Medial auditory thalamic nuclei are necessary for eyeblink conditioning.

Abstract

The auditory conditioned stimulus (CS) pathway that is necessary for delay eyeblink conditioning was investigated with induced lesions of the medial auditory thalamus contralateral to the trained eye in rats. Rats were given unilateral lesions of the medial auditory thalamus or a control surgery followed by twenty 100-trial sessions of delay eyeblink conditioning with a tone CS and then five sessions of delay conditioning with a light CS. Rats that had complete lesions of the contralateral medial auditory thalamic nuclei, including the medial division of the medial geniculate, suprageniculate, and posterior intralaminar nucleus, showed a severe deficit in conditioning with the tone CS. Rats with complete lesions also showed no cross-modal facilitation (savings) when switched to the light CS. The medial auditory thalamic nuclei may modulate activity in a short-latency auditory CS pathway or serve as part of a longer latency auditory CS pathway that is necessary for eyeblink conditioning.