Retention and durability of persistence acquired by young and infant rats.

Conducted 2 experiments in a runway apparatus with 72 young Holtzman rats. A classic partial reinforcement acquisition effect was obtained in Ss trained from 30 to 45 days of age but not in those trained from 18 to 25 days of age. In an immediate extinction test for half of the Ss, a partial reinforcement extinction effect (PREE) was found in both age groups, but there were differences in the extinction patterns. Following a 45-day retention interval and a continuous reinforcement reacquisition treatment for all groups, the PREE emerged clearly in adult Ss which had not undergone previous extinction. In those Ss which had previously been extinguished the PREE emerged again but was somewhat reduced. Results from the younger Ss suggest that relatively permanent persistence in approach to food can be formed in the days that normally immediately precede and follow weaning in laboratory rats. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Partial Reinforcement Extinction Effect Despite Equal Rates of Reinforcement During Pavlovian Conditioning.

In 4 experiments rats received appetitive Pavlovian conditioning followed by extinction. Food accompanied every trial with the conditioned stimulus (CS) for the continuously reinforced groups and only half of the trials for the partially reinforced groups. In contrast to previous experiments that have compared the effects of partial and continuous reinforcement, the rate at which food was delivered during the CS was the same for both groups. The strength of the conditioned response during extinction weakened more rapidly in the continuously than in the partially reinforced groups. The results demonstrate that the partial reinforcement extinction effect is a consequence of the nonreinforced trials with the CS, rather than the rate at which the unconditioned stimulus is delivered during the CS. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An evaluation of secondary reinforcement effects in a comparison of partial reinforcement and partial delay of reinforcement.

Studied the effects of partial reinforcement and partial delay on extinction performance. 72 naive female albino Sprague-Dawley rats served as Ss. Secondary reinforcement effects were controlled by using the same delay-of-magazine interval on nonreinforcement trials with partial reinforcement (delay of empty magazine) as occurred on delayed trials with partial delay (delay of magazine containing sucrose). 4 delay intervals (0, 15, 30, and 45 sec) were factorially combined with the schedule variable. Resistance to extinction was an increasing function for the length of the delay interval and was greater for partial reinforcement than for partial delay. No interaction was observed to occur between the length of the delay interval and type of reinforcement schedule. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Persistence of runway performance after septal lesions in rats.

Assigned 32 male Wistar albino rats to groups receiving bilateral septal lesions or control operations. Septal lesions prevented the partial reinforcement extinction effect after 48 acquisition trials. Septal Ss showed increased resistance to extinction following continuous reinforcement but decreased resistance to extinction following partial reinforcement. Analysis of the acquisition data indicated that the lesions retarded the development of approach-avoidance conflicts associated with reward and nonreward. In a 2nd study, 16 septal and 16 control Ss received 96 acquisition trials. Extended training allowed the development of conflict responses under partial reinforcement, and the Ss with lesions were indistinguishable from controls during extinction. Following continuous reinforcement, septal lesions produced slower extinction of response. It is concluded that the lesions interfered with the development of feedback from frustration, approach-avoidance conflicts, and frustration tolerance. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evidence for a transitional period for development of persistence in infant rats.

Conducted 4 experiments with a total of 188 rat pups to test the hypothesis that rat pups can learn persistence at age 11 days but cannot express this learning in their behavior until they are a few days older. Exp I used a space-trial procedure to investigate the relative reinforcing effects of milk suckling, dry suckling, and contact without suckling at ages 11 and 14 days. Exp II used the Exp I procedure, manipulating schedule of reward at 2 ages and under 2 of the reward conditions. Exp III manipulated the dry suckling reward schedule in 11- and 14-day-old pups. Exp IV manipulated partial and continuous reinforcement on Day 11 but tested for persistence on Day 14. Results suggest the existence of a traditional period in neonatal rats for the learning of persistence. Partial reinforcement training with suckling on an anesthetized dam as reward induced greater persistence in extinction of the approach response than did continuous reinforcement in rat pups 14 days old but not in 11-day-old pups. Other aspects of this period of development are discussed. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Appetitive learning and extinction in 11-day-old rat pups: Effects of various reinforcement conditions.

