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both levels where they occur (glomerular layer and deeper layers
respectively) in anesthetized rats. Finally, we used different
concentrations of each stimulus to check for changes in odor
threshold. Using intrinsic optical signals imaging and local field
potential recordings, we observed that odor maps and changes in
oscillatory patterns of activity in the OB are present for both types
of stimuli at low concentrations (0.1% hexanal or 2% almond
aroma) in the majority of fasted rats (8 / 9 animals tested) but only
in a small fraction of fed animals (3 / 9 animals tested). For higher
odor concentrations (0.5% hexanal or 5% almond aroma), most fed
animals responded (7 / 9 animals tested). We conclude that fasting
deeply impacts the overall odor detection threshold in the OB.
Acknowledgements: Agence Nationale de la Recherche
ANR-09-JCJC-0117-01
#17
PLATFORM PRESENTATIONS:
OLFACTION
Functional glomerular organization in the mouse accessory
olfactory bulb
Julian P Meeks, Gary F Hammen, Diwakar Turaga,
Timothy E Holy
Washington University School of Medicine Dept. of Anatomy and
Neurobiology Saint Louis, MO, USA
The mouse accessory olfactory system (AOS) processes sensory
information about nonvolatile chemical cues, including urinary
sulfated steroids. The first neural circuit in the AOS pathway, the
accessory olfactory bulb (AOB) receives peripheral input from
vomeronasal sensory neurons (VSNs) via thousands of synaptic
pooling structures called glomeruli. In the main olfactory system,
imaging techniques have allowed direct observation of glomerular
activity patterns in response to odors. The complex organization of
glomeruli in the AOB has thus far prevented similar approaches.
We applied a new high-speed volumetric imaging technique,
objective-coupled planar illumination (OCPI) microscopy,
to image presynaptic Ca
2+
in
ex vivo
preparations taken from mice
expressing the genetically-encoded calcium indicator
GCaMP2
in
VSNs. This approach produced reliable volumetric activity images
across multiple randomized trials. We analyzed activity patterns to
a panel of sulfated steroids in order to associate each active
glomerulus with a known functional class of VSNs. We then
analyzed glomerulus positions from each VSN class for evidence of
chemical-topographical organization, or “chemotopy”. We found
that absolute glomerulus position gave little information about
chemical receptive field. However, we found that certain VSN
classes maintained close relative glomerulus positions. When we
analyzed the relationship between chemical receptive fields and
relative glomerulus position, we found no positive link between
them. In fact, the classes with the most closely associated glomeruli
had the most dissimilar receptive fields. We conclude that AOB
glomerular organization is non-chemotopic, and suggest that the
tightly associated glomerular modules represent fundamental
processing units in the AOS. Acknowledgements: NIH
1F32DC009352 (JPM) NIH 1K99DC011780 (JPM) NIH
5R01DC010381 (TEH) NIH 5R01NS068409 (TEH)
#18
PLATFORM PRESENTATIONS:
OLFACTION
Chemosensory interactions in rat olfactory cortex
Joost X Maier
1,2
, Donald B Katz
1,2
1
Brandeis University Department of Psychology Waltham, MA,
USA,
2
Brandeis University Volen National Center for Complex
Systems Waltham, MA, USA
Interactions between the gustatory and olfactory systems are
responsible for perception of flavor, which is central to the ability
to learn food preferences and aversions. While many examples
of behavioral correlates of taste-smell integration exist, the
physiological basis for such interactions remains largely unknown.
Based directly on recent behavioral work, the present research
focuses on multimodal influences on neuronal activity in rat
olfactory cortex. Electrophysiological recordings were made from
gustatory and/or posterior piriform cortex (1.4 mm posterior to
Bregma, 5.5 mm lateral, >5.5 mm ventral) of awake Long-Evans
rats, using implanted arrays of up to 16 moveable microelectrodes.
We recorded LFP and spiking activity while rats were presented
with taste and odor stimuli. Tastes were delivered through intra-oral
cannulae; odors were actively sampled using a nose poke.
Simultaneous monitoring of respiratory activity through intra-nasal
cannulae allowed us to determine the exact timing of olfactory
stimulation. The results show that ~50% of PPC neurons respond to
taste stimuli. Control experiments in which we inactivated primary
gustatory and olfactory sensory epithelia confirmed stimulus-
specificity of taste responses. We further confirmed that recordings
were made from olfactory cortex using known anatomical and
functional hallmarks, such as responsiveness to odor stimuli, and
modulation of olfactory, but not gustatory responses by the
respiratory signal. Our data demonstrate that PPC is a multimodal
area, receiving both olfactory and gustatory input. This finding
strengthens the idea that crossmodal interactions play an integral
role in chemosensory processing, and may be responsible for
guiding adaptive behaviors related to food preference.
#19
PLATFORM PRESENTATIONS:
OLFACTION
Lateral entorhinal cortex top-down modulation of odor
coding in the piriform cortex
Donald A Wilson
1,2
, WenJin J. Xu
1,2
, Benjamin A Sadrian
1,2
1
NKI/Emotional Brain Institute Orangeburg, NY, USA,
2
NYU School of Medicine New York, NY, USA
The lateral entorhinal cortex (LEC) is the gateway for olfactory
input to the hippocampus. Layer II/III LEC neurons receive direct
input from both the olfactory bulb and piriform cortex, and in turn
project to the hippocampal dentate gyrus and CA3. However, the
LEC also projects back to the piriform cortex (PCx) and olfactory
bulb (Insausti et al., 1997), and stimulation of the LEC depresses
olfactory bulb input to the piriform cortex (Mouly & Scala, 2006).
Furthermore, local field potential analyses reveal that in odor
discrimination-trained animals the EC can signal the olfactory
system prior to odor onset, potentially preparing the system for
odor sampling (Kay et al., 1996; Martin et al., 2007). Given that
activity in the LEC is shaped by input from the hippocampus,
amygdala and cholinergic input from the medial septum, the
present study examined how LEC top-down input modulates PCX
odor coding in rats and mice. Single-unit and LFP recordings were
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