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The visual hyperstriatum of the 100-g chick has been investigated for responses evoked by electrical stimuli to the optic papilla. The visual hyperstriatum is not restricted to the anterior forebrain; posterior regions are also responsive, but for maximum response in amplitude the stimulating electrodes need to be re-positioned and, for reliable detection, a 10-fold gain in amplification is required.

Repeated stimulation can lead to a decrement in the amplitude of a response, or its disappearance. This is known as habituation. Responses recorded in the reticular formation of the brain to peripherally applied stimuli tend to habituate. Decerebration considerably reduces the occurrence of this habituation and naloxone reverses the effect. In decerebrate animals in which such responses rarely habituate, habituation can be induced by administration of D-Ala2,Met5-enkephalinamide and then reversed by a subsequent administration of naloxone. This would suggest that opiates are involved in habituation of responses recorded in the reticular formation of the frog.

The thalamic input to the barrelfield of rats with a solitary mystacial vibrissa (C3) intact was examined using succinic dehydrogenase techniques. Rats were lesioned on postnatal day (PD) 1 and brains examined at either 7, 12, 21 or 28 days later. The resultant segmentation in the hemisphere contralateral to the lesioned muzzle consisted of fused rows (A to E). At all ages row C differed from the other rows in that the center of the row was enlarged and separated from the row on either side of it. Thus the presence of a single vibrissa is sufficient to organize the thalamic input to its barrel.