Abstracts - Association for Chemoreception Sciences

generalist and specialized species can be found that collect
pollen and nectar either from many plant families (polylectic)
or from only few species (oligolectic). In some cases, both types
of food preferences can be found within the same genus, like in
the mason bee genus Osmia. Here we investigate how the floral
preference is reflected in the neuroanatomy of the olfactory
system. We employed confocal microscopy scanning and
3D-reconstruction for quantitative analyses of major neuropile
volumes. We counted the number of functional units (glomeruli)
within the antennal lobe, the first olfactory neuropile in insects,
and quantified synaptic structures in higher-order sensory
integration centers (mushroom bodies). The investigated Osmia
species showed significant differences in selected neuropile
volumes and also a large interspecies variance in glomerular
numbers, correlated to floral preference. The strictly oligolectic
species Osmia adunca showed the smallest number of glomeruli,
whereas all polylectic species showed larger glomerular numbers.
The mushroom bodies of polylectic and oligolectic species
showed the same density of synaptic structures, but expressed
significant volume differences in the subregions that process
olfactory information. Chemical analyzes of host-plant odors
and behavioral tests will be next steps to understand the large
impact of floral preference on the complexity of the olfactory
system in bees. Acknowledgements: DFG KE-1701 1/1
#P100 POSTER SESSION II:
OLFACTION DEVELOPMENT; TASTE CNS;
NEUROIMAGING; OLFACTION CNS
Temporal-spatial transformation in the piriform cortex
Alex Koulakov 1 , Honi Sanders 2 , Brian Kolterman 1 , Dima Rinberg 3 ,
John Lisman 1
1
Cold Spring Harbor Laboratory Cold Spring Harbor, NY, USA,
2
Brandeis University Waltham, MA, USA, 3 New York University
New York, NY, USA
Mitral cells of the olfactory bulb respond to stimuli with
brief and temporally precise transient changes in the firing
rate (sharp events) that tile the inhalation cycle. This suggests
that information about odorants can be encoded by the
temporal sequence of these events. Here we propose a class of
computational models for the olfactory cortex that can detect
such sequences and convert them into a spatial pattern that
can be recognized by standard attractor networks. We propose
that the olfactory cortex contains groups of cells that can be
sequentially activated by inputs from mitral cells synchronized at
different phases of the respiratory cycle. Neurons in each group
can be persistently activated by virtue of, for example, an intrinsic
bistability mechanism. The pattern of activation of neurons
in each group carries a snapshot of coincidences in mitral cell
sharp events at a particular phase of the breathing cycle. Due to
long-range intracortical connectivity, the activation of one group
“enables” bistability in another group which can then form a
snapshot of mitral cell activity at a later phase of the respiratory
cycle. In this way, persistent activation of groups of neuron
occurs sequentially, each in turn representing the olfactory bulb
activity at a certain phase of the sequence. We further show that
sharp events in mitral cell responses occur at a preferred phase of
gamma cycles (measured in the field potential). Given that there
are only a few gamma cycles within a sniff, the number of groups
needed to define gamma cycle specific snapshots of an odorant
is not large. Recognition may occur when the spatial pattern
becomes sufficient to distinguish among the potential odorants.
#P101 POSTER SESSION II:
OLFACTION DEVELOPMENT; TASTE CNS;
NEUROIMAGING; OLFACTION CNS
Unique Cholinergic Interneuron Populations in the Mouse
Accessory Olfactory Bulb: Neurochemical Expression and
Fiber Density
Kurt Krosnowski, Sarah Ashby, Weihong Lin
University of Maryland Baltimore County Baltimore, MD, USA
The accessory olfactory bulb (AOB) is a primary central
processing site of sensory information detected via the
vomeronasal organ. The AOB contains diverse populations of
intrinsic interneurons. We detected a largely unidentified choline
acetyltransferase-expressing (ChAT) cholinergic interneuron
population using ChAT (BAC) -eGFP mice. Here we classified
their neurochemical expression and distribution throughout
the AOB. We then determined if this cholinergic interneuron
population differs from other known populations of interneurons
in the AOB and main olfactory bulb (MOB). Similar to the
MOB (Krosnowski et al 2012), we found that all cholinergic
interneurons are neither dopaminergic nor GABAergic. While
most ChAT expressing cells in the external plexiform layer (EPL)
of the AOB are not glutamatergic, we found some coexpression
between ChAT-GFP and GluR2/3, a glutamatergic marker, in
contrast with results obtained from the MOB. Also, unlike the
cholinergic interneuron population in the MOB, the majority of
cholinergic interneurons in the AOB do not express a calcium
binding protein, calbindin-D28K. Further, clear differences can
be seen between cholinergic nerve fibers in the internal plexiform
layer (IPL) of the MOB and the AOB. Unlike in the MOB,
where the highest density of cholinergic nerve fibers was found
in the IPL, in the AOB, the IPL contains the fewest visible fibers.
Instead, the majority of cholinergic fibers in the AOB are found
in the EPL. Thus, our data supports the idea that the intrinsic
cholinergic interneuron populations in the AOB are distinct
from previously identified interneuron populations in both
the MOB and AOB and this suggests that they play a unique
role in signal processing in the accessory olfactory system.
Acknowledgements: NIH/NIDCD 009269, 012831 and ARRA
administrative supplement to WL
POSTER PRESENTATIONS
Abstracts are printed as submitted by the author(s).
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