Are memories for stimulus-stimulus associations or stimulus-response associations responsible for serial-pattern learning in rats?

Previous research has provided convincing evidence that rats can learn to anticipate the individual elements of a stimulus series consisting of differing amounts of food reinforcement. Rats prepared with lesions of the dorsal striatum or hippocampus were initially trained to acquire a three-element series consisting of 21 sucrose pellets, followed by 0- and 7-pellets (Noyes standard), respectively. During the initial 30 days of training, the animals were run in two adjacent runways; the runways included either of a white, rough runway or a black, smooth runway as additional series cues. Thus, training included both floor (S-R) cues and the series (inter-item memory) cues. Anticipation was defined as faster running on the 21- than on the 7-pellet element and 7- than on the 0-pellet element. While anticipation developed more slowly in the lesion groups than in the control group, all animals eventually demonstrated the ability to track the elements of the series. Reversal of the floor cues disrupted tracking in the hippocampus-lesioned and control animals; dorsal striatum-lesioned rats were also affected but did continue tracking. As a final test, shifting the order of the series produced a marked disruption in performance in the dorsal striatum-lesioned rats but not in the hippocampus-lesioned or control rats. The results are consistent with the proposal that integrated neural mediation is required for anticipation, with a system that includes the dorsal striatum necessary for the promotion of a reinforced approach response and a system that includes the hippocampus necessary for associating and temporarily maintaining an internal record of the different elements of the stimulus series.

An assessment of grade inflation in higher education.

Considerable research has been conducted on grade inflation and its pervasiveness. Given the significance of grade inflation on the quality of the educational experience and the reputations of colleges and universities, efforts to assess its presence and underlying causes should be supported and solutions developed. Because periodic changes in average grades in the short term may be anomalous, mean grade point averages (GPAs) for 262 undergraduate courses at a Liberal Arts college were examined for trends across a 10-yr. period. Analysis showed higher grades appeared within two of the colleges' four academic units, although the reasons remained unclear. Tentative explanations are explored.

Age-associated changes in cognitive function in highly educated adults: emerging myths and realities.

The effects of education and continued intellectual engagement on age-associated cognitive change were investigated in a sample of 102 members of the professional and college communities in the metro Atlanta Georgia area (ages 30-76). All participants were administered a 60-minute battery that measured different aspects of memory, intelligence and cognitive performance. Age-associated declines in performance were detected on the digit symbol measure of intelligence. Conversely, positive but non-significant trends were detected on the picture completion, arithmetic and similarities subtests. Age effects were also noted on some measures of the Wisconsin Card Sorting Test and both versions of the Trail Making Test. The findings suggest that at least among the highly educated, certain cognitive abilities may receive some degree of amelioration as a consequence of continued intellectual engagement. However, the effects may be associated more with compensation rather than protection against the effects of ageing.

The effects of nicotine on learning and memory: a neuropsychological assessment in young and senescent Fischer 344 rats.

The effects of chronic nicotine on the behavioral performance of young (4 month) and old (24 month) Fischer-344 rats were assessed on four behavioral tasks: activity chamber. rotating rod, serial pattern learning, and Morris water maze paradigm. Old and young nicotine-treated rats received an intraperitoneal injection of nicotine (0.20 mg/kg) 15 min prior to all behavioral testing, and old and young saline-treated rats received saline injections 15 min prior to all behavioral testing. Nicotine improved motor coordination and increased the general activity levels of the old rats compared to old saline-treated rats. There were no significant differences in the behaviors of the young rats in these behavioral evaluations. In young rats, nicotine improved the acquisition of a serial pattern, suggesting an improvement in working memory or related processes. Nicotine was found to increase swim speed in a Morris water maze paradigm with a hidden platform; however, no beneficial effects of nicotine in reference memory were obtained for either age group. These results suggests that nicotine may not be as beneficial in attenuating age-related learning and memory deficits as once proposed.

A strategy for screening memory functions in individuals with mental retardation.

In an attempt to develop a protocol for evaluating mentally retarded clients from a neurobehavioral perspective, a strategy for screening complex verbal, simple verbal, simple visual, and spatial working memory was developed. This strategy results in numeric values on each of the aspects of memory, and it can contribute to a "global index" of memory function. The strategy is described so that it might be adopted by other practitioners interested in screening their client's ability to store and retrieve newly acquired information. Descriptive data for 125 persons carrying diagnoses of mild, moderate, and severe mental retardation are presented. The procedure was found to discriminate well between the various levels of mental retardation, correlate reasonably well with IQ, and possess relatively good test-retest reliability.

