Behaviors Caused by Hypothalamic and Thalamic Lesions :: Neurological Chemistry Chemical Papers

Behaviors Caused by Hypothalamic and Thalamic Lesions In the field of neuropsychology, the area in the brain that includes the hypothalamus, the thalamus, and the subthalamus is referred to as the subcortex diencephalon (Kalat 2004). In the following section, lesions to these specific areas will be discussed. The results of the lesions will be addressed from the perspective of a neuropsychologist. Neuropsychological assessment refers to the objective evaluation of the cognitive, linguistic, perceptual, and psychomotor performances of a person with the aim of relating the status of his/her performances to the structural and functional condition of his/her brain (Steinhauer, Gruzelier, & Zubin 1991). Neuropsychological assessment can be approached from an experimental method in which the researcher has greater control of the variables affecting the situation but, generalization is more difficult and human subjects cannot be used in studies (Finger 1978). A clinical method is also used and, although this method does not experience the benefit of complete control, brain-behavior relationships are much easier to study because human subjects can be used in this method (Finger 1978). Both methods are usually combined to produce the most efficient and helpful information for the patient. The most prominent neuropsychological tests include the Wechsler Adult Intelligence Scale, the Halstead-Reitan battery, and the Wechsler Memory Scale (Steinhauer et. al. 1991). These tests provide the opportunity to analyze the components of performance and then identify probable disabilities that would explain the defective performance (Steinhauer, et. al. 1991). The main issue that will be examined in this section will be behavioral effects of lesions to specific parts of the hypothalamus and the thalamus. The hypothalamus is located near the base of the brain and is ventral to the thalamus (Dimond 1978, Kalat 2004). The hypothalamus is part of the limbic system and is responsible for motivational behaviors including emotion, eating, drinking, sexual activity, anxiety and aggression (Kalat 2004, Dimond 1978, Isaacson 1982, Beaumont 1983). The hypothalamus has widespread connections to the rest of the forebrain and also to the midbrain (Kalat 2004). The hypothalamus contains a number of distinct nuclei including the lateral nucleus which controls the initiation of eating and drinking, the ventromedial nucleus which controls the stopping of eating and drinking, the paraventricular nucleus which limits meal size, the supraoptic nucleus which controls the secretion of vasopressin, the suprachiasmic nucleus which constitutes the biological clock,