The termination of fibres from the cerebral cortex and thalamus upon dendritic spines in the caudate nucleus: a study with the Golgi method

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Abstract
The termination of fibres from the cerebral cortex and thalamus upon the dendritic spines of the medium spiny cell of the caudate nucleus has been studied with the Golgi method. Lesions were placed in the cerebral cortex, thalamus or cerebral cortex and thalamus of adult cats and kittens. After survival periods of between 6 and 52 weeks the animals were perfused with a mixture of formaldehyde and glutaraldehyde and the caudate nuclei impregnated by a Golgi technique. The distribution of spines along the dendrites of the medium spiny cell was determined in normal material by counting them over 20 /xm lengths of the dendrites, and was compared with their number and distribution after the various lesions. The density of spines on the dendrites varies with the distance from the cell body. The first 20 /xm length of dendrite is spine free, but thereafter the number increases to a peak between 60 and 80 /xm from the cell body after which the number per 20 /xm length decreases. The distribution pattern does not alter after any of the lesions, although the overall number of spines decreases. The decrease after lesions in the cerebral cortex or thalamus is the same, and after a combined lesion of thalamus and cortex is twice as great indicating that the fibres from both these regions end upon spines of the same cells. Statistical analysis shows that these results are significant.