Effect of ablation of auditory and "associative" cortex on the orienting reflex.

The present investigation was carried out as a further step in our attempt to establish the part played by various nervous structures and pathways in the orienting reflex and its habituation (Rogozea and Ungher 1965, 1966, 1968, Rogozea et al. 1969). We approached in this study the role played by the auditory and "associative" cortex. Experiments reported in the literature assessing auditory discrimination before and after ablation of the auditory cortical areas, provide information on the nervous processes requiring the presence of the auditory cortex. These data have shown that bilateral ablation of the auditory cortex does not impair the discrimination of frequency (Butler Bilateral removal of the auditory cortex was followed, instead, by a severe impairment in localization of sound in space (Neff et al. 1956) and in discrimination d both the duration (Scharloch et al. 1965) and temporal patterns (Diamond and Neff 1957) of tone. Sharpless and Jasper (1956) reported, with regard to the orienting reflex, that the specificity of habituation to the frequency parameter of the repetitive tone utilized is unaffected by bilateral ablation of the auditory cortex. The above mentioned data suggested to us the study of some quantitative (behavioral and EEG) parameters able to reveal changes in the orienting reflex and its habituation following ablation of the auditory and "associative" cortex.