CB7a

The supervenience relation

Background assumptions:

• The supervenience relation: consciousness supervenes on brain activity

It is a philosophical background assumption, it seems to be tacitly taken for granted by neuroscientists when studying consciousness

The neural correlates of consciousness = NCC

The principle of Covariance

For each and every conscious event, there is a corresponding brain event (not vice versa)

The principle of ontological dependence

The conscious events somehow owe their existence to the brain activity

denial of cartesian substance dualism

The neural correlates of consciousness

NCC

Standard Definition (Koch 2004): NCC is the minimally sufficient neural system or activity that invariably cooccurs together with a conscious experience of a specific kind

Design of NCC experiments

What are the neural correlates of the subjective experience ”X”? CONTROL CONDITION: experience X is absent (does not occur in the subjet’s mind)

EXPERIMENTAL CONDITION: experience X is present (does occur in the subject’s mind)

• everything else is equal or kept constant

what is the difference in brain activity between these two conditions? = NCC-X

Brain electrical activity:

Microelectrodes (animal studies)

EEG

MEG

Brain metabolism and blood flow:

fMRI

PET

Brain stimulation:

direct cortical stimulation

transcranial magnetic stimulation (TMS)

transcranial electrical stimulation (tDCs, tACs)

Structural Brain Imaging

• CT, CAT

• MRI

Functional Brain Imaging

• PET

• fMRI

Electromagnetic Brain Sensing

• EEG

• MEG

Electromagnetic Brain Stimulation

• TMS, tACs, tDCs

• direct

EEG and the conscious state

Slow wave EEG

• Less complex, les differentiated thalamocortical activity

• Consciousness requires complex high frequency activities between thalamus and cortex

Epileptic EEG activity

• Sudden abnormal bursts of electrical activity in the brain > epileptic seizures

Coma

• State of unarousable unresponsiveness

• Typically transient (1-2 weeks)

Vegetative state

• Cyclical patter of arousal: wake (eyes open) - sleep (eyes closed)

• Unresponsiveness, no behavioural evidence of awareness of self or environment

• Permanent if lasts over 1 year

Minimally conscious state

• Reliable but inconsistent awareness of self or environment, no reliable communication

How do anesthetics suppress consciousness?

They represent a wide variety of different molecules that have a wide variety of different effects on different parts, mechanisms, and receptors in the brain.

Thalamus is a common target of anesthetics , but there is also a theory that there isnt a single consciousness switch and it probably has something to do with changes in functional connectivity.

How to measure consciousness (when in global disorders)

1. Degree of baseline brain activity (metabolic activity, blood flow)

2. Responsiveness of neural networks

3. Functional connectivity of large scale neuronal networks

Arise from unconscious states

Thalamocortical connectivity

The cortex is completely quiet during the arise of consciousness and it seems like thalamus has a some input but other cortical mechanisms

Anesthesia awareness

Consciously perceiving some sensory perceptual stimuli from the environment

Anesthesia dreaming undergoing internally generated conscious experiences

Measure brain activity

Perturbational complexity index (PCI)

TMS + EEG

> 0,44 - conscious

< 0-31 unconscious