Fractionating the all-or-nothing definition of goal-directed and habitual decision-making

A role for the dorsolateral striatum in prospective action control

The dorsolateral striatum (DLS) is important for performing actions persistently, even when it becomes suboptimal, reflecting a function that is reflexive and habitual. However, there are also ways in which persistent behaviors can result from a more prospective, planning mode of behavior. To help tease apart these possibilities for DLS function, we trained animals to perform a lever press for reward and then inhibited the DLS in key test phases: as the task shifted from a 1-press to a 3-press rule (upshift), as the task was maintained, as the task shifted back to the one-press rule (downshift), and when rewards came independent of pressing. During DLS inhibition, animals always favored their initially learned strategy to press just once, particularly so during the free-reward period. DLS inhibition surprisingly changed performance speed bidirectionally depending on the task shifts. DLS inhibition thus encouraged habitual behavior, suggesting it could normally help adapt to changing conditions.

Habit and persistence

Voluntary behaviors (operants) can come in two varieties: Goal-directed actions, which are emitted based on the remembered value of the reinforcer, and habits, which are evoked by antecedent cues and performed without the reinforcer's value in active memory. The two are perhaps most clearly distinguished with the reinforcer-devaluation test: Goal-directed actions are suppressed when the reinforcer is separately devalued and responding is tested in extinction, and habitual behaviors are not. But what is the function of habit learning? Habits are often thought to be strong and unusually persistent. The present selective review examines this idea by asking whether habits identified by the reinforcer-devaluation test are more resistant to extinction, resistant to the effects of other contingency change, vulnerable to relapse, resistant to the weakening effects of context change, or permanently in place once they are learned. Surprisingly little evidence supports the idea that habits are permanent or more persistent. Habits are more context-specific than goal-directed actions are. Methods that make behavior persistent do not necessarily work by encouraging habit. The function of habit learning may not be to make a behavior strong or more persistent but to make it automatic and efficient in a particular context.

Sex and individual differences in the effect of chronic low-dose ethanol on behavioral strategy selection

BACKGROUND

The development of an alcohol use disorder (AUD) involves impaired behavioral control and flexibility. Behavioral inflexibility includes an inability to shift behavior in response to changes in behavioral outcomes. Low levels of ethanol drinking may promote the formation of inflexible, habitual reward seeking, but this may depend on the timing of ethanol exposure in relation to learning. The goal of this study was to determine whether a history of low-dose ethanol exposure promoted contingency-insensitive sucrose seeking and altered behavioral strategy selection.

METHODS

Male and female C57BL/6J mice were trained to perform a response (lever press) for sucrose on two different reinforcement schedules: one that is thought to promote inflexible responding (random interval) and one that maintains flexible responding (variable ratio [VR]). Following instrumental training each day, mice were exposed to saline or low-dose ethanol (0.5 g/kg; i.p.) either proximal (1 h after) or distal (4 h after) to learning. Mice were then tested for sensitivity to changes in contingency in a contingency degradation test.

RESULTS

A history of low-dose ethanol exposure shifted behavioral strategy selection, as measured by reward tracking behavior, but this depended on sex and reinforcement schedule history. Both male and female mice used different strategies depending on the reinforcement schedule, but only males exhibited ethanol-induced shifts in strategy selection. A history of low-dose ethanol exposure did not impact contingency sensitivity in males but promoted insensitivity in females specifically on the VR lever.

CONCLUSIONS

Female mice show distinct behavioral effects of repeated, low-dose ethanol exposure as compared to males, with sex differences in the use of reward tracking strategies to guide behavior. Future studies should investigate sex differences in the neural consequences of chronic low-dose ethanol exposure that may underlie behavioral changes.

Positive correlation between measures of habitual responding and motivated responding in mice

Habit and motivation are thought to be separate processes, with motivated behavior often considered to be goal directed, whereas habits are defined by the absence of goal-directed control over behavior. However, there has been increasing interrogation of the binary nature of habitual versus goal-directed behavior. Furthermore, although drug and alcohol exposure can promote the formation of habits, drug seeking itself can also be highly flexible, pointing toward the need for complex consideration of the parallel processes that drive behavior. The goal of the current study was to determine whether there was a relation between motivation-as measured by progressive ratio-and habit-as measured by contingency degradation-and whether this relation was affected by ethanol exposure history and sex. The results showed that these measures were positively correlated such that greater contingency insensitivity was associated with achieving higher break points on the progressive-ratio task. However, this relation depended on reinforcement schedule history, ethanol exposure history, and sex. These point to potential relations between measures of habit and motivation and stress the importance of carefully parsing behavioral findings and assays. These findings are also expected to inform future substance use research, as drug history may affect these relations.

