Mesothoracic input to the antennal lobe modulates the ability to track temporally complex stimuli.
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1
West Virginia University, Biology, United States
Recent studies indicate that wing beating causes an oscillating axial flow of air in the vicinity of the antennae and causing it to vibrate. These effects may increase odor-receptor interactions as well as physically disturb mechanosensory sensilla on the antennae and possibly olfactory receptor cells. It has long been known that a single pair of histamine immunoreactive cells, with bilateral dendrites in the mesothoracic ganglia, project bilaterally to the core of the antennal lobes (ALs). However, the functionality of these cells has never been determined. Recently we discovered that unitary spiking patterns and local field potentials from the AL, faithfully track olfactory and blank (mechano-sensory) stimuli, when pulsed at a frequency reflecting the wing beat (18-28Hz). However, this ability appears to rely on an intact “whole animal” preparation. Isolated head preparations used for intracellular recordings, have only observed stimulus tracking to ~10-15Hz. Using single cell, multi unit, psychophysical and pharmacological approaches, we have begun to explore the role of these histaminergic cells. Our preliminary multiunit results, where intact moths were impaled with 16 channel silicon probes and antennae were stimulated with both pulsed and continuous stimuli, indicate that pulse tracking is strongest for blank stimuli and odors with relatively lower volatility. Bath application of histamine significantly increased overall pulse tracking as indicated by power spectral density (PSD) analysis; this was due to increasing frequency responses. Intracellular evidence from our newly developed preparation with intact but exposed CNS, demonstrates that indeed both local and projection neurons are capable of tracking pulsed stimuli up to and in some cases beyond the upper wing beat frequency . However, if the neck connectives are cut, the firing rate of the damaged axons increases transiently and, thus, histamine is presumably up regulated within the AL resulting, again, in enhanced pulse tracking by AL cells. Finally, behavior pharmacological results, where moths were bilaterally injected with histamine antagonists and blindly tested across a concentration series of a previously conditioned odor, suggests that the loss of histamine function results in increased detection thresholds. Collectively, while there are still several unanswered questions, these results suggest two possible working hypotheses. First, that ascending input from mesothoracic ganglia provides a mechanism to enhance odor detection/identification in a manner similar to sniffing, or that it provides a mechanism to modulate non olfactory responses caused by the physical disturbance of the antennae by the wing beat.
Acknowledgements
We are greatful for the ongoing technical assistance from Shreejoy Tripathy, Joachim Schachtner and Regina Tiede. This work was supported by NIH-DC009417 to KCD
Keywords:
modulation,
Olfaction,
population coding,
Spatial Coding,
temporal coding
Conference:
Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012.
Presentation Type:
Poster Presentation (see alternatives below as well)
Topic:
Sensory: Olfaction and Taste
Citation:
Daly
KC,
Staudacher
EM,
Houot
B and
Burkland
R
(2012). Mesothoracic input to the antennal lobe modulates the ability to track temporally complex stimuli..
Conference Abstract:
Tenth International Congress of Neuroethology.
doi: 10.3389/conf.fnbeh.2012.27.00409
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Received:
02 May 2012;
Published Online:
07 Jul 2012.
*
Correspondence:
Dr. Kevin C Daly, West Virginia University, Biology, Morgantown, WV, 26505, United States, kevin.daly@mail.wvu.edu