Unlike structures in the brain that control body movements such as the brain stem, cerebellum, and spinal cord, whose energy consumption is related to movement execution and the maintenance of posture, the neocortex consumes energy at a high-level all the time irrespective of whether there are body movements or not (Herculano-Houzel 2011). Indeed, consciousness via neocortex cannot be turned off during one’s waking hours (Chomsky 2023) and at this time sensory-motor information is constantly being updated (i.e., through declarative learning: Hebb 1949, 1961, 1968) and consolidated during immobility and sleep (Wilson and McNaughton 1994). This process assures that the information can be used to trigger appropriate responses automatically based on environmental demands such as the need to get up in the morning, to shower and have a coffee, to perform one’s duties at work, to take a lunch break, to complete the remaining tasks of the day, and to finish up the day over dinner with family before going to bed to start the process once again.
It is most significant that the information transferred by neocortical brain-machine interfaces saturates after collecting signals from more than 40 neuron situated in the parietal, motor, and/or premotor cortices, as monkeys perform a forelimb task guided by vision (see Fig. 1). This explains, in part, why the information transfer rate of brain-machine interfaces is so low [i.e., typically less than 2.5 bits per second (under 8 possibilities per second); language on the other hand can deliver 40 bits per second (some trillion possibilities per second) using the entire brain, Tehovnik, Hasanbegović, Chen 2024]. Furthermore, unlike alpha motor neurons that are engaged reliably (and without exhaustion) for the execution of repetitive movements, this is not at all true of neocortical neurons which exhibit a high degree of discharge variability during movement repetition (Rokni et al. 2007; Sartori et al. 2017; Schaeffer and Aksenova 2018). This suggests that something else in addition to commanding movements (Evarts 1966, 1968; Robinson and Fuchs 1969) is going on in the neocortex. This something else is consciousness to update the information stores of the neocortex by way of thinking (Chomsky 1965; also see Darlington and Lisberger 2020). In fact, the business of inducing movements once automaticity sets in is relegated to as few neurons as possible at the level of neocortex and subcortex (Lehericy et al. 2005). The purpose of this reduction in neural participation is so that maximal neural effort can be dedicated to consciousness/learning to promote the storage of new information (e.g., Chen and Wise 1995ab), which is the main reason for having a brain in the first place (Hebb 1949, 1961, 1968).
Figure 1: The brain signals for the transfer of information to drive a brain-machine interface begin to saturate after collecting signals from more than 40 neurons using implanted electrode arrays in the neocortex of behaving monkeys performing, for example, a center-out task using the forelimbs. Single or multiple arrays surpassing 100 microwires in total were implanted throughout the neocortex often including the parietal, the motor, and the premotor cortices, all areas of the brain that contain neurons that respond to visually-guided forelimb movements. Data from figure 4 of Tehovnik and Chen (2015).
As someone who studied both AI and the fundamentals of Neuroscience and on top of that has a customer who works in this specific field here is my view on the question:
The statement that brain-machine interfaces support the idea that the neocortex was designed to mediate consciousness is partially true, but it doesn't provide the whole picture. Here's a breakdown of the argument and some additional points to consider:
The Argument:
- Unlike brain regions controlling movement, the neocortex consumes a lot of energy even when we're not moving.
- Consciousness seems to be constantly active during waking hours.
- The neocortex constantly updates sensory and motor information (learning and memory consolidation).
- Brain-machine interfaces can't capture all the information the neocortex processes.
These points suggest the neocortex might be doing something more than just controlling movement, potentially supporting consciousness.
Additional Points:
- Due to technological limitations, Brain-machine interfaces might not capture the full picture of neocortical activity.
- The neocortex likely plays a role in consciousness, but it might be part of a larger network involving other brain regions.
Brain-machine interface research provides interesting clues, but it's not conclusive evidence that the neocortex was solely designed for consciousness. The neocortex is a complex region with various functions, and consciousness might emerge from interacting with other brain areas.
Esranur Kaygin,
Thank you for breaking down the problem into its fundamental components, which is what neuroscientists will need to examine to test the thesis that the neocortex mediates mainly consciousness/learning and that the execution of movement once a subject is automated plays a lesser role. But I suspect that it will still be the neocortex (and not the cerebellum), for example, that will be charged with 1st degree murder after the trigger is pulled.