Wabash College, Department of Psychology
Wabash College, Department of Psychology
Wabash College, Department of Psychology
Wabash College, Department of Psychology
Knox College, Department of Psychology
Ph.D. in Neuroscience
University of Minnesota
Bachelor of Arts in Psychology
Most of my courses are offered in our Psychology and Neuroscience programs, where I have taught a wide range of topics (introductory levels, research methods, statistics, writing literature reviews).
I will be on sabbatical during the 2019-20 academic year, and will not be teaching. Students interested in research opportunities should feel free to contact me, but I may not be able to supervise additional projects until Fall 2020.
[Second half-semester course] An overview of human sexual anatomy, development, function, and diversity. Emphasis is on the psychological aspects of sexuality including the study of attitudes towards sexuality, sexual preference, love and marriage, contraception, and commercial sex. Particular attention is paid to the development and enactment of sex roles, the construction of gender, and sex differences.
An introduction to the study of the nervous system, with a focus on basic anatomy and physiology. Students will learn about the basic organization of the nervous system, neurophysiology, sensory processing, movement, development, and neuroplasticity through a systems approach to brain function. Several laboratory experiences will be built into the course to reinforce the principles discussed in class.
An introduction to the biological bases of behavior. Examination of nervous system structure and function is followed by an examination of the neurophysiological foundations of motor ability, sexual behavior, ingestive behavior, sleep and arousal, learning and memory, reinforcement, and language.
Students in this two half-course sequence will complete a year-long capstone project intended to integrate the content and skills they have learned in the major and develop expertise in an area of interest. This project will consist of either an empirical study or a community-based practicum. The empirical study will be one that the student plans and carries out with general guidance from a faculty mentor. For the community-based practicum option, students will work with a professional involved in the delivery of psychological services. All projects will culminate in an APA-style manuscript, poster presentation, and a talk at a regional undergraduate research conference.
Psychology is broadly defined as "the science of behavior and mental processes, and the application of research findings to the solution of problems." Psychology 101 is an introduction to this vast area of research. Our specific purposes in the course are fivefold: To gain an understanding of scientific investigation and an ability to evaluate psychological research critically. To gain experience in investigating important applied psychological questions. To notice how psychological principles are relevant in our everyday lives. To appreciate the history of psychology and the breadth of current psychological inquiry. To become familiar with major content areas of psychology.
Students in this course will become involved with research in an area of behavioral neuroscience. The topic covered will reflect contemporary research issues in the field and may differ in different years. Major course components will be discussion of primary literature in neuroscience and collaboration with the professor in conducting and writing up an experiment that is directed toward possible publication. Recent topics have focused on memory and drug addiction, and how neural recordings are used to understand how information is encoded by the brain.
An introduction to the principles of searching for and reporting on published literature in psychology. Students will learn strategies for searching databases, identifying credible sources, and developing a theoretical background on a topic. This course features extensive training and practice in writing APA-style manuscripts, and is intended to prepare students for PSY 495/496, Senior Project.
Students will enroll in the fall semester of the senior year and meet with the instructors approximately once every two weeks for journal article discussions focused on seminal publications in neuroscience.
Imagine you’ve created a machine that is able to make an exact, physical copy of any object. However, the process of making the copy requires that the machine destroys the original. So, if you put your phone in and turn on the machine, the phone is instantly vaporized. But, in another compartment you find an exact duplicate of your device. Such a machine would be quite interesting, but we might imagine that it has little practical value. However, what happens if you step into the machine, and turn it on? You are instantly (and, let’s assume painlessly!) vaporized, and out of the second compartment steps your exact duplicate. Who is this duplicate? Does he think he is you? If he does, then are you actually dead? What if the machine malfunctions and you are not vaporized: are you and your duplicate both “you”? If you then kill your duplicate, was there in fact a murder? What if he kills you? In this class, we will take these types of thought experiments seriously, and use them to look carefully at the problem of self, and what it means to be a person. Through works of science fiction, philosophical thought experiments, and stories about the lives of humans with brain damage, we will try to locate our “I”, our sense of self. We will also look at gender, sexuality and inquire about how these accidental facets impact our personal identity. Finally, we will look beyond our own selves to examine other kinds of persons, such as aliens, artificial intelligences and genetically modified humans, who might share the world with someday. Some of the texts we will read include Brok’s Into the Silent Land, selections from Rorty’s Philosophy and the Mirror of Nature, and a number of science fiction short stories and novels (such as The Mote in God’s Eye and Le Guin’s The Left Hand of Darkness). We will also watch several films in the course, including The Thirteenth Floor and Arrival.
