FIG. 5.

Percentage of sites with units across days. Bars denote SE of the data set on a given block of days. Number of arrays included in analysis, n, is listed on the x-axis. Over the course of the study, sites referenced to a common average reference yielded almost 60% more discernible units than when reference to standard electrical references. This increase in performance is attributable to a reduced noise floor, enhancing signal-to-noise ratio, and therefore increasing the number of discernible units. Unit recordings were strong initially, dipped dramatically in the days following surgeries, and returned to initial levels after the 4-wk point. This trend in recording performance has been noted in previous recording studies (Ludwig et al. 2006; Santhanam et al. 2007; Schwartz 2004).