Behavioral Health & Nervous Systems/Special Senses
Neuroanatomy by lesion
Learn the classic stroke syndromes. Lateral medullary (PICA): ipsilateral Horner syndrome, ataxia, facial pain/temperature loss, dysphagia, hoarseness, plus contralateral body pain/temperature loss. Medial medullary (anterior spinal artery): contralateral hemiparesis with tongue deviation toward the lesion. Internal capsule (lenticulostriate): pure contralateral motor and sensory deficit. Upper motor neuron lesions give spasticity, hyperreflexia, and Babinski sign; lower motor neuron lesions give flaccidity, atrophy, and fasciculations.
Pathways
Dorsal column carries vibration and proprioception and crosses in the medulla; spinothalamic carries pain and temperature and crosses within a few segments. Temporal retinal fibers cross at the chiasm, so a PCA infarct produces contralateral homonymous hemianopia with macular sparing because the occipital pole has dual MCA/PCA supply. CN III palsy gives a down-and-out eye with a dilated pupil; Horner syndrome gives ptosis, miosis, and anhidrosis.
Behavioral science
Distinguish classical from operant conditioning and fixed-ratio from variable-interval schedules. Sleep: slow-wave sleep in stage N3; REM shows saw-toothed waves, muscle atonia, and dreaming, with REM periods lengthening toward morning. Neurotransmitters: dopamine (mesolimbic reward), serotonin (raphe nuclei), norepinephrine (locus ceruleus), acetylcholine (nucleus basalis).
Traps
Confusing Wernicke aphasia (fluent, poor comprehension) with conduction aphasia (impaired repetition, intact comprehension). Treating a fixed, dilated pupil in a comatose patient as benign when it signals herniation. Conflating tolerance, dependence, and withdrawal. Missing a focal deficit by labeling symptoms functional.
Worked rule
Right PCA occlusion causes left homonymous hemianopia with macular sparing; right MCA occlusion causes left face and arm weakness with gaze preference toward the lesion and left neglect.