An introduction to the principles and techniques involved in the design and analysis of psychological research. Development of abilities in quantitative analysis and reasoning, decision-making, and hypothesis testing are aided by conducting behavioral research projects.
Psychoactive drugs (including alcohol, caffeine, nicotine, and many others) are widely used in many societies in order to manipulate behavior and experience. This course will examine drug use (both legal and illicit) from psychological perspectives ranging from the biological to the social. The main focus will be on the factors which promote the use of a drug, the acute and long term effects of drug use, and cross-cultural differences in patterns of drug use. Of particular interest will be factors that promote drug addiction and the consequences of long term use of addictive drugs
Most of my research projects relate to memory systems in one way or another. At Wabash, I have conducted one line of research studies with rats, examining goal-directed and habitual behaviors in lever pressing, and strategies used in navigation. Some of this work was supported by a research grant during 2010-13 to study the ability of cocaine to facilitate habit learning in rats.
In another line of research, I work to develop virtual navigation tasks to test humans in 3D virtual versions of rodent tasks. We have recently been interested in how individual differences in trait such as mindfulness relate to memory, and have used these virtual tasks to test if mindfulness and stress levels can predict impairments in using spatial navigation strategies.
In general, I work to provide research opportunities for our students in my regular courses (such as Psy 233 and Psy 333, our Behavioral Neuroscience courses, or our Research Methods and Statistics courses) and sometimes through independent study (using our Psy 287/8 or 387/8 courses). Students who are interested a more intense research experience are encouraged to talk with me about opportunities for summer research internships, or working early to design an effective senior capstone research project (Psy 495/496).
Senior capstone looking at the effect of sleep on strategies used by humans in virtual navigation.
Senior capstone testing if people who have extensive experience with meditation adopt different strategies during virtual navigation.
Senior capstone testing if damage to the infralimbic cortex or dorsolateral striatum can block the facilitation of habit learning by cocaine in rats.
Senior capstone testing the effect of working memory load on the use of place- and response-strategies in virtual navigation.
Senior capstone testing the ability of cocaine to facilitate habit learning in rats.
Senior capstone looking at the effect of pre-training glucose administration on strategies used by humans in virtual navigation.
Senior capstone looking at the effect of sleep on strategies used by humans in virtual navigation.
Validating a new experiential foraging task.
Research internship testing the relationship between trait mindfulness and the use of spatial navigation strategies in humans, and testing an spatial memory task in rats.
Research internship testing the effectiveness of mindfulness-based stress reduction to increase the use of spatial navigation strategies in adults reporting high levels of stress.
Research internship testing the relationship between trait mindfulness and the use of spatial navigation strategies.
Research internship testing if cocaine infusion into the infralimbic cortex or dorsolateral striatum can facilitate habit learning in rats.
Research internship testing if cocaine infusion into the infralimbic cortex can facilitate habit learning in rats.
Research internship testing if damage to the infralimbic cortex or dorsolateral striatum can block the facilitation of habit learning by cocaine in rats.
Research internship testing if damage to the infralimbic cortex can block the facilitation of habit learning by cocaine in rats.
Parks Intern in Psychology. Tested the effects of lesions to the dorsolateral striatum in rat on place- and response-learning in navigation.
Independent study testing the importance of the dorsolateral striatum in place- and response-learning.
Independent study testing humans in a virtual navigation experiment.
Independent study testing humans in a virtual navigation experiment. Results were presented at the Society for Neuroscience Annual Meeting (San Diego, 2007).
Independent study training rats in a complex maze.
Since I first started conducting human navigation research, I've used several video game engines (GameMaker, Torque, and Unity3D) to develop virtual navigation tasks for humans (where people move through virtual environments presented on desktop/laptop computers, or phones/tablets. Currently, the programs that I use for research are built using the Unity3D game engine, and each of the tasks I have implemented share a common underlying set of programs for running the navigation task and saving data. Together, these navigation tasks are called the Virtual Navigation Suite (VNS).
