A hippocampo-cortical pathway detects changes in the validity of an action as a predictor of reward

Hippocampal-entorhinal cognitive maps and cortical motor system represent action plans and their outcomes

Efficiently interacting with the environment requires weighing and selecting among multiple alternative actions based on their associated outcomes. However, the neural mechanisms underlying these processes are still debated. We show that forming relations between arbitrary action-outcome associations involve building a cognitive map. Using an immersive virtual reality paradigm, participants learned 2D abstract motor action-outcome associations and later compared action combinations while their brain activity was monitored with fMRI. We observe a hexadirectional modulation of the activity in entorhinal cortex while participants compared different action plans. Furthermore, hippocampal activity scales with the 2D similarity between outcomes of these action plans. Conversely, the supplementary motor area represents individual actions, showing a stronger response to overlapping action plans. Crucially, the connectivity between hippocampus and supplementary motor area is modulated by the similarity between the action plans, suggesting their complementary roles in action evaluation. These findings provide evidence for the role of cognitive maps in action selection, challenging classical models of memory taxonomy and its neural bases.

Prospective contingency explains behavior and dopamine signals during associative learning

Associative learning depends on contingency, the degree to which a stimulus predicts an outcome. Despite its importance, the neural mechanisms linking contingency to behavior remain elusive. In the present study, we examined the dopamine activity in the ventral striatum-a signal implicated in associative learning-in a Pavlovian contingency degradation task in mice. We show that both anticipatory licking and dopamine responses to a conditioned stimulus decreased when additional rewards were delivered uncued, but remained unchanged if additional rewards were cued. These results conflict with contingency-based accounts using a traditional definition of contingency or a new causal learning model (ANCCR), but can be explained by temporal difference (TD) learning models equipped with an appropriate intertrial interval state representation. Recurrent neural networks trained within a TD framework develop state representations akin to our best 'handcrafted' model. Our findings suggest that the TD error can be a measure that describes both contingency and dopaminergic activity.

Effects of sex and estrous cycle on action-outcome contingencies

Goal-directed and habitual-like behaviors are both necessary to efficiently and effectively navigate the environment. A dysregulation between these behaviors can lead to an overreliance on habitual-like behaviors and may contribute to symptoms experienced in some neuropsychiatric disorders such as substance use disorder. One behavioral task used to evaluate goal-directed and habitual-like behavior is an action-outcome task, contingency degradation, where an action (i.e., lever press) is degraded by decoupling the receipt of a reward from the action. However, little is known about how male and female rats and females across the estrous cycle respond during contingency degradation training and extinction testing. Here, we investigated how the variable of sex and estrous cycle influences contingency degradation training and extinction testing and the correlation between baseline anxiety-like behaviors and performance on contingency degradation extinction testing in adult male and female Long-Evans rats. We found that both males and females learned the contingency degradation task. However, during extinction testing, males respond more to the contingent lever than the non-contingent lever while females do not differ in their responses on the non-contingent and contingent levers. Lower baseline anxiety-like behavior predicted better performance on the contingency degradation test in males, but not females. Next, when we examined performance during extinction testing in females based on their estrous cycle stage on test day, we found that females in the proestrus and estrus stages of the estrous cycle do not differ in their responses on the non-contingent and contingent levers, while females in the metestrus and diestrus stages of the estrous cycle respond more on the contingent lever than the non-contingent lever on the extinction test day, similar to male rats. Our findings indicate that the estrous cycle influences how female rats respond during contingency degradation extinction testing that is dependent on their estrous cycle stage.

Activity of ventral hippocampal parvalbumin interneurons during anxiety

Anxiety plays a key role in guiding behavior in response to potential threats. Anxiety is mediated by the activation of pyramidal neurons in the ventral hippocampus (vH), whose activity is controlled by GABAergic inhibitory interneurons. However, how different vH interneurons might contribute to anxiety-related processes is unclear. Here, we investigate the role of vH parvalbumin (PV)-expressing interneurons while mice transition from safe to more anxiogenic compartments of the elevated plus maze (EPM). We find that vH PV interneurons increase their activity in anxiogenic EPM compartments concomitant with dynamic changes in inhibitory interactions between PV interneurons and pyramidal neurons. By optogenetically inhibiting PV interneurons, we induce an increase in the activity of vH pyramidal neurons and persistent anxiety. Collectively, our results suggest that vH inhibitory microcircuits may act as a trigger for enduring anxiety states.

Adaptive Responding to Stimulus-Outcome Associations Requires Noradrenergic Transmission in the Medial Prefrontal Cortex

A dynamic environment, such as the one we inhabit, requires organisms to continuously update their knowledge of the setting. While the prefrontal cortex is recognized for its pivotal role in regulating such adaptive behavior, the specific contribution of each prefrontal area remains elusive. In the current work, we investigated the direct involvement of two major prefrontal subregions, the medial prefrontal cortex (mPFC, A32D + A32V) and the orbitofrontal cortex (OFC, VO + LO), in updating pavlovian stimulus-outcome (S-O) associations following contingency degradation in male rats. Specifically, animals had to learn that a particular cue, previously fully predicting the delivery of a specific reward, was no longer a reliable predictor. First, we found that chemogenetic inhibition of mPFC, but not of OFC, neurons altered the rats' ability to adaptively respond to degraded and non-degraded cues. Next, given the growing evidence pointing at noradrenaline (NA) as a main neuromodulator of adaptive behavior, we decided to investigate the possible involvement of NA projections to the two subregions in this higher-order cognitive process. Employing a pair of novel retrograde vectors, we traced NA projections from the locus ceruleus (LC) to both structures and observed an equivalent yet relatively segregated amount of inputs. Then, we showed that chemogenetic inhibition of NA projections to the mPFC, but not to the OFC, also impaired the rats' ability to adaptively respond to the degradation procedure. Altogether, our findings provide important evidence of functional parcellation within the prefrontal cortex and point at mPFC NA as key for updating pavlovian S-O associations.

Context learning: Dividing up the camp

A new study reveals that ventral hippocampus integrates information about where we can get rewards into a decision to seek out those rewards. This helps maximise the number of rewards received, while reducing the effort we expend to procure them.