Consciousness – we hit its sweet spot
New Scientist, 5 July 2014, Helen Thomson, based on Koubeisse et al
Summary and review of the above article
A recent study suggests that a particular brain area, the claustrum, is at least necessary, although probably not sufficient, for consciousness. The claustrum is a sheet of neurons just below the cortex, and is connected to much of the cortex. Most consciousness theorists agree that there is a need to integrate activity from spatially separate regions of the brain. The original suggestion that the claustrum could be important for consciousness derived from Francis Crick and Christof Koch in the early 2000s; they suggested that the claustrum could bind together information arriving at different times.
Koubeissi et al have recently shown that it is possible to switch a human individual’s consciousness on and off, by applying electrical stimulation to the claustrum. A high frequency electric pulse to the claustrum can oblate consciousness, and cessation of the same pulse brings back consciousness. Surprisingly, synchrony increased in the frontal and parietal areas during this loss of consciousness, but it is suggested that too much synchrony can block the discrimination between different parts of the brain.
The claustrum looks to be necessary rather than sufficient. The research of recent years suggests that global gamma synchrony across spatially separated neuronal assemblies, and intense activity in small groups of neurons surrounding single neurons that respond to particular signals are both implicated in conscious processing. The claustrum might be expected to complete the final binding between different modalities such as sight, hearing and smell.