Hypothalamic substrates for brain stimulation-induced attack, teeth-chattering and social grooming in the rat

In this paper the boundaries of the hypothalamic response areas for brain stimulation-induced attack, social grooming and teeth-chattering were delimited. A total of 641 hypothalamic sites in 71 male CPW/WU Wistar rats were electrically stimulated. Positive sites for any behavioural response cluster into restricted hypothalamic areas. Discriminant analysis of both positive and negative electrode localizations yields areas with high, intermediate and low probabilities of inducing the behavioural response concerned. Each response has its own response area where probabilities are high. Neuroanatomical correlates of these response areas are discussed. The response area of attack is suggested to be an integrative processing area, stimulation of which overrules some aspects of integration and directly activates the behavioural program of attack. Although some authors consider all three responses to be part of the behavioural repertoire of aggression, the response areas are not identical. Social grooming and attack are considered to be induced from different neural systems. Similarly, attack and teeth-chattering have been shown to derive from different neural mechanisms, despite substantial overlap of both response areas. It is suggested that teeth-chattering derives from the simultaneous activation of both attack and flight tendencies. No further distinctions with respect to threshold current intensities can be made within responses areas. However, the underlying neural substrates are not homogeneous, for thresholds vary along the course of individual electrodes.