Photically evoked potentials and afterpotentials recorded from the visual cortex of the unanesthetized hedgehog

Evoked potentials to visual stimuli (VEP) were recorded from the visual cortex of the unanesthetized hedgehog (Erinaceus europaeus), a primitive placental mammal with relatively little differentiation of cortex and thalamus. The VEPs consisted of several distinct positive and negative voltage deflections. Reproducibility of the response was high, as indicated from the small intrasession and intersession response variability. Rhythmic afterpotentials (AP), previously reported for higher mammals, were readily elicited. They had a lower frequency (3/sec) than APs observed in other mammals. The use of the hedgehog in electrophysiological and psychophysiological research is suggested because data obtained from this primitive placental mammal may shed light on CNS functions of higher mammals, as well as mammalian forms 'lower' on the evolutionary scale.