Automated Analyses of Innate Olfactory Behaviors in Rodents

Abstract

Olfaction based behavioral experiments are important for the investigation of sensory coding, perception, decision making and memory formation. The predominant experimental paradigms employ forced choice operant assays, which require associative learning and reinforced training. Animal performance in these assays not only reflects odor perception but also the confidence in decision making and memory. In this study, we describe a versatile and automated setup, “Poking-Registered Olfactory Behavior Evaluation System” (PROBES), which can be adapted to perform multiple olfactory assays. In addition to forced choice assays, we employ this system to examine animal’s innate ability for odor detection, discrimination and preference without elaborate training procedures. These assays provide quantitative measurements of odor discrimination and robust readouts of odor preference. Using PROBES, we find odor detection thresholds are at lower concentrations in naïve animals than those determined by forced choice assays. PROBES-based automated assays provide an efficient way of analyzing innate odor-triggered behaviors.

Encoding Innately Recognized Odors via a Generalized Population Code

“…Odor preference is often assessed using place preference by associating odors with their spatial locations. However, intrinsic bias in spatial preference and scent marking can confound the readout 12,13 . To avoid intrinsic place bias, we have devised a computerized setup, PROBES, to perform automated single-chamber odor preference assays 12 .…”

“…However, intrinsic bias in spatial preference and scent marking can confound the readout 12,13 . To avoid intrinsic place bias, we have devised a computerized setup, PROBES, to perform automated single-chamber odor preference assays 12 . This setup provides an efficient and robust readout of the sampling of a single odor port in the habituation/dishabituation test ( Fig.…”

“…We performed 2-photon imaging to record mitral/tufted cell responses under awake conditions. Odors were presented using the olfactometer to deliver precisely timed stimuli 12 Fig. 2d, i).…”

“…Odor delivery was controlled by an automated olfactometer with custom written software developed in the National Instrument Labview programming environment12 . Odorant chemicals are including: 2-Hexanone (Abbr: HXO), Heptanal (Abbr: HPH), Eugenol (Abbr: EUG), 2-Methylbutyric acid (Abbr: 2-MBA), 2-phenylethylamine (Abbr: PEA) , isoamylamine (Abbr: IAMM) and were purchased from MilliporeSigma and freshly prepared in mineral oil at desired concentration.…”

High-throughput automatic training system for odor-based cognitive behaviors in head-fixed mice

“…Previous studies have demonstrated that rodents are very good at olfactory discrimination, memory, and decision (Abraham et al, 2004, Barnes et al, 2008, Cleland et al, 2002, Haddad et al, 2013, Hubener and Laska, 2001, Kepecs et al, 2007, Komiyama et al, 2010; Liu et al, 2014, Lu et al, 1993, Mihalick et al, 2000, Passe and Walker, 1985, Petrulis and Eichenbaum, 2003, Rinberg et al, 2006, Slotnick et al, 1991, Uchida and Mainen, 2003). Automatic behavioral systems have been developed for studying innate olfactory behaviors (Qiu et al, 2014). Olfactory behavioral testing has been developed in head-fixed rodents and greatly facilitates the understanding of neural circuits underlying olfaction (Verhagen et al, 2007; Wesson et al, 2008; Shusterman et al, 2011; Kato et al, 2013; Boyd et al, 2015) and odor-based cognition (Komiyama et al, 2010; Liu et al, 2014; Gadziola et al, 2015).…”