a decreased vision or blindness (anopsia) in half the visual field of one or both eyes, usually on one side of the vertical midline. The most common causes of this damage are stroke, brain tumor, and trauma.
omonymous vs. heteronymous visual deficits
Damage to the optic tract: Runs from the optic chiasm to the lateral geniculate nucleus (LGN).
Damage at this point is “homonymous” – defects involve one visual field
“heteronymous” involves parts of both visual fields so defects are non-overlapping – occurs at chiasm
Axons of lateral geniculate nucleus (thalamus) representing the upper visual fields travel forward into the temporal lobe as Meyer's loop before turning toward the occipital cortex.
defective vision or blindness in approximately one-fourth of the visual field
the visual field organization seen in the lateral genticulate nuclues in the thalamus
Taste transmission of the tongue is carried to the brainstem via two main nerves:
facial/chorda tympani in the anterior 2/3 of the tongue
glossopharyngeal nerve on the posterior third.
touch/temp sensation on the tongue is provided by the trigeminal nerve in the front end and glossopharyngeal at the back.
The vagus nerve provides “taste” sensation to the ______ region (larynx, epiglottis) but we don’t perceive information from these taste buds as sweet, salt, bitter, etc. Instead, they appear to be involved with detecting irritants that cause us to cough or gag.
Taste Bud Afferents... location and path
Primary afferents that innervate taste buds reach the brainstem with VII (anterior 2/3 of tongue – chorda tympani), IX (posterior 1/3 of tongue) and X (epiglottis and larynx).
They travel within the brainstem in the solitary tract and end in the nucleus of the solitary tract, mostly in the rostral end --> 3 paths (thalamus --> VPM --> insula; hypothalamus; and reticular formation (gagg, cough reflex)
gustatory primary afferents
CN VII, IX, X --> solitary tract (medulla) --> solitary nucleus