I also have software available for tracking movements (of rats) in navigation tasks, which I wrote when I had difficulty finding a suitable (free/inexpensive) tracking program for a student research project. This program is written in Matlab (ratTracker4Matlab)
Details about each program are given below.
Undergraduate co-authors indicated by *
Foraging tasks can provide valuable insights into decision-making, as animals choose how to allocate limited resources (such as time). In the “Restaurant Row” task, rodents move between several sites to obtain food rewards available after a variable delay, while in a translational version (the “Web-Surf”) lacking the navigation component, humans are offered short videos. Both tasks have provided novel insights into decision-making and have been applied to addiction vulnerability and the impact of drug exposure on decision-making. We tested new tasks (the “Movie Row” and “Candy Row”) which use virtual navigation to determine if the behavioral correlates of human decision-making are more broadly similar to those of rodents, and explored the relationship of task performance to smoking and obesity. Humans navigated a virtual maze presented on standard computers to obtain rewards (either short videos or candy) available after a variable delay. Behavior on the tasks replicated previous results for the Restaurant Row and Web-Surf. In conditions promoting deliberation, decision latency was elevated along with measures of vicarious trial-and-error (VTE), supporting VTE as a shared behavioral index of deliberation across species. Smoking status was not well-related to performance, while high BMI (> 25) individuals showed reduced sensitivity to a sunk-costs measure and stronger sensitivity to offer value for offers below the preferred delay. These data support the Movie and Candy Row as translational tools to study decision-making during foraging in humans, providing convergent results with a rodent navigation task and demonstrating the potential to provide novel insights relevant to public health.
Objective: Mindfulness has been an active area of research focused on the potential links to health. Recent work has also established that trait mindfulness is also related to cognition and decision-making. The present study tested the relationship between dimensions of trait mindfulness and measures of perception, cognition, and decision-making. Method: Forty-three undergraduate males and 126 online participants (54 females) completed a perceptual accuracy task, Stroop task, and surveys assessing five facets of trait mindfulness, problem solving, decentering, and mental health measures (stress, depression, anxiety). Results: Overall, only a subset of mindfulness facets were related to performance on the perceptual accuracy and Stroop tasks, partially replicating previous reports. Similarly, a subset of mindfulness dimensions was related to ethical decision-making and problem-solving success. In contrast, measures of poor mental health (stress, worry, depression) were non-specifically related to the majority of mindfulness facets. Relationships between mental health measures, but not measures of cognition and decision-making, were mediated by decentering. One exception was perceptual accuracy, which was related to several mindfulness facets, and mediated by decentering. Conclusions: Our findings indicate that separable dimensions of mindfulness are specifically related to distinct cognitive skills and decision-making, and that these relationships are largely distinct from those between mindfulness and psychological health.
The Morris Water Maze (MWM) is a standard task for assessing hippocampal-dependent learning and memory, but the cost of commercial versions of the task may be prohibitive for some undergraduate research projects. We describe the construction of a low-cost MWM for use with rats, and demonstrate the effectiveness of the MWM in a study of the effect of diet-induced obesity on cognitive function in rats. Previous studies have described an impairment in MWM performance in rats fed a high-fat diet combined with streptozotocin injection (to model Type 2 diabetes). We attempted to replicate this finding, and to test the ability of a novel anti-inflammatory treatment to reduce cognitive deficits in the diabetic model. Across five days of hidden-platform training, rats in all groups (normal pellet diet vs. high-fat diet, vehicle vs. treatment) improved on the water maze at similar rates. On a 30-second probe trial, each group showed a preference for the target quadrant used during training. On the probe trial, rats in the high-fat diet group receiving vehicle injections performed significantly better than rats on a normal pellet diet receiving vehicle injections, or on a high-fat diet receiving treatment. These results did not replicate previous findings that a high-fat diet combined with streptozotocin injections produces deficits in the water maze. However, the results did validate the effectiveness of a low-cost water maze constructed from commonly available materials for hidden platform water maze training, which we expect may be of use to other undergraduate researchers interested in learning and memory.
