Fig. 1. Assessing the statistical optimality of the internal model in the visual cortex.

(A) The posterior distribution represented by EA (bottom, red filled contours show pairwise activity distributions) in response to a visual stimulus (top) is increasingly dominated by the prior distribution (bottom, gray contours) as brightness or contrast is decreased from maximum (left) to lower levels (middle). In the absence of stimulation (right), the posterior converges to the prior and thus SA recorded in darkness represents this prior. (B) Multiunit activity recorded in V1 (middle column) of awake, freely viewing ferrets either receiving no stimulus (middle) or viewing natural (top) or artificial stimuli (bottom) is used to construct neural activity distributions in young and adult animals. Under natural and artificial stimuli conditions, EA distributions represent distributions of visual features (red and green panels) inferred from particular stimuli. Average EA distributions (aEA) evoked by different stimuli ensembles are compared to the distribution of SA recorded in darkness (black panels), representing the prior expectations about visual features. Quantifying the dissimilarity between the SA distribution and the aEA distribution reveals the level of statistical adaptation of the internal model to the stimulus ensemble. The internal model of young animals (left) is expected to show little adaptation to the natural environment and thus aEA for natural (and also for artificial) scenes should be different from SA. Adult animals (right) are expected to be adapted to natural scenes and thus to exhibit a high degree of similarity between SA and natural stimuli-aEA, but not between SA and artificial stimuli-aEA.