ABSTRACT
Predictive learning can engage a selective form of cognitive control that biases choice between actions based on information about future outcomes that the learning provides. This influence has been hypothesized to depend on a feedback circuit in the brain through which the basal ganglia modulate activity in the prefrontal cortex; however, direct evidence for this functional circuit has proven elusive. Here, using an animal model of cognitive control, we found that the influence of predictive learning on decision making is mediated by an inhibitory feedback circuit linking the medial ventral pallidum and the mediodorsal thalamus, the activation of which causes disinhibition of the orbitofrontal cortex via reduced activation of inhibitory parvalbumin interneurons during choice. Thus, we found that, for this function, the mediodorsal thalamus serves as a pallidal-cortical relay through which predictive learning controls action selection, which has important implications for understanding cognitive control and its vicissitudes in various psychiatric disorders and addiction.
Subject(s)
Cognition , Animals , Cognition/physiology , Male , Prefrontal Cortex/physiology , Basal Forebrain/physiology , Neural Pathways/physiology , Thalamus/physiology , Decision Making/physiology , Learning/physiology , Mice , Interneurons/physiologyABSTRACT
Streamlined action sequences must remain flexible should stable contingencies in the environment change. By combining analyses of behavioral structure with a circuit-specific manipulation in mice, we report on a relationship between action timing variability and successful adaptation that relates to post-synaptic targets of primary motor cortical (M1) projections to dorsolateral striatum (DLS). In a two-lever instrumental task, mice formed successful action sequences by, first, establishing action scaffolds and, second, smoothly extending action duration to adapt to increased task requirements. Interruption of DLS neurons in M1 projection territories altered this process, evoking higher-rate actions that were more stereotyped in their timing, reducing opportunities for success. Based on evidence from neuronal tracing experiments, we propose that DLS neurons in M1 projection territories supply action timing variability to facilitate adaptation, a function that may involve additional downstream subcortical processing relating to collateralization of descending motor pathways to multiple basal ganglia centers.
ABSTRACT
Evidence suggests that dopamine activity provides a US-related prediction error for Pavlovian conditioning and the reinforcement signal supporting the acquisition of habits. However, its role in goal-directed action is less clear. There are currently few studies that have assessed dopamine release as animals acquire and perform self-paced instrumental actions. Here we briefly review the literature documenting the psychological, behavioral and neural bases of goal-directed actions in rats and mice, before turning to describe recent studies investigating the role of dopamine in instrumental learning and performance. Plasticity in dorsomedial striatum, a central node in the network supporting goal-directed action, clearly requires dopamine release, the timing of which, relative to cortical and thalamic inputs, determines the degree and form of that plasticity. Beyond this, bilateral release appears to reflect reward prediction errors as animals experience the consequences of an action. Such signals feedforward to update the value of the specific action associated with that outcome during subsequent performance, with dopamine release at the time of action reflecting the updated predicted action value. More recently, evidence has also emerged for a hemispherically lateralised signal associated with the action; dopamine release is greater in the hemisphere contralateral to the spatial target of the action. This effect emerges over the course of acquisition and appears to reflect the strength of the action-outcome association. Thus, during goal-directed action, dopamine release signals the action, the outcome and their association to shape the learning and performance processes necessary to support this form of behavioral control.