Mindfulness is related to a number of positive health outcomes, such as decreased stress, anxiety and improved physical functioning. Recent studies have also identified cognitive benefits of mindfulness, including work by Hafenbrack, Kinias and Barsade (2014) who found that higher trait mindfulness and brief mindfulness inductions significantly improved decision-making, by reducing escalation of commitment to a course of action which has proven to be disadvantageous. Such work demonstrates that beyond well-being, mindfulness may be related to a broader range of cognitive benefits beyond health outcomes. However, while Hafenbrack, Kinias and Barsade proposed that mindfulness may reduce escalation of commitment by reducing the influence of sunk-costs on decision-making, methodological limitations make it difficult to determine if mindfulness is specifically related to sensitivity to the sunk-cost bias. The present study extends previous work by replicating the finding that trait mindfulness is related to reduced escalation of commitment, and by using additional measures of decision-making to test the relationship of mindfulness specifically to the sunk-cost bias. The results replicated previous findings, but suggest that mindfulness is consistently related to reduced escalation of commitment, and that the relationship between trait mindfulness and sunk-costs is weaker and inconsistent.
Human drug addiction is a complex disorder, in which exogenous substances are able to recruit and maintain behaviors involved in drug taking. Many drugs that are addictive in humans are able to act on natural brain systems for learning and memory, and while many memory systems may be affected by addictive drugs, work with operant tasks has shown that addictive drugs (e.g. cocaine and alcohol) are particularly effective in recruiting habit learning systems, compared to natural rewards. It is currently unknown if the ability of addictive drugs to facilitate habit learning depends on a direct action on habit learning systems in the brain, versus the rewarding properties of drug administration. To differentiate between these options, rats were trained to perform two actions (lever pressing), each of which was rewarded with a different natural reward. After acquiring the behavior, rats received three training sessions which were followed by post-training injections of saline or cocaine (5 or 10 mg/kg, i.p.). Using sensory-specific satiety, extinction tests revealed that lever pressing for actions which were paired with saline were sensitive to devaluation (typical of goal-directed behaviors) while actions which were paired with cocaine were not sensitive to devaluation (typical of habitual behaviors). Lesions of the infralimbic or dorsolateral striatum were able to block the action of post-training cocaine injections. These data indicate that, within individual rats, cocaine injections facilitate the transition of behavior to habitual control for actions that have been recently performed, without a general facilitation of habit learning, and that this action of cocaine requires brain areas that are critical for learning natural habits.
Decision-making studies across different domains suggest that decisions can arise from multiple, parallel systems in the brain: a flexible system utilizing action-outcome expectancies, and a more rigid system based on situation-action associations. The hippocampus, ventral striatum and dorsal striatum make unique contributions to each system, but how information processing in each of these structures supports these systems is unknown. Recent work has shown covert representations of future paths in hippocampus, and of future rewards in ventral striatum. We developed new analyses in order to use a comparative methodology and apply the same analyses to all three structures. Covert representations of future paths and reward were both absent from the dorsal striatum. In contrast, dorsal striatum slowly developed situation representations that selectively represented action-rich parts of the task. This triple dissociation suggests that the different roles these structures play are due to differences in information processing mechanisms.
The dorsal striatum plays a critical role in procedural learning and memory. Current models of basal ganglia assume that striatal neurons and circuitry are critical for the execution of overlearned, habitual sequences of action. However, less is known about how the striatum encodes task information that guides the performance of actions in procedural tasks. To explore the striatal encoding of task information, we compared the behavioral correlates of striatal neurons tested in two tasks: a multiple T-maze task in which reward delivery was entirely predictable based on spatial cues (the Multiple-T task), and a task in which rats ran on a rectangular track, but food delivery depended on the distance traveled on the track and was not dependent solely on spatial location (the Take-5 task). Striatal cells recorded on these tasks were divisible into three cell types: phasic-firing neurons (PFNs), tonically firing neurons (TFNs), and high-firing neurons (HFNs) and similar proportions of each cell type were found in each task. However, the behavioral correlates of each cell type were differentially sensitive to the type of task rats were performing. PFNs were responsive to specific task-parameters on each task. TFNs showed reliable burst-and-pause responses following food delivery and other events that were consistent with tonically active neurons (TANs) on the Take-5 (non-spatial) task but not on the Multiple-T (spatial) task. HFNs showed spatial oscillations on the Multiple-T (spatial) task but not the Take-5 (non-spatial) task. Reconstruction of the rats' position on the maze was highly accurate when using striatal ensembles recorded on the Multiple-T (spatial) task, but not when using ensembles recorded on the Take-5 (non-spatial) task. In contrast, reconstruction of time following food delivery was successful in both tasks. The results indicated a strong task dependency of the quality of the spatial, but not the reward-related, striatal representations on these tasks. These results suggest that striatal spatial representations depend on the degree to which spatial task-parameters can be unambiguously associated with goals.
