L2: Brain Basis of Consciousness

Brain correlates of consciousness (easy problem of consciousness)

• Goal is to correlate between brain activity and the level of consciousness (whether the person is conscious) or the content of consciousness (what the person is experiencing) 

• Research paradigms designed to manipulate the level OR content of consciousness while controlling for other factors (e.g. sensory processing and behaviour)

  • P’s typically asked to introspect and report their conscious experiences, while their brain activity is recorded

  • Level or content of consciousness is correlated with brain activity to identify the brain regions whose activity correlates with consciousness

Mapping vs. Generating Consciousness

Is finding brain correlates (mapping) of consciousness sufficient for understanding the brain basis of consciousness? (NO)

Brain correlates of consciousness: Traditional vs. Newer view

• Newer view that consciousness not necessarily correlated with intelligence

What provides a unique and natural paradigm for investigating the brain correlates of consciousness

Sleep

• During sleep, the brain is effectively disconnected from the environment on both the input side (sensory processing) and the output side (behaviour)

• Sensory processing and behaviour remain minimal and constant

  • As opposed to fluctuating

• By contrast, consciousness fluctuates between being ON (dreaming) and OFF (dreamless periods)

The dissociation between consciousness and sensory processing or behaviour in sleep paradigms allows researchers to do what?

• Identify the brain correlates of consciousness

• Disentangle them from the brain correlates of sensory processing or behaviour

Serial Awakening Paradigm

• Wake up research P’s every ten minutes

• Ask P’s to report

  • Presence vs. absence of conscious experience

  • Contents of conscious experience

  • Features (richness, complexity) of conscious experience 

• Put P’s back to sleep

  • After P’s do this for a while they ‘learn’ to fall asleep quickly after being woken up

• P’s wear EEG to record brain activity for the entire night 

Brain correlates of wake consciousness: Binocular rivalry

• A unique paradigm for investigating the brain correlates of consciousness

• Each eye is presented with a different image

• Conscious experience fluctuates between two images, despite the sensory stimuli remaining constant (as opposed to fluctuating)

• Stereoscope device used (to stop eyes converging)

• Effectively presenting two completely different visual images to each eye

• Both to the same sensory input, therefore conscious experience usually oscillates between the two images and then maybe a very quick converge of the two

What brain activity correlates with the content of consciousness

Posterior cortex

• Even with complete loss of frontal cortex, consciousness remains intact

Integrated Information Theory Framework

What is the nature of neural activation

• This framework broadens our understanding of neural activity by considering not only actual events, but also counterfactual cause-effect relationship