Food Restriction Level and Reinforcement Schedule Differentially Influence Behavior during Acquisition and Devaluation Procedures in Mice

Behavioral strategies are often classified based on whether reinforcer value controls reinforcement. Value-sensitive behaviors, in which animals update their actions when reinforcer value is changed, are classified as goal-directed; conversely, value-insensitive actions, where behavior remains consistent when the reinforcer is removed or devalued, are considered habitual. Basic reinforcement schedules can help to bias behavior toward either process: random ratio (RR) schedules are thought to promote the formation of goal-directed behaviors while random intervals (RIs) promote habitual control. However, how the schedule-specific features of these tasks interact with other factors that influence learning to control behavior has not been well characterized. Using male and female mice, we asked how distinct food restriction levels, a strategy often used to increase task engagement, interact with RR and RI schedules to control performance during task acquisition and devaluation procedures. We determined that food restriction level has a stronger effect on the behavior of mice following RR schedules compared with RI schedules, and that it promotes a decrease in response rate during devaluation procedures that is best explained by the effects of extinction rather than devaluation. Surprisingly, food restriction accelerated the decrease in response rates observed following devaluation across sequential extinction sessions, but not within a single session. Our results support the idea that the relationships between schedules and behavioral control strategies are not clear-cut and suggest that an animal's engagement in a task must be accounted for, together with the structure of reinforcement schedules, to appropriately interpret the cognitive underpinnings of behavior.

Chronic alcohol exposure alters action control via hyperactive premotor corticostriatal activity

Alcohol use disorder (AUD) alters decision-making control over actions, but disruptions to the responsible neural circuit mechanisms are unclear. Premotor corticostriatal circuits are implicated in balancing goal-directed and habitual control over actions and show disruption in disorders with compulsive, inflexible behaviors, including AUD. However, whether there is a causal link between disrupted premotor activity and altered action control is unknown. Here, we find that mice chronically exposed to alcohol (chronic intermittent ethanol [CIE]) showed impaired ability to use recent action information to guide subsequent actions. Prior CIE exposure resulted in aberrant increases in the calcium activity of premotor cortex (M2) neurons that project to the dorsal medial striatum (M2-DMS) during action control. Chemogenetic reduction of this CIE-induced hyperactivity in M2-DMS neurons rescued goal-directed action control. This suggests a direct, causal relationship between chronic alcohol disruption to premotor circuits and decision-making strategy and provides mechanistic support for targeting activity of human premotor regions as a potential treatment in AUD.

Revealing abrupt transitions from goal-directed to habitual behavior

A fundamental tenet of animal behavior is that decision-making involves multiple 'controllers.' Initially, behavior is goal-directed, driven by desired outcomes, shifting later to habitual control, where cues trigger actions independent of motivational state. Clark Hull's question from 1943 still resonates today: "Is this transition abrupt, or is it gradual and progressive?"1 Despite a century-long belief in gradual transitions, this question remains unanswered2,3 as current methods cannot disambiguate goal-directed versus habitual control in real-time. Here, we introduce a novel 'volitional engagement' approach, motivating animals by palatability rather than biological need. Offering less palatable water in the home cage4,5 reduced motivation to 'work' for plain water in an auditory discrimination task when compared to water-restricted animals. Using quantitative behavior and computational modeling6, we found that palatability-driven animals learned to discriminate as quickly as water-restricted animals but exhibited state-like fluctuations when responding to the reward-predicting cue-reflecting goal-directed behavior. These fluctuations spontaneously and abruptly ceased after thousands of trials, with animals now always responding to the reward-predicting cue. In line with habitual control, post-transition behavior displayed motor automaticity, decreased error sensitivity (assessed via pupillary responses), and insensitivity to outcome devaluation. Bilateral lesions of the habit-related dorsolateral striatum7 blocked transitions to habitual behavior. Thus, 'volitional engagement' reveals spontaneous and abrupt transitions from goal-directed to habitual behavior, suggesting the involvement of a higher-level process that arbitrates between the two.

