Cross-modal changes in primary visual cortex induced by somatosensory manipulation

This work shows that the manipulation of the somatosensory system (in form of whisker-deprivation) cross-modally influences the spared primary visual cortex of the fully adult mice. Revealed by a two choice discrimination behavioral task (visual water task) it cloud be shown, that the deprivation of the facial whiskers for twelve days improves visual acuity and contrast sensitivity by about 40%. This effect was confirmed by determining visual system thresholds using the method of optical imaging of intrinsic signals, a minimal-invasive technique to quantify and visualize cortical activity. Moreover it cloud be shown by using this method, that the deprivation of the facial whiskers restored experience- dependent plasticity, in form of ocular dominance plasticity, which is normally absent in fully adult mice. This effect could be abolished by the treatment with a drug that prevents Long-term-potentation (LTP) which suggests an involvement of the NMDA-receptor in the observed effect. To investigate the role of cortical inhibition, conveyed by GABAergic interneurons, which is described to play an important role for experience dependent plasticity in primary visual cortex, a GABAA-receptor agonist was given. The results, determined by using the method of optical imaging of intrinsic signals, showed that the effect was not prevented by this intervention. Instead of showing effects normal for young adults the treated animals showed a form of ocular dominance plasticity which normally only found during their early live span, the so called critical period. Furthermore it could be shown that the deprivation of the facial whiskers also affects plasticity in primary visual cortex without a manipulation of the visual system, after three days of somatosensory deprivation. It is a not-long lasting effect, whose mechanisms need more investigations. In addition to the improved cortex-dependent visual capabilities in adult mouse, the optokinetic reflex was better.


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