Construct validity of the MMPI-168(L) with mentally retarded adults and adolescents.

Fifty-three persons residing in an institution and diagnosed with mild or moderate mental retardation were assessed with a modification of the MMPI-168. Forty-one of the residents also had psychiatric diagnoses. Construct validity of the MMPI-168(L) was examined by correlating T scores obtained on the scales of this instrument with the results of an 8-item "Behavioral Survey." The survey required unit clinicians to rate the severity of behavioral disturbance in eight categories. Six of the items on the "Behavioral Survey" were found to correlate with one or more MMPI scales. Stepwise multiple regression procedures revealed additional collective relations between elevations on the MMPI and ratings of behavioral disturbance.

The flexible use of multiple cue relationships in spatial navigation: a comparison of water maze performance following hippocampal, medial septal, prefrontal cortex, or posterior parietal cortex lesions.

Rats prepared with lesions of the prefrontal cortex, posterior parietal cortex, hippocampus, or medial septal area were tested for acquisition of a number of variations of the open-field water maze using a version of place learning assessment described by Eichenbaum, Stewart, and Morris (1991). Specifically, the individual role of the aforementioned cortical and subcortical structures in tasks with differing representational demands on navigation were assessed. The results suggest that the sham-operated control, posterior parietal cortex-lesioned rats, and medial septal area-lesioned rats were able to navigate effectively under changing task conditions. Conversely, the navigational performances of the prefrontal cortex- and hippocampal formation-lesioned rats were impaired when task demands changed. The results are discussed in terms of the flexible use of multiple distal cues to guide navigation and the resulting loss of this flexibility after lesions to either the prefrontal cortex or the hippocampus.

Aging and intellectual ability in young, middle-aged, and older educated adults: preliminary results from a sample of college faculty.

52 members of the college community at a small liberal arts university (Ages 25-72) were administered a 60-min. battery of tests measuring different aspects of cognitive performance. Stepwise regression equations detected significant relationships between the predictor variables of age and education and measures of the WAIS-R, the Logical Memory subtests and Trails A. Age predicted performance on Trails A, the Digit Symbol subtest of the WAIS-R, the Logical Memory II component of the Wechsler Memory Scale-R, some measures of the Wisconsin Card Sorting Test, and Full Scale WAIS-R IQ. Education was a significant predictor of performance on the remaining WAIS-R subtests and the Failure. To Maintain Response Sets measure of the card sorting. However, the results of the present study also suggest that over-all cognitive decline with advancing age is not an eventuality, at least among the highly educated, intellectually active individuals.

Chronic administration of ORG 2766 for 6 months produces a subtle impairment in strategic learning by rats.

Rats were administered saline or 10 micrograms of the ACTH4-9 analog ORG 2766 on alternate days for 160 days (i.e. 80 injections total). Behavioral assessments began 1 week later. Locomotor competence was assessed by examining the number of slips and falls made by the animals on a rotating rod. The rats were also trained on a position task and 10 subsequent position reversals in a 'T' shaped water maze. Exposure to ORG 2766 failed to affect either locomotor competence or the overall number of errors committed while learning the original position habit and 10 reversals. However, the response accuracy of the ORG 2766-treated animals on trial 2 of the reversals was equivalent to that expected by chance (58% correct choices), whereas saline-treated animals effectively altered their behavior after experiencing nonreinforcement on the initial trial of a reversal (77% correct choices). This result is consistent with other observations revealing that ORG 2766 can influence attention and, therefore, some cognitive functions.

Serial pattern learning in senescent rats: a comparison of acquisition performance with young and hippocampal-lesioned rats.

The acquisition of a serial pattern was assessed in young (3-month), senescent (24-month), and hippocampal-lesioned rats. All animals were trained for 25 days on a four-element, nonmonotonic pattern consisting of 14, 0, 3, and 7 food pellets, respectively. Young rats were capable of distinguishing among the elements of the series, with the exception of the 3- and 7-pellet elements, as indexed by running times. Conversely, the senescent rats were largely incapable of patterned responding, and the tracking performance of the hippocampal-lesioned rats was intermediate between those of the young and old rats. Results are discussed in terms of the possible changes that accompany aging in rodents, including age-related changes in the hippocampal system.

Spatial and non-spatial learning in the rat following lesions to the nucleus locus coeruleus.

