Neurosurgery
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The relationship of charge density per phase, or QD/ph (expressed in units of microcoulombs per cm2 per phase of the charge-balanced wave form), and total charge (QDt) to neural damage has been investigated by light and electron microscopy after surface stimulation of the parietal cortex in normal cats. QD/ph values ranging from 40 to 400 were achieved by varying several stimulus parameters. ⋯ Although individual factors contributing to neural damage are isolated with difficulty, charge density and total charge seem to be predominant among the contributing parameters. In view of these findings, recommendations have been made for the selection of electrical stimulus parameters to be used in central nervous system prostheses.