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Consciousness

Chapter 19: Consciousness

A patient is diagnosed as having a brain infarct and presents primarily with contralateral hemiparesis and dysarthria. Which of the following regions is affected by the infarct?

A. Medial thalamic nuclei

B. Lateral thalamic nuclei

C. Dorsomedial thalamus

D. Ventromedial thalamus

E. Medial hypothalamus

B. The lateral region of the thalamus and the posterior limb of the internal capsule are supplied by choroidal branches of the internal carotid artery. Infarct of this artery most frequently results in contralateral hemiparesis and dysarthria. Although lesions associated with this artery may affect only motor functions, they may also cause loss of pain, touch, and sometimes visual functions. The other choices given in this question are not associated with this constellation of deficits.

A middle-aged woman, who is suffering from a rare autosomal recessive condition that results in calcification and degeneration of specific regions of the forebrain, is seen by a psychiatrist. The patient is given a battery of tests and is found to be unable to recognize fear in pictures presented to her. Nor is she able to draw a picture depicting fear; however, she is capable of drawing pictures depicting other emotions. A magnetic resonance imaging (MRI) scan indicates significant atrophy of tissue in a specific region of the brain. Which of the regions indicated below is the most likely target of this rare autosomal recessive condition?

A. Mammillary bodies

B. Septal area

C. Amygdala

D. Cingulate gyrus

E. Lateral hypothalamus

C. Studies conducted on fear conditioning in rats have demonstrated that the amygdala plays a very important role in this process. Rare evidence obtained from patients has shown that individuals suffering from a rare autosomal recessive condition called Urbach-Wiethe disease, in which there is bilateral atrophy of the portion of the temporal lobe that includes the amygdala, have no sense of the emotion of fear. They are unable to recognize it and are not capable of depicting it in a drawing. Other regions listed in this question have not been linked to the emotion of fear.

A 65-year-old man suddenly finds himself unable to recognize the speech of individuals and the sounds of animals, whistles, or bells, but is still able to discriminate tones and hear sounds. On an MRI, a lesion was detected in which of the following regions?

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