Subject(s)
Corpus Striatum , Dopamine , Goals , Animals , Dopamine/metabolism , Corpus Striatum/metabolism , Humans , Conditioning, Operant/physiology , RewardABSTRACT
Background: Establishing the motivational influences on human action is essential for understanding choice and decision making in health and disease. Here we used tests of value-based decision making, manipulating both predicted and experienced reward values to assess the motivational control of goal-directed action in healthy adolescents and those with obsessive-compulsive disorder (OCD). Methods: After instrumental training on a two action-two outcome probabilistic task, adolescents (n = 21) underwent Pavlovian conditioning using distinct stimuli predicting either the instrumental outcomes, a third outcome, or nothing. We then assessed functional magnetic resonance imaging during choice tests in which we varied the predicted value, using specific and general Pavlovian-instrumental transfer, and the experienced value, using outcome devaluation. To establish functional significance, we tested a matched cohort of adolescents with OCD (n = 20). Results: In healthy adolescents, both predicted and experienced values influenced the performance of goal-directed actions, mediated by distinct orbitofrontal-striatal circuits involving the lateral orbitofrontal cortex (OFC) and medial OFC, respectively. However, in adolescents with OCD, choice was insensitive to changes in either predicted or experienced values. These impairments were related to hypoactivity in the lateral OFC and hyperactivity in the medial OFC during specific Pavlovian-instrumental transfer and hypoactivity in the anterior prefrontal cortex, caudate nucleus, and their connectivity in the devaluation test. Conclusions: We found that predicted and experienced values exerted a potent influence on the performance of goal-directed actions in adolescents via distinct orbitofrontal- and prefrontal-striatal circuits. Furthermore, the influence of these motivational processes was severely blunted in OCD, as was the functional segregation of circuits involving medial and lateral OFC, producing dysregulated action control.
ABSTRACT
Cortico-striatal neurocircuits mediate goal-directed and habitual actions which are necessary for adaptive behaviour. It has recently been proposed that some of the core symptoms of autism spectrum disorder (ASD) and Gilles de la Tourette syndrome (GTS), such as tics and other repetitive behaviours, may emerge because of imbalances in these neurocircuits. We have recently developed a model of ASD and GTS by knocking down Immp2l, a mitochondrial gene frequently associated with these disorders. The current study sought to determine whether Immp2l knockdown (KD) in male mice alters flexible, goal- or cue- driven behaviour using procedures specifically designed to examine response-outcome and stimulus-response associations, which underlie goal-directed and habitual behaviour, respectively. Whether Immp2l KD alters neuron density in cortico-striatal neurocircuits known to regulate these behaviours was also examined. Immp2l KD mice and wild type-like mice (WT) were trained on Pavlovian and instrumental learning procedures where auditory cues predicted food delivery and lever-press responses earned a food outcome. It was demonstrated that goal-directed learning was not changed for Immp2l KD mice compared to WT mice, as lever-press responses were sensitive to changes in the value of the food outcome, and to contingency reversal and degradation. There was also no difference in the capacity of KD mice to form habitual behaviours compared to WT mice following extending training of the instrumental action. However, Immp2l KD mice were more responsive to auditory stimuli paired with food as indicated by a non-specific increase in lever response rates during Pavlovian-to-instrumental transfer. Finally, there were no alterations to neuron density in striatum or any prefrontal cortex or limbic brain structures examined. Thus, the current study suggests that Immp2l is not necessary for learned maladaptive goal or stimulus driven behaviours in ASD or GTS, but that it may contribute to increased capacity for external stimuli to drive behaviour. Alterations to stimulus-driven behaviour could potentially influence the expression of tics and repetitive behaviours, suggesting that genetic alterations to Immp2l may contribute to these core symptoms in ASD and GTS. Given that this is the first application of this battery of instrumental learning procedures to a mouse model of ASD or GTS, it is an important initial step in determining the contribution of known risk-genes to goal-directed versus habitual behaviours, which should be more broadly applied to other rodent models of ASD and GTS in the future.
Subject(s)
Autism Spectrum Disorder , Tics , Tourette Syndrome , Animals , Male , Mice , Autism Spectrum Disorder/genetics , Goals , Neurons/metabolism , Tourette Syndrome/genetics , Tourette Syndrome/metabolismABSTRACT
The loss of neurons in parafascicular thalamus (Pf) and their inputs to dorsomedial striatum (DMS) in Lewy body disease (LBD) and Parkinson's disease dementia (PDD) have been linked to the effects of neuroinflammation. We found that, in rats, these inputs were necessary for both the function of striatal cholinergic interneurons (CINs) and the flexible encoding of the action-outcome (AO) associations necessary for goal-directed action, producing a burst-pause pattern of CIN firing but only during the remapping elicited by a shift in AO contingency. Neuroinflammation in the Pf abolished these changes in CIN activity and goal-directed control after the shift in contingency. However, both effects were rescued by either the peripheral or the intra-DMS administration of selegiline, a monoamine oxidase B inhibitor that we found also enhances adenosine triphosphatase activity in CINs. These findings suggest a potential treatment for the cognitive deficits associated with neuroinflammation affecting the function of the Pf and related structures.
