Christine Norman

Amphetamine increases aversive conditioning to diffuse contextual stimuli and to a discrete trace stimulus when conditioned at higher footshock intensity.

Amphetamine can increase conditioning to poor predictors of reinforcement in selective learning tasks (e.g. latent inhibition, LI). In the present study, a noise stimulus was contiguous with footshock or presented at a trace interval. A flashing light background stimulus was used to measure contextual conditioning. Experiment 1 used 1.5 mg/kg and 6 mg/kg dl-amphetamine. Experiments 2 and 3 used 0.5 mg/kg and 1.5 mg/kg d-amphetamine. Unconditioned stimuli parameters (intensity, number, duration) were also manipulated from one experiment to the next. Amphetamine consistently increased conditioning to the background stimulus, and increased conditioning to the trace stimulus at higher footshock intensity (Experiment 3). Thus, amphetamine increased conditioning only to relatively uninformative predictors. The effect on conditioning to trace conditioned stimuli depended on the level of reinforcer but increased conditioning to background did not. Throughout, there was no effect of amphetamine on conditioning of the contiguous stimulus. Thus, the results did not simply arise because amphetamine increased conditioning under any condition in which conditioning without amphetamine was poor. The results are discussed in terms of amphetamine effects on breadth of attention and LI to context.

Electrolytic lesions to nucleus accumbens core and shell have dissociable effects on conditioning to discrete and contextual cues in aversive and appetitive procedures respectively.

The nucleus accumbens (n. acc.) has been implicated in conditioning to both discrete and contextual cues but its precise role is as yet controversial because conflicting patterns of effect have been reported. These inconsistencies may relate to the extent to which the lesions used encroach on different subfields of n. acc. and the use of different task variants. The present study compared the effects of selective lesions of shell and core subfields of nucleus accumbens (n. acc.) across aversive and appetitive trace conditioning variants. In both experiments, an auditory stimulus was contiguous with footshock or food, or presented at a trace interval. A continuous flashing light in each case provided an experimental background stimulus. Conditioning to the cues provided by the experimental chambers was also assessed. Rats with electrolytic lesions to the n. acc. shell and core showed different patterns of effect in aversive (Experiment 1) and appetitive (Experiment 2) variants of this procedure. In Experiment 1, the core lesion reduced the difference between trace and contiguously conditioned groups, in responding to the discrete noise stimulus. However, neither lesion had any detectable effect on contextual conditioning. In Experiment 2, the shell lesion clearly increased contextual conditioning, selectively in the trace conditioned group, but neither lesion had any detectable effect on discrete cue conditioning. Thus, whilst the shell and core lesions produced dissociable effects on discrete cue and contextual conditioning, the conclusions to be drawn depend on the procedural variant in use.

Effects of chronic infusion of neurotensin and a neurotensin NT1 selective analogue PD149163 on amphetamine-induced hyperlocomotion

Neurotensin (NT) has been proposed as an endogenous antipsychotic based in part on the similarity in behavioural effects to antipsychotic drugs, for example, attenuation of both amphetamine-induced hyperlocomotion (AH) and amphetamine disrupted pre-pulse inhibition in the rat. However, there is some evidence that repeated administration of NT or an analogue produces behavioural tolerance to such effects. The present experiments sought to confirm and extend these findings by testing the effects on AH of 7 days central administration of NT and the NT 1 selective analogue PD 149163 and the effects of 21 days central administration of NT. NT and PD149163 continuously administered for 7 days produced no effect on AH (in contrast to attenuation with a single injection here and previously reported), whereas 21 days of NT administration potentiated AH. Together, these studies report that the effects of NT or a NT analogue on AH depends on the duration of administration of peptide. The results are discussed in comparison with the reported antipsychotic properties of acute administration of NT and possible mechanisms involving NT1 receptors.

Selectively increased trace conditioning under the neurotensin agonist PD 149163 in an aversive procedure in which SR 142948A was without intrinsic effect

There is evidence to suggest that neurotensin (NT) may enhance cognitive function. The present study, therefore, examined the role of NT in associative learning between a conditioned stimulus (CS) and an unconditioned stimulus (UCS). This was tested in a trace procedure using conditioned suppression of drinking with a noise CS and foot shock UCS. We compared the effects of an NT agonist (PD 149163, 0.25 and 1 mg/kg) with those of an NT antagonist (SR 142948A, 0.01 and 0.1 mg/kg). Conditioning after drug treatment was followed by drug-free tests of associative learning. At 0.25 but not 1 mg/kg, PD 149163 selectively increased conditioning over the trace interval: there was no such increased conditioning in the 0s group. This increased conditioning over the trace is an effect that is reliably produced by dopamine (DA) agonists in the same procedure. However, dissimilar to the effects of DA agonists, conditioning to box context, was reduced under PD 149163. Doses of SR 142948A, selected on the basis of their effects in similar aversively motivated tests of latent inhibition, were without intrinsic effect in the present procedure. The dose-related dissociation between trace and contextual conditioning effects under PD 149163 is considered as cognitive enhancement.

The Role of Impulsivity, Sensation Seeking, Coping, and Year of Study in Student Gambling: A Pilot Study

Students are among the most prevalent gamblers with the highest incidence of problem gambling. Furthermore, research into gambling has noted certain personality traits and coping mechanisms to be highly predictive of gambling in student populations. The present study examined the role of impulsivity, sensation seeking, coping strategies, and year of study in predicting gambling frequency in students. An opportunity sample of 109 university students (53 first year students and 56 final year students) were administered a survey including the Arnett Inventory of Sensation Seeking, the Barrett Impulsiveness Scale, and the Student Coping Scale. The results indicated that impulsivity and being in the first year of study were significantly predictive of gambling frequency. The findings suggest the importance of personality traits, the year of study, and specific coping mechanisms in understanding motivations to gamble. The findings particularly suggest the importance of providing gambling educational awareness among first year students.

