Beyond the cortical column: abundance and physiology of horizontal connections imply a strong role for inputs from the surround
- 1 Bernstein Center Freiburg, Neurobiology and Biophysics, Faculty of Biology, University of Freiburg, Freiburg, Germany
- 2 Bernstein Center for Computational
Neuroscience and Neuroinformatics and Theoretical Neuroscience, Freie
Universität Berlin, Berlin, Germany
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.
Keywords: reliability, synaptic transmission, dendritic integration, cortical column, temporal coding
Citation: Boucsein C, Nawrot MP, Schnepel P and
Aertsen A (2011) Beyond the cortical column: abundance and physiology of
horizontal connections imply a strong role for inputs from the
surround. Front. Neurosci. 5:32. doi: 10.3389/fnins.2011.00032
Received: 23 November 2010;
Paper pending published: 10 January 2011;
Accepted: 28 February 2011;
Published online: 01 April 2011.
Copyright: © 2011 Boucsein, Nawrot, Schnepel and
Aertsen. This is an open-access article subject to an exclusive license
agreement between the authors and Frontiers Media SA, which permits
unrestricted use, distribution, and reproduction in any medium, provided
the original authors and source are credited.
*Correspondence: Clemens Boucsein,
University of Freiburg, Bernstein Center Freiburg and Neurobiology
& Biophysics, Schänzlestrasse 1, D-79104 Freiburg, D-79104, Germany,
clemens.boucsein@biologie.uni-freiburg.de