Could we ever find consciousness in the brain?

Neuroscience can find where and when the brain's activity tracks what you consciously experience, but it still cannot say why any of it feels like something. The search has a name: the neural correlates of consciousness, or NCC, defined as the minimal set of neuronal events and mechanisms observed to occur along with the mental states to which they are related. Discovering neural correlates does not offer a causal theory that explains how particular systems experience anything, the so-called hard problem of consciousness.

One precisely controllable trick is binocular rivalry. Two different images are shown, one to each eye, and observers see one image or the other alternately; the brain does not allow simultaneous perception of both. The physical stimulus stays fixed while the experience flips, so researchers can look for brain activity that follows the percept. In monkeys trained to signal what they saw, most cells in the primary visual cortex responded to one or the other retinal stimulus with little regard to what the animal perceived. In the inferior temporal cortex, almost all neurons responded only to the perceptually dominant stimulus: a "face" cell fired only when the animal indicated that it saw the face.

Even so, the philosopher David Chalmers maintains that a neural correlate of consciousness, unlike correlates for memory, will fail to offer a satisfactory explanation of the phenomenon; he calls this the hard problem. Rival theories compete to say what consciousness is, and in 2019 the Templeton Foundation announced funding in excess of $6,000,000 to test two of them against each other. In the first results, revealed in June 2023, two of three predictions from integrated information theory passed and none from its rival did. A number of scholars then called integrated information theory pseudoscience, while others defended it. The contest is not settled.