Extra cesllular recording from multiple neighboring cells: response properties in parietal cortex
Multiple single unit extracellular recordings were made using tetrodes in macaque posterior parietal cortex while the animal was performing a visual memory saccade task. Recordings were made over a 2×2 mm area at both superficial and deep locations in one hemisphere. Signals were analyzed using an Expectation-Maximization algorithm for spike separation based on spike peak height or the first two principle components of spike shape. 27 sites were selected for analysis based on task response and clarity of separation, yielding 85 total neurons with a mode of 3 cells per site. The response criteria and stereotaxic location used were consistent with identifying neurons within the lateral intraparietal area (LIP).