Sensitivity to outcome devaluation in operant tasks is better predicted by food restriction level than reinforcement training schedule in mice

Behavioral strategies are often classified based on whether reinforcement is controlled by the value of the reinforcer. Value-sensitive behaviors, in which animals update their actions when reinforcer value is changed, are classified as goal-directed; conversely, value-insensitive actions, where behavior remains consistent when the reinforcer is removed or devalued, are considered habitual. Understanding the features of operant training that bias behavioral control toward either strategy is essential to understanding the cognitive and neuronal processes on which they rely. Using basic reinforcement principles, behavior can be biased toward relying on either process: random ratio (RR) schedules are thought to promote the formation of goal-directed behaviors while random intervals (RI) promote habitual control. However, how the schedule-specific features of these task structures relate to external factors to influence behavior is not well understood. Using male and female mice on distinct food restriction levels, we trained each group on RR schedules with responses-per-reinforcer rates matched to their RI counterparts to control for differences in reinforcement rate. We determined that food restriction level has a stronger effect on the behavior of mice following RR schedules than mice following RI schedules and that food restriction better predicted sensitivity to outcome devaluation than training schedule. Our results support the idea the relationships between RR or RI schedules with goal-directed or habitual behaviors, respectively, are more nuanced than previously appreciated and suggest that an animal's engagement in a task must be accounted for, together with the structure of reinforcement schedules, to appropriately interpret the cognitive underpinnings of behavior.

Does stress consistently favor habits over goal-directed behaviors? Data from two preregistered exact replication studies

Instrumental learning is controlled by two distinct parallel systems: goal-directed (action-outcome) and habitual (stimulus-response) processes. Seminal research by Schwabe and Wolf (2009, 2010) has demonstrated that stress renders behavior more habitual by decreasing goal-directed control. More recent studies yielded equivocal evidence for a stress-induced shift towards habitual responding, yet these studies used different paradigms to evaluate instrumental learning or used different stressors. Here, we performed exact replications of the original studies by exposing participants to an acute stressor either before (cf. Schwabe and Wolf, 2009) or directly after (cf. Schwabe and Wolf, 2010) an instrumental learning phase in which they had learned that distinct actions led to distinct, rewarding food outcomes (i.e., instrumental learning). Then, following an outcome devaluation phase in which one of the food outcomes was consumed until participants were satiated, action-outcome associations were tested in extinction. Despite successful instrumental learning and outcome devaluation and increased subjective and physiological stress levels following stress exposure, the stress and no-stress groups in both replication studies responded indifferently to valued and devalued outcomes. That is, non-stressed participants failed to demonstrate goal-directed behavioral control, thereby rendering the critical test of a shift from goal-directed to habitual control in the stress group inapt. Several reasons for these replication failures are discussed, including the rather indiscriminate devaluation of outcomes that may have contributed to indifferent responding during extinction, which emphasize the need to further our understanding of the boundary conditions in research aimed at demonstrating a stress-induced shift towards habitual control.

Task history dictates how the dorsolateral striatum controls action strategy and vigor

The dorsolateral striatum (DLS) is linked to the learning and honing of action routines. However, the DLS is also important for performing behaviors that have been successful in the past. The learning function can be thought of as prospective, helping to plan ongoing actions to be efficient and often optimal. The performance function is more retrospective, helping the animal continue to behave in a way that had worked previously. How the DLS manages this all is curious. What happens when a learned behavior becomes sub-optimal due to environment changes. In this case, the prospective function of the DLS would cause animals to (adaptively) learn and plan more optimal actions. In contrast, the retrospective function would cause animals to (maladaptively) favor the old behavior. Here we find that, during a change in learned task rules, DLS inhibition causes animals to adjust less rapidly to the new task (and to behave less vigorously) in a 'maladaptive' way. Yet, when the task is changed back to the initially learned rules, DLS inhibition instead causes a rapid and vigorous adjustment of behavior in an 'adaptive' way. These results show that inhibiting the DLS biases behavior towards initially acquired strategies, implying a more retrospective outlook in action selection when the DLS is offline. Thus, an active DLS could encourage planning and learning action routines more prospectively. Moreover, the DLS control over behavior can appear to be either advantageous/flexible or disadvantageous/inflexible depending on task context, and its control over vigor can change depending on task context.

Significant Statement

Basal ganglia networks aid behavioral learning (a prospective planning function) but also favor the use of old behaviors (a retrospective performance function), making it unclear what happens when learned behaviors become suboptimal. Here we inhibit the dorsolateral striatum (DLS) as animals encounter a change in task rules, and again when they shift back to those learned task rules. DLS inhibition reduces adjustment to new task rules (and reduces behavioral vigor), but it increases adjustment back to the initially learned task rules later (and increases vigor). Thus, in both cases, DLS inhibition favored the use of the initially learned behavioral strategy, which could appear either maladaptive or adaptive. We suggest that the DLS might promote a prospective orientation of action control.

