Figure 4.

Evidence for a negative impact of increased gliosis on recording quality. (A–D) Representative images from four animals demonstrate the range of endpoint histological outcomes (from “good” to “poor,” left to right). Neuronal nuclei (NeuN, green) and astrocytes (GFAP, red) surrounding probe tracts are shown, and the associated average neuronal and non- neuronal density data are listed [area binned cell counts, neuronal density (ND), and non-neuronal density (NND), in cells mm⁻²]. Recording segments with signal-to-noise-ratio (SNR) values representative of the average value for each animal are depicted. Recording quality improved with decreased NND and increased ND/NND (P < 0.05, Spearman's ρ, n = 6). Impedance increased with increased NND (P < 0.05, Spearman's ρ, n = 6). Scale bar, 100 μm. This figure was generated after additional analysis on data collected in Purcell et al. (2009). Figure and caption adapted with permission from Salatino et al. (2017). Copyright 2017, Springer Nature. Chronic changes from glial scarring are associated with irreversible, compensable signal disruptions.