Supranormal orientation selectivity of visual neurons in orientation-restricted animals

Altered sensory experience in early life often leads to remarkable adaptations so that humans and animals can make the best use of the available information in a particular environment. By restricting visual input to a limited range of orientations in young animals, this investigation shows that stimulus selectivity, e.g., the sharpness of tuning of single neurons in the primary visual cortex, is modified to match a particular environment. Specifically, neurons tuned to an experienced orientation in orientation-restricted animals show sharper orientation tuning than neurons in normal animals, whereas the opposite was true for neurons tuned to non-experienced orientations. This sharpened tuning appears to be due to elongated receptive fields. Our results demonstrate that restricted sensory experiences can sculpt the supranormal functions of single neurons tailored for a particular environment. The above findings, in addition to the minimal population response to orientations close to the experienced one, agree with the predictions of a sparse coding hypothesis in which information is represented efficiently by a small number of activated neurons. This suggests that early brain areas adopt an efficient strategy for coding information even when animals are raised in a severely limited visual environment where sensory inputs have an unnatural statistical structure

P1-28: Supranormal Orientation Selectivity of Visual Neurons in Orientation-Restricted Animals

Altered sensory experience in early life often leads to remarkable adaptations in humans and animals. Consistent with this, previous studies have reported that restricting visual inputs in young animals can make drastic long-lasting changes in the early sensory areas of their brains. Typically, the majority of sensory neurons are allocated to stimulus features to which the animals were exposed. However, if that is the only change, it will make the sensory encoding highly redundant with many neurons signaling the same features. Are there additional changes, heretofore unnoticed, to functional properties of single neurons in such adaptation processes? Here we show that stimulus selectivities like the sharpness of tuning of single neurons in the primary visual cortex are modified to match a particular environment that has a restricted range of orientations. Specifically, we found in orientation-restricted animals that neurons tuned to an experienced orientation show sharper orientation tuning than neurons in normal animals, whereas the opposite was true for neurons tuned to non-experienced orientations. The sharpened tuning appears to be due to elongated receptive fields. Additionally, quality of signals such as the signal-to-noise ratio can be improved by averaging the activities of a population of neurons unless the same noise source is shared. Correlation of noise shared across neurons in the orientation-restricted animals was comparable to that in normal animals, confirming the potential for such improvements. Our results demonstrate that restricted sensory experiences can sculpt the supranormal functions of neurons tailored for a particular environment