DISTRIBUTION IN TIME AND SPACE OF PREPYRIFORM ELECTRICAL ACTIVITY

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Abstract
The surface-negative potential evoked in the prepyriform cortex of the cat by stimulation of the lateral olfactory tract spreads tangentially with a measurable latency and without a preceding positive wave. Lesions of the surface block the spread of the potential. The potential spreads to the base without latency and with inversion; small lesions in the superficial layer diminish the amplitude of the evoked potential recorded in the lesion, whereas similar lesions in the base do not diminish the evoked potential recorded there. A map of the evoked potential shows that it is the product of a dipole field of current. One pole lies in the molecular layer and contains the electromotive forces (e.m.f.) of the dipole; the other pole lies in and below the cellular layers of the cortex and is passive. It is concluded that the evoked potential spreads tangentially over the surface because of successive activation of the e.m.f. in or around the dendrites of the pyramidal cells. This e.m.f. drives current into the interior of the cells; the deep potential is produced by the passive emergence of this current from the axons. The spontaneous prepyriform electrical activity is generated by the same e.m.f. and has substantially the same distribution as the prepyriform evoked potential.