Polysynaptic Potentiation at Different Levels of Rat Olfactory Pathways Following Learning

Abstract

This study was aimed at investigating the consequences of learning on late polysynaptic components of evoked field potential signals recorded in parallel at different levels of the olfactory pathways. For this, evoked field potentials induced by electrical stimulation of the olfactory bulb were recorded simultaneously in the anterior piriform cortex, the posterior piriform cortex, the lateral entorhinal cortex, and the dentate gyrus. The different parameters of late components were measured in each site before and after completion of associative learning in anesthetized rats. In the learning task, rats were trained to associate electrical stimulation of one olfactory bulb electrode with the delivery of sucrose (positive reward) and stimulation of a second olfactory bulb electrode with the delivery of quinine (negative reward). In this way, stimulation of the same olfactory bulb electrodes used for inducing field potentials served as a discriminative cue in the learning paradigm. The data confirmed previous observation that learning was associated with a lowering in late-component-1 intensity of induction in the posterior piriform cortex. The use of simultaneous recording allowed us to further specify the consequences of learning on late-component distribution in the studied network. Indeed the data showed that whereas before learning, late component 1 was rather uniformly distributed among the recorded sites; following learning, its expression was facilitated preferentially in the posterior piriform cortex and lateral entorhinal cortex. Furthermore, learning was accompanied by the emergence of a new late component (late component 2), which occurred simultaneously in the four recording sites. The possible involvement of potentiation of polysynaptic components in recognition and/or consolidation processes will be discussed

Ontogeny of odor-LiCl vs. odor-shock learning: Similar behaviors but divergent ages of functional amygdala emergence

“…These data are consistent with the important role of the adult piriform cortex in olfactory conditioning (Litaudon et al 1997;Barkai and Saar 2001;Mouly et al 2001;Mouly and Gervais 2002;Tronel and Sara 2002;Sevelinges et al 2004Sevelinges et al , 2007Wilson et al 2004). However, the specific roles of the anterior and posterior piriform in preference and aversion learning are not consistent with the adult literature, where both have been found important for learning (Hasselmo and Barkai 1995;Litaudon et al 1997;Barkai and Saar 2001;Haberly 2001;Mouly et al 2001;Tronel and Sara 2002;Sevelinges et al 2004;Wilson et al 2004).…”

“…Here we expand assessment of the developing pups' odoraversion learning circuit by including the anterior and posterior piriform cortex, which have previously been demonstrated to be important for both pup and adult odor learning (Litaudon et al 1997;Barkai and Saar 2001;Mouly et al 2001;Mouly and Gervais 2002;Tronel and Sara 2002;Moriceau and Sullivan 2004;Sevelinges et al 2004;Wilson et al 2004;Roth et al 2006). We also extend the assessment of the development of odor-aversion learning by directly comparing a range of odor-aversion learning paradigms and including different intensities of shock.…”

“…In contrast to adult odor-LiCl learning, which relies on the amygdala (Touzani and Sclafani 2005), this early-life, odoraversion learning relies on the olfactory bulb until the pup approaches weaning age, when the amygdala is incorporated into the learning circuitry (Shionoya et al 2006). In contrast, if infant rats receive an odor paired with a moderately painful stimulus (0.5-mA foot or tail shock, or tail pinch) the amygdala appears to be incorporated into this learning circuitry around postnatal day Here we expand assessment of the developing pups' odoraversion learning circuit by including the anterior and posterior piriform cortex, which have previously been demonstrated to be important for both pup and adult odor learning (Litaudon et al 1997;Barkai and Saar 2001;Mouly et al 2001;Mouly and Gervais 2002;Tronel and Sara 2002;Moriceau and Sullivan 2004;Sevelinges et al 2004;Wilson et al 2004;Roth et al 2006). We also extend the assessment of the development of odor-aversion learning by directly comparing a range of odor-aversion learning paradigms and including different intensities of shock.…”

“…We used rats ranging from an age of complete dependence on the mother through an age of independence at weaning. We focused on the amygdala basolateral complex, which is implicated in adult fear conditioning and odor-malaise learning (Bermudez-Rattoni et al 1986;LeDoux 2000;Batsell and Blankenship 2002;Gale et al 2004;Holland and Gallagher 2004), and the anterior and posterior piriform cortex, olfactory pathway areas that have previously been implicated in infant odor-aversion and odor-preference learning Roth and Sullivan 2005;Roth et al 2006) as well as adult odor learning (Ferry and Di Scala 1997;Litaudon et al 1997;Barkai and Saar 2001;Mouly et al 2001;Mouly and Gervais 2002;Tronel and Sara 2002;Sevelinges et al 2004;Wilson et al 2004;Touzani and Sclafani 2005).…”

Beta- and gamma-frequency coupling between olfactory and motor brain regions prior to skilled, olfactory-driven reaching

“…We therefore chose to record from the paleocortical pPIR because it is the main output region of the extended olfactory system (Litaudon et al 1997;Haberly 2001) and it monosynaptically projects to the orbitofrontal cortex, entorhinal cortex, basolateral amygdala, and other sites involved in motivationally based decision-making (Johnson et al 2000;Haberly 2001). Also, the pPIR has been strongly implicated in complex odor task learning (Chabaud et al 1999;Haberly 2001;Mouly and Gervais 2002), that in rats is thought to be on a par with the executive-task abilities displayed by primates in the visual and auditory domains (Otto and Eichenbaum 1992;Dusek and Eichenbaum 1997;Dusek and Eichenbaum 1998;Schoenbaum and Setlow 2001). We recorded from the rat isocortical, caudal M1 and the subcortical, nuclear mRN because both areas (Kolb et al 2000) are involved in the processing underlying successful performance of the skilled reaching maneuver required for GO trials on our task (Whishaw and Gorny 1996;Hyland 1998;Hermer-Vazquez et al 2004).…”