The present experiment examined the effects of unilateral or bilateral locus coeruleus lesions on general activity, acquisition of a non-monotonic serial pattern (14-0-3-7 food pellets, respectively), and response learning acquisition in a Greek cross version of the Morris water maze. Sham-operated control rats were capable of tracking the elements of the serial pattern while rats with a unilateral locus coeruleus lesion were moderately impaired, and those with bilateral locus coeruleus lesions were severely impaired. A similar pattern of working memory deficits emerged in an analysis of the response-learning data in the Greek cross. The results are discussed in terms of the current understanding of norepinephrine and the locus coeruleus in learning and memory processes.

Influence of the alpha 2 noradrenergic antagonist piperoxane on longevity in the Fischer-344 rat: a preliminary report.

Piperoxane is an alpha 2-noradrenergic antagonist with demonstrated excitatory effects on neurons in the locus coeruleus, causing a corresponding increase in norepinephrine in many forebrain areas. 16 male Fischer-344 rats approximately 16 months of age were injected with 3 mg/kg of piperoxane or .09% saline. The piperoxane-treated rats lived an average of 127.1 days longer than the saline-treated rats. The results are discussed in terms of the effects of strategies designed to enhance brain levels of catecholamine and their effect on the aging process. A discussion of further research is also presented.

In vitro and in vivo effects of cocaine and selected local anesthetics on the dopamine transporter.

The effects of selected local anesthetics on in vitro and in vivo measurements of dopamine transporter activity were determined to investigate the role of local anesthetic activity in the neuronal actions of cocaine. Cocaine inhibited [3H]2-beta-carbomethoxy-3-beta-(4-fluorophenyl)tropane 1.5-naphthalenedisulfonate (CFT) binding and [3H]dopamine uptake with estimated Ki and IC50 values of 0.6 microM and 0.7 micorM, respectively. Of the local anesthetics tested, only dimethocaine showed full displacement of CFT binding (0-30 microM tested) and full inhibition of dopamine uptake (0-100 microM tested). Dimethocaine was only slightly less potent than cocaine with an estimated Ki of 1.4 micorM and an IC50 value of 1.2 microM for [3H]CFT binding and dopamine uptake. At a maximum concentration of 100 microM, the ester containing local anesthetics procaine, tetracaine, piperocaine and the amide containing local anesthetic dibucaine and bupivacaine partially inhibited dopamine uptake by 47-70%. The ester containing local anesthetic propoxycaine and the amide containing local anesthetics prilocaine, etidocaine, procainamide, and lidocaine inhibited dopamine uptake by 8-30% at 100 microM. A 10 min administration of cocaine, dimethocaine, or procaine in the dialysis solution produced dose-dependent, reversible increases in endogenous dopamine efflux from the striata of awake rats. Cocaine and dimethocaine produced similar 12-fold increases in dialysate dopamine at concentrations of 0.1 mM and 1 mM respectively. Procaine (10 mM) produced a 6-fold increase in dialysate dopamine while lidocaine (1 mM) produced a reproducible and reversible decrease (30%). These results show that the cocaine-like actions of certain local anesthetics such as dimethocaine and procaine result from their direct actions of dopamine uptake inhibitors.

Animal rights activism and animal welfare concerns in the academic setting: levels of activism and the perceived importance of research with animals.

Past research suggests that public support for the use of animal models as means to improve the human condition is present but many individuals have expressed ambivalence. In the present study, various sectors of the academic community (students and faculty) as well as the general population, were surveyed to assess their positions on the need for, and value of animal research, the value of psychological research in which animals are employed, and the respondents' consummatory habits. The results suggested that more information needs to be provided about the role of animal experimentation, including a discussion of the benefits produced by using animals to answer psychological questions.

An investigation of the role of the hippocampus and the amygdala in the encoding of a serial pattern: Effects of a long inter-element interval.

Previous research has provided convincing evidence that rats can learn to anticipate each element of a stimulus series consisting of differing reinforcement quantities. The present experiment examined the effects of electrolytic lesions of the hippocampus, amygdala, or combined hippocampal and amygdala lesions on the acquisition of a 14-7-3-0 monotonic pattern with a 5 min inter-element interval. Anticipation was operationally defined as faster running on 14- than on 7-pellet elements, 7- than on 3-pellet elements, and 3- than 0-pellet elements. Male Sprague-Dawley rats (sham and lesioned) received two trials a day for 30 days on the 14-7-3-0 pattern of food pellets. Anticipatory tracking developed rapidly in the control animals and not until the end of training in the hippocampus + amygdala-lesioned rats, while the rate of acquisition in the single lesion groups was intermediate between the two. The results are discussed in terms of temporal and working memory processes. Mediation of the temporal and affective attributes of memory are considered for each structure. The present experiment provided additional evidence for a hippocampal role in maintenance of a temporal record of the elements of the series, thus providing the rat with the ability to track which stimulus elements have been presented and to anticipate future elements. Finally, via a role in processing the affective and reinforcing properties of the task, the amygdala appears to play a role in mnemonic processes.

