Visual unit, EEG and sustained potential shift responses in the brains of toads (Bufo bufo) during alert and defensive behavior.

Cranially mounted differential preamplifiers allowed visual unit activity, EEGs and sustained potential shifts to be monitored from the tectum of freely moving toads (Bufo bufo). Alert behavior was elicited by a moving visual stimulus. Movement of the stimulus in the receptive field of a unit elicited its activity and increased the amplitude of the high frequency component of the local EEG, accompanied by a sustained potential shift. When an animal received a "prod" with a perspex rod, defensive behavior ensued accompanied by slight activity of the visual unit, a large increase in the amplitude of the lower frequency component of the EEG and a large, sustained, potential shift. The results are discussed in relation to the specific neuronal unit responses of the animal and to possible sensitising functions of the non-specific EEG and sustained potential shift responses.