Chemical Discrimination and Localization using Biologically Based Olfactory Processing

Project: Research project

Description

Current biomimetic models for odor classification lack detail knowledge of how the reinforcement signal is administered in each of the processing layers involved in odor recognition (Fig. 1). Smiths laboratory will revealfc the role of reinforcement learning, which is most likely due in large part to octopamine release from VUM neurons (Fig. 1) at two major sites of olfactory processing: (1) Antennal Lobe, mediated by changes of the local inhibition and (2) Mushroom Bodies, mediated by alternations of the inhibitory synapses from feedback neurons to Kenyon cell neurons and the octopamine release. We expect that repeated odor exposure with reinforcement is represented differently in the AL and MB, and produces results opposite from unreinforced learning. We also expect that equivalent associations will increase similarity. Our standard procedure is to open a small hole in the head capsule to expose the brain, after which electrodes are inserted into the visually apparent Antennal Lobe and Mushroom Body output areas (Fig 2). We typically record EMG activity in a muscle active during feeding {Smith, 1989 #1453} to monitor conditioned responses. In this situation subjects learn to discriminate one odor as the CS+ from another as the CS-, which is a protocol similar to the ones we propose above. All electrodes carry a fluorescent marker (Die-I) for later confirmation of positioning using confocal microscopy (Fig 3). Once electrodes are in place the hole is sealed with KWIK-SIL (WPI, Sarasota FL), which stabilizes the electrode and prevents desiccation of the brain. Electrodes consist of three polyurethane-coated copper wires glued together with wax onto tungsten wire attached to a glass capillary. The wires and capillary are connected to a headstage for the Neuralynx 16-channel amplifier system that will be dedicated to this work. Signals used for spike detection are measured differentially from all pairwise comparisons of the three electrodes inserted into the AL and MB. Recorded files are analyzed by importing into Spike2 software using a sampling frequency of 20 KHz.
StatusFinished
Effective start/end date5/1/104/30/13

Funding

  • DOD-NAVY: Office of Naval Research (ONR): $80,000.00

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Odors
Electrodes
Processing
Neurons
Wire
Brain
Reinforcement
Confocal microscopy
Reinforcement learning
Waxes
Biomimetics
Polyurethanes
Tungsten
Muscle
Sampling
Copper
Feedback
Glass