Imaging The Human During Sleep

Question 1

Brain imagining of the sleeping brain

Answer 1

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

Question 2

Maqueta et al 1996

Answer 2

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

Question 3

Brain areas showing a positive correlation with REM

Answer 3

Pons, thalamus, amygdalaoid conplexes, right parietal operculum, anterior Cingulate gyrus

Issues- PET studies give blurry images, not as good as fMRI

Question 4

Brain areas showing a negative correlation with REM

Answer 4

Pre-frontal cortex, parietal areas, precuneus & adjacent posterior cingulate gyrus

Question 5

authors interpretation of deactivations- Maquet et al (1996)

Answer 5

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

Question 6

Braun et al (1997)

Answer 6

37 pp
10 pp with good REM data
PET scan

Question 7

Decreases during slow wave sleep

Answer 7

Pons
Thalamus
Hypoathalamus
Caudate nucleus 
Lateral & medial regions of the prefrontal cortex

Question 8

Comparing nREM to wakefulness

Answer 8

Deactivation of frontal lobe

Cerebellum switched off (because not moving)

Pons switched off

Brain-stem & midline decrease from wake to NREM

Question 9

Increases during REM sleep compared with nREM baseline

Answer 9

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

Question 10

No difference relative to slow wave sleep & REM sleep

Answer 10

Orbital

Dorsolateral prefrontal

Inferior parietal lobes

All 3 areas decreased

Question 11

Increases at waking relative to REM

Answer 11

Orbital frontal

Dorsolateral prefrontal

Inferior parietal loves

All 3 areas increase

Question 12

Authors conclusions

Answer 12

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

Question 13

Nofzinger et al (1997)

Answer 13

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

Question 14

Areas of the brain not needed for dreaming

Answer 14

Motor cortex

Pre-frontal cortex

Primary visual cortex

Cerebellum

Question 15

Effects of dreaming on lesions in various parts of the brain

Answer 15

If medial frontal lobe damaged, lose dreaming

If parietal lobe damaged, excessive or intrusive dreaming

Question 16

Later studies

Answer 16

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

Question 17

The default network

Answer 17

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

Question 18

When are the default areas active?

Answer 18

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

Question 19

Overlap with REM areas

Answer 19

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

Question 20

Embodied simulation

Answer 20

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