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Poster Abstracts:
Reducing Irrelevant Relations Facilitates Learning
Rules from a Response Series Lacking a Consistent Motor Sequence in
Rats. PDF
Shannon M. A. Kundey (Hood College) & Stephen B.
Fountain (Kent State University)
Earlier we reported that rats could learn a
response pattern in a circular array of levers that was not a set motor
sequence. Rats learned either a structured (12345678) or an unstructured
(17356428) subpattern interleaved with responses on randomly presented
levers (X): 1X2X3X4X5X6X7X8X or 1X7X3X5X6X4X2X8X, respectively. The
structured, but not the unstructured, group learned their pattern. In a
new study, we hypothesized that irrelevant
relations between random elements and fixed subpattern elements might
have slowed learning in the earlier study, as they do in humans (Hersh,
1974). Using the same structured and unstructured subpatterns used
earlier, we restricted the set from which random elements were drawn so
that irrelevant relations were prevented. As before, rats learned the
structured subpattern faster than the unstructured subpattern. However,
learning by the structured group was facilitated. The results provide
further evidence that sequential structure across nonadjacent elements
can mediate better pattern learning even when the rule relating those
elements cannot be abstracted from a set motor pattern. Furthermore, the
results suggest that irrelevant relations in serial patterns interfere
with detecting and encoding pattern structure in rats as they do in
humans.
Scopolamine dissociates cognitive processes
responsible for phrasing effects versus violation element performance in
rats. PDF
Amber M. Chenoweth & Stephen B. Fountain (Kent
State University)
In serial pattern learning, “phrasing cues”
positioned at chunk boundaries can facilitate learning transitions
between chunks which are harder to learn than elements within chunks. We
have shown before that disruptions in chunk boundary performance occur
when phrasing cues are removed or when scopolamine, a muscarinic
cholinergic antagonist, is administered. The present study examined the
effects of both manipulations combined. Rats were trained to nosepoke
one of two patterns in a circular array: Perfect:
123-234-345-456-567-678-781-812 Violation:
123-234-345-456-567-678-781-818 where digits indicate positions of
correct responses, dashes indicate 3-s phrasing cues, intertrial
intervals were 1 s, and the last element of the Violation sequence
violated pattern structure. After acquisition, phrasing cues were
removed concurrently with injections of either scopolamine (0.6 mg/kg)
or saline. Scopolamine produced a large deficit in performance
relative to saline at chunk boundaries where phrasing cues previously
signaled responses, but produced no effect at the violation element.
These results indicate that scopolamine dissociated the cognitive
systems necessary for performing chunk boundary versus violation element
responses. Given that we have already shown that these processes are
dissociable from within-chunk rule learning, the results suggest that at
least three dissociable cognitive processes are used concurrently in rat
sequential learning.
Serial Pattern Learning in Rats: Rule Induction
and Pattern Tracking in Patterns Containing 2, 4, or 8 Interleaved
Random Elements. PDF
Karen E. Doyle & Stephen B. Fountain (Kent State
University)
In a serial pattern learning task, rats typically
acquire a simple rule-based pattern rapidly whereas presentation of the
same simple pattern with interleaved random elements severely retards
acquisition. Since previous results have indicated that rats encode
rules when learning a serial pattern presented in this manner, it is
unclear why introduction of interleaved random elements impairs learning
to such an extreme. One possible explanation for this impairment is that
random elements increase the difficulty of parsing together related
elements from the simple pattern in order to extract the rule. The
present study was designed to examine whether performance would improve
if more of the simple pattern were presented between interleaved random
elements by altering the number and positioning of those elements. Rats
learned to perform a simple pattern of responses in a circular array of
8 nosepoke receptacles. The simple pattern was 1-2-3-4-5-6-7-8, where
digits indicate the successive clockwise positions of correct responses
in the array. Random elements were interleaved after every 1, 2, or 4
elements of the pattern. Acquisition occurred faster when fewer
interleaved elements were presented in the same simple pattern,
suggesting that interleaved random elements interfered with rule
detection.
Sex Differences in Adult Rat Serial Pattern
Learning. PDF
Laura R. G. Pickens, Kristen L. Kolar, & Stephen
B. Fountain (Kent State University)
Several studies have demonstrated that males
perform better than females in spatial learning tasks such as the radial
and water maze in rats (cf. Williams & Meek, 1991; Jonasson, 2005). Male
rats also exhibit greater contextual freezing than females in Pavlovian
fear conditioning (Maren et al., 1994). We examined whether similar sex
differences would appear in rat serial pattern learning. Male and female
Long Evans rats (12 per group) were trained for 49 days on a 24-element
serial pattern: 123-234-345-456-567-678-781-818, where digits indicate
the clockwise position of correct receptacles within a circular array of
an octagonal chamber. Acquisition analyses revealed a sexual dimorphism
for chunk boundary and violation element types, with males learning
significantly faster than females. We will also discuss trial-by-trial
data and provide an analysis of error types to ascertain whether or not
male and female rats differ qualitatively in how they encode their
serial pattern. One conclusion from these results with perhaps
far-reaching implications is that sex differences may be more common in
different rat learning paradigms involving complex cognitive processes
than has been previously appreciated.
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