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

Perceptual Evidence for Interhemispheric Visual Integration

Visual scenes in the left and right halves of visual fields are processed in separate cortical hemispheres of the brain. Corpus callosum is thought to play an important role in stitching together the split at the vertical meridian. Yet we do not notice any consequence of such interhemispheric integration in our daily lives. Can we find any perceptual evidence for such integration? Specifically, do visual tasks involving interhemispheric integration require extra processing time due to transmission delays of signals that must be exchanged via corpus callosum? To address these questions, we used a visual illusion known as the flash lag effect as a ruler for space and time. Two configurations of flash lag stimuli were presented to normal human subjects. In one configuration, the stimuli were presented to only one visual hemifield so that the processing could be completed within a single cortical hemisphere. In the other configuration, moving and flashed parts of the stimuli were presented to separate hemifields straddling the vertical meridian. Positions of flashed stimuli were manipulated to find a spatial offset necessary to cancel the lag. Our results show that the stimulus configuration that involves interhemispheric integration requires 40∼50ms of extra processing time

High dynamic range current detection using a diamond quantum sensor

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Demonstration of deep-space synchronous two-way laser ranging with a laser transponder aboard Hayabusa2

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