Studied the acquisition and extinction of approach behavior in 96 11-day-old albino Sprague-Dawley rat pups in 3 experiments. The reinforcement in Exps I & II was 15 sec of nonnutritive suckling on an anesthetized lactating female. In Exp I, detention duration, 0- or 15-sec in the goal box on nonreward (N) trials, was studied in 2 groups whose acquisition training consisted of alternating blocks of rewarded and nonrewarded trials with a short (5-sec) intertrial interval. Exp II combined an examination of the effect of detention length with whether or not the mother was physically present, though inaccessible, on N trials with partially or continuously rewarded groups. Detaining Ss on N trials slowed the rate of extinction when the mother was present but increased the rate of extinction when she was absent. There was no evidence of a partial reinforcement extinction effect in any of the groups. The effectiveness of 6 types of reinforcement on promoting acquisition of approach behavior was assessed in Exp III. Equally good acquisition, but differences in extinction was obtained with an adult conspecific as the reinforcer, independent of sex and suckling, but there was no acquisition of approach responding when a sibling or no conspecific was in the goal box. These data extend earlier findings of appetitive learning and extinction in infant rats. They do not support the view that inhibitory mechanisms are absent in the rat until the 3rd or 4th wk of life. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of acquisition training schedule on extinction and reinstatement of cocaine self-administration in male rats.

Partial reinforcement is known to increase resistance to extinction (Rn) relative to training with continuous reinforcement. This phenomenon, referred to as the partial reinforcement extinction effect, is one of the most robust in learning and conditioning studies. Experiment 1 investigated manipulations known to affect the partial reinforcement extinction effect and determined their possible relevance for drug use patterns. Male rats received intravenous cocaine self-administration training under partial reinforcement (FR-10) training or continuous reinforcement (FR-1) conditions with either a low (0.25 mg/kg infusion) or a high cocaine dose (1.00 mg/kg infusion). Animals were placed on an extinction (recurrent nonreward) schedule for 10 days (1-hr sessions) prior to being tested for cue-induced reinstatement (single 2-hr session). Experiment 2 involved acquisition of cocaine self-administration under FR-1 conditions of short training (15 days) or extended training (30 days) with a low dose (0.25 mg/kg infusion) or a medium dose (0.50 mg/kg infusion) of cocaine reward prior to extinction or reinstatement. Experiment 1 showed that rats trained with FR-10-high dose outcomes exhibited greater Rn than the remaining groups. Additionally, FR-10-high dose and FR-10-low dose rats were more likely to return to active drug seeking during the reinstatement test. In Experiment 2, rats trained under FR-1-medium dose conditions were more persistent during extinction following short acquisition training than comparable rats experiencing extended acquisition training. The reinstatement test was conducted following extinction, in which it was observed that overtraining under FR-1-medium dose reward schedules resulted in a decrease in the tendency to return to active drug seeking. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contrast, resistance to extinction, and forgetting in rats.

Conducted 3 experiments with a total of 176 naive male albino rats, in which the depression effect decreased progressively over retention intervals ranging from 1-68 days, which were interpolated between the pre- and postshift stages of a Crespi experiment; at 68 days the depression effect was entirely absent. A 68-day interval between acquisition and extinction eliminated the inverse relationship between resistance to extinction (RTE) and amount of reward in consistently reinforced Ss. The same retention interval eliminated the spaced-trials partial reinforcement effect (PRE) but not the massed-trials PRE. Results are consistent with the views that (a) the inverse relation between RTE and amount of reward is a special case of negative contrast, (b) different mechanisms are responsible for the PRE in massed and spaced trials, and (c) the spaced-trials mechanism is negative contrast. (25 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of discrimination and reversal learning for olfactory and visual stimuli in aged rats.

The present study investigated age-related differences in discrimination and reversal learning for olfactory and visual stimuli in 6-month and 24-month-old rats. Rats were trained to discriminate between two pseudo-randomly selected odors or objects. Once each animal reached a criterion on discrimination trials, the reward contingencies were reversed. Young and aged rats acquired the olfactory and visual discrimination tasks at similar rates. However, on reversal trials, aged rats required significantly more trials to reach the learning criterion on both the olfactory and visual reversal tasks than young rats. The deficit in reversal learning was comparable for odors and objects. Furthermore, the results showed that rats acquired the olfactory task more readily than the visual task. The present study represents the first examination of age-related differences in reversal learning using the same paradigm for odors and objects to facilitate cross-modal comparisons. The results may have important implications for the selection of memory paradigms for future research studies on aging. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of acute trimethyltin exposure on appetitive acquisition and extinction performance in the adult rat.

16 adult male Sprague-Dawley rats were given an intragastric infusion of 7 mg/kg of trimethyltin chloride (TMT), and 16 additional Ss (controls) received saline, to investigate TMT's effect on Ss' appetitive acquisition and extinction performance. Ss from each condition were divided into 2 equal groups and trained with either partial or continuous reinforcement (PRF or CRF) in a straight-alley maze 21 days after dosing. The acquisition training phase contained 40 trials (4 trials/day) and was followed by 20 trials of extinction training (4 trials/day). Analyses performed on total speed revealed that TMT Ss performed at lower levels during acquisition than controls, regardless of schedule condition. Also, the rate of resistance to extinction was significantly reduced for TMT Ss compared with that of controls, regardless of the training schedules used during acquisition. A PRF extinction effect was observed for both control and TMT Ss, independent of dose regimen. PRF training occasioned greater persistence during extinction than did CRF training. Findings are discussed in terms of issues relating to TMT-induced hippocampal lesions. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Delay classical conditioning in young and older rabbits: Initial acquisition and retention at 12 and 18 months.

