Development and choice behavior in probabilistic and problem-solving tasks.
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Adolescent↗
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The effects of pyridostigmine bromide on progressive ratio performance in male and female rats.
Small doses of pyridostigmine bromide (PB) affect the acquisition and maintenance of food-maintained behavior in laboratory animals. The present experiment was designed to investigate the effects of this drug on food motivation. Male and female rats were trained to respond on a progressive-ratio schedule of reinforcement and treated with different doses of PB. PB dose-dependently decreased breaking points and response rates in male and female rats. Gender differences were not observed. The results indicate that decreased food motivation may be a factor that contributes to the behavioral effects of PB administration.
Animals↗
Dopamine depletion in nucleus accumbens influences locomotion but not force and timing of operant responding.
This experiment examined the role of dopamine (DA) in the nucleus accumbens in regulating beam pressing and locomotor responses. Six rats were rewarded with sucrose on a partial reinforcement schedule for pressing force-sensitive beams. Open-field locomotor activity, and the force and timing characteristics of operant motor responses were recorded. It is known that low doses of apomorphine decrease DA tone through activating DA autoreceptors, resulting in suppression of both operant responses and locomotion. Our results showed that DA depletion in the nucleus accumbens, induced by bilateral injection of 6-hydroxydopamine, did not affect the force and timing of operant responses: neither did it reverse the suppressive effects of low doses of apomorphine on the force and timing of operant responses. However, accumbens DA depletion did block the suppressive effect of apomorphine on open-field locomotion. These results were interpreted as support for the hypothesis that the suppressive effects of low doses of apomorphine on locomotion, but not on operant beam pressing, are mediated mainly by DA autoreceptors in the mesolimbic pathway.
Amphetamine↗
A comparison of the effects of risperidone, raclopride, and ritanserin on intravenous self-administration of d-amphetamine.
These experiments were conducted to examine the effects of simultaneous blockade of dopamine D2 and 5-hydroxytryptamine2 (5-HT) receptor function on responding for intravenous infusions of d-amphetamine. Rats were trained to self-administer d-amphetamine intravenously according to a progressive ratio schedule of reinforcement, in which response requirements increased for successive infusions until responding extinguished. In the first experiment it was shown that increases in the unit infusion dose of d-amphetamine resulted in an increase in the number of amphetamine infusions earned. Thus, the strength of responding for d-amphetamine was linked to the dose of drug received. The mixed D2 and 5-HT2 receptor antagonist risperidone (0.1, 0.2, and 0.4 mg/kg) reduced responding for d-amphetamine (60 microg/kg infusion). The selective D2 antagonist raclopride (0.1, 0.2, and 0.4 mg/kg) also reduced responding for d-amphetamine. In contrast, the selective 5-HT2 antagonist ritanserin (0.63, 1.25, and 2.5 mg/kg) failed to alter amphetamine self-administration. Combined injections of raclopride (0.05 or 0.1 mg/kg) and ritanserin (2.5 mg/kg) were no more effective than injections of raclopride alone in reducing responding for d-amphetamine. Overall, these results suggest that 5-HT2 receptor blockade plays a negligible role in the rewarding effects of d-amphetamine measured by intravenous self-administration, and does not contribute to the suppressant effects of risperidone on this behavior.
Animals↗
Reinforcing effects of caffeine, ephedrine, and their binary combination in rats.
The reinforcing effects of caffeine, ephedrine, and caffeine + ephedrine combinations were tested in rats maintained to self-administer 0.5 mg/kg/injection of cocaine in daily 4 h limited access periods. The dose-response relationship for cocaine demonstrated a a typical inverted U-shaped function. The dose-dependent administration of cocaine was stable over the 3-day substitution epochs. Similar to earlier reports, neither caffeine nor ephedrine engendered stable patterns of self-injections. Combinations of caffeine + ephedrine produced biphasic patterns of administration only on the first day of substitution. Days 2 and 3 of the caffeine-ephedrine substitution periods engendered variable and inconsistent reinforcer deliveries that did not significantly differ from saline substitution tests. These reduced patterns of self-administered caffeine-ephedrine combinations were not attributed to behavioral toxicity. Progressive-ratio tests demonstrated rank ordered break points of: food > cocaine > caffeine ephedrine combination = caffeine = ephedrine = saline. Caffeine-ephedrine pretreatments failed to show any significant change in the administration of the maintenance dose of cocaine except at the highest combination dose tested. Although previous data from this laboratory demonstrated symmetrical crossgeneralization between the discriminative effects of caffeine-ephedrine combinations and cocaine, the present data suggest limited reinforcing effects of these combinations in rats.
