Despite ample behavioral evidence for probabilistic learning in the brain, the neural underpinnings of this process remain unclear. It has been recently hypothesized that spontaneous activity in primary sensory areas could be a marker for this learning process (Fiser et al, 2010). In this view, the increase in similarity between spontaneous and stimulus-evoked activity over development reflects a progressive adaptation of the animal’s internal model to the statistics of the environment. Indeed, recordings in the developing visual system of the ferret confirmed that the structure of spontaneous activity gradually adapts with age to that of visually evoked activity and that this adaptation is specific to natural stimuli (Berkes et al, 2011). However, this finding leaves open the option that the gradual adaptation is due to genetically controlled developmental processes that has little to do with the animal’s visual experience. One test of the theory is to disrupt visual experience and measure whether this intervention reduces the similarity between spontaneous and stimulus evoked activity for naturalist stimuli. To perform such a test, we collected neural activity of the primary visual cortex of N=14 lid-sutured awake behaving ferrets at three different age groups of P44, P80 and P120. The animals had no visual experience only diffuse light through their eye lids up to the moment of data collection. Extracellular multi-unit activity was collected with a 16 channel line electrode from the superficial layers of V1. We analyzed the spontaneous and stimulus evoked activity and compared them to normally reared controls. The analysis revealed that, while in control animals in the oldest age group spontaneous activity is most similar to activity evoked by natural stimulation, in lid-sutured animals responses to natural scenes show the same degree of similarity as those evoked by noise. The effect is specific to this distinction, as the general statistics of V1 activity in lid-sutured animals develop very similarly to controls. Overall, these results confirm that while intrinsic development of visual circuitry is strongly controlled by developmental factors, learning is one of the driving forces behind the observed increases in similarity between the spontaneous and stimulus evoked activity.

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