Effects of Motivational Downshifts on Specific Pavlovian-Instrumental Transfer in Rats

BACKGROUND

Pavlovian stimuli predictive of appetitive outcomes can exert a powerful influence on the selection and initiation of action, a phenomenon termed outcome-selective Pavlovian-instrumental transfer (sPIT). Rodent studies suggest that sPIT is insensitive to motivational downshift induced by outcome devaluation, an effect that is, however, relatively underexplored.

METHODS

Here we examined in detail the effects of distinct shifts in motivation from hunger to a state of relative satiety on sPIT in rats.

RESULTS

A motivational downshift by outcome-specific devaluation immediately prior to testing markedly reduced overall lever responding and magazine entries but left intact the sPIT effect. A motivational downshift prior testing by (1) giving ad libitum rather than restricted access to maintenance diet in the home cage for 24 hours or by (2) a systemic blockade of hormone secretagogue receptor subtype 1A receptors to inhibit orexigenic actions of ghrelin both reduced overall lever responding and magazine entries. Moreover, these latter motivational downshifts reduced the sPIT effect; however, the sizes of the sPIT effects were still large.

CONCLUSIONS

Collectively, our rodent findings indicate that major effects of various motivational downshifts are overall inhibition of lever pressing and magazine approach, possibly reflecting reduced general motivation. The observed effects of motivational downshifts on sPIT have implications with regard to the role of general motivating effects in sPIT and to the contribution of Pavlovian-instrumental interactions to excessive food seeking as well as obesity in humans.

A Push For Examining Subjective Experience in Value-Based Decision-Making

Subjective experience is a powerful contributor to value-based decision-making. Not every decision is the same, nor made in isolation. Rather, decision-making relies on historical information and internal states for adaptive control. Hence, it is inherently continuous with respect to time - one decision or action evolves into the next. However, forays into the neurobiological underpinnings of decision-making have too frequently ignored the contribution of such continuous subjective experience, instead tying circuit activity and brain area involvement to discrete averaged behaviors and task parameters. While much information has been gained through these investigations, recent works have demonstrated the potential for a greater understanding of neural mechanisms when the continuous, experiential nature of behavior is integrated into the investigation. Such integration has important implications for disease states with disordered decision-making such as addiction, where subjective experience is a large contributor to the disorder.

Probing the decision-making mechanisms underlying choice between drug and nondrug rewards in rats

Delineating the decision-making mechanisms underlying choice between drug and nondrug rewards remains a challenge. This study adopts an original approach to probe these mechanisms by comparing response latencies during sampling versus choice trials. While lengthening of latencies during choice is predicted in a deliberative choice model (DCM), the race-like response competition mechanism postulated by the Sequential choice model (SCM) predicts a shortening of latencies during choice compared to sampling. Here, we tested these predictions by conducting a retrospective analysis of cocaine-versus-saccharin choice experiments conducted in our laboratory. We found that rats engage deliberative decision-making mechanisms after limited training, but adopt a SCM-like response selection mechanism after more extended training, while their behavior is presumably habitual. Thus, the DCM and SCM may not be general models of choice, as initially formulated, but could be dynamically engaged to control choice behavior across early and extended training.

Call for a more balanced approach to understanding orbital frontal cortex function

Orbital frontal cortex (OFC) research has historically emphasized the function of this associative cortical area within top-down theoretical frameworks. This approach has largely focused on mapping OFC activity onto human-defined psychological or cognitive constructs and has often led to OFC circuitry bearing the weight of entire theoretical frameworks. New techniques and tools developed in the last decade have made it possible to revisit long-standing basic science questions in neuroscience and answer them with increasing sophistication. We can now study and specify the genetic, molecular, cellular, and circuit architecture of a brain region in much greater detail, which allows us to piece together how they contribute to emergent circuit functions. For instance, adopting such systematic and unbiased bottom-up approaches to elucidating the function of the visual system has paved the way to building a greater understanding of the spectrum of its computational capabilities. In the same vein, we argue that OFC research would benefit from a more balanced approach that also places focus on novel bottom-up investigations into OFC's computational capabilities. Furthermore, we believe that the knowledge gained by employing a more bottom-up approach to investigating OFC function will ultimately allow us to look at OFC's dysfunction in disease through a more nuanced biological lens. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