Animals↗
The D3 antagonist PNU-99194A potentiates the discriminative cue produced by the D3 agonist 7-OH-DPAT.
Based on correlations between potencies of various dopamine D2/D3 agonists to substitute for the 7-OH-DPAT discriminative cue and their in vitro (mitogenesis test) potencies, it has been suggested that the 7-OH-DPAT cue is mediated by activity at the D3 subtype. We sought to verify that the 7-OH-DPAT cue could be blocked by PNU-99194A, a commercially available preferential D3 antagonist. Rats were trained (FR10 two-lever, food-reinforced schedule) to press one lever following 7-OH-DPAT (0.1 mg/kg i.p.) and the other lever following saline. Rats were then tested with various doses of 7-OH-DPAT alone or in combination with PNU-99194A. 7-OH-DPAT (0.003 to 0.3 mg/kg) engendered dose-dependent substitution; PNU-99194A (1 to 10 mg/kg) failed to antagonize the cue induced by 0.1 mg/kg of 7-OH-DPAT and, at 10 mg/kg, given in combination with 0.003 to 0.1 mg/kg of 7-OH-DPAT, PNU-99194A markedly shifted the 7-OH-DPAT dose-effect curve to the left, i.e., potentiated the 7-OH-DPAT cue. If PNU-99194A is a preferential D3 antagonist, the present data do not confirm the previous hypothesis that the 7-OH-DPAT cue is mediated by the D3 subtype.
Animals↗
Reinforcement omission, non-contingent reinforcement, and limbic lesions in rats.
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Animals↗
Food-motivated performance in rats with ventromedial hypothalamic lesions: effects of body weight, deprivation, and preoperative training.
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Animals↗
Hippocampal electrical activity and behavior elicited by nonreward.
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Animals↗
Proactive behavioral effects of theta-blocking septal stimulation in the rat.
The induction of hippocampal theta rhythm using low-frequency septal stimulation has been shown to proactively (1) facilitate the acquisition and (2) increase resistance to extinction of a food-rewarded fixed-ratio (FR) bar-press response (Holt & Gray, Quarterly Journal of Experimental Psychology, 35B, 97-118, 1983). Both (1) and (2) are also seen after septal lesions. This suggests that Holt and Gray's (1983) results may have been due either to stimulation-produced theta waves (the "theta" hypothesis), or a small septal lesion produced by the stimulating current (the "lesion" hypothesis). Both hypotheses were tested in the present experiment using high-frequency septal stimulation. In one of two treatment conditions male Sprague-Dawley rats, chronically implanted with a bilateral septal stimulating electrode and a unilateral bipolar hippocampal recording electrode, received (1) trains of continuous pulses at 77 Hz which blocked the hippocampal theta rhythm, or (2) trains of pulses at 100 Hz interrupted by a 30-msec interval at a frequency of 7.7 Hz. Control animals were implanted but not stimulated. Acquisition of a discrete-trial bar-press response on a fixed ratio 5 reinforcement schedule immediately followed the treatment phase. After 15 days' acquisition all animals were extinguished over the subsequent 12 days. Results indicated that both types of septal stimulation reduced resistance to extinction of barpressing; theta-blocking stimulation produced the greater effect. Theta-blocking stimulation retarded the acquisition of bar-pressing in the early stages of training. These overall results are exactly opposite to those produced by low-frequency (7.7 Hz) theta-driving septal stimulation (Holt & Gray, 1983) and contrary to the predictions of the lesion hypothesis. Furthermore, these findings support the idea that long-term changes in behavior may depend on stimulation-produced changes in the hippocampal theta rhythm.
Animals↗
The effect of training procedures on fixed-interval responding following septal lesions in rats.
