title: Characterizing olfactory binary mixture interactions in Fischer 344 rats using behavioral reaction times.
abstract: Response times provide essential subthreshold perceptual data that extend beyond accuracy alone. Behavioral reaction times (RTs) were used to characterize rats' ability to detect individual odorants in a series of complimentary binary odorant mixture ratios. We employed an automated, liquid-dilution olfactometer to train Fischer 344 rats (N = 8) on an odor identification task using nonreinforced probe trials. Binary mixture ratios composed of aliphatic odorants (citral and octanol) were arranged such that relative contributions of the 2 components varied systematically by a factor of 1% (v/v). Odorant concentrations for the target (S+), control (S-), and mixture (S+:S-) odorants were presented relative to threshold for each rat. Rats were initially trained to respond by licking at a spout to obtain liquid reward for either citral or octanol as the reinforced target (S+) odorant. After achieving 100% accuracy, rats were transferred to variable ratio (VR 2) reinforcement for correct responding. Nonreinforced probe trials (2 per block of 22 trials) were tested for each mixture ratio and recorded as either S+ (rats lick-responded in the presence of the mixture) or S- (rats refrained from licking), thereby indicating detection of the trained, S+ odorant. To determine the perceived salience for each ratio, RTs (latency from odorant onset to lick response) were recorded for each trial. Consistent with previous studies, RTs for both odorants were shortest (~150-200ms) when the probe trials consisted of a single, monomolecular component. Binary mixtures that contained as little as 1% of the S-, nontarget odorant, however, were sufficiently different perceptually to increase behavioral RTs (i.e., rats hesitated longer before responding); RTs changed systematically as a function of the binary ratio. Interestingly, the rate of RT change was dependent on which odorant served as the S+, suggesting an asymmetric interaction between the 2 odorants. The data demonstrate the value of behavioral RT as a sensitive measure of suprathreshold perceptual responding.
authors: Program in Behavioral and Cognitive Neuroscience, Department of Psychology, University of Florida, Gainesville, FL 32611, USA.
authors: Wendy M
authors: WM
authors: Yoder
authors: Interdisciplinary Studies Major in Neurobiological Sciences, University of Florida, Gainesville, FL 32611, USA.
authors: Leslie
authors: L
authors: Gaynor
authors: Health Science Program, University of Florida, Gainesville, FL 32611, USA.
authors: Ethan
authors: E
authors: Windham
authors: Interdisciplinary Studies Major in Neurobiological Sciences, University of Florida, Gainesville, FL 32611, USA.
authors: Michelle
authors: M
authors: Lyman
authors: Interdisciplinary Studies Major in Neurobiological Sciences, University of Florida, Gainesville, FL 32611, USA.
authors: Olivia
authors: O
authors: Munizza
authors: Program in Behavioral and Cognitive Neuroscience, Department of Psychology, University of Florida, Gainesville, FL 32611, USA, Department of Psychiatry, University of Florida, Gainesville, FL 32611, USA, Department of Neuroscience, University of Florida, Gainesville, FL 32611, USA and.
authors: Barry
authors: B
authors: Setlow
authors: Jennifer L
authors: JL
authors: Bizon
authors: Program in Behavioral and Cognitive Neuroscience, Department of Psychology, University of Florida, Gainesville, FL 32611, USA, Center for Smell and Taste, University of Florida, Gainesville, FL 32611, USA dwsmith@ufl.edu.
authors: David W
authors: DW
authors: Smith
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D008297:Male; D009812:Odorants; D064367:Olfactometry; D051381:Rats; D011916:Rats, Inbred F344; D011930:Reaction Time; D012684:Sensory Thresholds / Q000502:physiology; D012903:Smell / Q000502:physiology*
keywords: Fischer 344 rats; binary mixtures; odor discrimination; perception; psychophysics; reaction times