Mucosal activity patterns as a basis for olfactory discrimination: comparing behavior and optical recordings

• Published in: Brain research 2003-08, Vol.981 (1), p.1-11
• Main Authors: Kent, P.F, Mozell, M.M, Youngentob, S.L, Yurco, P
• Format: Article
• Language: English
• Subjects: Aldehydes - pharmacology; Animals; Behavior; Behavior, Animal; Biological and medical sciences; Brain Mapping; Conditioning, Operant - physiology; Diagnostic Imaging; Discrimination Learning - physiology; Dose-Response Relationship, Drug; Fluorescent Dyes - pharmacokinetics; Fundamental and applied biological sciences. Psychology; Individuality; Mucosal activity pattern; Nasal Septum - drug effects; Nasal Septum - physiology; Odorant quality perception; Odorants; Olfactory Mucosa - anatomy & histology; Olfactory Mucosa - drug effects; Olfactory Mucosa - physiology; Olfactory system and olfaction. Gustatory system and gustation; Optical imaging; Perception; Psychophysics - methods; Pyridinium Compounds - pharmacokinetics; Rat; Rats; Rats, Long-Evans; Sensory Thresholds; Smell - physiology; Stimulation, Chemical; Turbinates - drug effects; Turbinates - physiology; Vertebrates: nervous system and sense organs
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/S0006-8993(03)02512-5

In over half a century numerous studies have demonstrated that different odorants produce individually different spatial patterns of neural receptor activity on the olfactory mucosa. However, the thought that these differential activity patterns could be the neural code underlying olfactory perception has not been tested directly. In the present study using operant techniques, rats were trained to differentially identify five odors from a homologous series of iso-intensive straight-chain aldehydes that differed serially by only one carbon atom, viz. hexaldehyde to decaldehyde. The rats identified each of the five odorants with greater than 90% correct identification. The degree of perceptual similarity between any pair of the five odorants was determined. Using multidimensional scaling techniques (MDS) the similarity measures yielded a two-dimensional perceptual odorant space. Optical techniques were used to record the olfactory mucosal activity patterns in response to these same five iso-intensive aldehydes. The mucosal activity elicited by each odorant revealed individually distinct band-like patterns that varied both within and across these bands. More importantly, the relative differential responsivity of the bands was related to chain length. An MDS analysis of the dissimilarity measure between all possible pairs of odorant induced activity patterns yielded a two-dimensional neurophysiologic odorant space. Further analysis indicated that the neurophysiologic and psychophysically determined odorant spaces were highly correlated ( F 1,39=23.9, P=nil). These results give additional credence to the concept that the odorant-induced mucosal activity patterns may serve as the substrate for the perception of odorant quality.