Two experiments were conducted to assess the effects of training procedures on fixed-interval (FI) performance of rats with septal lesions. In Experiment 1, rats with septal lesions that had extensive preoperative FI experience responded at higher rates than did control rats in early periods of the FI and at lower rates during the later period of the FI for the first 10 sessions after surgery. Their subsequent FI behavior became equivalent to that of control rats. In Experiment 2, septal rats that were trained on an FI schedule of reinforcement entirely after surgery by gradually increasing the FI requirements had FI performance equivalent to that of rats with control operations. The results suggest that septal lesions result in a transient disruption in the FI performance of rats with previous FI experience without affecting the acquisition of appropriate FI behavior.
Animals↗
Real time measurement of stimulated dopamine release in the conscious rat using fast cyclic voltammetry: dopamine release is not observed during intracranial self stimulation.
Fast cyclic voltammetry (FCV) was used to measure real time release of electrically stimulated endogenous dopamine in the nucleus accumbens (NAc) of conscious freely moving rats for up to 17 days. The method of electrode construction, implantation, electrical stimulation and recording of changes of extracellular dopamine concentration in the conscious rat are described. Rats trained on a continuous reinforcement schedule to perform intracranial self stimulation (ICSS) were implanted with electrodes for FCV. During ICSS, no faradaic signal was observed at an electrode implanted in the NAc. Decreasing the intensity of the stimulating current abolished ICSS, increasing the stimulating current disrupted ICSS. Operator delivered electrical stimulations using currents greater than those needed for ICSS yielded dopamine signals. It is concluded that during ICSS, sufficient dopamine does not reach the extracellular fluid space to yield a faradaic signal detectable by FCV.
Animals↗
Effects of chronic cocaine on impulsivity: relation to cortical serotonin mechanisms.
Drug addiction can be considered an impulse control disorder in that addicts exhibit increased impulsivity on both behavioural and self-report measures. We investigated whether chronic cocaine affects delay of gratification and/or behavioural disinhibition in rats using the delayed reinforcement and Go/No-go paradigms. Animals were treated with saline or cocaine (15 mg/kg) three times per day for 14 days; all behavioural tests occurred prior to daily injections. To assess the effectiveness of the cocaine treatment, sucrose intake, behavioural sensitization and serotonin (5-HT)-dependent (dorsal raphe-stimulated) cortical activation were also measured. Chronic cocaine caused a transient (days 7-8) increase in impulsivity in the delayed reinforcement paradigm, but did not influence behaviour in the Go/No-go paradigm. As expected, chronic cocaine increased behavioural sensitization scores, although it did not affect sucrose consumption. Although, cocaine treatment did not affect dorsal raphe-stimulated electrocorticographic activation, the serotonergic receptor antagonist methiothepin (0.1 mg/kg) was more effective in blocking cortical activation in cocaine- than in saline-treated animals. The electrocorticographic changes may be the result of a pre-synaptic 5-HT deficit and the compensatory supersensitivity of post-synaptic 5-HT receptors. Given the differential time courses of the behavioural and electrocorticographic data, however, this change probably does not mediate the effects of chronic cocaine in the delayed reinforcement paradigm.
Analysis of Variance↗
Classical conditioning after temporal lobe lesions in man: sparing of simple discrimination and extinction.
Recent reports of impaired conditional discrimination learning in temporal lobectomy subjects have raised the question of response inhibition deficits in these patients. In the present study, left and right temporal lobectomy subjects and healthy controls completed an eyelid conditioning task, which required simple two-tone discrimination learning, followed by extinction. There were no group differences with regard to discrimination learning or extinction. General deficits in response inhibition are therefore not likely to account for the impairment in conditional discrimination observed in temporal lobectomy patients.
Acoustic Stimulation↗
Lesions of the basolateral amygdala abolish the ability of drug associated cues to reinstate responding during withdrawal from self-administered cocaine.