The relationship between apathy and impulsivity in large population samples

Apathy and impulsivity are debilitating conditions associated with many neuropsychiatric conditions, and expressed to variable degrees in healthy people. While some theories suggest that they lie at different ends of a continuum, others suggest their possible co-existence. Surprisingly little is known, however, about their empirical association in the general population. Here, gathering data from six large studies (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$n = 3755$$\end{document}n=3755), we investigated the relationship between measures of apathy and impulsivity in young adults. The questionnaires included commonly used self-assessment tools—Apathy Evaluation Scale, Barratt Impulsiveness Scale (BIS-11) and UPPS-P Scale—as well as a more recent addition, the Apathy Motivation Index (AMI). Remarkably, across datasets and assessment tools, global measures of apathy and impulsivity correlated positively. However, analysis of sub-scale scores revealed a more complex relationship. Although most dimensions correlated positively with one another, there were two important exceptions revealed using the AMI scale. Social apathy was mostly negatively correlated with impulsive behaviour, and emotional apathy was orthogonal to all other sub-domains. These results suggest that at a global level, apathy and impulsivity do not exist at distinct ends of a continuum. Instead, paradoxically, they most often co-exist in young adults. Processes underlying social and emotional apathy, however, appear to be different and dissociable from behavioural apathy and impulsivity.

Habit, choice, and addiction

Addiction was suggested to emerge from the progressive dominance of habits over goal-directed behaviors. However, it is generally assumed that habits do not persist in choice settings. Therefore, it is unclear how drug habits may persist in real-world scenarios where this factor predominates. Here, we discuss the poor translational validity of the habit construct, which impedes our ability to determine its role in addiction. New evidence of habitual behavior in a drug choice setting are then described and discussed. Interestingly, habitual preference did not promote drug choice but instead favored abstinence. Here, we propose several clues to reconcile these unexpected results with the habit theory of addiction, and we highlight the need in experimental research to face the complexity of drug addicts' decision-making environments by investigating drug habits in the context of choice and in the presence of cues. On a theoretical level, we need to consider more complex frameworks, taking into account continuous interactions between goal-directed and habitual systems, and alternative decision-making models more representative of real-world conditions.

Selective Deficits in Contingency-Driven Ethanol Seeking Following Chronic Ethanol Exposure in Male Mice

BACKGROUND

People with alcohol use disorders exhibit an overreliance on habitual response strategies which may result from a history of chronic alcohol exposure. Although habits are defined by behavior that persists despite changes in outcome value and in action-outcome relationships, most research investigating the effects of ethanol exposure on habits has focused only on outcome devaluation. A clear understanding of the effects of chronic alcohol exposure on the ability to flexibly update behavior may provide insight into the behavioral deficits that characterize alcohol use disorders.

METHODS

To dissociate the effects of chronic intermittent ethanol (CIE) exposure on contingency-mediated sucrose versus ethanol seeking, adult male C57Bl/6J mice were assigned to 2 separate experiments. In the first experiment, mice were trained to self-administer ethanol prior to 2 cycles of interleaved CIE exposure by vapor inhalation. In a second experiment, mice were trained to self-administer sucrose and ethanol in separate training sessions prior to 4 cycles of interleaved CIE. The use of contingencies to mediate reward seeking was assessed using a contingency degradation paradigm.

RESULTS

In mice trained to self-administer only ethanol, 2 weeks of CIE resulted in escalated self-administration. At this time point, CIE-exposed mice, but not air-exposed controls, exhibited ethanol seeking that was insensitive to changes in action-outcome contingency, consistent with habitual ethanol seeking. In mice trained to self-administer ethanol and sucrose rewards in sequential sessions, no escalation in self-administration across 4 weeks of CIE was observed. Under these conditions, neither Air- nor CIE-exposed mice reduced ethanol seeking in response to contingency degradation. In contrast, sucrose seeking remained goal-directed.

CONCLUSIONS

Our results suggest that chronic ethanol exposure impairs contingency-driven ethanol seeking more readily than sucrose-seeking behavior. Further, these findings indicate that the transition from contingency-mediated ethanol seeking occurs more rapidly than for sucrose seeking under similar ethanol exposure conditions.

Interfacing behavioral and neural circuit models for habit formation

Habits are an important mechanism by which organisms can automate the control of behavior to alleviate cognitive demand. However, transitions to habitual control are risky because they lead to inflexible responding in the face of change. The question of how the brain controls transitions into habit is thus an intriguing one. How do we regulate when our repeated actions become automated? When is it advantageous or disadvantageous to release actions from cognitive control? Decades of research have identified a variety of methods for eliciting habitual responding in animal models. Progress has also been made to understand which brain areas and neural circuits control transitions into habit. Here, I discuss existing research on behavioral and neural circuit models for habit formation (with an emphasis on striatal circuits), and discuss strategies for combining information from different paradigms and levels of analysis to prompt further progress in the field.