The representation of information about taste and odor in the orbitofrontal cortex

Complementary neurophysiological recordings in macaques and functional neuroimaging in humans show that the primary taste cortex in the rostral insula and adjoining frontal operculum provides separate and combined representations of the taste, temperature, and texture (including viscosity and fat texture) of food in the mouth independently of hunger and thus of reward value and pleasantness. One synapse on, in the orbitofrontal cortex, these sensory inputs are for some neurons combined by learning with olfactory and visual inputs, and these neurons encode food reward in that they only respond to food when hungry and in that activations here correlate with subjective pleasantness and with individual differences in and cognitive modulation of the hedonic value of food. Information theory analysis shows a robust representation of taste in the orbitofrontal cortex, with an average mutual information of 0.45 bits for each neuron about which of six tastants (glucose, NaCl, HCl, quinine-HCl, monosodium glutamate, and water) was present, averaged across 135 gustatory neurons. The information increased with the number of neurons in the ensemble, but less than linearly, reflecting some redundancy. There was less information per neuron about which of six odors was present from orbitofrontal olfactory neurons, but the code was robust in that the information increased linearly with the number of neurons, reflecting independent information encoded by different neurons. Although some neurons were sharply tuned to individual tastants, the average encoding was quite distributed. © 2009 Springer Science + Business Media, LLC

Gender-selective neural populations: evidence from event-related fMRI repetition suppression

Accurate recognition of gender in another individual is integral to successful human social interaction and to mate selection. When we encounter another person, we are effortlessly able to identify their gender, most often through the information conveyed by their facial features. Faces comprise the most abundantly encountered cue used to classify human gender. Considering the importance of facial information in gender perception, relatively little is known about the mechanisms involved in perceiving gender through human facial cues. We used an event-related fMRI repetition suppression paradigm to explore the neural circuitry underlying gender perception from facial information. Participants viewed brief consecutive images consisting of either gender-same face pairings (two male faces or two female faces) or images of gender-different face pairings (a male face preceded or followed by a female face), while attending to facial attractiveness in both conditions. Using a region-of-interest approach, we found repetition suppression on gender-same trials within the left ventral temporal fusiform gyrus and in the right collateral sulcus. Whole-brain voxel-wise analyses revealed selectivity for face gender again in the right collateral sulcus, in addition to the left cuneus and the right lateral occipital gyrus. Our results indicate that in addition to the face-selective FFA, cortical areas that are not traditionally considered to be “face-selective” are involved in the perception of gender-based facial cues