Non-spatial learning following posterior parietal or hippocampal lesions.

Posterior parietal, hippocampal, or sham-lesioned rats were tested for the acquisition of a non-monotonic serial learning task. The performance of control rats and those with a posterior parietal lesion was similar, while those with hippocampal damage demonstrated a working memory deficit. The results are integrated with contemporary conceptualizations of hippocampal and posterior parietal cortex involvement in learning and memory for non-spatial tasks.

Spatial learning following posterior parietal or hippocampal lesions.

Rats with either posterior parietal (PPC) or dorsal hippocampal (HIP) lesions were tested for open-field activity, acquisition of a multiple T water maze habit, and presence of a 'cognitive map' of the water maze arena. The performances of control and PPC-lesioned rats were similar on all behavioral measures. However, the HIP-damaged rats demonstrated higher levels of general activity, severe deficits in both working and reference memory in the multiple T water maze task, and failed to develop a cognitive map of the water maze arena.

Encoding of a nonmonotonic serial pattern: role of the dorsal hippocampus and amygdala.

The present experiment examined the effects of lesions of the hippocampus, amygdala, or combined hippocampal + amygdala lesions on the acquisition of a presumably difficult serial pattern. Lesioned rats, sham-surgical and nonsurgical control rats were trained in a runway to track one of a four-element series of Noyes food pellets consisting of 14-0-3-7 pellets, respectively. Control rats were capable of tracking the elements of the series. Tracking developed in the amygdala-lesion group by the middle stages of training, but tracking did not develop in the hippocampal-lesion group until the end of training and failed to develop in the hippocampus + amygdala-lesion group. The results are discussed in terms of hippocampus and amygdala involvement in working memory processes. The role of each structure in processing the temporal and affective attributes of the task is considered. Presumably, the hippocampus is necessary for tasks requiring the sequential coding of information. The hippocampus appears to maintain a temporal record of the elements of the series providing the rat with the ability to track which stimulus elements have been presented and which have not. In addition, by processing the affective attributes of the task, the amygdala appears to mediate mnemonic processes.

Effects of septal lesions on a higher-order conditioned taste aversion: a preliminary analysis.

Septal-lesioned rats (n = 7) and nonsurgical controls (n = 7) were exposed to a higher-order conditioned taste aversion procedure and the effects of septal lesions on the development of a higher-order conditioned taste aversion examined. In Phase 1, septal and control rats were permitted to consume a sodium chloride solution and illness was produced by an injection of cyclophosphamide. Following a recovery period, in Phase 2, both groups were allowed access to a saccharin solution followed by 1 ml of sodium chloride placed directly inside the mouth of the rat. Subsequent preference tests for the septal-lesion group, the control group, and a second unconditioned control group (n = 5) showed the former two groups learned the higher-order conditioned taste aversion, as demonstrated by a marked aversion to the saccharin solution, and the septal lesions attenuated the severity of the conditioning process.

Serial learning: a review of the behavioral and physiological research with the rat.

The literature on the behavioral effects of manipulations in the length, complexity, interrun interval and intertrial interval of serial patterns presented to rats is selectively reviewed. The dominant theories of serial learning in rats are summarized and the evidence for each provided. Included in the discussion of rat serial learning are the theoretical models of: (a) Capaldi and associates who suggest that rats learn stimulus-stimulus associations, whereby each element in a series signals each succeeding element [e.g., (14)], (b) Hulse and associates who suggest that rats generate a specific rule defining the formal structure of a serial pattern [e.g., (55,56)], and (c) Roitblat, Pologe, and Scopatz (73) who suggest that rats may not learn either a specific rule or stimulus-stimulus associations. Instead, the rat develops knowledge of the serial position of an element's position in the list. In addition, the role of position cues and enumeration as dominant strategies are considered. Finally, the effects of manipulations in brain physiology on rat serial learning is discussed.