Neuroanatomical segregation of texture-sensitivity in feline striate cortex

Recordings were obtained from striate cortical neurones in cats lightly anaesthetized with nitrous oxide/oxygen supplemented with halothane as necessary: muscle relaxant (gallamine triethiodide) was administered intravenously. Complex neurones were subdivided on the basis of their length summating properties for an optimally oriented bar into "standard", "special" or "intermediate" categories, and on their degree of sensitivity to motion of random texture into weakly and strongly texture-sensitive categories. In addition, a range of receptive field properties were compared, which included directional and orientational selectivity; end-stopping; receptive field dimensions; ocular dominance; and resting discharge levels. These properties were related to both neuronal class (simple or complex) and to the "special" and "standard" subdivisions of the complex neurone category ("intermediate" complex neurones were excluded from further analysis due to lack of numbers). Extracel1ular recordings were made from single neurones, with micropipettes filled with 12"/. East Green FCF in 2M sodium chloride. Extracellular dye-marks were made at the site of recording from each strongly texture-sensitive complex neurone. Microelectrode tracks were reconstructed with the aid of histologically recovered identifying dye-marks, in sections which had been counterstained with cresyl violet to reveal cortical lamination. This enabled calculation of brain shrinkage, and also labelled the layers containing the strongly texture-sensitive complex neurones. Under deep anaesthesia, animals were terminally perfused with phosphate-buffered saline (1 litre at 38 degrees Centigrade: pH 7.3) followed by 1 litre of IV, glutaraldehyde and 37. formaldehyde fixative. This study provides direct anatomical confirmation of the inference made by Hammond it MacKay ('75, ’77), and the 2-deoxyglucose studies by Wagner, Hoffmann and Zwerger ('81), that strongly texture-sensitive complex neurones lie in two bands, a superficial band in lower layer III, extending down into upper layer IV and a deeper band in layer V. A population of standard complex neurones, resident in both bands, was found to be strongly texture-sensitive, whilst strongly texture-sensitive special complex neurones were restricted to the deeper band in layer V