Taste agnosia following gustatory neocortex ablation: dissociation from odor and generality across taste qualities

In Experiment 1, rats trained to avoid drinking in the presence of a compound odor (benzyl acetate) and taste (sucrose) conditional stimulus (CS) lost the taste habit but retained the odor habit following gustatory neocortex (GN) ablation. Conversely, olfactory bulb ablation resulted in loss of the odor habit but retention of the taste habit. In Experiment 2, rats lacking GN did not retain preoperatively instated learned aversions to a suprathreshold quinine hydrochloride (bitter) taste solution which had been employed as a CS. However, rats with GN lesions that were virtually identical to those of the bitter-trained group retained a preoperatively learned aversion to a hydrochloric acid (sour) CS. Experiment 3 demonstrated that reliable agnosia for an acid CS could be produced by lesions that extended more deeply into perirhinal areas near the claustrum at the level of the GN. It is concluded that the agnosia following GN ablation is relatively specific to gustation and that agnosia for preoperatively acquired taste aversion habits occurs for all four basic gustatory stimuli following anterolateral cortex ablations centered on the GN.