Clean Data!

Unfiltered voltage recordings from cat primary visual cortex. This shows about a half second of activity on four separate electrodes separated by a few millimeters in response to a visual stimulus.

Low frequency (local field potential) oscillations are clearly visible in the raw trace and correspond to the aggregate synaptic activity within a local region (~200-300 µm in diameter from the electrode site).  The vertical lines (higher frequency activity) correspond to the activity potentials (“spikes”) of individual neurons occurring at a timescale of 5-10 milliseconds within around 100 µm from the electrode tip.