Abstract
Current concepts of cortical information processing and most cortical network models largely rest on the assumption that well-studied properties of local synaptic connectivity are sufficient to understand the generic properties of cortical networks. This view seems to be justified by the observation that the vertical connectivity within local volumes is strong, whereas horizontally, the connection probability between pairs of neurons drops sharply with distance. Recent neuroanatomical studies, however, have emphasized that a substantial fraction of synapses onto neocortical pyramidal neurons stems from cells outside the local volume. Here, we discuss recent findings on the signal integration from horizontal inputs, showing that they could serve as a substrate for reliable and temporally precise signal propagation. Quantification of connection probabilities and parameters of synaptic physiology as a function of lateral distance indicates that horizontal projections constitute a considerable fraction, if not the majority, of inputs from within the cortical network. Taking these non-local horizontal inputs into account may dramatically change our current view on cortical information processing.
Highlights
Reviewed by: Dirk Feldmeyer, RWTH Aachen University, Germany Gordon M
*Correspondence: Current concepts of cortical information processing and most cortical network models largely rest on the assumption that well-studied properties of local synaptic connectivity are sufficient to understand the generic properties of cortical networks.This view seems to be justified by the observation that the vertical connectivity within local volumes is strong, whereas horizontally, the connection probability between pairs of neurons drops sharply with distance
Quantification of connection probabilities and parameters of synaptic physiology as a function of lateral distance indicates that horizontal projections constitute a considerable fraction, if not the majority, of inputs from within the cortical network.Taking these non-local horizontal inputs into account may dramatically change our current view on cortical information processing
Summary
Precision In temporal coding schemes, this parameter often describes the ability of a neuron to translate synaptic input into precisely timed spike output. Precise timing relates to the millisecond or even sub-millisecond range, i.e., a precision in the order of the action potential duration or even higher It can be argued whether the experimentally observed temporal spike locking to time-varying stimuli in primary sensory areas with a precision that merely reflects the stimulus dynamics should be considered a substrate for temporal coding at all, or whether it might rather be a pre-requisite for it at later processing stages (Aertsen et al, 1979; Harris, 2005; Tiesinga et al, 2008). Another striking and important difference to earlier studies on the physiology of synaptic connections is that in www.frontiersin.org
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