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Our research focuses on studying the
psychological and neural processes involved in rat cognition with a
special interest in how animals organize complex behavior. Our current
hypothesis is 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, then 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 seems to be well-suited for this
purpose. The method we developed (Fountain et al., 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 (Figure 1) or, in earlier studies, 8 levers similarly
arranged (Figure 2). The task is to learn to choose the 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, as shown in Figures 1 and 2. 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. This method is easily
learned by the rat without pretraining procedures other than nose poke
shaping. It is an improvement over earlier methods used with rats
because it allows us to study how rats learn long, elaborate serial
patterns and because it 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. In addition, our research has shown recently that
this method can be used to assess the effects of adolescent exposure to
nicotine that causes later adult cognitive impairments. Thus, our
research focuses in three areas:
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