2006 Comparative Cognition Society Annual Meeting

Stephen B. Fountain & Amber M. Chenoweth (Kent State University)

In serial pattern learning, it is common to find that the transitions to new chunks of a serial pattern are more difficult to anticipate than elements within chunks. Providing “phrasing cues” at chunk boundaries can facilitate learning about these transitions in normal rats. Further, our lab has found evidence that atropine, a muscarinic cholinergic antagonist, impairs acquisition of chunk boundaries, regardless of the presence of phrasing cues. We examined the differences between two groups of rats given daily i.p. injections of either saline or atropine sulfate (50 mg/kg) and trained to press levers in a specific order (the serial pattern) for brain-stimulation reward in an octagonal operant chamber. Two phrasing cue removal probes revealed that both control and atropine-exposed rats anticipated chunk boundaries. However, the results also showed that intact central cholinergic systems are necessary for rats to exhibit organized strategies for dealing with cue changes in transfer conditions.

Poster Presentation Abstracts:
 

Central Cholinergic Systems are Necessary for Learning and Retaining “Exceptions-to-the-Rule” in Rat Serial Pattern Learning.   PDF

Amber M. Chenoweth & Stephen B. Fountain (Kent State University)

We examined the effects of atropine, a muscarinic cholinergic antagonist, on acquisition and retention of serial patterns.  Rats were given daily i.p. injections of either saline or atropine sulfate (50 mg/kg) and trained to press levers in a specific order (the serial pattern) for brain-stimulation reward in an octagonal operant chamber. The two groups learned the following pattern: 123 234 345 456 567 678 781 818. Atropine exposure impaired acquisition for chunk boundary elements (the first element of chunks) and the violation element of the pattern, but did not impair acquisition for within-chunk elements. Performance was unchanged in a subsequent drug-free day. Similar deficits were observed in a retention test where saline-trained rats were exposed to atropine for one day. The results indicate that intact central cholinergic systems are necessary for learning and retaining appropriate responses at places in sequences where pattern structure changes.
 

“Extreme” Sequential Learning: Rats Learn 60-Element Interleaved Serial Patterns.  PDF

Amber M. Chenoweth, Steven A. Wolfe, & Stephen B. Fountain (Kent State University)

Humans have the ability to chunk together information from nonadjacent serial positions in sequential patterns. For example, human subjects typically learn the pattern, A-M-B-N-C-O-D-P-E-Q, by cognitively sorting pattern elements into component interleaved subpatterns: A-B-C-D-E and M-N-O-P-Q. Our earlier studies demonstrating similar capacities in rats showed that patterns composed of two interleaved subpatterns were difficult to learn, but that subpattern difficulty was nonetheless determined by subpattern structure. In the present study, we investigated rats' ability to learn a 60-element interleaved pattern where one subpattern was one of two 30-element hierarchically organized patterns composed of either “runs” or “trills” chunks. The other subpattern was composed of a repeating element. Subpattern acquisition rates were correlated with the structural properties of component subpatterns. The results indicate that rats are sensitive to the patterning of nonadjacent elements even in extremely long serial patterns and that several factors contribute to pattern tracking in interleaved patterns.
 

A Serial Reaction Time Task for Rats: Individual Differences in Sequence Encoding.  PDF

Stephen B. Fountain & Amber M. Chenoweth (Kent State University)

The serial reaction time (SRT) task is a popular procedure for assessing sequential learning capacity in human neuropsychology and functional imaging studies. We developed an operant SRT procedure for rats that is a close analogue of the human SRT procedure. It encourages rats to respond as quickly as possible to the successive positions of a light that appears in one of four positions in a horizontal array. Rats press corresponding levers under the array of lights for brief pulses of hypothalamic brain-stimulation reward. “Reaction times” (RTs) are similar to those observed in human studies, averaging 1000 msec or less for 1000-trial sessions. Rats learned a simple repeating pattern in this task in a single session; RTs were shorter for repeating patterns than for random sequences presented in blocks in the same session. Rats showed individual differences in sequence encoding that appeared in their first session and remained consistent across sessions.
 

Adolescence Exposure to Nicotine Impairs Adult Serial-Pattern Learning in Rats

James D. Rowan (Wesleyan College), Amanda R. Willey, Eric P. Nolley, Brian M. Kelley (Bridgewater College), and Stephen B. Fountain (Kent State University)

This experiment examines the effects of early exposure to Nicotine on adult higher cognitive function. Weanling rats were injected 5 days a week for 5 weeks with 3.0, 1.0, 0.3 mg/kg nicotine or saline based on body weight (1 ml/kg). After 5 weeks off, all subjects were trained on the perfect run pattern (123 234 345 456 567 678 781 812) for 28 days receiving 5 patterns a day. Analysis of the data found the performance of the 1.0mg/kg nicotine group was significantly impaired compared with all other groups. To our knowledge, this is the first evidence that long-term, low-level adolescent nicotine exposure significantly impairs higher cognitive functioning in adulthood.  
 

Medial Caudate Putamen Lesions and Rat Serial Pattern Learning.  PDF

Denise P.A. Smith & Stephen B. Fountain (Kent State University)

In prior research in our lab, MK-801, an NMDA receptor antagonist, disrupted serial pattern learning in rats when the serial pattern was a sequence of 24 response elements arranged in eight 3-element chunks. The final element of the sequence violated the overall pattern structure. MK-801 rats learned within-chunk elements as fast as controls, but showed permanent inability to learn the violation response and, to a lesser degree, chunk boundary responses. In the present study, 6 rats received medial caudate putamen excitotoxic lesions later confirmed by histological analysis. Rats were then trained on the same pattern as in previous studies. Medial caudate putamen lesions caused learning deficits for within-chunk elements and the violation element, but not for chunk-boundary elements. Deficits were generally less severe than those caused by MK-801. These results support the claim that serial pattern learning is subserved by multiple dissociable brain and cognitive systems.

Other Activities:

We are always trying to move ahead in the field...  Professor Rowan shows excellent form.

(Trying to take our work seriously without taking ourselves too seriously.)