Two experiments examined the use of place and response strategies by humans navigating virtual multiple T mazes. In Experiment 1, probe trials revealed that participants commonly used place and response strategies, and place strategies were more frequent early in training, whereas response strategies were more frequent late in training. Compared with women, men learned the correct path through the maze more quickly and developed a more stable route through the maze. In Experiment 2, participants were trained to locate 2 targets. One target required participants to use either a place or response strategy, whereas the other target could be found using either strategy. Accuracy improved faster for place training compared with response training, and women outperformed men in both groups. Probe trials testing transfer of the imposed strategy to the other target found faster transfer for place training than for response training and that women demonstrated faster transfer than men. Accuracy on probe trials was correlated with poor route stability in the place-trained group and with good route stability in the response-trained group, indicating that navigation strategy use may be related to measures of improvement in performance on normal trials.
While the use of multi-channel electrodes (stereotrodes and tetrodes) has allowed for the simultaneous recording and identification of many neurons, quantitative measures of the quality of neurons in such recordings are lacking. In multi-channel recordings, each spike waveform is discriminated in a high-dimensional space, making traditional measures of unit quality inapplicable. We describe two measures of unit isolation quality, Lratio and Isolation Distance, and evaluate their performance using simulations and tetrode recordings. Both measures quantified how well separated the spikes of one cluster (putative neuron) were from other spikes recorded simultaneously on the same multi-channel electrode. In simulations and tetrode recordings, both Lratio and Isolation Distance discriminated well- and poorly-separated clusters. In data sets from the rodent hippocampus in which neurons were simultaneously recorded intracellularly and extracellularly, values of Isolation Distance and Lratio were related to the correct identification of spikes.
Transient coherent neural oscillations, as indicated by local field potentials, are thought to underlie key perceptual and cognitive events. We report a transient, state-dependent 50 Hz oscillation recorded from electrodes placed in the striatum of awake, behaving rats. These coherent oscillations, which we term gamma(50), occurred in brief (150 ms) events co-incident with the initiation of movement. On navigation tasks, the animal's speed increased dramatically at the precise moment of the gamma(50) event. This synchronous oscillation may provide a key to understanding striatal function, as well as basal ganglia pathology, which often impairs the control of voluntary movements.
The striatum plays an important role in “habitual” learning and memory and has been hypothesized to implement a reinforcement-learning algorithm to select actions to perform given the current sensory input. Many experimental approaches to striatal activity have made use of temporally structured tasks, which imply that the striatal representation is temporal. To test this assumption, we recorded neurons in the dorsal striatum of rats running a sequential navigation task: the multiple T maze. Rats navigated a sequence of four T maze turns to receive food rewards delivered in two locations. The responses of neurons that fired phasically were examined. Task-responsive phasic neurons were active as rats ran on the maze (maze-responsive) or during reward receipt (reward-responsive). Neither mazenor reward-responsive neurons encoded simple motor commands: maze-responses were not well correlated with the shape of the rat's path and most reward-responsive neurons did not fire at similar rates at both food-delivery sites. Maze-responsive neurons were active at one or more locations on the maze, but these responses did not cluster at spatial landmarks such as turns. Across sessions the activity of maze-responsive neurons was highly correlated when rats ran the same maze. Maze-responses encoded the location of the rat on the maze and imply a spatial representation in the striatum in a task with prominent spatial demands. Maze-responsive and reward-responsive neurons were two separate populations, suggesting a divergence in striatal information processing of navigation and reward.
Humans and animals trained on sequential reaction tasks show decreases in reaction time and increases in anticipatory movements even long after they have ceased to make errors. Humans show these changes even when they do not explicitly recognize that they performed a repeating sequence. We have developed a task which rats learn to perform error-free quickly, but in which they continue to show path-refinement on a single day. This task may enable the study of performance strategy changes occurring within a single day.
Undergraduate presenter indicated by *
Obesity is associated with increased discounting of future monetary rewards, suggesting that altered decision-making may contribute to the risk for obesity. Here we examined the relationship between measures of decision-making, obesity and dieting success using an online sample (Amazon’s Mechanical Turk service) and an undergraduate male sample. Participants completed monetary or food-based delay-discounting surveys, and a set of experiential foraging tasks (the Movie Row and Candy Row tasks). Rodent versions of the foraging tasks have also been used to demonstrate specific deficits in decision-making in drug-abstinent mice.
