Multi channel recording system

The multi-channel recording system was manufactured by Blackrock Microsystems Limited (Salt Lake City, UT, USA). Electrophysiological data were recorded from the implanted micro-wire electrode arrays. Four pre-amplification headstages were used to record from 32 electrodes. The analog signals were filtered by a band-pass filter set between 0.3 Hz and 7500 Hz. Then the signals were digitized by the neural signal processor. The LFPs were recorded at 1 kHz/s sampling rate. The single unit spikes were manually sorted online by Central, a computer software provided by Cerebus (Blackrock Microsystems Ltd., Salt Lake City, UT, USA).

We used a linear electrode array (U-probe, Plexon; 24 recording channels spaced 100 um apart, each 15 um in diameter) to record neuronal activity simultaneously from different cortical depths of the primary visual cortex. The linear array was inserted into the cortex on each day of experiments under the control of a microelectrode drive (NAN Instruments), and its depth was adjusted to extend through all V1 layers. Electrical signals from electrodes were amplified and digitized with a multichannel recording system (Blackrock Microsystems). The local field potential is defined as the low-pass-filtered (300 Hz) signal, and multiunit activity (MUA) is detected by applying a voltage threshold with a signal-to-noise ratio of 5.5 on the high-pass-filtered (1000 Hz) signal.