High-frequency gamblers show increased resistance to extinction following partial reinforcement

Behaviours that have been rewarded intermittently persist for longer during periods of non-reward than behaviours that have been rewarded continuously. This classic phenomenon is known as the partial reinforcement extinction effect. For decades it has been generally understood that this phenomenon is fundamental to the persistence of gambling in the absence of winning. One obvious, yet untested hypothesis arising from this is that persistent (here, high-frequency) gamblers might be more sensitive to partial reinforcement contingencies. Therefore, our aim was to test the hypothesis that compared to low-frequency gamblers, high-frequency gamblers would show greater resistance to extinction following partial reinforcement in a computer based experiment. Participants were 19 high-frequency gamblers and 21 low-frequency gamblers, all healthy non-smokers aged between 18 and 52. Following partial or continuous reinforcement, persistence of responding in extinction was measured as the number of times a target response was made. After partial reinforcement, high-frequency gamblers made the target response a greater number of times in extinction (compared to low-frequency gamblers). Moreover, the partial reinforcement extinction effect was larger in high-frequency gamblers than in low-frequency gamblers. It remains to be seen whether increased sensitivity to partial reinforcement is a cause or effect of persistent gambling. Nevertheless, the present study represents an important first step in investigating the role of simple partial reinforcement contingencies in determining resistance to extinction in gamblers, the importance of which, whilst hitherto recognised, has never been demonstrated experimentally.

Amphetamine decreases the expression and acquisition of appetitive conditioning but increases the acquisition of anticipatory responding over a trace interval

The effects of amphetamine on selective learning were tested in a trace conditioning procedure, in which the informativeness of the conditioned stimulus (CS) (noise) was manipulated through the introduction of a time interval before the delivery of the unconditioned stimulus (UCS) (food). The results showed that d-amphetamine (0.5 and 1.5 mg/kg) impaired both the expression (Experiment 1b) and acquisition (Experiment 2) of appetitive conditioning. This was true for both trace and contiguously conditioned groups. The effects of the 0.5 mg/kg dose of d-amphetamine were not attributable to general motor (measured pre-CS) or motivational (measured post-UCS) effects of the drug. Moreover, the same pattern of effects (impaired appetitive conditioning, irrespective of the trace interval between CS and UCS) was confirmed in drug-free extinction tests. By contrast to the general depression in the acquisition and expression of associative learning observed under amphetamine, the 0.5 mg/kg dose promoted the acquisition of anticipatory responses made later in the trace interval (in Experiment 2 but, again, not the expression of previous conditioning in Experiment 1b). This suggests a dissociable effect of low-dose d-amphetamine on learning about the temporal relationship between CS and UCS.

Disruption of latent inhibition to a contextual stimulus with systemic amphetamine

This experiment examined the effects of 0.5 and 1.5 mg/kg doses of amphetamine (AMP) in male Wistar rats, on conditioning to a contextual stimulus that for half the animals has been pre-exposed, in an appetitive conditioning procedure. Amphetamine was administered during both pre-exposure (3 days) and acquisition (15 days). Latent inhibition (LI, reduced conditioning in pre-exposed relative to non-pre-exposed rats) was seen in controls but not at either AMP dose. This abolition of LI was seen under AMP at two levels of responding in acquisition and confirmed in drug free extinction. It suggests that, like conditioning to discrete stimuli, conditioning to contextual stimuli is subject to LI and can be disrupted by AMP.

Evaluation of the use of pharmacological treatment with prisoners experiencing high levels of hypersexual disorder

Abstract This paper presents an evaluation of the impact of pharmacological treatment in reducing hypersexual disorder in adult males who have been incarcerated following conviction for a sexual offence. The evaluation compares two types of pharmacological treatment, one of which is part of the current NICE guidance for treatment of hypersexuality (Antiandrogens), whilst the other type (SSRIs) is off-label use in the UK for hypersexuality. The participant pool comprised 127 adult male prisoners serving sentences for sexual offences in a UK prison. Participants had been voluntarily referred for pharmacological treatment to manage hypersexual disorder. The results demonstrated a significant reduction of hypersexual disorder pre- and post-medication and contribute to the evidence base for the use of pharmacological treatment with individuals for whom hypersexual disorder may be a salient factor in their offending. Limitations of the current research are discussed.

Lesions of the nucleus accumbens shell can reduce activity in the elevated plus-maze

Across different behavioural tasks, nucleus accumbens (n.acc) lesions have generated conflicting effects on locomotor activity and in particular, the relative roles of the n.acc shell and core subfields in this have been controversial. To date there is only one study examining effects of lesions to the medial n.acc on elevated plus-maze (EPM) behaviour; these lesions were shown to increase both locomotor and exploratory activity. Given the well-documented distinction between shell and core, the present study sought to extend previous research by testing lesions selective to each n.acc subfield in the EPM. Results showed no statistical differences between core lesioned and sham-operated animals on any measure. In contrast, shell lesions consistently reduced locomotion and exploratory activity. This direction of effects is opposite to that previously observed after medial n.acc. lesions. In conclusion, locomotion and exploratory activity were clearly reduced by shell but not core lesions, consistent with other evidence for the functional heterogeneity of n.acc shell and core.