Neuroscience PRITE Review

60 yo right‑handed man, getting lost and writing only on the right half of paper. Left‑sided hemi‑neglect—where is the lesion?

• Left parietal lobe

• Right frontal lobe

• Right parietal lobe

• Left occipital lobe

Answer explanation

The nondominant (usually right) inferior‑posterior parietal cortex integrates visual, tactile, and proprioceptive inputs into a unified spatial map of contralateral space. Injury disconnects awareness of the left side of the body and environment, producing hemi‑neglect, constructional apraxia, and dressing apraxia. Patients may deny ownership of the affected limb or attribute its movement to others (anosognosia and asomatognosia). Frontal, temporal, or occipital lesions can impair attention or vision but do not create the characteristic neglect syndrome.

66 yo with long‑standing hypertension develops vertigo, diplopia, nausea, vomiting, hiccups, left‑sided facial numbness, nystagmus, hoarseness, limb ataxia, staggering gait, and a tendency to fall to the left—diagnosis?

• Medial medullary stroke

• Lateral medullary stroke

• Cerebellar hemorrhage

• Pontine infarction

Answer explanation

Occlusion of the posterior‑inferior cerebellar artery causes the Wallenberg (lateral medullary) syndrome. Ipsilateral symptoms—facial numbness (trigeminal nucleus), Horner syndrome, nystagmus, hoarseness, dysphagia (nucleus ambiguus), and limb ataxia—arise alongside contralateral loss of body pain and temperature (spinothalamic tract). Vestibular nuclei involvement explains vertigo and vomiting, whereas damage to respiratory centers produces hiccups. Midline (medial) medullary or pontine strokes give different crossed findings.

26 yo with headaches and right‑hand clumsiness for weeks; exam shows dysdiadochokinesia, intention tremor, and mild dysmetria with an otherwise normal neurologic exam—where would MRI show damage?

• Basal ganglia

• Cerebellum

• Primary motor cortex

• Internal capsule

Answer explanation

The cerebellar hemispheres coordinate timing and amplitude of ipsilateral limb movements. Lesions produce intention tremor (worsening as the limb approaches a target), dysmetria on finger–nose testing, and impaired rapid alternating movements (dysdiadochokinesia). Because descending motor pathways cross twice, deficits appear on the same side as the cerebellar injury. Basal ganglia or corticospinal tract lesions impair initiation or strength rather than precision of movement.

78 yo post‑ischemic‑stroke patient with mild hemiplegia is unaware of weakness, neglects one side when dressing/grooming, and misattributes limb movements—brain area affected?

• Right parietal lobe

• Left frontal lobe

• Right temporal lobe

• Left parietal lobe

Answer explanation

The right inferior parietal lobule constructs internal representations of body schema and external space. Damage leads to hemispatial neglect, extinction to double stimulation, and denial of paresis (anosognosia). The patient may confabulate explanations for involuntary limb movement (alien‑limb phenomena). Left parietal lesions impair language‑related praxis; temporal lesions affect memory or emotion but not spatial attention.

Adult neurogenesis occurs predominantly in which brain area?

• Caudate nucleus

• Dentate gyrus of hippocampus

• Prefrontal cortex

• Amygdala

Answer explanation

Neural progenitor cells in the subgranular zone of the dentate gyrus divide, migrate a short distance into the granule‑cell layer, and differentiate into excitatory granule neurons. These newborn cells integrate into hippocampal circuits, contribute to pattern separation, and may support mood regulation and memory. In the adult human brain, robust neurogenesis outside the dentate gyrus and olfactory bulb is minimal or controversial.

Left anterior cerebral‑artery infarct most likely produces what clinical picture?

• Right facial droop with aphasia

• Weakness of contralateral foot and leg sparing face and arm with abulia

• Complete homonymous hemianopia

• Ipsilateral Horner syndrome

Answer explanation

The ACA supplies medial aspects of frontal and parietal lobes, including leg motor cortex and anterior cingulate. Infarction produces contralateral leg weakness and sensory loss, urinary incontinence, and abulia or reduced initiation due to cingulate damage. The face and arm are spared because they reside in lateral motor cortex (MCA territory). Posterior cerebral infarcts cause homonymous hemianopia, and Horner syndrome reflects sympathetic pathway injury.

Rapid change to profane, irresponsible behavior over six months suggests pathology in which lobe?

• Temporal lobe

• Parietal lobe

• Frontal lobe

• Occipital lobe

Answer explanation

The orbitofrontal and ventromedial regions of the frontal lobe modulate social conduct, impulse control, and foresight. Lesions, tumors, or frontotemporal degeneration here yield disinhibition, jocularity, profanity, and poor financial or sexual judgment. Temporal lobe pathology more typically causes memory or emotional disturbances, parietal lesions impair spatial awareness, and occipital damage affects vision.

Rapid onset of right facial weakness, left‑sided limb weakness, and diplopia indicates what process?

• Multiple sclerosis relapse

• Brain‑stem infarction

• Subdural hematoma

• Myasthenic crisis

Answer explanation

Crossed neurological deficits—cranial‑nerve palsy on one side with contralateral hemiparesis—localize to the brain‑stem, typically the pons where corticospinal fibers run near cranial‑nerve nuclei. Sudden onset in a vascular risk patient points to ischemic stroke of a basilar or pontine perforator artery. Demyelination evolves over days, subdural hematoma causes progressive cortical signs, and myasthenia involves fatigable weakness without sensory findings.

Orexin (hypocretin) is synthesized in which part of the brain?

• Ventromedial hypothalamus

• Lateral hypothalamic nuclei

• Nucleus basalis of Meynert

• Dorsal raphe nucleus

Answer explanation

A small cluster of neurons in the lateral and posterior hypothalamus produces orexin‑A and orexin‑B. These neuropeptides project widely to monoaminergic and cholinergic arousal centers, stabilizing wakefulness and promoting appetite. Loss of orexin cells causes narcolepsy with cataplexy, while overstimulation increases food‑seeking behavior.

Which brain area is activated by subliminal presentation of emotional faces?

• Primary visual cortex

• Amygdala

• Caudate head

• Dorsolateral prefrontal cortex

Answer explanation

The amygdala receives rapid, coarse visual input through subcortical pathways and responds to emotional expressions even when the stimulus is masked from conscious awareness. This permits swift autonomic and behavioral reactions to potential threats before detailed cortical analysis occurs. Primary visual cortex activity alone does not trigger such autonomic changes, and prefrontal engagement follows later for regulation.