P3b signal

Consciousness theory rocked  ::  Anil Ananthaswamy, based on Brian Silverstein & Michael Snodgrass  ::  https://www.newscientist.com/

Summary and review of the above article

There appears no reason to reconsider the main drift of the distinctions between unconscious processing and conscious processing that has emerged in recent neuroscience, solely in the light of Silverstein and Snodgrass’s findings relative to the P3b signal. intendiX2 (1)The P3b signal was formerly known as the P300 signal, but this latter is now seen as having two sub-components; the first of these, the P3a signal is mainly involved with directing attention, while P3b is involved with responding to more unusual stimuli, as opposed to routine stimuli. The signal is often correlated with conscious process of information in frontal brain regions. However, Silverstein and Snodgrass showed that it could also be stimulated by signals that were too short, or were masked so that they could not enter consciousness, but could nevertheless effect unconscious processing.

Unjustified conclusion

What is not justified is to jump to the conclusion that unconscious processing plays an overriding role in frontal brain processing. A large body of neuroscience has demonstrated that the sensory cortex processing of stimuli is unconscious until it reaches the highest level of the sensory cortex, and is then subsequently projected to frontal areas, such as the orbitofrontal, ventromedial prefrontal and dorsolateral prefrontal. m1-11-12-biosci-reviews-sinet-f-1c-fig3Activity in these areas is involved with consciousness of sensory inputs and their evaluation and subsequent planning and behaviour. Brain structure and activity is dramatically different here, in terms of much higher neural activity levels, larger pyramidal neurons and a related thicker cortex. This is not to say there are not many unconscious inputs, but this does not justify trying to play down the role of consciousness in decision processing.

It is too early to say what exactly the role of P3b is either unconscious or conscious processing. The most likely suggestion at this stage seems to be that the unconscious signal is a general alert, while in consciousness it may stimulate an evaluation and decision-making process.

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