Figure 3: Time-scale and influence of novelty in coupling variability across brain areas.

(a) Group data (n = 8): coupling on global variability across different time scales. On the vertical axis is shown the correlation between the coefficient of variation of population rate found in primary sensory cortices: S1, V1, and HP, and on the horizontal axis is shown the different bin sizes for the calculated coefficients of variation, one per pair of area/animal. Highlighted is the default bin size used in the main text (50 ms). The median of rCV significantly differs from zero (p < 0.01) in all conditions. (b) Samples of spiking correlation matrices based on the activity found in HP, S1 and V1 during (left) pre-exposure, (middle) exposure, and (right) post-exposure to novel objects, sorted by loadings of first principal component calculated based on correlated spiking activity during exposure. (c) Group data (n = 8) of Pearson’s correlation among the coefficient of variation of neuronal population activity found in S1, V1 and HP during pre-exposure (pre), exposure (exp) and post-exposure (post) to novel objects. (d) General proposal for coupling in variability in cortical activity. At small spatial scales of local cortical neuronal populations in the primary sensory cortex and hippocampus, local neuronal populations (circles) show strong shared variability and share very similar levels of variability across time, whereas at large scales, the primary sensory areas do not necessarily share their level of variability (spiking mode) but strongly share timing when the variability changes This last type of shared variability is only modest between cortex and hippocampus. (e) Illustration of the variability axis.