Pars Intermedia: Unitary Electrical Activity Regulated by Light

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Science  10 Jan 1969:
Vol. 163, Issue 3863, pp. 195-197
DOI: 10.1126/science.163.3863.195


In the pars intermedia of frogs in the dark two types of spontaneously firing neuronal units have been found; one can be inhibited by and the other is indifferent to increases in illumination. The receptor for the light-inhibited units appears to be the pineal organ. Transection experiments indicate that the axons to the two kinds of units in the pars intermedia are separately grouped in the floor.