Neural coordination

consciousnessNeural Coordination and Human Cognition

Catherine Tallon-Baudry

In:- Dynamic Coordination in the Brain: From Neurons to Mind – MIT Press

Brain imaging in recent years has led to the brain being seen in terms of a large number of functional regions, and this in turn creates a need to explain how the activities of these regions are coordinated. This chapter emphasises the distinction between learned routes in the brain and the coordination that is needed to deal with new perceptions and behaviours. Initial waves of feed forward activity are mainly related to unconscious processing. Feedback and recurrent processing between parts of the brain have been related to processing over a longer duration and may be related to conscious activity.

Delta waves in the brain are related to sleep, theta to memory, while beta and gamma are associated with attention and the binding together of activity in different areas of the brain. The author refers to “a large and converging body of evidence that grouping features into a coherent percept is accompanied by changes in the gamma range” (1. Jensen et al, 2007, 2. Tallon-Baudry, 2009), although oscillatory synchrony in the alpha range is also found (3. Mima et al, 2001, 4. Freunberger et al, 2008). Brain networks influence oscillatory synchrony from the theta to the gamma range. The laying down and retrieval of memories involves both the theta and gamma oscillatory synchrony. Short-term memory activity involves both beta and gamma oscillations. Local gamma oscillations relate to activity in the visual, medial temporal lobe and frontal areas. Particular cognitive processes can relate to gamma oscillations in different locations. Selective attention can involve gamma oscillations at particular subfrequencies and in particular brain areas. Distinct bands with the gamma range relate to both visual awareness and spatial attention. The frequency content of oscillations in the gamma band has been suggested to code for features such as spatial frequency or the direction of sound.

Oscillations could be used to group and separate chunks of data from what went before and came after. This has been related to beta oscillations. There has been a further tentative suggestion that very slow oscillations could be related to the ‘psychological present’ or the few seconds which form a perceptual unity that does not require the effort of recall. It is further suggested that distinct oscillatory frequencies could be used to accomplish a task requiring more than one function, such as searching for a person in a crowd. This is taken to suggest that activity between different frequency bands can be coordinated in the brain. Experimental evidence suggests that spatially distant areas of the brain oscillate in the same frequency range and with constant phase relationship and that this activity can play a cognitive role (5 & 6. Tallon-Baudry 2001 &4, 7. Melloni et al, 2007, 8. Doesburg et al, 2008). Amplitude as well as phase coupling can occur between frequency bands at S.integrating information and distinguishing between information.

 

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