Behaviors Caused by Hypothalamic and Thalamic Lesions

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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,

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