SOME ASPECTS OF THE TRANSCEPHALIC DC CIRCUIT

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Abstract
The transcephalic DC potential is a maintained and functionally significant voltage recorded over the frontal and occipital emissary vein distributions on the midline of the scalp. Two possible sources for the potential are considered, cortical and cutaneous, and the latter is rejected on empirical grounds as the main voltage source. From consideration of the electrical properties of bone and of the blood, a path of least resistance is described, linking the cortex and the scalp. On the basis of this circuit pathway, a number of specific hypotheses are derived concerning the relative potentials, polarities and resistances to be found over regions of the cortex, skull and scalp and these predictions were found to be consistent with experimental results. These findings greatly strengthen the probability that the cortex is the main generator of the TCDC potentials, but also indicate that certain other structures probably modulate the circuit as well by acting as variable resistances.