Evoked Single Cortical Unit Activity in the Primary Cortical Receiving Areas

Abstract

RENSHAW et al.¹ analysed single cortical cell activity in the hippocampus by means of a micropipette electrode. Since 1951, the technique has been used by us for isolating peripherally evoked single cortical unit activity in the primary somatosensory, auditory and visual receiving areas of the cat and the monkey. Either barbiturate (dial or nembutal), chloralose or magnesium sulphate anæsthesia was used. The preparation was frequently paralysed with d-tubocurarine or B-erythroidine. The micro-electrodes used were either nichrome wire sharpened to a tip diameter of 6‐10 µ and insulated to the tip, or glass micropipettes, drawn to a tip diameter of 4–12 µ The latter were filled with 3 M potassium chloride to reduce their resistance² and led into a cathode follower input. Action potentials were conventionally amplified (both r.c. and d.c. coupling) and displayed on twin-beam cathode-ray oscilloscopes. The cortex was fixed in 10 per cent formalin, sectioned at 50 microns and stained with thionin for identification of electrode tracks.