Visually evoked potential plasticity

One of the methods evoking plasticity in the visual system is its repeated stimulation with appropriate visual stimuli. Repeated exposure to sensory stimuli can induce neuronal network changes in the cortical circuits and improve the perception of these stimuli in the primary visual cortex (V1). The aim of our studies was to investigate the effect of repetitive visual training on the magnitude of visual responses in the primary visual cortex and in the superior colliculus (SC), the subcortical structure of the extrageniculate visual pathway in rats. Our study showed that a three-hour, passive visual training with light flashes stimuli enhanced visual responses both at the cortical level and in the superior colliculus. The next part of our study concerned the explanation of which input projection is responsible for the observed training effect in SC, especially whether the increase of collicular response depends on the enhancement in the V1. SC receives information both from the retina and from layer 5 of the V1. The experiment with pharmacological blocking V1 did not suppress training-related plasticity in the SC.

The results obtained in this study indicated for the first time the superior colliculus as a possible target for the training strategies improving the efficiency of the visual process, e.g. in the case of primary visual cortex injuries.


dr Katarzyna Kordecka, e-mail: kkordecka@ichf.edu.pl


Cortical Inactivation Does Not Block Response Enhancement in the Superior Colliculus

Katarzyna Kordecka, Andrzej T. Foik, Agnieszka Wierzbicka and Wioletta J. Waleszczyk


Repetitive visual stimulation is successfully used in a study on the visual evoked potential (VEP) plasticity in the visual system in mammals. Practicing visual tasks or repeated exposure to sensory stimuli can induce neuronal network changes in the cortical circuits and improve the perception of these stimuli. However, little is known about the effect of visual training at the subcortical level. In the present study, we extend the knowledge showing positive results of this training in the rat’s Superior colliculus (SC). In electrophysiological experiments, we showed that a single training session lasting several hours induces a response enhancement both in the primary visual cortex (V1) and in the SC. Further, we tested if collicular responses will be enhanced without V1 input. For this reason, we inactivated the V1 by applying xylocaine solution onto the cortical surface during visual training. Our results revealed that SC’s response enhancement was present even without V1 inputs and showed no difference in amplitude comparing to VEPs enhancement while the V1 was active. These data suggest that the visual system plasticity and facilitation can develop independently but simultaneously in different parts of the visual system.

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