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Alexandre Ben Amor, Elvire Vaucher; The effects of a cholinergic deficit on visual learning in rats. Journal of Vision 2007;7(9):229. doi: https://doi.org/10.1167/7.9.229.
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The cholinergic system participates in the continual reorganization of the cortical sensory map. During patterned visual stimulation, acetylcholine is released in the primary visual cortex (V1) and a deficit of this neurotransmitter diminishes neuronal activity of this area. Here, we evaluated if an acetylcholine deficit affects perceptual learning capacity of rats performing a visual discrimination task.
Rats were trained in a visual water maze to determine visual acuity (Prusky et al., 2000). Subjects were then divided into two groups whereby one group received intra-ventricular injections of 192 IgG-saporin in order to lesion the cholinergic fibers and a sham lesion group. After 21 days post-surgery, rats were tested for recall of the visual acuity task and learned an orientation task modified to the water maze. In the orientation task, animals learned to discriminate between a 90° stimulus (reference pattern) and one that varied between 45° and 90°. An 80% success rate was used to define successful learning of the task. Immunostaining of cholinergic fibres in V1 and basal forebrain showed a complete loss of cholinergic innervation of V1. The visual acuity of the lesioned and the sham-operated rats did not differ from pre-surgery levels. The ability of the lesioned group to learn the orientation task was significantly lower than the sham-operated group (p=0.015). More trials were necessary for the lesioned group to be able to discriminate between a 75° vs 90° pattern compared to control animals (73 ± 8 and 42 ± 6, respectively). These results suggest that a deficit in acetylcholine may cause a deficit in visual learning.
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