Abstracts - Association for Chemoreception Sciences

#P210 POSTER SESSION V:
CENTRAL OLFACTION; CHEMOSENSORY
PSYCHOPHYSICS & CLINICAL STUDIES
Odor fear conditioning and olfactory system slow-wave sleep
Dylan C. Barnes 1,2 , Julie Chapuis 1 , Donald A. Wilson 1,2,3
1
EBI, NKI Orangeburg, NY, USA, 2 CUNY New York, NY, USA,
3
NYU Medical School New York, NY, USA
Sleep plays an active role in memory consolidation. Sleep
structure (REM/ Slow-wave sleep [SWS]) is modified after
conditioning, and in some cortical circuits, SWS is associated
with replay of the learned experience. Interestingly, the sleep
modifications can be local, only affecting activity in the brain
regions active during the training. Here, we wanted to ascertain
possible changes in sleep structure within olfactory cortex
following odor fear conditioning. We recorded local field
potentials (LFP) from the anterior piriform cortex (aPCX) in
behaving animals and analyzed odor-evoked changes during fear
conditioning and subsequent sleep structure modifications.
Long-Evans hooded rats were chronically implanted with
telemetry electrodes in the aPCX. Rats were placed in a
conditioning box for 30 min on three baseline days, conditioned
with ten paired odor-shock stimuli on the fourth day, and tested
with five odor pulses on the fifth day. On the conditioning and
test days, behavioral (freezing or vocalization), autonomic (heart
rate) and LFP responses to the conditioned odor were examined.
After each daily session, we placed the animal in a dark, sound
attenuating chamber and recorded LFPs and EMG for 4 hours.
Preliminary data show that rats learned behavioral and autonomic
fear responses to the odor and that aPCX odor-evoked beta (15-
40 Hz) oscillatory activity may correlate with the magnitude of
the fear response. Furthermore, aPCX SWS increased following
odor-shock conditioning compared to baseline days. Unpaired
control rats showed neither odor fear responses nor an increase in
SWS. Finally, the activity of aPCX single-units during SWS was
shaped by recent odor experience and there was enhanced
functional connectivity between the aPCX and hippocampus
during SWS compared to other period. Acknowledgements:
NIDCD to D.A.W. Fyssen Foundation Fellowship to J.C.
#P211 POSTER SESSION V:
CENTRAL OLFACTION; CHEMOSENSORY
PSYCHOPHYSICS & CLINICAL STUDIES
A neural pathway underlying dynamic control of odor-induced
responses to a wide range of odor concentrations
Hong Lei, Hong-Yan Chiu, John G. Hildebrand
Department of Neuroscience, University of Arizona Tucson,
AZ, USA
The olfactory system of any animal species must be able to cope
with a wide range of odor concentrations that often fluctuate
instantaneously in large magnitude in nature. Little is known on
how olfactory circuits at the first synaptic center – the olfactory
bulb in vertebrates or antennal lobe (AL) in insects – adjust their
sensitivity to quickly encode the concentration fluctuations. We
have conducted a series of experiments in the AL of the hawk
moth, Manduca sexta, to gain insights on this gating mechanism.
In moth AL a special set of enlarged glomeruli located at the
beginning portion of male AL – the macroglomerular complex or
MGC – is devoted to process the conspecific female sex
pheromones. The output (projection) neurons (or PNs) of MGC
can be readily identified using juxtacellular recording method in
conjunction with pheromonal stimulation. Upon stimulation of a
series of 5 odor pulses, PNs often produce the strongest response
to the 1st odor pulse and then weaker but constant responses to
the rest of pulses, suggesting there is a fast inhibitory feedback
pathway regulating the PN’s sensitivity, most likely via
GABAergic local interneurons (LNs). We therefore used a known
GABA-A receptor antagonist, picrotoxin, to manipulate the
putative feedback pathway. After the drug was added, the cell
activity changed from randomly bursting to non-spiking pattern;
response to odors was also much reduced but the after-inhibition
period following each response was increased. These results
indicate that PNs are tonically inhibited by GABAergic LNs. As
a feedback gating mechanism, the same pathway may regulate the
output of PNs depending on the activity level of the same PNs,
thus expanding the dynamic range of the PNs to respond to wide
range of odor concentrations. Acknowledgements: NIH grant
R01-DC-02761 to JGH
#P212 POSTER SESSION V:
CENTRAL OLFACTION; CHEMOSENSORY
PSYCHOPHYSICS & CLINICAL STUDIES
Transformation of olfactory information by neural networks
in the honey bee ‘olfactory cortex’
Martin F Strube-Bloss, Marco A Herrera-Valdez, Brian H Smith
School of Life Sciences Arizona State University Tempe, AZ, USA
Mushroom bodies (MBs) in the insect brain are higher-order
structures involved in integration of olfactory, visual, and
mechano-sensory information. They receive direct input from the
antennal lobes, which are the analogs of the mammalian olfactory
bulb. Our objective was to investigate how the neural circuitry in
the MB transforms the input from the antennal lobes. Therefore,
we recorded simultaneously the spiking activity from neurons
providing input to and output from this neuronal structure. Input
to each MB is provided by about 800 projection neurons (PNs) of
the antennal lobe (AL). PNs send their axons to the input region
of each MB, which consists of approximately 170,000 Kenyon
Cells [KC]. Output from each MB is carried by around 400
extrinsic neurons (ENs) projecting into different brain areas. We
recorded simultaneously single unit activity from PNs and ENs
while presenting two single odors (A, B) and their mixture (XA,B).
At both neuronal stages the responses of a single unit to XA,B was
not a simple liner transformation of the response to A and B. We
applied principal component analysis (PCA) to visualize the
timing of the establishment of stimulus representations at MB
input and output to estimate the latency of transfomation of the
signal by the MB network. Furthermore we analyzed the
contribution of a single unit to the ensemble representation of
odor A, B and XA,B separately for PNs and ENs. Surprisingly at
both levels units dominating the ensemble representation of A are
not the ones dominating B or XA,B. The characterization of these
complex responses and the degree of modification after processing
in the MB is necessary for further investigation of influence of
plasticity at the different stages of odor processing.
Acknowledgements: This research was funded by NIH NCRR
RR014166 to BHS, and by a subcontract of NIH NIDCD
(DC007997) to BHS.
P O S T E R S
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