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ANATOMY OF THE FOREBRAIN

For each vignette, select the labeled structure in the figure that is most likely affected. Each lettered option may be used once, multiple times, or not at all.

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A 78-year-old woman is found unconscious in her home and then is rushed to the emergency room of a local hospital. Upon waking, the patient is administered a neurological examination and magnetic resonance imaging (MRI). The patient is shown to have had some cortical brain damage from the stroke. Consequently, she has difficulty in understanding language and is diagnosed with a form of receptive aphasia. Which neurons in this figure project their axons to the region of cortex affected by the stroke?

A.

B.

C.

D.

E.

F.

G.

H.

The answer is A. (Nolte, pp 280-287, 390-413, 558-563, 594-605. Siegel and Sapru, pp 208-222, 353-354, 413-416, 419-423, 447-453.) This section is taken at the level of the posterior thalamus and, because of the oblique cut, also includes parts of the midbrain and pons. The pulvinar (A), a very large nucleus situated at this level of the thalamus, projects extensively to wide regions of the inferior parietal lobule. Portions of the inferior parietal lobule and superior temporal cortex include the region referred to as Wernicke area, which is associated with receptive aphasia. The caudate nucleus (H) and putamen (not labeled), collectively referred to as the neostriatum, have been implicated in Huntington disease and show reduced levels of the neurotransmitter, GABA. The hippocampal formation (C) is associated with a number of different processes, including short-term memory and as a seizure focus during temporal lobe epilepsy. Thus, a lesion of this structure will likely produce deficits in short-term memory, and trauma to this region will result in temporal lobe epilepsy. The lateral geniculate nucleus (D), situated in the far ventrolateral aspect of the posterior thalamus, is a relay nucleus for the transmission of visual information to the cortex. Damage to this structure would result in a homonymous hemianopsia. The centromedian (CM) nucleus (B), identified by its encapsulated appearance, can be found in posterior levels of the thalamus, where it receives inputs from the brainstem reticular formation and projects to the neostriatum as well as to wide regions of the cerebral cortex. In this manner, it plays a role in the functions of the reticular formation, and presumably those associated with regulation of sleep-wakefulness and mood states.

For each vignette, select the labeled structure in the figure that is most likely affected. Each lettered option may be ...

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