State dependence of olfactory perception as a function of taste cortical inactivation

Abstract

As anyone who has suffered through a head cold knows, food eaten when the olfactory system is impaired tastes 'wrong', an experience that leads many to conclude that taste stimuli are processed normally only when the olfactory system is unimpaired. Evidence that the taste system influences olfactory perception, however, has been vanishingly rare. We found just such an influence; if taste cortex was inactivated when an odor was first presented, later presentations were properly appreciated only if taste cortex was again inactivated.

Figure 1. Food preferences are socially transmitted through odor cues

a. Social transmission of food preference (STFP). b. Rats made anosmic before training later showed no preference for the demonstrated (white bars) food over the undemonstrated (grey bars) food. Control rats developed normal preferences. Here and in all figs, *=significant (see text).

Figure 2. STFP depends on taste cortex

a. Left—a coronal slice through taste cortex, showing a representative cannula track. Right—a schematic of the same slice, reprinted with permission, showing the locations of all cannula tips. Filled triangles=muscimol infusions; open circles=control (vehicle) infusions. AI/DI/GI: agranular/dysgranular/granular insular cortex; Pir: piriform cortex; S1: somatosensory cortex. Scale bar=1mm. b. Taste cortical inactivation during STFP training inhibited learning of preference for the demonstrated food, regardless of whether training was face-to-face (left bars) or across a mesh screen (right bars). c. Cortical inactivation before testing inhibited preference learning.

Figure 3. State-dependency of olfactory processing

A. Double inactivation of taste cortex—once before training and again before testing—rescued normal learned preferences (compare to rats receiving control infusions). b. A coronal slice (reprinted with permission15) showing the spread of muscimol around a representative cannula tip is confined to taste cortex. Same abbreviations as in Figure 2A. Scale bar=1mm.