Subject(s)
Dementia , Parkinson Disease , Rats , Animals , Neuroinflammatory Diseases , Cholinergic Neurons/physiology , Parkinson Disease/drug therapy , Corpus Striatum/physiology , Cholinergic Agents , CognitionABSTRACT
Cognitive-behavioral testing in preclinical models of Alzheimer's disease has failed to capture deficits in goal-directed action control. Here, we provide the first comprehensive investigation of goal-directed action in a transgenic mouse model of Alzheimer's disease. Specifically, we tested outcome devaluation performance in male and female human amyloid precursor protein (hAPP)-J20 mice. Mice were first trained to press left and right levers for pellet and sucrose outcomes, respectively (counterbalanced), over 4 d. On test, mice were prefed one of the outcomes to satiety and given a choice between levers. Devaluation performance was intact for 36-week-old wild-types of both sexes, who responded more on the valued relative to the devalued lever (Valued > Devalued). By contrast, devaluation was impaired (Valued = Devalued) for J20 mice of both sexes, and for 52-week-old male mice regardless of genotype. After additional lever press training (i.e., 8-d lever pressing in total), devaluation was intact for all mice, demonstrating that the initial deficits were not a result of a nonspecific impairment in reward processing, depression, or locomotor activity in J20 or aging mice. Follow-up analyses revealed that microglial expression in the dorsal CA1 region of the hippocampus was associated with poorer outcome devaluation performance on initial, but not later tests. Together, these data demonstrate that goal-directed action is initially impaired in J20 mice of both sexes and in aging male mice regardless of genotype, and that this impairment is related to neuroinflammation in the dorsal CA1 hippocampal region.
Subject(s)
Alzheimer Disease , Mice , Male , Humans , Female , Animals , Alzheimer Disease/genetics , Alzheimer Disease/metabolism , Amyloid beta-Protein Precursor/genetics , Amyloid beta-Protein Precursor/metabolism , Goals , Mice, Transgenic , Hippocampus/metabolism , Disease Models, AnimalABSTRACT
A recent paper by Kutlu et al. (2022) argues that changes in dopamine release during stimulus pre-exposure reflect non-associative changes in attention to the conditioned stimulus that are causally related to latent inhibition effects. Associative accounts of pre-exposure-induced changes in associability suggest, however, that such conclusions may be premature.
Subject(s)
Conditioning, Classical , Dopamine , Animals , Dopamine/physiology , Conditioning, Classical/physiology , MemoryABSTRACT
We review recent studies assessing the role of the bed nucleus of the stria terminalis (BNST) in the motivational control of instrumental conditioning. This evidence suggests that the BNST and central nucleus of the amygdala (CeA) form a circuit that modulates the ventral tegmental area (VTA) input to the nucleus accumbens core (NAc core) to control the influence of Pavlovian cues on instrumental performance. In support of these claims, we found that activity in the oval region of BNST was increased by instrumental conditioning, as indexed by phosphorylated ERK activity (Experiment 1), but that this increase was not due to exposure to the instrumental contingency or to the instrumental outcome per se (Experiment 2). Instead, BNST activity was most significantly incremented in a test conducted when the instrumental outcome was anticipated but not delivered, suggesting a role for BNST in the motivational effects of anticipated outcomes on instrumental performance. To test this claim, we examined the effect of NMDA-induced cell body lesions of the BNST on general Pavlovian-to-instrumental transfer (Experiment 3). These lesions had no effect on instrumental performance or on conditioned responding during Pavlovian conditioning to either an excitory conditioned stimulus (CS) or a neutral CS (CS0) but significantly attenuated the excitatory effect of the Pavlovian CS on instrumental performance. These data are consistent with the claim that the BNST mediates the general excitatory influence of Pavlovian cues on instrumental performance and suggest BNST activity may be central to CeA-BNST modulation of a VTA-NAc core circuit in incentive motivation.
