Animal Cognition, Neuroscience, & Neurotoxicology
of Sequential Behavior
Our research focuses on studying the psychological and neural processes involved in rat cognition with a special interest in how animals organize complex behavior through time, that is, sequential behavior. Our research has shown that multiple cognitive systems contribute to this process at the same time through parallel processing, and much of our work focuses on determining the nature of the psychological and neural systems that allow animals to organize their behavior. If we are to determine whether multiple cognitive processes act concurrently to produce sequential behavior, we need to study forms of sequential behavior that are sufficiently complex that they will likely recruit multiple processes concurrently. Our serial pattern learning task for rats is well-suited for this purpose.
The Serial Multiple Choice (SMC) task we developed (Fountain et al., 1995, 2006) is a functional analogue of nonverbal human pattern learning tasks that require human subjects to learn to choose items from an array in the proper sequential order (Knopman & Nissen, 1991; Hartman, Knopman, & Nissen, 1989; Restle, 1970; Restle & Brown, 1970b; 1970c; Willingham, Nissen, & Bullemer, 1989; Willingham, 1998; Reber, 1989; 1973). In our task, rats learn to choose from a circular array of 8 nose poke receptacles or, in earlier studies, 8 levers similarly arranged as shown here:
The task for the rat is to learn to choose the response manipulanda in the proper sequential order. The nose poke receptacles or levers are designated 1 through 8 in clockwise order with number 8 adjacent to number 1 in the circular array. All of the receptacles are illuminated by small lights at the beginning of each trial and the rat may nose poke in any of the 8 receptacles. If the correct receptacle is chosen, then the rats receive water. If an incorrect receptacle is chosen, then all of the lights in the receptacles except the correct one are turned off and the rat must choose it to be reinforced before continuing. Rats and mice can learn complex, highly-structured response sequences via this method.
With receptacle 1 at the "top" of the apparatus in this case, follow the bouncing head below through the sequence:
Our latest innovation in nosepoke sequence learning methods involves training animals to respond to a circular array of spots on a touchscreen like the one shown below. In the first study in this line in collaboration with Dr. Aaron Blaisdell's UCLA laboratory, pigeons were taught to peck at a touchscreen for grain to perform long sequential patterns in such a chamber (Garlick, Fountain, & Blaisdell, 2017). We have recently begun full-scale studies of how rats perform serial patterns in the touchscreen chamber shown below and we have examined rats ability to learn the same complex serial patterns in this task that we have studies in octagonal chambers. Current work is examining the neurobiological foundations of rats' capacities to learn complex information in this task.
These nosepoke methods in octagonal chambers and in touchscreen chambers are easily learned by rats without pretraining procedures other than nosepoke response shaping. All of these methods are an improvement over earlier methods used with rats because they allows us to study how rats learn long, elaborate serial patterns and because they provides measures of correct-response rates, error rates, and "intrusion" rates (i.e., the number of specific kinds of errors produced at particular locations in the pattern) on a trial-by-trial basis throughout the serial pattern. With this method, we can create serial patterns with many items that could be associated, with spatial and temporal cues that could be relevant, with particular pacing or rhythmic structures, and with patterns of movements that could potentially be coded internally as motor patterns or as rule-based structures. Typically, many of these cues and features are concurrently available to the rat as the sequence training takes place, and, as we have shown, it appears that rats concurrently make use of multiple sources of cues and behavioral processes to learn to navigate these serial patterns. We have used this method to begin to characterize the cognitive and neural systems responsible for sequential behavior. In addition, our research has shown that this method can be used to assess the effects of adolescent drug exposure that causes later adult cognitive impairments. Thus, our research focuses in the following areas: