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Proceedings of the National Academy of Sciences of the United States of America logoLink to Proceedings of the National Academy of Sciences of the United States of America
. 1995 Aug 29;92(18):8279–8282. doi: 10.1073/pnas.92.18.8279

Two types of calcium response limited to single spines in cerebellar Purkinje cells.

W Denk 1, M Sugimori 1, R Llinás 1
PMCID: PMC41140  PMID: 7667282

Abstract

Of fundamental importance in understanding neuronal function is the unambiguous determination of the smallest unit of neuronal integration. It was recently suggested that a whole dendritic branchlet, including tens of spines, acts as the fundamental unit in terms of dendritic calcium dynamics in Purkinje cells. By contrast, we demonstrate that the smallest such unit is the single spine. The results show, by two-photon excited fluorescence laser scanning microscopy, that individual spines are capable of independent calcium activation. Moreover, two distinct spine populations were distinguished by their opposite response to membrane hyperpolarization. Indeed, in a subpopulation of spines calcium entry can also occur through a pathway other than voltage-gated channels. These findings challenge the assumption of a unique parallel fiber activation mode and prompt a reevaluation of the level of functional complexity ascribed to single neurons.

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Selected References

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