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#P79 WITHDRAWN
#P80
POSTER SESSION II:
TRIGEMINAL SYSTEM; TASTE CNS;
NEUROIMAGING; OLFACTION CNS
Short Axon cells provide both excitatory and inhibitory drive
to the mitral/tufted cells
Dinu F. Albeanu, Arkarup Banerjee, Fred Marbach, Matthew Koh
Cold Spring Harbor Laboratory Cold Spring Harbor, NY, USA
Short-axon (SA) cells, in the glomerular layer, receive inputs from
olfactory sensory neurons and/or external tufted (ET) cells and
release GABA and Dopamine, synapsing onto juxtaglomerular
cells as far as tens of glomeruli away (Kiyokage et al., 2010).
Computational models (Cleland et al, 2007) have suggested that
SA cells may be involved in long-range normalization of bulb
output, but to date their function in the intact brain has not been
investigated. We used a Cre-loxP approach to target neuronal
activity reporters (GCAMP3), or light gated switches
(Channelrhodopsin2 and Halorhodopsin) to SA cells. We imaged
GCAMP3 responses by wide-field microscopy to odor stimulation
across a range of concentrations. Odorants induced transient, yet
widespread SA responses, in contrast to focal glomerular patterns
observed via intrinsic optical imaging. To understand the roles
played by the SA network on the bulb output, we recorded
extracellularly from M/T cells using tetrodes in anaesthetized mice.
In conjunction, we selectively activated/inactivated SA cells by
shining blue/yellow light either throughout the dorsal bulb surface
or in specific spatial patterns employing a digital micro-mirror
device (DMD). Pairing odor presentation at various concentrations
with light, indicates that SA cells provide both excitatory and
inhibitory drive to the M/T cells in a stimulus specific fashion.
At low odorant concentrations, SA cells provide excitatory input,
whereas in response to stronger stimuli, both excitatory and
inhibitory drives are present. We propose that the SA network
regulates the dynamic range of M/T cell firing by amplifying the
weak inputs and down-scaling the stronger ones.
#P81
POSTER SESSION II:
TRIGEMINAL SYSTEM; TASTE CNS;
NEUROIMAGING; OLFACTION CNS
Emergent spatially distributed synaptic clusters in a large-scale
network model of the olfactory bulb
Yuguo Yu
1
, Thomas S. McTavish
1
, Michael L. Hines
2
,
Gordon M. Shepherd
1
, Michele Migliore
3
1
Department of Neurobiology, Yale School of Medicine New Haven,
CT, USA,
2
Department of Computer Science, Yale University
New Haven, CT, USA,
3
Institute of Biophysics, National Research
Council Palermo, Italy
Odor stimuli set up patterns of activity in the olfactory glomerular
layer of the olfactory bulb, which are further processed by a
network of mitral and granule cells through their dendrodendritic
synaptic interactions. To obtain insight and guide future
experiments into the role of these interactions, we constructed and
analyzed a computational model of 500 mitral cells and 10,000
granule cells randomly connected with an experimentally-estimated
10% probability. In order to have a realistic representation of the
glomerular activation during an odor presentation we used the
experimental findings of Mori et al. (2006) to model the activity
generated in 73 identified glomeruli by 72 specific odor inputs
corresponding to 12 different chemical series. We show that in
response to a given odor pattern in the glomeruli, clustered patterns
of distributed mitral cell and granule cell synaptic clusters naturally
emerge. As the clusters evolve, so do the network dynamics.
Granule cells become more active permitting lateral inhibition of
weakly driven glomeruli and synchrony between the more strongly
activated glomeruli. The resulting clusters of inhibitory synapses
appear to play a critical role in transforming the network from a
relatively random high-firing rate mode into a more synchronized,
sparsely low-firing rate mode. The model gives insight into the
possible correlation between odor chemical structure and synaptic
cluster size and location, and predicts the possible interactions
between different odors. Acknowledgements: NIH/NIDCD
R01 DC 009977-01
#P82
POSTER SESSION II:
TRIGEMINAL SYSTEM; TASTE CNS;
NEUROIMAGING; OLFACTION CNS
Multiple memory traces after associative learning in the
honey bee antennal lobe
C Giovanni Galizia, Lisa Rath, Paul Szyszka
University of Konstanz Konstanz, Germany
Learning the simple association between two stimuli gives rise to
multiple memory traces in the brain. These memory traces are
expressed as altered synaptic connections and neural excitability,
evolve over time, and are distributed across brain areas. Here we
ask how associative learning affects early sensory processing.
We investigated the effect of associative odor-reward learning on
odor processing in the honey bee primary olfactory area, the
antennal lobe, by combining classical conditioning with in vivo
calcium imaging of secondary olfactory neurons, the projection
neurons in the antennal lobe. We trained bees in a differential
conditioning paradigm in which one odor was paired with a reward
while another odor was presented without a reward. We found
associative plasticity of odor representations 2 to 5 hours after
discriminative odor learning, which increased the difference
between rewarded and unrewarded odors. Moreover, the learning-
induced changes in a glomerulus could be predicted from its
response profile before training. The data is consistent with a neural
network model of the antennal lobe, which we based on two plastic
synapse types and two well-known learning rules: associative,
reinforcer-dependent Hebbian plasticity at synapses between
olfactory receptor neurons and projection neurons, and reinforcer-
independent Hebbian plasticity at synapses between local
interneurons and olfactory receptor neurons. The observed changes
strengthen the idea that odor learning optimizes odor
representations and facilitates the detection and discrimination of
learned odors. Acknowledgements: DFG and BMBF
54 | AChemS Abstracts 2012
Abstracts are printed as submitted by the author(s)
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