Classical conditioning of the nictitating membrane-eyeblink response in young (age 7 mo) and older (age 36 mo) New Zealand white rabbits in a delay paradigm with 400-msec CS–unconditioned stimulus/stimuli (UCS) interval was examined for initial acquisition and retention. Older animals required significantly more acquisition trials to reach learning criterion. Age differences in acquisition were temporary. Older rabbits responded at a level comparable to that of young rabbits such that total performance over the 630 trials of acquisition was not different. Rabbits in the explicitly unpaired control groups exhibited no age differences in unconditioned response (UCR) amplitude or latency measures. 12- and 18-mo retests demonstrated no significant age effects on retention. Patterns of retention differed between age groups. Older rabbits required fewer trials to obtain the learning criterion at each phase of testing. Younger rabbits maintained a stable performance throughout training. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ontogeny of persistence: immediate and long-term persistence in rats varying in training age between 17 and 65 days

In Experiment 1, six age groups of rats were trained to run an alley for either partial (PRF) or continuous reinforcement (CRF). Training was during a 2-day period starting at six different ages, and extinction was initiated about 12 hr later. There was a clear partial reinforcement extinction effect (PREE) at all ages and, particularly after PRF training, an inverse relationship between resistance to extinction and age. In Experiment 2, retention and durability of persistence as well as immediate persistence were tested following acquisition at three different ages. The immediate extinction tests confirmed the results of Experiment 1. In the delayed extinction tests, greater resistance to extinction following PRF than following CRF was found in all age groups after both the retention and durability manipulations. In neither test was there an effect of age in original acquisition on the magnitude of adult persistence. These experiments confirm earlier findings of remarkable persistence in rats trained and tested at weanling age, show that the persistence is even greater in pre-weanlings, and show that it is retained into young adulthood.     

Behavioral and neuroanatomical effects of prenatal, postnatal, or combined exposure to ethanol in weanling rats.

Separate and combined effects of prenatal and postnatal exposure to ethanol on activity, emotionality, learning, and hippocampal neuroanatomy were examined in infant rats. Neonatal rats from mothers that were fed either a liquid ethanol (E) or control (C) diet were artificially reared on either 3% ethanol (E) or isocaloric maltose/dextrin (C). Pups in 4 treatment groups (EE, EC, CE, and CC) were compared. Differences in activity and emotionality were slight. Ethanol affected both the partial reinforcement acquisition effect and the partial reinforcement extinction effect. Hippocampal cell density (compared with Group CC) showed a 12% reduction in CA1 pyramidal cells and an 11% reduction in mature granule cells in Groups EC and EE; the CA4 area (compared with Group CC) was significantly larger after postnatal exposure (Groups CE and EE). Significant positive correlations were found between rate of extinction after partial reinforcement (PRF) training and CA1 pyramidal cell density in Groups CC and CE. A significant negative correlation was found between extinction rate after PRF training and CA4 area in Group EE. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interhemispheric transfer of extinction of the active avoidance reaction in rats.

Employed cortical spreading depression (CSD) in 38 hooded Druckrey rats to study the lateralization of extinction of a jumping avoidance reaction. Under unilateral CSD, 181 nonreinforced trials were needed to extinguish the avoidance reaction acquired in 3 100-trial sessions of intact-brain training. During a 2nd extinction session, either with the same or with the contralateral hemisphere depressed, the mean number of trials to the extinction criterion (9 avoidance reactions in 10 consecutive trials) was 39 or 186, respectively. 5 extinction trials performed with the brain intact 1 hr before extinction with contralateral CSD decreased the number of trials to extinction to 98. Thus, extinction of active avoidance can be lateralized and interhemispherically transferred in the same way as acquisition of this habit. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Retention of response persistence in weanling and adolescent rats.

