans are done
A set of brain areas that activate at the same time whenever not otherwise employed I.e. when not being asked to do a task in fMRI scanner
When are the default areas active?
When thinking about nothing, daydreaming, worrying, drifting, mind-wandering
Vivid recall of recent real autobiographical memories
Vivid recall of previously created imaginary experiences
Imagined experiences- the imagination network
Overlap with REM areas
Overlap in the brain areas activated when with mind wandering & with experiential self (stories of what happen to us & who we are), self reflection, self criticism, rumination, thinking about what others think
It allows the creation of a setting in which a simulated event can unfold whether past, present, future or hypothetical
Notable are the medial frontal & medial parietal regions
So these areas seen to be active during sleep may be this imaginative waking cognitive capacities occurring during sleep
Embodied simulation
In REM sleep, in addition to medial frontal activations, there’s
- total deactivation of primary sensory areas (occlusion of external stimuli during long periods of drifting waking thought)
- increased activation of secondary visual, auditory & sensory areas (not seem in dat dreaming)
- strong deactivation of dorso-lateral prefrontal cortex (access to waking life memories blocked)
- strong brain-stem sources of cortical activation
