The Journal of Neuroscience, February 1, 2002, 22(3):740-747
Cell Type- and Subcellular Position-Dependent Summation of
Unitary Postsynaptic Potentials in Neocortical Neurons
Gábor
Tamás1, 2,
János
Szabadics1, and
Peter
Somogyi2
1 Department of Comparative Physiology, University of
Szeged, Szeged H-6726, Hungary, and 2 Medical Research
Council Anatomical Neuropharmacology Unit, Department of
Pharmacology, University of Oxford, Oxford, OX1 3TH, United Kingdom
Theoretical studies predict that the modes of integration of
coincident inputs depend on their location and timing. To test these
models experimentally, we simultaneously recorded from three neocortical neurons in vitro and investigated the effect
of the subcellular position of two convergent inputs on the response summation in the common postsynaptic cell. When scattered over the
somatodendritic surface, combination of two coincident excitatory or
inhibitory synaptic potentials summed linearly in layer 2/3 pyramidal
cells, as well as in GABAergic interneurons. Slightly sublinear
summation with connection specific kinetics was observed when
convergent inputs targeted closely placed sites on the postsynaptic cell. The degree of linearity of summation also depended on the type of
connection, the relative timing of inputs, and the activation state of
Ih. The results suggest that, when few
inputs are active, the majority of afferent permutations undergo linear
integration, maintaining the importance of individual inputs. However,
compartment- and connection-specific nonlinear interactions between
synapses located close to each other could increase the computational
power of individual neurons in a cell type-specific manner.
Key words:
cerebral cortex; integration; IPSP; EPSP; interneuron; pyramidal cell
Copyright © 2002 Society for Neuroscience 0270-6474/02/223740-08$05.00/0