This study investigated the ability of bilateral excitotoxic lesions of the basolateral amygdala (BLA) to disrupt cocaine self-administration, responding during extinction sessions, and stimulus cued recovery of extinguished responding in rats. BLA and sham lesions following 7 days of 3 h limited access cocaine self-administration sessions (0.33 mg/infusion) on a fixed ratio 1 (FR1) schedule of reinforcement failed to alter cocaine intake and responding on 7 subsequent days of self-administration. This lack of effect suggests that the BLA is not paramount for the maintenance of cocaine's reinforcing effects. In contrast, BLA lesions, but not sham lesions, following 7 to 14 days of cocaine self-administration attenuated responding on a lever associated with cocaine infusions on the first day of extinction sessions and blocked the ability of drug associated stimuli to reinstate extinguished responding following 20 daily extinction sessions. However, lesions of the BLA did not attenuate stimulus cued recovery of responding following 43 days of withdrawal. These results are consistent with the hypothesis that the BLA is important for the conditioned incentive properties of reinforcers, but not primary reinforcement itself.
Amygdala↗
Chronic L-deprenyl treatment alters brain monoamine levels and reduces impulsiveness in an animal model of Attention-Deficit/Hyperactivity Disorder.
Effects of chronic L-deprenyl administration on hyperactive behaviour and brain monoamine levels were studied in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. SHR were hyperactive, impulsive and had impaired sustained attention when tested with a multiple 2-min fixed interval (FI) 5-min extinction (EXT) schedule of reinforcement. Even low, 0.25 mg/kg, doses of chronically-administered L-deprenyl reduced the impulsiveness (bursts of responses with short interresponse times) of SHR, without altering the general hyperactivity or the impaired sustained attention. The drug had no effect on WKY behaviour. The levels of noradrenaline (NA), dopamine (DA), serotonin (5-hydroxytryptamine, 5-HT) and their metabolites, measured in neostriatum, nucleus accumbens and frontal cortex, showed that L-deprenyl effectively inhibited monoamine oxidase (MAO) activity. These results suggest that impulsiveness is a behavioural component that may be operating independent of the other components, like hyperactivity and deficient sustained attention, and that can be reduced by chronic MAO-B inhibition with L-deprenyl in this strain of rats. The positive effect of L-deprenyl on impulsiveness is discussed as due either to normalization of an asymmetric dopaminergic activity in the nucleus accumbens, or to a restoration of normal DA function in the prefrontal cortex.
Animals↗
A multielement analysis of contingent versus contingent-interrupted music.
A multielement design was employed to evaluate the comparative effects of contingent music and contingent-interrupted music procedures. Two profoundly mentally retarded children who attended a community day training center participated. During the contingent music procedure, access to brief periods of listening to music was contingent upon the display of a specified criterion of appropriate behavior. Alternately, during the contingent-interrupted music procedure, access to music was provided at the beginning of the session, and it remained on until an inappropriate behavior occurred. The two procedures were implemented to decrease crying and increase unsupported sitting. The multielement design required that each procedure and a baseline condition be alternated across sessions. Results demonstrated that the contingent-interrupted music procedure was more effective for both reducing crying and increasing proper sitting. Implications for research with music as a reinforcer were discussed.
Behavior Therapy↗
Risk-sensitive foraging in rats: the effects of response-effort and reward-amount manipulations on choice behavior.
The literature on risk-sensitive foraging theory provides several accounts of species that fluctuate between risk-averse and risk-prone strategies. The daily energy budget rule suggests that shifts in foraging strategy are precipitated by changes in the forager's energy budget. Researchers have attempted to alter the organism's energy budget using a variety of techniques such as food deprivation, manipulation of ambient temperatures, and delays to food reward; however, response-effort manipulations have been relatively neglected. A choice preparation using a wheel-running response and rats examined risk-sensitive preferences when both response effort and reward amounts were manipulated. Concurrently available reinforcement schedules (FI/60 and VI/60) yielded equivalent food amounts per unit time in all treatments. Two levels of response effort (20 or 120 g tangential resistance) and two levels of reward amount (three or nine pellets) were combined to form four distinct response-effort/reward-amount pairings. Increasing reward amounts significantly shifted choice toward the FI schedule in both response-effort conditions. The incidence of choice preference and the magnitude of shifts in choice were greater for the high response-effort conditions than for the low response-effort conditions. Implications of the significant interaction between response effort and reward amount are discussed in terms of a general energy-budget model.
Journal Article↗