White Matter Tracts Quiz
Regions do the work, but tracts decide what the damage looks like. A lesion in the white matter can disconnect two intact areas and produce a deficit neither region would produce alone, which is why tract anatomy is worth learning properly rather than skimming.
This quiz highlights two regions and asks which pathway joins them, then draws the tract on the model.
The three kinds of fibre
Association fibres connect regions within one hemisphere — the arcuate fasciculus linking Wernicke's to Broca's is the famous one, and cutting it produces conduction aphasia, where comprehension and speech are both intact but repetition fails.
Commissural fibres cross between hemispheres, overwhelmingly through the corpus callosum. Projection fibres run vertically between cortex and cord, funnelling through the internal capsule — which is why a small capsular stroke can cause a dense hemiplegia when a much larger cortical lesion might not.
Disconnection syndromes
The clinical payoff of tract anatomy is the disconnection syndrome: intact modules, severed link. Conduction aphasia from arcuate damage. Alexia without agraphia, where a patient can write but not read what they just wrote, from a lesion cutting visual cortex off from language areas. These make no sense as regional deficits and perfect sense as wiring faults.
Common questions
What does the arcuate fasciculus do?
It connects Wernicke's area to Broca's area, carrying language between comprehension and production. Damage causes conduction aphasia — fluent speech and preserved understanding, but a striking inability to repeat what was just heard.
What is the difference between association and projection fibres?
Association fibres connect regions within the same hemisphere. Projection fibres run vertically between the cortex and lower structures such as the brainstem and spinal cord, passing through the internal capsule.