Specific roles of NMDA and AMPA receptors in direction-selective and spatial phase-selective responses in visual cortex

Cells in the superficial layers of primary visual cortex (area 17) are dist inguished by feedforward input from thalamic-recipient layers and by massiv e recurrent excitatory connections between neighboring cells. The connectio ns use glutamate as transmitter, and the postsynaptic cells contain both NM DA and AMPA receptors. The possible role of these receptor types in generat ing emergent responses of neurons in the superficial cortical layers is unk nown. Here, we show that NMDA and AMPA receptors are both involved in the g eneration of direction-selective responses in layer 2/3 cells of area 17 in cats. NMDA receptors contribute prominently to responses in the preferred direction, and their contribution to responses in the nonpreferred directio n is reduced significantly by GABAergic inhibition. AMPA receptors decrease spatial phase-selective simple cell responses and generate phase-invariant complex cell responses.