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12 | AChemS Abstracts 2012
Abstracts are printed as submitted by the author(s)
and flavor. We show that unexpected oral stimulation results in
suppression of visual cortex and up-regulation of sensory, attention
and reward regions and we demonstrate that labels about the
nutritional value of the flavors being consumed impact
hypothalamic responses and perceived pleasantness. We also
find that the magnitudes of such effects are often influenced by
individual factors such as body mass index and sensitivity to
reward. Taken together the findings underscore the principle that
sensation involves neural circuits beyond those specialized for
sensory representation. What is ultimately perceived results from
elaborate network interactions guided by behavioral optimization
rather than a veridical representation of the world.
Acknowledgements: NIDCD R01DC6706 PepsiCo
#6
SYMPOSIUM: THE FLAVOR OF THINGS TO
COME: EXPECTATION & THE PROCESSING
OF CHEMOSENSORY INFORMATION
Effects of cue-triggered expectation on cortical processing
of taste
Alfredo Fontanini
Department of Neurobiology and Behavior, SUNY Stony Brook
Stony Brook, NY, USA
Food does not appear in one’s mouth unexpectedly. Tasting is
typically the outcome of a behavioral sequence promoted by
anticipatory cues. The sight of a dish, its odor or the sound of a
drink being poured are all signals that trigger expectations about
the availability of a gustatory stimulus. As a result gustatory
information is often perceived against the background of prior
expectations. Expectation influences neural activity in two ways:
it alters the background state of cortical networks and modulates
responses to sensory stimulation. I will present evidence for a link
between these two phenomena. Results from a combination of
electrophysiological, behavioral and pharmacological techniques
will be featured. I will discuss evidence showing how anticipatory
cues can activate the gustatory cortex (GC) in behaving rodents.
Recordings from rats trained to perform a one-cue self-
administration paradigm or a two-cues auditory go/no-go task will
be shown. These data will provide evidence for a functional role of
cue-induced anticipatory activity in GC. Additionally, responses to
cued self-deliveries of tastants will be compared with those evoked
by unexpected or erroneously-expected stimuli. Differences in the
coding will be described and related to priming activity triggered
by anticipatory cues. A functional link between anticipatory activity
and changes in taste processing will be presented. Finally, data will
be shown on how the effects of expectation in GC depend on top-
down inputs from the basolateral amygdala. Results from multiple
experimental approaches will be used to unveil the circuits
mediating the effects of amygdala’s inputs. Altogether our data will
provide a new model explaining how changes in the state of
cortical circuits can shape the processing of expected and
unexpected stimuli. Acknowledgements: This work was supported
by National Institute of Deafness and Other Communication
Disorders Grants R01-DC010389 and R03-DC008885
#9
PRESIDENTIAL SYMPOSIUM:
NEURAL EPIGENETICS & OLFACTION
Dnmt3a-dependent Non-promoter DNAMethylation Facilitates
Transcription of Neurogenic Genes
Hao Wu
1
, Volkan Coskun
2
, Jifang Tao
2
, Wei Xie
3
, Weihong Ge
1
,
Kazuaki Yoshikawa
4
, En Li
5
, Yi Zhang
6
, Yi Eve Sun
1,2
1
Department of Molecular and Medical Pharmacology, University
of California Los Angeles (UCLA) Los Angeles, CA, USA,
2
Department of Psychiatry and Biobehavioral Sciences, Intellectual
Development and Disabilities Research Center at Semel Institute
for Neuroscience, UCLA Los Angeles, CA, USA,
3
Molecular
Biology Institute, UCLA School of Medicine Los Angeles, CA, USA,
4
Laboratory of Regulation of Neuronal Development, Institute for
Protein Research, Osaka University Osaka, Japan,
5
Novartis
Institutes for Biomedical Research Cambridge, MA, USA,
6
Howard
Hughes Medical Institute, Department of Biochemistry and
Biophysics, Lineberger Comprehensive Cancer Center, University
of North Carolina at Chapel Hill Chapel Hill, NC, USA
DNA methylation at proximal promoters facilitates lineage
restriction by silencing cell-type specific genes. However,
euchromatic DNA methylation frequently occurs in regions outside
promoters. The functions of such non-proximal promoter DNA
methylation are unclear. Here we show that the de novo DNA
methyltransferase Dnmt3a is expressed in postnatal neural stem
cells (NSCs) and is required for neurogenesis. Genome-wide
analysis of postnatal NSCs indicates that Dnmt3a occupies and
methylates intergenic regions and gene bodies flanking proximal
promoters of a large cohort of transcriptionally permissive genes,
many of which encode regulators of neurogenesis. Surprisingly,
Dnmt3a-dependent non-proximal promoter methylation promotes
expression of these neurogenic genes by functionally antagonizing
Polycomb repression. Thus, non-promoter DNA methylation by
Dnmt3a may be utilized for maintaining active chromatin states of
genes critical for development.
#10
PRESIDENTIAL SYMPOSIUM:
NEURAL EPIGENETICS & OLFACTION
Mechanisms of Odorant Receptor Gene Silencing
John Ngai
Dept of MCB and Helen Wills Neuroscience Institute,
University of California Berkeley, CA, USA
In the vertebrate olfactory system, individual olfactory sensory
neurons typically express just one odorant receptor (OR) gene from
a large repertoire that ranges from 50~150 genes in fish to >1000
genes in rodents. The highly regulated expression of OR genes
according to the “one receptor, one neuron” rule defines the
functional identity of the sensory neuron by determining the
odorants to which the cell responds. ORs also play a role in the
precise targeting of the olfactory sensory neurons’ axons in the
olfactory bulb, which underlies the anatomical basis of the
olfactory sensory map. How is the expression of one OR gene
established and maintained in each neuron? Previous studies have
shown that individual sensory neurons can in rare instances
sequentially express multiple OR genes, with such gene switching
events occurring more frequently when the initial OR gene
expressed by the cell is a pseudogene. These observations support a
model in which a functional OR, once selected, silences the
expression of all other OR genes in the genome. In this manner,
OR gene silencing prevents gene switching and ensures the stable
expression of a single OR in each olfactory sensory neuron.
O R A L A B S T R A C T S