In the foraging tasks (Movie Row and Candy Row), participants navigated through a 3D virtual environment on a square track. Rewards (4-sec video clips displayed on a virtual movie screens in the Movie Row task or candy/snacks delivered to magazine for the Candy Row task) were available from four zones on the track. Only a subset of undergraduates completed the Candy Row task. As participants arrived at a zone, the reward category and a random delay were presented. Participants could accept the offer or move on to the next reward site. Behavior on the Candy Row task (using physical rewards) was similar to that of the Movie Row tasks (using videos as rewards), suggesting that these two versions of the task were sensitive to individual differences in rewards. Performance on the monetary and food-based versions of the delay-discounting measure were also positively correlated, but delay discounting measures were not well related to measures from the foraging tasks.
Obesity (determined from self-reported weight and height) was not related to delay discounting measures (k) for money or food, or to the number of rewards earned on the foraging tasks and delay thresholds (how long participants were willing to wait for a reward). Exploratory analyses found that obesity was associated with reduced regret on the Movie Row task. Self-reported change in body mass index (BMI) over the previous year was related to reported use of several dieting strategies (such as attempting to consume less food, avoiding carbohydrates), but not to measures of delay-discounting. However, several dieting strategies interacted with the discounting rate (k). Among participants who reported that they had attempted to eat less food to manage their weight, only participants with low discounting rates showed a reduction in BMI, while for participants who did not report using this strategy, there was no relationship between k and changes in BMI. These results suggest that obesity and dieting success may be related to several different disruptions in decision-making systems.
Foraging tasks provide valuable insights into decision-making, as animals make decisions about how to allocate limited resources (such as time). In the “Restaurant Row” task, rodents obtain food rewards at several sites. In the “Web-Surf” task, humans are offered short videos from different categories. In both tasks, rewards are available after a variable delay. While rodents physically move between reward sites, humans transition to the next video type by pressing a button. Rodents and humans show similar patterns of behavior on these tasks, supporting their use to study decision-making across species. We tested a new human task (“Movie Row”), which combines elements of the Restaurant Row and Web-Surf tasks.
In the Movie Row task, participants navigate through a 3-d virtual environment on a rounded track. A movie screen is positioned at each corner of the track, where 4-sec video clips are available from one of four categories (kittens, bike accidents, landscapes, and dancing). As participants arrive at a screen, the category and loading time (delay) is presented. Participants accept offers by stepping onto a platform and looking at the screen, or skip an offer by moving to the next reward site. Delays range from 3 to 29 seconds (though longer delays were possible in the second version).
Two versions of the task were tested, the first in a sample of 30 male undergraduates who completed the Movie Row task in a laboratory. The second version was tested in an online sample of 51 participants (30 females, mean age = 42.2 years) recruited through Amazon’s Mechanical Turk.
Behavior on the Movie Row was similar to that of the Web-Surf task. Revealed video preferences, assessed by delay thresholds (the delay below which they would accept, above which they would skip an offer) were positively correlated with stated preferences, with more than 64% of participants having a correlation greater than +0.75 with the average video rankings and with post-experiment rankings of each video category. Decision consistency (the proportion of offers where participants deviated from their delay threshold) was lower on the first (in-person) version (M = 0.12, SD = 0.05) than the second (online) version (M = 0.20, SD = 0.11), higher than the reported mean for the Web-Surf task (M = 0.07), but similar to the Restaurant Row task (M = 0.12).
These data support the Movie Row task as translational tool to study foraging behavior in humans, providing convergent results with a rodent navigation task and a human stay/go foraging task. And, by including a virtual navigation component, the task may be useful in testing if behavioral measures identified in the rodent Restaurant Row task translate to human virtual navigation.
Aim: Disorders such as Alzheimer’s Disease involve memory deficits and grey matter loss in the hippocampus and entorhinal cortex are predictors of future clinical diagnosis. Early identification of memory deficits is critical for treatment. Our lab has developed a navigation task, the Concurrent Spatial Discrimination Learning Task (CSDLT), to assess the use of hippocampal-dependent memory in healthy adults.
