A Reevaluation of the Possible Role of Noradrenaline in Cortical Plasticity
Hahn, Christine G., 1962-
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When one eye of a young kitten is closed for a few days or more, the visual system of the animal somehow alters so that visual stimulation to the deprived eye no longer elicits strong or consistent responses from the cells of the cortex after the eye is reopened. This phenomenon, which has also been observed in young monkeys and other mammals, is called ocular dominance plasticity, and disappears with increasing age of the animal. The mechanisms behind the effects of monocular deprivation are poorly understood, but several studies suggest that the changes occur in the cerebral cortex itself. In the late 1970's, Kasamatsu & Pettigrew suggested began a that the series of intriguing experiments which neurotransmitter noradrenaline was critical for ocular dominance plasticity. We attempted to further test this hypothesis by depleting noradrenaline in kitten cerebral cortex by a new method, the injection of the neurotoxin DSP-4, and then testing for ocular dominance plasticity by recording from cells of the visual cortex with microelectrodes during visual stimulation. We also recorded from kittens depleted of noradrenaline by Kasamatsu and sent to us. Neither experiment evidenced any connection between noradrenaline depletion and ocular dominance plasticity, for noradrenaline-depleted kittens displayed ocular dominance shifts comparable to controls. The hypothesis of noradrenaline-dependent plasticity is weakened by our results.