The temporal structure of conscious mental states

RESUMO

The brain may work as a space-time machine. On the one hand, time may be spatially represented in neuronal assemblies, i.e., spatially "quantized". On the other, spatially segregated neuronal activity imposes a requirement on temporal integration mechanisms. Both theoretical and empirical evidence supports a model of integration by periodic oscillations. The model assumes two hierarchically organized, oscillatory frequency ranges. Fast oscillations have a period around the gamma range (30 ms) and may be used to define functional temporal states, inside which time relations are not discernible. These time quanta define mental-neural events. At the next level of the hierarchy, events are automatically and sequentially integrated up to a limit of more or less 3 seconds, which defines the slow oscillatory period. Events integrated into a 3 seconds temporal window constitute a semantic unitary subjective experience, the subjective present or now. Time experience is a construct derived from counting the number of events in a given period. Up to 3 seconds, mechanisms of consciousness equate to those of time perception. Subjective experience of continuous time flow is built upon semantic relatedness between different psychological moments.