Synchronization and assembly formation in the visual cortex.

Publisher Summary This chapter describes the experimental findings demonstrating that distributed neural populations in the visual cortex process information in a cooperative way. Evidence accumulated that temporal relations among the responses of concurrently activated neurons convey information, which is unavailable from the single-cell responses alone. A large body of data is compatible with the hypothesis that visual objects are represented by assemblies of synchronously firing neurons. The experimental approaches used in the chapter range from the level of multiple single cells to EEG and MEG recordings and from anaesthetized animal preparations to human experiments with active costive tasks. The central claim of the temporal binding hypothesis is that, relations between features in visual space are represented by synchronization of neural responses, but the concept neither specifies what elementary features are used as building blocks for ensemble formation nor how they are encoded. Therefore, the synchronous assembly concept is compatible with the existence of very different levels of receptive fields (RF) complexity along the non-classical, state-dependent, and visual pathways. The temporal binding hypothesis is also compatible with different strategies how elementary pieces of information are encoded. Evidence for the relevance of precise spike timing of single-cell responses for information processing in the visual cortex casts doubts on average firing rate as the dominant code is used in neuronal processing.