MCQ – 88915

Correct Answer � D Explanation

Answer D) HippocampusShort-term memory loss is often the earliest sign of Alzheimer disease, the most common cause of progressive dementia in the United States.

Hippocampus

• The earliest sites of neurodegeneration in Alzheimer disease are structures in the medial temporal lobe such as the hippocampus and parahippocampal cortex, which are critical for memory formation.

Amygdala

• The amygdala is a structure of the limbic system that plays a role in the processing of emotions. 

• Involvement of the amygdala in Alzheimer disease causes emotional lability, depression, and/or anhedonia. 

• Damage to a different structure would more likely explain the short-term memory loss in this patient with a normal affect.

• Bilateral damage to the amygdala results in Klüver-Bucy syndrome, which is characterized by emotional lability, anxiety, hypersexuality, hyperorality, and hyperphagia.

Ventral posterolateral nucleus

• The ventral posterolateral nucleus is a structure of the thalamus involved in relaying sensory input from the spinothalamic tract and dorsal column to the primary somatosensory cortex. 

• This nucleus does not play a role in memory formation and is not affected in early Alzheimer disease. 

• The medial dorsal nucleus of the thalamus and the anterior thalamic nucleus are involved in memory formation.

Nucleus accumbens

• The nucleus accumbens is a basal forebrain structure that has a role in the reward pathway. This structure does not play a major role in semantic (factual) recall.

• Degeneration of other basal forebrain structures such as the nucleus basalis of Meynert can cause memory loss and cognitive decline in Alzheimer disease.

• Decreased GABA secretion by the nucleus accumbens is seen in Huntington disease and anxiety disorders.