ABSTRACT
Although the hey-day of motivation as an area of study is long past, the issues with which motivational theorists grappled have not grown less important: i.e. the development of deterministic explanations for the particular tuning of the nervous system to specific changes in the internal and external environment and the organisation of adaptive behavioural responses to those changes. Here, we briefly elaborate these issues in describing the structure and function of the 'positive valence system'. We describe the origins of adaptive behaviour in an ascending arousal system, sensitive to peripheral regulatory changes, that modulates and activates various central motivational states. Associations between these motivational states and sensory inputs underlie evaluative conditioning and generate the representation of the 'unconditioned' stimuli fundamental to Pavlovian conditioning. As a consequence, associations with these stimuli can generate Pavlovian conditioned responses through the motivational control of stimulus event associations with sensory and affective components of the valence system to elicit conditioned orienting, consummatory and preparatory responses, particularly the affective responses reflecting Pavlovian excitation and inhibition, arousal and reinforcement, the latter used to control the formation of habits. These affective processes also provoke emotional responses, allowing the externalisation of positive valence in hedonic experience to generate the goal or reward values that mediate goal-directed action. Together these processes form the positive valence system, ensure the maintenance of adaptive behaviour and, through the association of sensory events and emotional responses through consummatory experience, provide the origins of reward.
Subject(s)
Adaptation, Psychological , Reward , Humans , Arousal , Emotions , MotivationABSTRACT
The present article explored the fate of previously formed response-outcome associations when the relation between R and O was disrupted by arranging for O to occur independently of R. In each of three experiments response independent outcome delivery selectively reduced the R earning that O. Nevertheless, in Experiments 1 and 2, the R continued to show sensitivity to outcome devaluation, suggesting that the strength of the R-O association was undiminished by this treatment. These experiments used a two-lever, two-outcome design introducing the possibility that devaluation reflected the influence of specific Pavlovian lever-outcome associations. In an attempt to nullify the influence of these incidental Pavlovian cues Experiment 3 used a single bidirectional vertical lever that rats could press left or right for different outcomes. Again, response-independent outcome presentations selectively depressed the performance of the R that delivered the response-independent O. However, in this situation, the response independent O also reduced the sensitivity of R to outcome devaluation; whereas the nondegraded R was sensitive to devaluation, the degraded R was not. We conclude that selective degradation of the instrumental contingency can weaken a specific R-O association while leaving other R-O associations intact. Furthermore, the use of a bidirectional vertical lever in Experiment 3 revealed that unidirectional and spatially separated instrumental manipulanda, such as levers or chains, may produce Pavlovian cues capable of forming incidental associations with the instrumental outcome that can obscure the relative influence of R-O associations after various manipulations. (PsycInfo Database Record (c) 2022 APA, all rights reserved).
Subject(s)
Conditioning, Operant , Cues , Rats , Animals , Conditioning, Operant/physiology , Rats, Long-EvansABSTRACT
RATIONALE: Attempts to lose weight often fail despite knowledge of the health risks associated with obesity and determined efforts. We previously showed that rodents fed an obesogenic diet displayed premature habitual behavioural control and weakened flexible decision-making based on the current value of outcomes produced by their behaviour. Thus, habitual control may contribute to failed attempts to modify eating behaviours. OBJECTIVES: To examine the effects of an obesogenic diet on behavioural control and glutamate transmission in dorsal striatum regions and to assess the ability of N-acetylcysteine (NAC) to reverse deficits. METHODS: Here, we examined diet-induced changes to decision-making and used in vitro electrophysiology to investigate the effects of diet on glutamate transmission within the dorsomedial (DMS) and dorsolateral (DLS) striatum, areas that control goal-directed and habitual behaviours, respectively. We administered NAC in order to normalize glutamate release and tested whether this would restore goal-directed performance following an obesogenic diet. RESULTS: We found that an obesogenic diet reduced sensitivity to outcome devaluation and increased glutamate release in the DMS, but not DLS. Administration of NAC restored goal-directed control and normalized mEPSCs in the DMS. Finally, NAC administered directly to the DMS was sufficient to reinstate sensitivity to outcome devaluation following an obesogenic diet. CONCLUSIONS: These data indicate that obesogenic diets alter neural activity in the basal ganglia circuit responsible for goal-directed learning and control which leads to premature habitual control. While the effects of diet are numerous and widespread, normalization of glutamatergic activity in this circuit is sufficient for restoring goal-directed behaviour.
