Consciousness

Consciousness offers a major challenge to the neurosciences. Even though consciousness is by definition subjective and private to the organism concerned, we consider it to be an intrinsic feature of biological processes in the brain. As such, it should be viewed in the Darwinian perspective of natural selection which implies that the conscious brain function does have survival value and cannot be a mere epiphenomenon. We attempted a neurophysiological approach by assessing perceptual processing of simple somatic sensory inputs in humans. We found that short-latency cortical potentials evoked by a target finger stimulus attended by the subject are strongly enhanced, thus manifesting a remarkable potentiation of the cognitive representations in primary parietal cortex. About 80 msec later, the dorsolateral prefrontal cortex discloses enhanced electrogeneses which we believe to reflect activation of somatic representations in 'working memory'. A functional 'binding' between these critical areas has been revealed by the transient and selective synchrony of 40 Hz oscillations recorded in the cortical areas of the parietal and prefrontal cortices. We consider these re-entrant interactions at 40 Hz to be an essential part of the conscious brain mechanisms that achieve the identification of an object (in this example, a finger) and the decision to release a motor behavioral response.