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Scientific Understanding of Consciousness |
Memory as Synaptic ReconstructionMemory is not simply recall -- Memory involves a reactivated synaptic reconstruction of the neural network pattern of the original event. The signal flows through this reconstructed neural network pattern constitutes the memory image. Memory recall is a regeneration of a prior arrangement of synaptic connections over widely distributed areas of the brain. Very likely, hundreds of millions of synaptic connections are involved. The specific arrangement of synaptic connections is not precise. Each time the memory is regenerated, a somewhat different set of neurons and synapses could be active, but enough of the original synaptic connectivity pattern will be involved to result in approximately the same mental image for the reconstructed thought. Memories will tend to change and fade over time. Newly stored memories will typically utilize some of the same neurons and synapses used by older memories. The newly stored memories could modify the synapses used by older memories. This multiuse of the synapses forming memories will eventually lead to fading of memories as newer memories are formed with reused and modified combinations of synaptic strengths and connections. Memory cannot simply be equated with synaptic change, although changes in synaptic strength are essential for it. Each event of memory is dynamic and context-sensitive. Memory involves a repetition of a mental act that is similar to but not identical with previous acts. Memory is recategorical; it does not replicate an original experience exactly. Memory should be looked on as a property of degenerate nonlinear interactions in a multidimensional network of neuronal groups. Such interactions allow a non-identical "reliving" of a set of prior acts and events. Memories are necessarily associative and never identical. (Edelman; Wider than the Sky, 52-53) Memories are not stored in facsimile fashion; they must undergo a complex process of reconstruction during retrieval. (Damasio; Feeling of What Happens, 227) Retroactivation process uses the rich connectional patterns of feed-forward and feedback that characterize the architecture of cortical regions and subcortical nuclei. (Damasio; Making Images, 20)
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