Optogenetic activation of basolateral amygdala projections to nucleus accumbens core promotes cue-induced expectation of reward but not instrumental pursuit of cues

Reward-associated conditioned stimuli (CS) can acquire predictive value, evoking conditioned approach behaviors that prepare animals to engage with forthcoming rewards. Such CS can also acquire conditioned reinforcing value, becoming attractive and pursued. Through their predictive and conditioned reinforcing properties, CS can promote adaptive (e.g., locating food) but also maladaptive responses (e.g., drug use). Basolateral amygdala neurons projecting to the nucleus accumbens core (BLA→NAc core neurons) mediate the response to appetitive CS, but the extent to which this involves effects on the predictive and/or conditioned reinforcing properties of CS is unclear. Thus, we examined the effects of optogenetic stimulation of BLA→NAc core neurons on conditioned approach behavior and on the instrumental pursuit of a CS, the latter a measure of conditioned reinforcement. Water-restricted, adult male rats learned that a light-tone compound cue (CS) predicts water delivery. Pairing optogenetic stimulation of BLA→NAc core neurons with CS presentation potentiated conditioned approach behavior, and did so even under extinction conditions, when water was omitted. This suggests that BLA→NAc core neurons promote cue-induced expectation of rewards. Rats also received instrumental conditioning sessions during which they could lever press for CS presentations, without water delivery. Optogenetic stimulation of BLA→NAc core neurons either during these instrumental test sessions or during prior CS-water conditioning did not influence lever responding for the CS. This suggests that BLA→NAc core neurons do not influence the conditioned reinforcing effects of CS. We conclude that BLA→NAc core neurons promote cue-induced control over behavior by increasing cue-triggered anticipation of rewards, without influencing cue 'wanting'.

Contextual Modulation of Binary Decisions in Dyadic Social Interactions

The present experimental design allowed binary decisions (i.e., to choose between proactive approaching or withdrawing behavior). These decisions were made on complex social interaction scenarios displayed on videos. The videos were taken from a first-person perspective. They were preceded by one sentence each that provided additional information about the context of the displayed scenario. The sentence preceding the video and the video jointly provided a context of emotional valence. That context varied from trial to trial. We observed that provocative and threatening videos produced predominantly fear and anger responses. Fear was associated with withdrawal decisions, while anger led to approach decisions. Negative contextual information increased the probability of approach decisions in aggressive provocative videos; positive contextual information enhanced the chance of approach decisions in socially positive videos. In neutral situations, displayed in videos, the probability of the approach behavior was reduced in case of negative contextual information. Yet, the probability for approach behavior was increased if positive contextual information preceded neutral videos. Our experimental setup provided a paradigm that can be adapted and accommodated for the examination of future research questions on social decisions in multidimensional, complex social situations.

Pair-bonding leads to convergence in approach behavior to conspecific vocalizations in California mice (Peromyscus californicus)

Pair-bonding allows for division of labor across behavioral tasks such as protecting a territory, caring for pups or foraging for food. However, how these labor divisions are determined, whether they are simply intrinsic differences in the individual’s behavior or a coordinated behavioral response by the pair, remains unknown. We used the monogamous, biparental and territorial California mouse (Peromyscus californicus) to study how behavioral approach to an aggressive vocal stimulus in a novel environment was affected by pair-bonding. Using a three-chambered vocal playback paradigm, we first measured the amount of time individuals spent in close proximity to aggressive bark vocalizations. We found that animals could be categorized as either approachers or avoiders. We then paired individuals based on their initial approach behavior to an opposite sex individual who displayed either similar or different approach behaviors. These pairs were then retested for approach behavior as a dyad 10–11 days post-pairing. This test found that pairs showed convergence in their behavioral responses, such that pairs who were mismatched in their approach behaviors became more similar, and pairs that were matched remained so. Finally, we analyzed the ultrasonic vocalizations (USV) produced and found that pairs produced significantly more USVs than individuals. Importantly, increased USV production correlated with increasing behavioral convergence of pairs. Taken together, this study shows that pair-bonded animals alter their approach behaviors to coordinate their response with their partner and that vocal communication may play a role in coordinating these behavioral responses. Overall, our findings indicate that pair-bonding generates an emergent property in pairs, adjusting their combined approach behavior towards a new aggressive stimulus representing a potential challenge to the bonded pair. Such findings may be broadly important for social bonding in other social systems.

