Research On Measurement And Recognition Of Rats’ Olfaction And Gustation Based On Implanted Electrodes

The biological chemosensory system has an exquisite capacity to recognize and discriminate thousands of distinct chemical substances in very low concentrations, which is much better than current artificial chemosensory systems in speed and accuracy of chemical recognition. Research on mammalian olfacotry and gustatory sense is worthwhile in theory value and practical significance to increase knowledege of odorant and tastant recognition and design novel biomimic chemical recognition systems with higher sensitivity and specificity.Electrophysiological techniques are widely applied in reasearch of mechanism of olfacotry/gustatory perception, nerve pathways and neural decoding with merits of low cost. easy operation and long-term measurments. In this thesis, the experiment platform was constructed for research of olfacotry and gustatory sense based on electrophysiological recording.16-channel microwire electrode arrays were implanted into the olfactory bulb and gustatory cortex of anesthetized rats to record neural activities during chemical stimulation. We investigated the law of neural response to different olfacotry and gustatory stimuli. In addition, we develop a novel in vivo bioelectronic nose for odor recognition based on electrophysiological measurements of olfactory bulb and olfactory decodingThe main contents and contributions of this thesis are as follows:(1) Establishing the experiment platform for electrophysiological research of olfacotry and gustatory sense in anesthetized rats. The platform included odor and tastant delivery module, respiratory monitoring module, electrophysiological signal recording module and data analysis module. Procedures of animal preparation and electrode implantation were illustrated in detail. The recording site of electrode array was examined by postmortem histological reconstruction of the electrode track in olfactory bulb and gustatory cortex slice.(2) Test methodology was established to evaluate whether an olfacotry and gustatory neuron responted to a kind of stimulus. Neural activities within and without stimulation were represented in the PCA space and a neuron was considered as responsive if the distance between stimulant and spontaneous activity was larger than the standard distance.(3) Uncovering the correlations between respiratory cycles and olfactory bulb activities.Spike distribution of stimulant and spontaneous activity within different respiratory phase was calculated. Odors could change spike distribution in diferent ways.(4) Investigating the response time and adaptation time of olfactory bulb mitral cells to odors. The length and beginning of odor stimulation were set in the experiments. Exploring odorant concentration-dependent neural activity and low detection limit of mitral cells and setting up the appropriate concentration of odor stimulation in the experiments. The specificity of olfactory bulb was investigated by assessing spike activity and local field potential within diferent stimuli.(5) Designing a novel in vivo bioelectronic nose based on implanted electrodes. Neural responses of olfactory bulb to different odorants were measured in anesthetized rats in vivo by implanted 16-channel microwire electrode arrays and then extract odor information by using population vector algorithm from spike activity and ellipsoid modeling from local field potential. Smell was assessed by neural decoding methods based on support vector machine and k-nearest neighbors.(6) Investigating rats’gustatory nerve pathways. Electrophysiological activities of gustatory cortex were measured by inplanted electrods and analysed. A preliminary study on specificity of gustatory cortex to different tastants was carried out for further reasearch.