Subject(s)
Acetylcysteine , Corpus Striatum , Rats , Male , Animals , Acetylcysteine/pharmacology , Learning , Glutamic Acid , DietABSTRACT
Evidence suggests that, in Pavlovian conditioning, associations form between conditioned stimuli and multiple components of the unconditioned stimulus (US). It is common, for example, to regard USs as composed of sensory and affective components, the latter being either appetitive (e.g., food or water) or aversive (e.g., shock or illness) and, therefore, to suppose different USs of the same affective class activate a common affective system. Furthermore, evidence is growing for the suggestion that, in competitive learning situations, competition between predictive stimuli is primarily for association with the affective system activated by the US. Thus, a conditioned stimulus (CS) previously paired with one US will block conditioning to another CS when both are presented together and paired with a different US of the same affective class, a phenomenon called transreinforcer blocking. Importantly, similar effects have been reported when steps are taken to turn the pretrained CS into a conditioned inhibitor, which activates the opposing affective state to the excitor that it inhibits. Thus, an appetitive inhibitor can block conditioning to a second CS when they are presented together and paired with foot shock. Here we show that the same is true of an aversive inhibitor. In two experiments conducted in rats, we found evidence that an aversive inhibitor blocked conditioning to a second CS when presented in a compound and paired with food. Such findings demonstrate that affective processes and their opponency organize appetitive-aversive interactions and establish the valences on which they are based, consistent with incentive theories of Pavlovian conditioning.
ABSTRACT
From an associative perspective the acquisition of new goal-directed actions requires the encoding of specific action-outcome (AO) associations and, therefore, sensitivity to the validity of an action as a predictor of a specific outcome relative to other events. Although competitive architectures have been proposed within associative learning theory to achieve this kind of identity-based selection, whether and how these architectures are implemented by the brain is still a matter of conjecture. To investigate this issue, we trained human participants to encode various AO associations while undergoing functional neuroimaging (fMRI). We then degraded one AO contingency by increasing the probability of the outcome in the absence of its associated action while keeping other AO contingencies intact. We found that this treatment selectively reduced performance of the degraded action. Furthermore, when a signal predicted the unpaired outcome, performance of the action was restored, suggesting that the degradation effect reflects competition between the action and the context for prediction of the specific outcome. We used a Kalman filter to model the contribution of different causal variables to AO learning and found that activity in the medial prefrontal cortex (mPFC) and the dorsal anterior cingulate cortex (dACC) tracked changes in the association of the action and context, respectively, with regard to the specific outcome. Furthermore, we found the mPFC participated in a network with the striatum and posterior parietal cortex to segregate the influence of the various competing predictors to establish specific AO associations.SIGNIFICANCE STATEMENT Humans and other animals learn the consequences of their actions, allowing them to control their environment in a goal-directed manner. Nevertheless, it is unknown how we parse environmental causes from the effects of our own actions to establish these specific action-outcome (AO) relationships. Here, we show that the brain learns the causal structure of the environment by segregating the unique influence of actions from other causes in the medial prefrontal and anterior cingulate cortices and, through a network of structures, including the caudate nucleus and posterior parietal cortex, establishes the distinct causal relationships from which specific AO associations are formed.