Can Dogs Limbo? Dogs’ Perception of Affordances for Negotiating an Opening

Very little research has focused on canines’ understanding of their own size, and their ability to apply this understanding to their surroundings. The current study tests domestic dogs’ judgment of their body size in relation to a changing environment in two novel experimental situations: when encountering an opening of decreasing height (Study 1) and when negotiating an opening when carrying a stick in their mouth (Study 2). We hypothesized that if dogs understand their own body size, they will accurately judge when an opening is too small for their body to fit through, showing longer latencies to approach the smaller openings and adjusting their body appropriately to get through—although this judgment may not extend to when their body size is effectively increased. In line with these hypotheses, we found that the latency for subjects to reach an aperture they could easily fit through was significantly shorter than to one which was almost too small to fit through. We also found that the order of subjects’ adjustments to negotiate an aperture was invariant across individuals, indicating that dogs’ perception of affordances to fit through an aperture is action-scaled. Preliminary results suggest that dogs’ approach behavior is different when a horizontal appendage is introduced, but that dogs were able to alter their behavior with experience. These results are consistent with the hypothesis that dogs understand their own body size and the affordances of their changing environment.

Characterizing approach behavior of Drosophila melanogaster in Buridan’s paradigm

The Buridan’s paradigm is a behavioral task designed for testing visuomotor responses or phototaxis in fruit fly Drosophila melanogaster. In the task, a wing-shortened fruit fly freely moves on a round platform surrounded by a 360° white screen with two vertical black stripes placed at 0° and 180°. A normal fly will tend to approach the stripes one at a time and move back and forth between them. A variety of tasks developed based on the Buridan’s paradigm were designed to test other cognitive functions such as visual spatial memory. Although the movement patterns and the behavioral preferences of the flies in the Buridan’s or similar tasks have been extensively studies a few decades ago, the protocol and experimental settings are markedly different from what are used today. We revisited the Buridan’s paradigm and systematically investigated the approach behavior of fruit flies under different stimulus settings. While early studies revealed an edge-fixation behavior for a wide stripe in the initial visuomotor responses, we did not discover such tendency in the Buridan’s paradigm when observing a longer-term behavior up to minutes, a memory-task relevant time scale. Instead, we observed robust negative photoaxis in which the flies approached the central part of the dark stripes of all sizes. In addition, we found that stripes of 20°-30° width yielded the best performance of approach. We further varied the luminance of the stripes and the background screen, and discovered that the performance depended on the luminance ratio between the stripes and the screen. Our study provided useful information for designing and optimizing the Buridan’s paradigm and other behavioral tasks that utilize the approach behavior.

Nucleus accumbens neurons encode initiation and vigor of reward approach behavior

