Response properties of single cells in monkey striate cortex during reversible inactivation of individual lateral geniculate laminae.

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Abstract
Response properties of single cells in rhesus macaque striate cortex were assessed before, during and after reversible anesthetic blocks of retinotopically corresponding parts of single lateral geniculate nucleus (LGN) layers. Dorsal parvocellular layers (6 and 5) contribute selectively to on- or light-edge responses while the ventral pair (4 and 3) contribute selectively to off- or dark-edge responses of cortical cells. Individual simple cells having a single excitatory subfield receive excitatory input from either parvocellular or magnocellular LGN layers but not from both. Multiple-subfield simple cells commonly receive convergent excitatory inputs from both parvocellular and magnocellular layers. Some cells receive only a parvocellular or only a magnocellular input. At least 33% of complex cells receive convergent parvocellular and magnocellular inputs. At least 31% receive excitatory parvocellular inputs alone; 12% receive excitatory magnocellular input alone. Inactivation of an LGN layer sometimes had facilitatory effects on cortical cells. For complex cells this was always a general facilitation of a preexisting response. For simple cells, facilitation was general for some cells, specific to particular subfields for other cells and sometimes produced new responses. Neither orientation nor direction selectivity depend exclusively on Parvocellular or magnocellular inputs from LGN.