Examination of the spatial and temporal distribution of sensory cortical activity using a 100-electrode array

This paper introduces improved techniques for multichannel extracellular el ectrophysiological recordings of neurons distributed across a single layer of topographically mapped cortex. We describe the electrode array, the surg ical implant techniques, and the procedures for data collection and analysi s. Neural events are acquired through an array of 25 or 100 microelectrodes with a 400-mu m inter-electrode spacing. One advantage of the new methodol ogy is that implantation is achieved through transdural penetration, thereb y reducing the disruption of the cortical tissue. The overall cortical terr itory sampled by the 25-electrode array is 1.6 x 1.6 mm (2.56 mm(2)) and by the 100-electrode array 3.6 x 3.6 mm (12.96 mm(2)). Using a recording syst em with 100 channels available, neural activity is simultaneously acquired on all electrodes, amplified, digitized, and stored on computer. In our dat a, average peak-to-peak signal/noise ratio was 11.5 and off-line waveform a nalysis typically allowed the separation of at least one well-discriminated single-unit per channel. The reported technique permits analysis of cortic al function with high temporal and spatial resolution. We use the technique to create an 'image' of neural activity distributed across the whisker rep resentation of rat somatosensory (barrel) cortex. (C) 1999 Elsevier Science B.V. All rights reserved.