The nucleus accumbens (NAc) is considered an interface between motivation and action, with NAc neurons playing an important role in promoting reward approach. However, the encoding by NAc neurons that contribute to this role remains unknown. Here, we trained male rats to find rewards in an 8-arm radial maze. The activity of 62 neurons, mostly in the shell of the NAc, were recorded while rats ran towards each reward place. General linear model (GLM) analysis showed that variables related to the vigor of the locomotor approach, like speed and acceleration, and the fraction of the approach run completed were the best predictors of the firing rate for most NAc neurons. Nearly 23% of the recorded neurons, here named locomotion-off cells, were inhibited during the entire approach run, suggesting that reduction in firing of these neurons promotes initiation of locomotor approach. Another 24% of the neurons presented a peak of activity during acceleration followed by a valley during deceleration (peak-valley cells). Together, these neurons accounted for most of the speed and acceleration encoding identified in the GLM analysis. Cross-correlations between firing and speed indicated that the spikes of peak-valley cells were followed by increases in speed, suggesting that the activity of these neurons drives acceleration. In contrast, a further 19% of neurons presented a valley during acceleration followed by a peak just prior to or after reaching reward (valley-peak cells). These findings suggest that these three classes of NAc neurons control the initiation and vigor of the locomotor approach to reward.Significance StatementDeciphering the mechanisms by which the NAc controls the vigor of motivated behavior is critical to better understand and treat psychiatric conditions in which motivation is dysregulated. Manipulations of the NAc profoundly impair subjects’ ability to spontaneously approach reward-associated locations, preventing them from exerting effort to obtain reward. Here, we identify for the first time specific activity of NAc neurons in relation to spontaneous approach behavior. We discover three classes of neurons that could control initiation of movement and the speed vs. time trajectory during locomotor approach. These results suggest a prominent but heretofore unknown role for the NAc in regulating the kinematics of reward approach locomotion.

A probabilistic evaluation of human activity space for proactive approach behavior of a social robot

Intelligent robot companions contribute significantly to improve the living standards of people in the modern society. Therefore, humanlike decision-making skills are sought after during the design of such robots. On the one hand, such features enable the robot to be easily handled by its human user. On the other hand, the robot will have the capability of dealing with humans without disturbing them by its behavior. Perception of Behavioral Ontology prior to an interaction is an important aspect in this regard. Furthermore, humans make an instant evaluation of task-related movements of others before approaching them. In this article, we present a mechanism to monitor how the activity space is utilized by a particular user on a temporal basis as an ontological assessment of the situation and then determine an appropriate approach behavior for a proactive robot to initiate an interaction with its user. This evaluation was then used to determine appropriate proxemic behavior to approach that person. The usage of activity space varies depending on the task of an individual. We used a probabilistic approach to find the areas that are the most and least likely to be occupied within the activity space of a particular individual during various tasks. As the robot approaches its subject after analyzing the spatial behavior of the subject within his/her activity space, spatial constraints occurred as a result of which robot’s movement could be demolished. Hence, a more socially acceptable spatial behavior could be observed from the robot. In other words, an etiquette based on approach behavior is derived considering the user’s activity space. Experiment results used to validate the system are presented, and critical observations during the study and implications are discussed.

LH LepR neurons directly drive sustained food seeking behavior after AgRP neuronal deactivation via neuromodulation of NPY

1.AbstractAgouti-related protein (AgRP) has been believed to be the main driver of feeding behaviors ever since its discovery. However, recent studies using fiber photometry and optogenetics proved that feeding behaviors are not directly driven by AgRP neurons (temporal discrepancy between neuronal activity and behavior). To resolve this paradox, we conducted novel multi-phase feeding experiments to scrutinize the dynamics of AgRP. Fiber photometry study showed that AgRP neurons start to deactivate even before the initiation of the food search phase. Using optogenetics, we could prove that the feeding behavior induced by AgRP neuron activation had substantial temporal delay and the feeding behavior was sustained for substantial time even after cessation of optogenetic activation. These results indicate that AgRP neurons are not the direct driver of feeding behavior and another downstream neuron is the driver of feeding behavior. Leptin receptor (LepR) neurons in the lateral hypothalamus (LH). LH LepR neurons were activated before voluntary food search behavior initiation and showed robust increase after food approach behavior. Artificial activation of LH LepR neurons drives food search and food approach behavior. In accordance, chemogenetic activation of LepR neurons increased food search and food approach behaviors. Lastly, slice calcium imaging results showed the possibility that NPY from the AgRP neurons could be the downstream neuromodulator of AgRP neuron, driving LH LepR neuron activation. Overall, our study shows that AgRP neurons are not the direct drivers of feeding behavior, whereas LH LepR neurons directly drive sustained food seeking behavior.