Untangling the Web

Abstract

NEUROSCIENCE Pyramidal cells in layer V of the neocortex form a major excitatory projection system in the brain. Their activity is modulated by a network of excitatory and inhibitory inputs from local intracolumnar neurons and from neurons in other columns. Schubert et al. have analyzed the origin, strength, and spatial distribution of synaptic inputs onto layer V pyramidal cells in the rat somatosensory cortex. Morphologically and functionally, two major classes of pyramidal cells, intrinsically bursting (IB) and regular spiking (RS), were differentiated. Both received excitatory input from all cortical layers. Inputs from layers V and VI were more homogenous, whereas those from layers IV and II/III showed a patchy distribution. Excitatory inputs from layer VI were stronger for IB than for RS cells, and IB cells received only weak inhibitory inputs, mainly of local origin. In contrast, inhibitory inputs onto RS cells were much stronger and originated predominantly from layers II/III and V of the same column and from layer V of the adjacent columns. Thus, the IB cells may be important for integration of excitatory inputs across several cortical columns, and the RS cells may be better suited for information processing within a cortical column. — PRS J. Neurosci. 21 , 3580 (2001).