Methods: In the virtual navigation task, participants navigate on a 12-arm radial maze, to find objects hidden at the end of the arms of the maze. The twelve arms are divided into six pairs of adjacent arms, which are presented in a pseudorandom order. In each pair, one arm is rewarded, and participants are trained until they can correctly choose the rewarded arm in each pair. After reaching criterion, participants complete a set of probe trials in which they are presented with a recombined set of adjacent arms, in which the previously rewarded arm is paired with a new unrewarded arm. In the recombined pairs, participants relying on a hippocampal strategy will learn the location of the correct arm relative to distal cues, hence perform well on this probe trial. Participants using non-hippocampal strategies make more errors, tending to choose an arm based on its stimulus-response associations (e.g. “choose the left path”). In this study, we developed a short static version of the CSDLT task, in which participants are presented with images of the pairs of arms, but were not required to navigate in virtual reality to the end of the arm on each trial. Instead, participants click on a button to select the arm displayed on an image. Participants are given feedback whether their choice was correct or incorrect. To validate the short version of the CSDLT task, we tested participants recruited through Amazon’s Mechanical Turk (mTurk) service on an automated version of the original CSDLT task, and the new shortened version.
Results: Participants (n = 35 who completed both tasks) completed the short CSDLT task much faster (M = 7.4 minutes, SD = 4.2) compared to the original CSDLT (M = 18.2, SD = 7.3, t(34) = 8.3, p < 0.0001, d = 1.4). Performance on the probe trials was correlated across the two tasks (r(33) = 0.412, p = 0.014) and a similar relationship was obtained when the short version was administered as the first (r(18) = 0.47, p = 0.036) or second (r(13) = 0.49, p = 0.061) task.
Conclusion: These preliminary data support the use of the shortened CSDLT task to assess an individual’s preference for spatial strategies in navigation. While this task was not validated against MRIs, it may be helpful as a screening tool for an initial rapid assessment in clinics when time is limited, which can be followed by more extensive testing in at risk individuals.
A previous study by Packard and McGaugh (1996) examined the use of spatial and egocentric navigation strategies by training rats to obtain a food reward in a plus-shaped maze. With one arm closed off to form a T-shaped maze, rats were trained to find food placed in one arm of the T. During the training phase, the rat began and retrieved food from the same locations. On a probe trial, rats were placed in the arm opposite to the starting location. If the rat could accurately locate the reward, it was demonstrating a place strategy. Conversely, if the rat turned in the same direction as it did in the training phase, it was navigating via a response strategy. However, the experimental paradigm used by Packard and McGaugh may have its limitations. When conducting a probe trial in a plus-shaped maze, it is difficult to confirm that animals are relying specifically on either a place or response strategy, as any choice made by the animal, even a random search, counts as a strategy: when approaching the food reward, rats were only able to turn in two directions. As a result, the rats have no other choice than to exhibit either a response or place strategy. In the present study, we introduced a modified maze design that included other areas where the rat could travel during a probe trial, using a symmetrical maze with four starting locations and four goal locations. Using this new maze configuration, we aimed to replicate the findings of Packard and McGaugh. We hypothesized that rats will adopt a place strategy, and transition to a response strategy after extended training. We expected also that two rats with excitotoxic lesions of the hippocampus would show a deficit in the use of a place strategy. We also will examine other behavioral measures (reaction time, latency to reach the food reward, and consistency of the path taken to the reward) to identify other measures (beyond accuracy) that identify the use of place and response strategies. We expect that rats using a place strategy to take significantly longer reaction time, and will take a more variable path to the food reward.
