Learning & Behavior最新文献

Roy and colleagues (Nature Communications, 13.1, 1-16, 2022) examined neuronal ensembles associated with contextual fear conditioning memory across multiple brain regions, referred to as a unified engram complex. Their four-step approach incorporating brain-wide mapping of activated neurons, engram indexing, and optogenetic and chemogenetic manipulations could offer a novel, holistic approach to implement in our continued search for the engram.

Tests of visuospatial memory following short (<1 s) and medium (1 to 30 s) delays have revealed characteristically different patterns of behavior in humans. These data have been interpreted as evidence for different memory systems operating during short (iconic memory) and long delays (working memory). Leising et al. (2019, Behavioural Processes, 169, Article 103957 ) found evidence for both systems in pigeons and humans completing a location change-detection task using a visual mask that disrupted accuracy following a short (100 ms), but not a long (1,000 ms) delay. Another common finding is that adding to-be-remembered items should disrupt accuracy after a long, but not short, delay. Experiments 1a and 1b reported this memory system crossover effect in pigeons and people, respectively, tested on location change detection with delays of 0, 100, and 1,000 ms and displays of two to 16 items. Experiments 2a and 2b reported that the color of the items had little (pigeons) or no (humans) effect on change-detection accuracy. Pigeons tested in Experiment 3 with longer delays (2,000, 4,000, and 8,000 ms) and large set sizes demonstrated the crossover effect with most displays but did not demonstrate an abrupt drop in accuracy characteristic of iconic memory. In Experiment 4, accuracy with novel types of change (color, shape, and size) was better after a 0-ms delay and above-chance levels on color and shape trials. These data demonstrate the memory system crossover effect in both humans and pigeons and expand our knowledge of the properties of memory systems across species.

Fear conditioning studies have occurred mostly in the laboratory, but recently researchers have started to adapt fear conditioning procedures for remote application. Standardization of aversive stimulus material not causing unnecessarily strong discomfort remains an issue especially relevant to research without experimental supervision. The present study introduces a novel semi-subjective method to calibrate aversive sounds in a remotely conducted fear conditioning paradigm. To demonstrate feasibility and proof of concept, 165 participants completed the paradigm, calibrating the loudness of an aversive sound without the guidance of an experimental instructor. This study also aimed to replicate existing findings of participant groups that differed in their early CS-UCS contingency awareness. Participants were classified as Accurate (UCS more likely after the CS+ than CS-), Poor (UCS more likely after the CS- than CS+, or UCS unlikely after either CS), and Threat Biased (UCS equally likely after the CS+ and CS-). Results indicated both the feasibility and efficacy of the paradigm, with participants showing typical patterns of fear learning. Threat Biased participants showed significantly higher uncertainty towards safety signals. There were no differences between the groups in terms of personality traits, thus questioning whether these attributes mediate differences in fear learning and the emergence of anxiety disorders. Using semi-subjective sound calibration appears to be functional, and future studies may consider implementing the new method when remotely administering fear conditioning paradigms.

Exposure therapy is an effective intervention for anxiety-related problems. The mechanism of this intervention has been the extinction procedure in Pavlovian conditioning, and this application has provided many successful instances for the prevention of relapse. However, traditional associative theories cannot comprehensively explain many findings. In particular, it is difficult to explain the recovery-from-extinction effects, which is the reappearance of the conditioned response following extinction. In this paper, we propose an associative model that is a mathematical extension of Bouton's (1993, Psychological Bulletin, 114, 80-99) model for the extinction procedure. The core of our model is that the asymptotic strength of the inhibitory association depends on the degree of excitatory association retrieved in a context in which a conditioned stimulus (CS) is presented and that the retrieval is determined by the similarity between contexts during both reinforcement and non-reinforcement and the retrieval context. Our model provides an explanation of the recovery-from-extinction effects, and implications for exposure therapy.