Subject(s)
Gyrus Cinguli , Learning , Animals , Corpus Striatum , Humans , Magnetic Resonance Imaging , Parietal Lobe , Prefrontal Cortex , Problem-Based LearningABSTRACT
Parkinson's disease (PD) has historically been considered a motor disorder induced by a loss of dopaminergic neurons in the substantia nigra pars compacta. More recently, it has been recognized to have significant non-motor symptoms, most prominently cognitive symptoms associated with a dysexecutive syndrome. It is common in the literature to see motor and cognitive symptoms treated separately and, indeed, there has been a general call for specialized treatment of the latter, particularly in the more severe cases of PD with mild cognitive impairment and dementia. Animal studies have similarly been developed to model the motor or non-motor symptoms. Nevertheless, considerable research has established that segregating consideration of cognition from the precursors to motor movement, particularly movement associated with goal-directed action, is difficult if not impossible. Indeed, on some contemporary views cognition is embodied in action control, something that is particularly prevalent in theory and evidence relating to the integration of goal-directed and habitual control processes. The current paper addresses these issues within the literature detailing animal models of cognitive dysfunction in PD and their neural and neurochemical bases. Generally, studies using animal models of PD provide some of the clearest evidence for the integration of these action control processes at multiple levels of analysis and imply that consideration of this integrative process may have significant benefits for developing new approaches to the treatment of PD.
Subject(s)
Cognitive Dysfunction , Parkinson Disease , Animals , Cognitive Dysfunction/etiology , Disease Models, Animal , Dopaminergic Neurons , Humans , Parkinson Disease/complicationsABSTRACT
Stress reduces cognitive flexibility and dopamine D1 receptor-related activity in the prelimbic cortex (PL), effects hypothesized to depend on reduced corticotropic releasing factor receptor type 1 (CRFr1) regulation of dopamine neurons in the ventral tegmental area (VTA). We assessed this hypothesis in rats by examining the effect of chronic unpredictable restraint stress (CUS), mild acute stress, or their combination on cognitive flexibility, CRFr1 expression in the VTA and D1-related activity in PL. In Experiment 1, rats received either CUS or equivalent handling for 14 days before being trained to press two levers to earn distinct food outcomes. Initial learning was assessed using an outcome devaluation test after which cognitive flexibility was assessed by reversing the outcomes earned by the actions. Prior to each reversal training session, half the CUS and controls receiving acute stress with action-outcome updating assessed using a second devaluation test and CRFr1 expression in the VTA assessed using in-situ hybridisation. Although CUS did not itself affect action-outcome learning, its combination with acute stress blocked reversal learning and decreased VTA CRFr1 expression after acute shock. The relationship between these latter two effects was assessed in Experiment 2 by pharmacologically disconnecting the VTA and PL, unilaterally blocking neurons expressing CRFr1 in the VTA and D1 receptors in the contralateral PL during reversal learning after acute stress. Acute stress again blocked reversal learning but only in the group with VTA-PL disconnection, demonstrating that VTA CRFr1-induced facilitation of dopaminergic activity in the PL is necessary for maintaining cognitive flexibility after acute stress. [250].
ABSTRACT
BACKGROUND: Since Cajal's visualisations of the synaptic spine, this feature of the neuron has been of interest to neuroscientists and has been investigated usually in reference to degeneration or proliferation of dendrites and their neurons. Synaptic spine measurement often forms a critical element of any study investigating neuronal morphology. However, the way researchers have counted spines hasn't changed for almost a century. Some of the currently used legacy methods fail to accommodate obscured spines or factor-in visibility differences between histological stains. NEW METHOD: Here we investigate the neuronal dendrite and its synaptic spines, and reveal that using confocal or bright-field technologies may in fact obfuscate spine counts. A mathematical model is developed for the distribution of synaptic spines within the rat, that should, by nature of the formula and the impartiality of probability quotients, be applied to estimate the number of synaptic spines across any length of dendrite that has protrusions within any species. RESULTS: Using this estimation method, we show that, depending on the method of image capture, there are in fact more spines present than typically counted on lengths of dendrite, something that may have biased morphological studies in the past. COMPARISON WITH EXISTING METHODS: This new estimation method has been collapsed down into an easy-to-use free website. With input of only four fields, we provide the researcher with a more accurate estimation of the amount of spines on a length of dendrite. This was made possible by fluorescing a Golgi stain and comparing two-photon, bright-field and confocal images. CONCLUSIONS: An easy web-based resource has been made available to use this new method for spine calculation. Using this method improves the validity of spine measurement and provides a means to review previously published work.
