Consciousness, Sleep and Learning

fMRI

• Measured ‘BOLD’

• Blood Oxygen Level Dependent Signal

fMRI strengths

• Functional, in real-time

• Good spatial resolution

• No radiation

fMRI limitations

• Poor temporal resolution

• Subject is very restricted

• Aversive environment

Resting state

State against which activation of brain regions is compared in imaging research

At rest

Brain is the most energy-hungry organ

• 2% of body weight

• 20% of energy use in adults

• 40% in children

Constant consumption of energy

• Active only adds 10% max

• Redistribution of activity, rather than net changes in total activity

Default mode network

Medial Cortical Regions

• Frontal, Temporal and parietal

Becomes more active when we are not focused on a task

Stimulus Independent Thought

• Introspection, Daydreaming

Self-referential

Includes regions associated with ‘theory of mind’

Creativity?

Paradoxical Function Facilitation

• Turning down A, enhances B

• Damage to A, enhances B

• Damage to, or turning off of the prefrontal cortex

Creativity

Default mode network (medial cortical regions) are inhibited by prefrontal regions when engaged in a task

• Especially language

This top-down inhibition weakens with aging

Can be severely impaired in certain dementias

• Frontotemporal dementia (Picks disease)

• Primary Progressive Aphasia

• Rare, early, unrecognised sign is a sudden, intense, repetitive creativity

Frontotemporal dementia

• Most common form of dementia in patients under 65

• 20% have known familial cause

• 40% have strong family history

• Poor outlook - limited treatment and slow progression

• Often restricted to one hemisphere

• Lots of variance in presentation

Presentation of frontotemporal dementia

• Progressive deterioration of behaviour/cognition

• Behavioural disinhibition

• Apathy/inertia

• Loss of sympathy/empathy

• Decline of executive function

1. Memory is largely spared

2. Contrast with Alzheimer’s Dementia

3. Verbal/language impairment

Changes in diet

Not psychiatric

Anne Adams

• Cell biologist

• Quit science in mid 40s and decided to become a painter

• Painted obsessively, with repetitive motifs

• Eventually diagnosed with a form of frontotemporal dementia

• 57% of people with bvFTD have committed a crime

Ventromedial Prefrontal Cortex

Decision making based on

• Moral judgements

• Emotions

• Values

• Integration of ‘gut’ and ‘logic’

• Self-referential

• Impulse

Disorders of consciousness

• Coma

• Vegetative State

• Delirium

• Hallucinations

• Dementia

• Temporal Lobe Epilepsy

Epilepsy

• Synchronous (abnormal) firing of large groups of neurons

Electroencephalography (EEG)

• Measures electrical activity in the cerebral cortex

• Groups of neurons firing together

• Does not really measure action potentials

• Characteristic ‘waves’

• Oscillations

• Temporal, rather than spatial

Temporal lobe epilepsy

Simple partial seizures - not loss of consciousness - auras

• Emotional

• Auditory, olfactory, gustatory

• Deja vu

Complex partial seizures - most common type of seizure in TLE - impaired consciousness

• Unusual behaviour

• Automatisms (e.g., lip smacking)

Secondarily generalised to tonic-clonic seizures

• Extends beyond the temporal lobe

• ‘Full blown’ seizures

Hypergraphia

Writing copiously (not necessarily in a creative way) and keep voluminous diaries

Hypo-sexuality

Decreased interest in sexual matters often resulting in marital disharmony

Emotional viscosity or stickiness

Anxiety, obsessional, dwells on minor matters, experiences difficulty in terminating conversations

• Increased interest in spiritual or ideational issues in the absence of pragmatic interests

Turbulent emotions

• Irritability, agitation, restlessness, paranoia etc.

Mood swings

More commonly depression or dysphoria with occasional elation

Psychotic and quasi-psychotic phenomena

• Intermittent hallucinations, delusional thinking etc.

Hyper-religiosity

• Very religious, often ritualistically so, out of sync with family/cultural background

Sensory and motor pathways

Ascending- sensory

Descending - motor

Stages of sleep

• Rapid eye movement (REM sleep)

• Non-REM sleep

Stage 1

Stage 2

Stage 3

• More NREM early in the night, more REM later

Non-REM sleep

• Processing the days experience

• Consolidating memories

Especially declarative memories

• Clear out the hippocampus

Long term memories eventually stored in the cortex

REM sleep

• Integrating new memories with existing

• Emotional processing of new memories

• Dreaming
  Cognitively acting out memories and experiences
  Brain is very active, body is not

• Thalamus prevents outgoing motor commands

• Muscle atonia

What happens when you sleep

Thalamic gate is closed, in and out

• (In) we don’t attend to external stimuli

• (Out) we don’t (really) act out our dreams

Repeated cycles of (re)consolidation

Integration of new knowledge with

• Prior knowledge

• Prior emotions

• Modifying connections between neurons

Clearing of ‘temporary store’ in the hippocampus

Sleep deprivation leads to

Drastically impaired learning

• Failure to ‘clear’ the temporary store in the hippocampus

Atrophy

• Smaller hippocampus

• Smaller prefrontal cortex

All sorts of other problems

Sleep deprivation can also lead to

Death

Fatal Familial Insomnia

• Rare genetic disorder

• Progressive neurodegeneration of the thalamus

• Symptoms develop mid-adulthood

• Die from lack of sleep

Alcohol impairs sleep

Initially causes sedation

• Quicker to fall asleep

• Quicker to reach NREM3

Reduces REM sleep

Over-relaxes certain muscles

• Snoring, resulting in waking up more often

Rebound effects of alcohol metabolism cause wakefulness

Impairs memory