For humans, a distinction has been made between implicit and explicit learning. Implicit learning is thought to involve automatic processes of the kind involved in much Pavlovian conditioning, while explicit learning is thought to involve conscious hypothesis testing and rule formation, in which the subject's statement of the rule has been taken as evidence of explicit learning. Various methods have been used to determine if nonverbal animals are able to learn a task explicitly - among these is the 1-back reinforcement task in which feedback from performance on the current conditional discrimination trial is provided only after completion of the following trial. We propose that it is not whether an organism can learn the task, but whether they learn it rapidly, all-or-none, that provides a better distinction between the two kinds of learning. We had humans learn a symbolic matching, 1-back reinforcement task. Almost half of the subjects failed to learn the task, and of those who did, none described the 1-back rule. Thus, it is possible to learn this task without learning the 1-back rule. Furthermore, the backward learning functions for humans differ from those of pigeons. Human subjects who learned the task did so all-or-none, suggesting explicit learning. In earlier research with pigeons, they too showed significant learning of this task; however, backward learning functions suggested that they did so gradually over the course of several sessions of training and to a lower level of asymptotic accuracy than the humans, a result suggesting implicit learning was involved.

Prior research suggests that interval timing performance is sensitive to reinforcer devaluation effects and to the rate of competing sources of reinforcement. The present study sought to replicate and account for these findings in rats. A self-paced concurrent fixed-interval (FI) random-ratio (RR) schedule of reinforcement was implemented in which the FI requirement varied across training conditions (12, 24, 48 s). The RR requirement-which imposed an opportunity cost to responding on the FI component-was adjusted so that it took about twice the FI requirement, on average, to complete it. Probe reinforcer devaluation (prefeeding) sessions were conducted at the end of each condition. To assess the effect of contextual reinforcement on timing performance, the RR requirement was removed before the end of the experiment. Consistent with prior findings, performance on the FI component tracked schedule requirement and displayed scalar invariance; the removal of the RR component yielded more premature FI responses. For some rats, prefeeding reduced the number of trials initiated without affecting timing performance; for other rats, prefeeding delayed responding on the FI component but had a weaker effect on trial initiation. These results support the notion that timing and motivational processes are separable, suggesting novel explanations for ostensible motivational effects on timing performance.

Recent research suggests that the piriform cortex simultaneously represents spatial and olfactory information. These findings may provide further insight into the non-topographic principles of odor coding.

Social learning during foraging has been found in a wide range of animals, including numerous bird species. Still, the mechanisms underlying this cognitive capacity remain largely unstudied and the use of divergent methods limits our understanding of their taxonomic distribution. Using an ecologically relevant design, the open diffusion experiment, we tested whether 11 Southern ground-hornbills (Bucorvus leadbeateri) were able to show imitation on the two-action task. Three experimental groups were created. In the slide and pull group, subjects ('observers') watched a trained conspecific ('demonstrator') opening a box using a specific technique. Naïve individuals from the control group, however, did not receive a social demonstration. All birds of the slide and pull group succeeded in opening the box, whereas all subjects of the control group failed the task. We found consistent inter-individual differences among some observers, with only two birds (one in each group) using the same technique and part of the box contacted by the demonstrator. Our results suggest that at least fine-tune enhancement underlies behavioural diffusion in this novel model species, which provides new research opportunities with direct implications for conservation.

Research in the last century has provided insight into the systems, cellular, and molecular processes involved in the formation, storage, recall, and update of memory engrams - the physical manifestation of the long sought-after philosophical and psychological concept of memory traces. Recent technologies allow scientists to visualize the key molecular players involved in segregating, ordering, and linking memories close in time, for future treatment of "disorders of the engram" where memory linking is deficient (e.g., cognitive aging or Alzheimer's) or excessive (e.g., PTSD).

Here, we address Hansen Wheat et al.'s commentary in this journal in response to Salomons et al. Current Biology, 31(14), 3137-3144.E11, (2021). We conduct additional analyses in response to Hansen Wheat et al.'s two main questions. First, we examine the claim that it was the move to a human home environment which enabled the dog puppies to outperform the wolf puppies in gesture comprehension tasks. We show that the youngest dog puppies who had not yet been individually placed in raisers' homes were still highly skilled, and outperformed similar-aged wolf puppies who had higher levels of human interaction. Second, we address the claim that willingness to approach a stranger can explain the difference between dog and wolf pups' ability to succeed in gesture comprehension tasks. We explain the various controls in the original study that render this explanation insufficient, and demonstrate via model comparison that the covariance of species and temperament also make this parsing impossible. Overall, our additional analyses and considerations support the domestication hypothesis as laid out by Salomons et al. Current Biology, 31(14), 3137-3144.E11, (2021).