Mindfulness training (mindfulness-based stress reduction, MBSR) has been found to be effective in reducing stress and improving cognitive function, and to produce changes in regional grey matter density in brain areas including the hippocampus. Most studies of MBSR’s effects on cognitive function have focused on improvements in attention and working memory, but some studies have found improvements in declarative memory following MBSR training. Other work has shown that even in participants who have not completed mindfulness training, regional grey matter density in the hippocampus is positively associated with measures of dispositional (trait) mindfulness. Here, we investigated if dispositional mindfulness was associated with the use of hippocampally-dependent navigation strategies in a set of virtual navigation tasks. Participants (n = 111) were recruited through Amazon’s Mechanical Turk service after completing the Five Facet Mindfulness Scale (FFM). Participants completed up to four new, automated versions of standard navigation tasks: the 4 on 8 virtual maze (Iaria, Petrides, Dagher, Pike, & Bohbot, 2003), the Concurrent Spatial Discrimination Task (CSDLT, Etchamendy, Konishi, Pike, Marighetto, & Bohbot, 2012), a wayfinding task set in a virtual town and a virtual water maze. Results from the behavioral tasks fit our expectations based on previous research (performance on the wayfinding and water maze task was strongly related, and flexible performance on the CSDLT was associated with better performance on the wayfinding and water maze task). Only the 4 on 8 task was associated with trait mindfulness, with participants who reported using hippocampus-dependent spatial strategies also reporting higher scores on the Describe FFM subscale but not other FFM subscales. In a second study, participants completed the Calgary Symptoms of Stress Inventory (C-SOSI), and participants (n = 96) with high (C-SOSI > 50) and low (C-SOSI < 50) stress scores were recruited to complete the FFM and the 4 on 8 virtual maze. C-SOSI scores were negatively correlated with several FFM subscales, and participants reporting high levels of stress were less likely to use hippocampus-dependent spatial strategies (though, a small number of participants reporting very high scores, C-SOSI > 100, were more likely to use spatial strategies). These data provide some support for the claim that hippocampus-dependent spatial strategies may be associated with both dispositional mindfulness and self-reported stress. Programs which aim to reduce stress by increasing mindfulness (as in MBSR programs) may thus be associated with an increase in the use of hippocampally-dependent navigation strategies.
Many addictive drugs facilitate release of dopamine in the basal ganglia, and drug addiction may involve the recruitment of brain systems that support habitual behaviors. Work with operant tasks has shown that relative to natural rewards, rats develop habits for actions rewarded with drugs such as cocaine and alcohol. Using post-training injections of cocaine, our lab has shown that cocaine can act directly to facilitate habit learning, and that the infralimbic cortex is required for habit facilitation by cocaine. The present study addressed if cocaine infusion directly into the infralimbic cortex was sufficient for the facilitation of habit learning. Twenty seven Sprague-Dawley rats were implanted with bilateral cannula targeting the infralimbic cortex. Rats were trained after surgery to perform two actions (lever pressing) which were rewarded with either grain or sucrose flavored pellets. After acquiring both lever presses, rats received three training sessions on each lever, rewarded on a random interval 30 second schedule (RI-30s). After each RI-30s training session, rats received infusions of cocaine (200 micograms/microliter) or vehicle. Using sensory-specific satiety, extinction tests revealed that for the lever paired with cocaine infusions, lever pressing was not sensitive to devaluation of the reward while the lever paired with saline injections were sensitive to devaluation. These data suggest that drugs such as cocaine can act directly during memory consolidation in brain areas required for habitual behavior in order to facilitate habit learning.
Many addictive drugs facilitate release of dopamine in the basal ganglia, and drug addiction may involve the recruitment of brain systems that support habitual behaviors. Work with operant tasks has shown that relative to natural rewards, rats develop habits for actions rewarded with drugs such as cocaine and alcohol. Using post-training injections of cocaine, our lab has shown that cocaine can act directly to facilitate habit learning, and that the infralimbic cortex is required for habit facilitation by cocaine. The present study addressed if cocaine infusion directly into the infralimbic cortex was sufficient for the facilitation of habit learning. Sixteen Sprague-Dawley rats were implanted with bilateral cannula targeting the infralimbic cortex. Rats were trained after surgery to perform two actions (lever pressing) which were rewarded with either grain or sucrose flavored pellets. After acquiring both lever presses, rats received three training sessions on each lever, rewarded on a random interval 30 second schedule (RI-30s). After each RI-30s training session, rats received infusions of cocaine (200 g/L) or vehicle. Using sensory-specific satiety, extinction tests revealed that for the lever paired with cocaine infusions, lever pressing was not sensitive to devaluation of the reward while the lever paired with saline injections were sensitive to devaluation. These data suggest that drugs such as cocaine can act directly during memory consolidation in brain areas required for habitual behavior in order to facilitate habit learning.
I am always happy to talk with current students, prospective students and alumni about our programs and opportunities in psychology and neuroscience. If you are on campus during the semester, feel free to drop by my office in Baxter Hall (room B317). For other professional and research questions, please feel free to contact me by email.