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Whole BrainWhole Brain New Scientist: 28 March 2009: Anil Ananthaswamy: based on Raphael Gaillard of INSERM Raphael Gaillard of INSERM took the opportunity provided by the need to insert intercranial electrodes during medical treatments to test aspects of consciousness. The sample of electrodes across 10 volunteers covered most parts of the brain. Words were flashed in front of the volunteers, some of which they were conscious of, and some of which were masked so that there would only be unconscious processing. During the first 30 milliseconds there was not much difference between conscious and unconscious processing. After that time, there were several types of brain processing that only occurred where the subjects were conscious of the words concerned. The frequency and phase of neurons in different parts of the brain synchronised, and then in turn set of synchronised signals in other parts of the brain. For instance activity in the occipital lobes seemed to set off activity in the frontal lobes. The fact that this only occurred when subjects were aware of the words being shown, meant that this synchronisation was viewed by the researchers as a correlate of consciousness. The synchronisation of activity was spread over large parts of the brain leading the researchers to hypothesise that consciousness is spread over a large part of the brain rather than being concentrated in any one ‘seat of consciousness’. The clear distinction here between conscious and non-conscious processing appears to contradict a core theme of Dennett to the effect that there is no such distinction between conscious and non-conscious activity. It also seems to argue against the once popular ‘electric plug’ theory of consciousness. This argued that consciousness was concentrated in and around the brain stem, because if anything seriously damaged the brain stem consciousness ceased. This research would rather seem to suggest that the brain stem is necessary but not sufficient for human consciousness. The findings appear compatible with the idea that the widespread gamma synchrony is a correlate of consciousness. This view was made popular by, although not discovered by Crick and Koch in the 1990s, but fell from favour when it was discovered that the synchrony was with dendritic rather than axonal activity. |
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