Neil McMillan

Episodic-Like Memory in Rats: Is It Based on When or How Long Ago?

Recent experiments with rats suggest that they show episodic-like or what-where-when memory for a preferred food found on a radial maze. Although memory for when a salient event occurred suggests that rats can mentally travel in time to a moment in the past, an alternative possibility is that they remember how long ago the food was found. Three groups of rats were tested for memory of previously encountered food. The different groups could use only the cues of when, how long ago, or when + how long ago. Only the cue of how long ago food was encountered was used successfully. These results suggest that episodic-like memory in rats is qualitatively different from human episodic memory.

Pigeons Make Errors as a Result of Interval Timing in a Visual, but Not a Visual-Spatial, Midsession Reversal Task

It has been shown previously that pigeons make surprising errors on a visually based midsession reversal task (Cook & Rosen, 2010; Rayburn-Reeves, Molet, & Zentall, 2011). We trained birds with red and green sidekeys, with one color rewarded in the first 40 trials (S1) and the other color rewarded in the latter 40 trials (S2). Importantly, in Phases 1 and 3, red and green were always presented on the same side, whereas in Phase 2 sidekeys were presented on the left and right equally often. In Phases 2 and 3, probe sessions with intertrial intervals (ITIs) longer or shorter than the training intertribal interval (ITI) were interjected among baseline sessions. Results showed that pigeons presented with visual-only cues used interval duration since the beginning of the session to predict when the reversal of reward contingency would occur, but pigeons presented with color and spatial dimensions confounded for predicting reward tended to use a more optimal reward-following strategy of choice based on local reinforcement.

Rats respond for information: Metacognition in a rodent?

In 2 experiments, rats were trained to press a centrally located lever that delivered immediate food reinforcement and turned on a light signal that indicated the location of a further food reward. After rats learned to press the lever and use the light cue to find food, immediate reinforcement for lever pressing was discontinued. In Experiment 1, rats continued to press the lever for information about the location of reward in a T-maze, but control groups yoked to the experimental group for amount of reward, and conditioned reinforcement showed complete extinction of lever pressing. Rats tested on an 8-arm radial maze in Experiment 2 also continued to press a lever that did not yield immediate reinforcement but provided a light cue indicating which randomly chosen arm of the maze contained food; lever pressing declined significantly, however, when the same arm contained food on every trial. Comparisons of testing conditions between and within experiments suggested that probability of lever pressing increased as the amount of information gained increased. The comparative implications of these findings for metacognition are discussed.

The effects of cue competition on timing in pigeons

We studied the effects of cue competition on timing in both overshadowing and blocking operant procedures with pigeons. A white center key delivered reward when pecked 30s after a red or green sidekey was presented and 10s after presentation of the alternate color on the other sidekey. In Experiment 1, key presentations were concurrent during training trials for overshadow-condition pigeons, while side key presentations were separated across training trials for control birds. In Experiment 2, half of the birds (Blocking group) were given pre-exposure trials to either the 10-s or 30-s sidekey condition. Both blocking-condition and control birds were then given trials of concurrent side key presentations. Peak time curves were compared between experimental and control conditions. The results showed blocking of timing accuracy of a long (30-s) stimulus by a short (10-s) stimulus, but no evidence for overshadowing of timing accuracy.

Mitigating road impacts on animals through learning principles

Roads are a nearly ubiquitous feature of the developed world, but their presence does not come without consequences. Many mammals, birds, reptiles, and amphibians suffer high rates of mortality through collision with motor vehicles, while other species treat roads as barriers that reduce gene flow between populations. Road effects extend beyond the pavement, where traffic noise is altering communities of songbirds, insects, and some mammals. Traditional methods of mitigation along roads include the creation of quieter pavement and tires and the construction of physical barriers to reduce sound transmission and movement. While effective, these forms of mitigation are costly and time-consuming. One alternative is the use of learning principles to create or extinguish aversive behaviors in animals living near roads. Classical and operant conditioning are well-documented techniques for altering behavior in response to novel cues and signals. Behavioral ecologists have used conditioning techniques to mitigate human–wildlife conflict challenges, alter predator–prey interactions, and facilitate reintroduction efforts. Yet, these principles have rarely been applied in the context of roads. We suggest that the field of road ecology is ripe with opportunity for experimentation with learning principles. We present tangible ways that learning techniques could be utilized to mitigate negative roadside behaviors, address the importance of evaluating fitness within these contexts, and evaluate the longevity of learned behaviors. This review serves as an invitation for empirical studies that test the effectiveness of learning paradigms as a mitigation tool in the context of roads.

Experience affects immediate early gene expression in response to conspecific call notes in black-capped chickadees (Poecile atricapillus).

Black-capped chickadees (Poecile atricapillus) produce numerous vocalizations, including the acoustically complex chick-a-dee call that is composed of A, B, C, and D notes. D notes are longer in duration and lower in frequency than the other note types and contain information regarding flock and species identification. Adult wild-caught black-capped chickadees have been shown to have similar amounts of immediate early gene (IEG) expression following playback of vocalizations with harmonic-like acoustic structure, similar to D notes. Here we examined how different environmental experiences affect IEG response to conspecific D notes. We hand-reared black-capped chickadees under three conditions: (1) with adult conspecifics, (2) with adult heterospecific mountain chickadees, and (3) without adults. We presented all hand-reared birds and a control group of field-reared black-capped chickadees, with conspecific D notes and quantified IEG expression in the caudomedial mesopallium (CMM) and caudomedial nidopallium (NCM). We found that field-reared birds that heard normal D notes had a similar neural response as a group of field-reared birds that heard playback of reversed D notes. Field-reared birds that heard normal D notes also had a similar neural response as birds reared with adult conspecifics. Birds reared without adults had a significantly reduced IEG response, whereas the IEG expression in birds reared with heterospecifics was at intermediate levels between birds reared with conspecifics and birds reared without adults. Although acoustic characteristics have been shown to drive IEG expression, our results demonstrate that experience with adults or normal adult vocalizations is also an important factor.

