Behind every behaviour (in the physical world of res extensa) there is a predicted ‘fictive’ neural activity occurring in specific neural circuits (in the inner world of res cogitans) before the corresponding behaviour is ultimately generated by an appropriate pattern of motor activity.
Neuroscience has developed effective strategies to relate neural activity to specific behaviours as I described in detail for the swimming of the lamprey. In general, these internal neural activities are the neural correlates of these behaviours. The main issue then is to identify the kind of neural activity that corresponds to what we call mental states.
The search for the physical bases of mental states requires the identification of the complex spatio-temporal patterns of nerve activity at the relevant levels of the neural building associated with given mental functions. The search for the relation between brain activity and conscious experiences is what Francis Crick and Christof Koch have called the neural correlates of consciousness (NCC)1.
Neural correlates of consciousness were defined as the minimally sufficient neural activation responsible for a given conscious percept or subjective experience2. The basic idea is that mental states become conscious when large numbers of neurons fire in synchrony with one another, say, oscillations within the 35 to 75 cycles per second (gamma brain waves). Other candidates for the NCC have emerged over the past two decades, including reentrant cortical feedback loops in thalamocortical systems, and activation of the parietal cortex3.
We are now equipped with a background in the suitable principles of physics to describe complex neural phenomena. Mapping such patterns of neural activity in time and space is equivalent to identifying the four-dimensional physical structures underlying brain processes including the ones which occur at its higher loops, ie those underlying mental states.
I propose, as have some other neuroscientists but very few philosophers, that there is a specific state of the brain associated with each specific state of mind. From this it follows that for every inner subjective experience, there must be an associated unique spatio-temporal pattern of neural activity, the neural correlate of that subjective experience. However, a full representation of the neural states within such complex systems is still beyond reach of current methods.
Assuming some consensus is achieved that mental events can be described experimentally, the spatio-temporal patterns of neural activity associated to these specific mental states become graphic representations of four-dimensional ‘mental’ events. By identifying the space and time coordinates of these events as four-dimensional phenomena, they acquire a physical objectivity and can be studied like any other natural phenomena. Any four-dimensional pattern of neural activity found to be necessary and sufficient to generate a particular mental state would fulfil the prerequisites to provide a physical description of that state.
- C Koch et al (2016): Neural correlates of consciousness: progress and problems. Nature Reviews Neuroscience 17, 307-321;
C Koch (2019): The Feeling of Life Itself: Why Consciousness Is Widespread but Can’t Be Computed. MIT Press;
A Seth (2022): Being You, A New Science of Consciousness. Faber / Allen & Unwin. ↩︎ - G Tononi & C Koch (2008): The neural correlates of consciousness: An update. Annals of the New York Academy of Sciences 1124, 239-261. ↩︎
- GM Edelman & G Tonini (2000): Consciousness: How Matter Becomes Imagination. Basic Books. ↩︎