The neural basis of taste
In chemosensory perception, ethologically relevant stimuli, such as an odor or a taste, are detected by receptors at the periphery and then processed by sensory pathways receiving strong feedback from limbic and reward-related brain regions. The primary gustatory cortex (GC), in particular, is an ideal model system to study how representations of sensory stimuli arise, and how expectations affects them via top-down projections from higher-cortical areas. In a series of papers in collaboration with the Fontanini and La Camera labs at Stony Brook University, we established a biologically plausible model explaining how bottom-up and top-down processes interact to shape sensory perception during taste processing.
Whereas previous work mainly studied neural activity evoked by taste, we focussed on spontaneous activity as a means to uncover the circuit intrinsic dynamics. The observed dynamical feature of ongoing neural activity can be explained in terms of a clustered network model, characterized by the emergence of a long timescale (~100 ms). Neural activity evoked by taste, and its modulation by expectation can be predicted in terms of the dynamical features of ongoing activity.
Whereas previous work mainly studied neural activity evoked by taste, we focussed on spontaneous activity as a means to uncover the circuit intrinsic dynamics. The observed dynamical feature of ongoing neural activity can be explained in terms of a clustered network model, characterized by the emergence of a long timescale (~100 ms). Neural activity evoked by taste, and its modulation by expectation can be predicted in terms of the dynamical features of ongoing activity.
- L. Mazzucato, A. Fontanini, G. La Camera. "Dynamics of multistable states during ongoing and evoked cortical activity." Journal of Neuroscience 35.21 (2015): 8214-8231. [arXiv:1508.00165] - [download pdf]
- L. Mazzucato, A. Fontanini, G. La Camera. "Stimuli reduce the dimensionality of cortical activity." Frontiers in systems neuroscience 10 (2016). [arxiv:1509.03621] - [download pdf]
- L. Mazzucato, G. La Camera, A. Fontanini. "Expectation-induced modulation of metastable activity underlies faster coding of sensory stimuli." [preprint on biorxiv]
Prefrontal cortex preferentially responds to aversive tastants
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Most of the research on cortical processing of taste has focused on either the primary gustatory cortex (GC) or the orbitofrontal cortex (OFC). However, these are not the only areas involved in taste processing. Gustatory information can also reach another frontal region, the medial prefrontal cortex (mPFC), via direct projections from GC. mPFC has been studied extensively in relation to its role in controlling goal-directed action and reward-guided behaviors, yet very little is known about its involvement in taste coding. We compared responses to palatable and aversive taste stimuli between GC and mPFC. Neurons in mPFC can encode the chemosensory identity of gustatory stimuli. However, responses in mPFC are sparser, more narrowly tuned, and have a later onset than in GC. Although taste quality is more robustly represented in GC, taste palatability is coded equally well in the two areas. Whereas GC responds with equal strength to both palatable and aversive tastes, mPFC shows a stronger response to aversive tastes.
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