Measuring Play Fighting in Rats: A Multilayered Approach.

Rough-and-tumble play or play fighting is an important experience in the juvenile period of many species of mammals, as it facilitates the development of social skills, and for some species, play fighting is retained into adulthood as a tool for assessing and managing social relationships. Laboratory rats have been a model species for studying the neurobiology of play fighting and its key developmental and social functions. However, play fighting interactions are complex, involving competition and cooperation; therefore, no single measure to quantify this behavior is able to capture all its facets. Therefore, in this paper, we present a multilayered framework for scoring all the relevant facets of play that can be affected by experimental manipulations and the logic of how to match what is measured with the question being asked. © 2022 Wiley Periodicals LLC.

The role of the medial prefrontal cortex in updating reward value and avoiding perseveration.

The medial prefrontal cortex (mPFC) plays a major role in goal-directed behaviours, but it is unclear whether it plays a role in breaking away from a high-value reward in order to explore for better options. To address this question, we designed a novel 3-arm Bandit Task in which rats were required to choose one of three potential reward arms, each of which was associated with a different amount of food reward and time-out punishment. After a variable number of choice trials the reward locations were shuffled and animals had to disengage from the now devalued arm and explore the other options in order to optimise payout. Lesion and control groups' behaviours on the task were then analysed by fitting data with a reinforcement learning model. As expected, lesioned animals obtained less reward overall due to an inability to flexibly adapt their behaviours after a change in reward location. However, modelling results showed that lesioned animals were no more likely to explore than control animals. We also discovered that all animals showed a strong preference for certain maze arms, at the expense of reward. This tendency was exacerbated in the lesioned animals, with the strongest effects seen in a subset of animals with damage to dorsal mPFC. The results confirm a role for mPFC in goal-directed behaviours but suggest that rats rely on other areas to resolve the explore-exploit dilemma.

Are 50-kHz calls used as play signals in the playful interactions of rats? I. Evidence from the timing and context of their use.

During playful interactions, rats emit increased levels of 50-kHz vocalizations. It is possible that these vocalizations are used as play signals that promote and maintain playful contact. The study investigated this possibility. It was predicted that if these vocalizations are used as play signals, they should be more prevalent (1) before an attack, (2) in attacks leading to wrestling, and (3) in males compared to females, as males play more roughly. Moreover, given that there are at least 15 different subtypes of 50-kHz calls, it is possible that different calls are used in different contexts. Therefore, our prediction (4) was that different subtypes would be used for initiating and terminating playful contact. Pairs of same-sex juveniles were tested so that video recordings of their play and audio recordings of their vocalizations were synchronized. 50-kHz vocalizations occur more often before an attack and in male pairs. Specific calls were associated with specific types of behaviors and these associations differed between male and female rats. However, calls were not more frequent in attacks leading to wrestling than in attacks leading to withdrawal. The data provide qualified support for the hypothesis that 50-kHz vocalizations function as play signals.

The synthesis and use of the owl's auditory space map.

The barn owl ( Tyto alba) is capable of capturing prey by passive hearing alone, guided by a topographic map of auditory space in the external nucleus of its inferior colliculus. The neurons of this auditory space map have discrete spatial receptive fields that result from the computation of interaural differences in the level (ILD) and time-of-arrival (ITD) of sounds. Below we review the synthesis of the spatial receptive fields from the frequency-specific ITDs and ILDs to which the neurons are tuned, concentrating on recent studies exploiting virtual auditory space techniques to analyze the contribution of ILD. We then compared the owl's spatial discrimination, assessed behaviorally, with that of its space map neurons. Spatial discrimination was assessed using a novel paradigm involving the pupillary dilation response (PDR), and neuronal acuity was assessed by measuring the changes in firing rate resulting from changes in source location, scaled to the variance. This signal-detection-based approach revealed that the change in the position of the neural image on this map best explains the spatial discrimination measured using the PDR. We compare this result to recent studies in mammalian systems.