A limited role for mediodorsal thalamus in devaluation tasks.

Abstract

Six experiments were performed to determine the role of mediodorsal thalamus (MD) in the devaluation task, varying the type of contingencies (Pavlovian or operant), the number of reinforcers (one versus two) and the order of experiments (in naïve or experimentally experienced rats). MD lesioned rats were impaired in devaluation performance when switched between Pavlovian and operant devaluation tasks, but not when switched from one Pavlovian devaluation task to another Pavlovian devaluation task. MD lesions caused no devaluation impairment in a multiple reinforcer Pavlovian devaluation task. These results suggest that MD lesions impair performance in devaluation tasks as a result of an inability to switch the form of associations made from one type of outcome-encoding association to another. This is in accord with previous literature suggesting that MD is needed for strategy set shifting. The results further suggest that MD is a necessary part of devaluation circuits only in cases in which previous associations need to be suppressed in order for new associations to be learned and control behavior, and otherwise the devaluation circuit does not require MD. KeywordsMediodorsal thalamus; devaluation; set-shifting; reward Devaluation tasks involve training a relationship that earns or predicts a valuable outcome, such as a lever press that earns a type of food or a light that predicts the delivery of food (Adams & Dickinson, 1981;Holland & Rescorla, 1975). The value of this outcome is then reduced by motivational (e.g., satiation) or associative methods (e.g., a food aversion is established by food-toxin pairings). After such outcome devaluation, responding based on the relationship that predicts or earns food is typically reduced. Similarities in task demands to human decision making, as well as similarities in neural underpinnings, suggests that the devaluation task provides a model of goal expectancy-guided behavior (as reviewed in Pickens & Holland, 2004).Many reports have examined the neural circuitry involved in acting according to the current value of goals. For example, lesions of amygdala, or specific lesions of basolateral complex of amygdala (BLA), cause impairments in many versions of the devaluation task (Balleine, Killcross, & Dickinson, 2003;Blundell, Hall & Killcross, 2003;Hatfield, Han, Conley, Gallagher, & Holland, 1996;Malkova, Gaffan & Murray, 1997). Several laboratories have also found that bilateral orbitofrontal cortex (OFC) lesions (Gallagher, McMahan & Schoenbaum, 1999;Izquierdo, Suda & Murray, 2004; but see Ostlund & Balleine, 2007) or lesions that disconnect amygdala and OFC (Baxter, Parker, Lindner, Izquierdo, & Murray, 2000) impair performance in devaluation tasks. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptAnother brain area that may be needed for devaluation is mediodorsal thalamus (MD). MD, BLA and OFC are all interconnected (Carmichael & Price, 1995;Ghashghaei & Barbas, 2002;Groenewegen, 1988;Ray & Price, 1992) and the three brain areas share s...

Mediodorsal Thalamus Hypofunction Impairs Flexible Goal-Directed Behavior

“…This differs from, a recent study that found no effect of MD lesions on devaluation independent of the time of the lesion (31). Our findings are in agreement with this later study as we did not found any deficits in outcome devaluation, whether inhibiting the MD during testing or throughout instrumental training.…”

Dissociable effects of anterior and mediodorsal thalamic lesions on spatial goal-directed behavior

“…The failure of animals with lesions of the MD to show any sensitivity to devaluation is consistent with previous data, which used either pure instrumental Ostlund and Balleine 2008;Pickens 2008) or Pavlovian (Pickens 2008) setups, which all indicate that the MD plays a general role in the representation of outcome value, resulting from Pavlovian or instrumental contingencies. It must be noted that this deficit is unlikely to result from a deficit in discriminating the devalued vs. nondevalued rewards since MD rats behaved as the control Sham animals during the consumption test which followed devaluation.…”

“…All the aforementioned brain areas share abundant connections with limbic thalamic nuclei (Gabbott et al 2005;Groenewegen 1988;Hoover and Vertes 2007) such as the anterior thalamic nuclei (ATN) and mediodorsal (MD) nuclei. While the ATN is known to support spatial navigation (Jankowski et al 2013;van Groen and Kadish 2002;Warburton et al 1999Warburton et al , 2001Wilton et al 2001;Wolff et al 2008a, b), the role of MD in goaldirected behavior has been the focus of recent studies in essentially non-spatial, instrumental settings (Mitchell et al 2007;Ostlund and Balleine 2008;Pickens 2008). Still few studies have directly compared the differential impact of lesion to either the ATN or the MD on goal-directed behavior and none of them involved processing of spatial information .…”

Functional heterogeneity of the limbic thalamus: From hippocampal to cortical functions

“…This impairment in the animals' ability for goal-directed behavior has recently been confirmed using pharmacogenetic MD inhibition (Parnaudeau et al, 2014). Whereas this role of the MD in purely instrumental situations seems well established, it may also be involved in cases where a Pavlovian component is present (Alcaraz et al, 2014;Pickens, 2008). However, posttraining lesions have been shown to have little effect on goal-directed behaviors (Ostlund and Balleine, 2008).…”