ZENK expression following conspecific and heterospecific playback in the zebra finch auditory forebrain

Abstract Zebra finches (Taeniopygia guttata) are sexually dimorphic songbirds, not only in appearance but also in vocal production: while males produce both calls and songs, females only produce calls. This dimorphism provides a means to contrast the auditory perception of vocalizations produced by songbird species of varying degrees of relatedness in a dimorphic species to that of a monomorphic species, species in which both males and females produce calls and songs (e.g., black‐capped chickadees, Poecile atricapillus). In the current study, we examined neuronal expression after playback of acoustically similar hetero‐ and conspecific calls produced by species of differing phylogenetic relatedness to our subject species, zebra finch. We measured the immediate early gene (IEG) ZENK in two auditory areas of the forebrain (caudomedial mesopallium, CMM, and caudomedial nidopallium, NCM). We found no significant differences in ZENK expression in either male or female zebra finches regardless of playback condition. We also discuss comparisons between our results and the results of a previous study conducted by Avey et al. [1] on black‐capped chickadees that used similar stimulus types. These results are consistent with the previous study which also found no significant differences in expression following playback of calls produced by various heterospecific species and conspecifics [1]. Our results suggest that, similar to black‐capped chickadees, IEG expression in zebra finch CMM and NCM is tied to the acoustic similarity of vocalizations and not the phylogenetic relatedness of the species producing the vocalizations.

Pigeons perform poorly on a midsession reversal task without rigid temporal regularity

Animals make surprising anticipatory and perseverative errors when faced with a midsession reversal of reinforcer contingencies on a choice task with highly predictable stimulus–time relationships. In the current study, we asked whether pigeons would anticipate changes in reinforcement when the reinforcer contingencies for each stimulus were not fixed in time. We compared the responses of pigeons on a simultaneous choice task when the initially correct stimulus was randomized or alternated across sessions. Pigeons showed more errors overall compared with the typical results of a standard midsession reversal procedure, and they did not show the typical anticipatory errors prior to the contingency reversal. Probe tests that manipulated the spacing between trials also suggested that timing of the session exerted little control of pigeons’ behavior. The temporal structure of the experimental session thus appears to be an important determinant for animals’ use of time in midsession reversal procedures.

Cue Integration in Spatial Search for Jointly Learned Landmarks but Not for Separately Learned Landmarks.

The authors investigated how humans use multiple landmarks to locate a goal. Participants searched for a hidden goal location along a line between 2 distinct landmarks on a computer screen. On baseline trials, the location of the landmarks and goal varied, but the distance between each of the landmarks and the goal was held constant, with 1 landmark always closer to the goal. In Experiment 1, some baseline trials provided both landmarks, and some provided only 1 landmark. On probe trials, both landmarks were shifted apart relative to the previously learned goal location. Participants searched between the locations specified by the 2 landmarks and their search locations were shifted more toward the nearer landmark, suggesting a weighted integration of the conflicting landmarks. Moreover, the observed variance in search responses when both cues were presented in their normal locations was reduced compared to the variance on tests with single landmarks. However, the variance reduction and the weightings of the landmarks did not always show Bayesian optimality. In Experiment 2, some participants were trained only with each of the single landmarks. On subsequent tests with the 2 cues in conflict, searching did not shift toward the nearer landmark and the variance of search responses of these single-cue trained participants was larger than their variance on single-landmark tests, and even larger than the variance predicted by using the 2 landmarks alternatively on different trials. Taken together, these results indicate that cue combination occurs only when the landmarks are presented together during the initial learning experience.

It’s All a Matter of Time: Interval Timing and Competition for Stimulus Control

Many modern humans explicitly experience time through its cultural constructs: We check our watches to determine if we have to leave for a meeting, we give directions based on how many minutes one should walk down a particular street before turning, and we hit snooze on our alarm clocks and dread the 10-min countdown to when we must roll out of bed. However, these daily experiences represent a sliver of how much time affects our lives, and our reliance on language-based social constructs such as “seconds” and “hours” belies an impressive, evolutionarily inbuilt system of timers that constantly govern behavior and cognition. It is not until we observe the breadth and accuracy of timing in nonhuman animal species that we can truly grasp how important these systems are. Interval timing is the timing of stimulus durations of seconds to minutes to hours, and has been of great interest to researchers in a wide variety of behavioral and cognitive neuroscience disciplines (Buhusi & Meck, 2005). Whereas circadian timing is coordinated by the suprachiasmatic nucleus and is concerned with regulating daily (24-hr) patterns such as the sleep cycle and feeding, and millisecond timing is a largely cerebellar process that assists mostly in motor coordination, Interval timing has been widely studied in humans and animals across a variety of different timescales. However, the majority of the literature in this topic has carried the implicit assumption that a mental or neural “clock” receives input and directs output separately from other learning processes. Here we present a review of interval timing as it relates to stimulus control and discuss the role of learning and attention in timing in the context of different experimental procedures. We show that time competes for control over behavior with other processes and suggest that when moving forward with theories of interval timing and general learning mechanisms, the two ought to be integrated.