Two experiments (192 Sprague-Dawley rats) examined parameters affecting retention of continuously reinforced (CRF) and partially reinforced (PRF) runway training in weanling and adolescent Ss. In Exp I, weanling Ss were given CRF or PRF training and 12 hrs, 3 days, or 10 days later were given 8 CRF reacquisition trials followed by extinction. In Exp II, weanling and adolescent Ss were given CRF or PRF runway training and extinguished 10 days later following 0, 8, or 24 CRF reacquisition trials. Results suggest that (a) weanlings characteristically display a partial reinforcement extinction effect (PREE) of unusually large magnitude if extinguished within 12 hrs of training, (b) this large-magnitude PREE dissipates within 3 days of training regardless of the number of CRF reacquisition trials preceding extinction, (c) no PREE of any magnitude is seen in weanlings or adolescents following a 10-day interval unless CRF reacquisition trials precede extinction, and (d) retention of the PREE is poor or nonexistent in Ss trained as adolescents and extinguished 10 days later, even with CRF reacquisition preceding extinction. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Durability and generalizability of persistence training.

40 male and 40 female college students experienced either partial reinforcement (persistence training) or continuous reinforcement on either of 2 instrumental tasks (finger shuttle or button press) as therapy for failure-induced depression and subsequently were exposed to protracted failure (extinction). Following this initial extinction phase all Ss received continuous reinforcement on a common instrumental task (button press) as therapy and then encountered extinction (consecutive failure trials) for a 2nd time. Results show that increased persistence occasioned by partial-reinforcement therapy was able to survive interpolated periods of extinction and continuous reinforcement; that is, durable persistence training effects were shown. Furthermore, persistence training effects were shown to be generalizable (the persistence advantage associated with partial-reinforcement therapy transferred across topographically different responses), but the generalization process was not a complete one. The results are discussed within the frameworks of frustration theory and alternative cognitive theories. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Partial reinforcement effects in classical aversive conditioning in rabbits and human beings.

Investigated the partial reinforcement extinction effect (PREE) in classical aversive conditioning. In Exp I the nictitating membrane responses of approximately 120 naive New Zealand rabbits were conditioned at a 250-msec interstimulus interval under continuous reinforcement, partial reinforcement with the unconditioned stimulus (UCS) omitted (Group PO), or partial reinforcement with the UCS delayed to 1,500 msec (Group PD). These 3 groups were factorially extinguished under UCS-omitted, UCS-unpaired, or UCS-delayed extinction regimens. A significant PREE was obtained, but only for PO training and UCS-omitted extinction. Exp II, employing 50 undergraduates in a masked eye blink conditioning task, produced parallel results. A general discrimination view of the classical PREE seems applicable, but one in which neither cognitive factors nor intertrial conditioning of reinforcement aftereffects plays a significant role. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reinforcement delay: A selective review of the last decade.

Presents a review of data and theories on delay of primary reinforcement in discrete trial instrumental learning. The major areas of investigation that are reviewed include delay of negative reinforcement; measurements of delay effects; cue utilization in acquisition and extinction; resistance to extinction as a function of constant delay, partial delay, and patterns of partial delay; contrast; and discrimination learning. (3 p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Heart rate, blood pressure, and running speed responses to mesencephalic locomotor region stimulation in anesthetized rats

Responses of aging brain to physical training was evaluated by quantifying the substrates, glucose, lactic acid, and nucleic acids in cerebral cortex (CC) and medulla oblongata (MO) of the brain in rats. Rats of 1 month (young), 6 months (adult), 12 months (middle-aged) and 18 months (old) of age were swim-trained for 30 days. Glucose content of CC and MO increased with training whereas blood glucose decreased in trained young and adult animals with middle-aged and old animals maintaining constant blood glucose. Brain lactate in these two regions decreased with training in all age groups. However, the old animals showed an elevation in blood lactic acid in trained state, while the other age groups showed a decrease. Nucleic acid content, decreased with age, especially the RNA content in MO showing a larger depletion. However, there was no discernible influence of physical exercise on these parameters. Physical training has influenced the aging brain's adaptability, as seen by increase in its glucose content in young animals and also possible utilization of lactate as an additional substrate in old animals as evidenced by an increase in blood lactic acid.     

Effects of ageing on visual discrimination learning in Drosophila melanogaster

Two experiments examined conditioned suppression of the Proboscis Extension Response (PER), unconditionally released by sucrose stimulation of gustatory tarsal receptors, in young (7-day-old), middle-aged (30-day-old) and old (50-day-old) Drosophila melanogaster males, reared at 25 degrees C. Individual flies were trained in a differential conditioning procedure in which a white stimulus signalled a quinine reinforcer, whereas a black stimulus was non-reinforced. When trained from the outset with the discriminative procedure, flies of all ages acquired the discrimination, although the acquisition of PER suppression to the white stimulus was retarded in middle-aged and old flies. The retardation of the acquisition of PER suppression in middle-aged and old flies was replicated in a second study in which the files received simple conditioning to the white stimulus prior to discrimination training.