Subject(s)
Dendrites , Dendritic Spines , Animals , Dendrites/physiology , Neurons/physiology , Rats , Staining and LabelingABSTRACT
BACKGROUND: Changes in dopaminergic neural function can be induced by an acute inflammatory state that, by altering the integrity of the neurovasculature, induces neuronal stress, cell death and causes functional deficits. Effectively blocking these effects of inflammation could, therefore, reduce both neuronal and functional decline. To test this hypothesis, we inhibited vascular adhesion protein 1 (VAP-1), a membrane-bound protein expressed on the endothelial cell surface, that mediates leukocyte extravasation and induces oxidative stress. METHOD: We induced dopaminergic neuronal loss by infusing lipopolysaccharide (LPS) directly into the substantia nigra (SN) in rats and administered the VAP-1 inhibitor, PXS-4681A, daily. RESULTS: LPS produced: an acute inflammatory response, the loss of dopaminergic neurons in the SN, reduced the dopaminergic projection to SN target regions, particularly the dorsolateral striatum (DLS), and a deficit in habit learning, a key function of the DLS. In an attempt to protect SN neurons from this inflammatory response we found that VAP-1 inhibition not only reduced neutrophil infiltration in the SN and striatum, but also reduced the associated striatal microglia and astrocyte response. We found VAP-1 inhibition protected dopamine neurons in the SN, their projections to the striatum and promoted the functional recovery of habit learning. Thus, we reversed the loss of habitual actions, a function usually dependent on dopamine release in DLS and sensitive to striatal dysfunction. CONCLUSIONS: We establish, therefore, that VAP-1 inhibition has an anti-inflammatory profile that may be beneficial in the treatment of dopamine neuron dysfunction caused by an acute inflammatory state in the brain.
Subject(s)
Amine Oxidase (Copper-Containing)/metabolism , Anti-Inflammatory Agents, Non-Steroidal/pharmacology , Cell Adhesion Molecules/metabolism , Corpus Striatum/metabolism , Dopaminergic Neurons/metabolism , Habits , Learning/physiology , Allyl Compounds/pharmacology , Allyl Compounds/therapeutic use , Amine Oxidase (Copper-Containing)/antagonists & inhibitors , Animals , Anti-Inflammatory Agents, Non-Steroidal/therapeutic use , Cell Adhesion Molecules/antagonists & inhibitors , Corpus Striatum/drug effects , Dopaminergic Neurons/drug effects , Inflammation/drug therapy , Inflammation/metabolism , Learning/drug effects , Male , Rats , Rats, Wistar , Sulfonamides/pharmacology , Sulfonamides/therapeutic useABSTRACT
The present experiments examined whether extinction of a stimulus predicting food affects the ability of that stimulus to energize instrumental performance to obtain food. We first used a general Pavlovian instrumental transfer (PIT) paradigm in which rats were first given Pavlovian conditioning with a stimulus predicting one type of food outcome and were then trained to lever press for a different food outcome. We found that the Pavlovian stimulus enhanced performance of the lever press response and that this enhancement was preserved after extinction of that stimulus (Experiment 1) even when the context was manipulated to favor the expression of extinction (Experiment 2). Next, we assessed whether extinction influenced the excitatory effect of a stimulus when it was trained as a discriminative stimulus. Extinction of this stimulus alone had no effect on its ability to control instrumental performance; however, when extinguished with its associated lever press response, discriminative control was lost (Experiments 3 and 4). Finally, after instrumental and Pavlovian training, we extinguished a Pavlovian stimulus predicting one food outcome with a lever press response that delivered a different outcome. In a general PIT test, we found this extinction abolished the ability of the Pavlovian stimulus to elevate responding on a lever trained with a different outcome, revealing for the first time that extinction can abolish the general PIT effect. We conclude that extinction can produce an inhibitory association between the stimulus and the general response type, whether Pavlovian or instrumental, performed during the extinction training.