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An autoshaping procedure was used to test the notion that conditioned stimuli (CSs) gain greater incentive salience during adolescence than young adulthood under conditions of social isolation rearing and food restriction. Rats were single-housed and placed on food restriction during 10 daily training sessions in which a lever (CS+) was presented then followed immediately by a food unconditioned stimulus (US). A second lever (CS−) was presented on intermixed trials and was not reinforced. Despite the fact that food delivery was not contingent on the rats' behavior, all rats exhibited behaviors directed towards the lever (i.e., sign-tracking). In the adolescent group, the rate of lever pressing and the percentage of trials with a lever press were higher than in young adults. Initially, group differences were observed when rats were retrained when the adolescents had reached young adulthood. These findings support the hypothesis that cues that come to predict reward become imbued with excessive motivational value in adolescents, perhaps contributing to the hyper-responsiveness to reward-related stimuli typically observed during this period of development. [ABSTRACT FROM AUTHOR]

Cues associated with rewarding events acquire value themselves as a result of the incentive value of the reward being transferred to the cue. Consequently, presentation of a reward-paired cue can trigger reward-seeking behaviours towards the cue itself (i.e. sign-tracking). The ventral pallidum (VP) has been demonstrated to be involved in a number of motivated behaviours, both conditioned and unconditioned. However, its contribution to the acquisition of incentive value is unknown. Using a discriminative autoshaping procedure with levers, the effects of disrupting VP activity in rats on the emergence of sign-tracking was investigated using chemogenetics, i.e. Designer Receptors Exclusively Activated by Designer Drugs (DREADDs). Transient disruption of VP neurons [activation of the inhibitory hM4D(Gi) DREADD through systemic injections of clozapine N-oxide (CNO) prior to each autoshaping session] impaired acquisition of sign-tracking (lever press rate) without having any effect on approach to the site of reward delivery (i.e. goal-tracking) or on the expression of sign-tracking after it was acquired. In addition, electrophysiological recordings were conducted in freely behaving rats following VP DREADD activation. The majority of VP units that were responsive to CNO injections exhibited rapid inhibition relative to baseline, a subset of CNO-responsive units showed delayed excitation, and a smaller subset displayed a mixed response of inhibition and excitation following CNO injections. It is argued that disruption of VP during autoshaping specifically disrupted the transfer of incentive value that was attributed to the lever cue, suggesting a surprisingly fundamental role for the VP in acquiring, compared with expressing, Pavlovian incentive values. [ABSTRACT FROM AUTHOR]

ABSTRACT Although both genetic and non-genetic factors are known to contribute to the occurrence of Attention-Deficit Hyperactivity/Disorder (ADHD), little is known about how they impact specific symptoms. We used a cross-fostering approach with an established animal model of ADHD, the Spontaneously Hypertensive Rat strain (SHR), to test the influence of genotype and maternal behavior on ADHD-related behaviors. SHRs and their normo-active genetic relative, Wistar Kyoto rats (WKY), were cross-fostered to an unfamiliar dam of either the same or different strain. Behavioral testing took place when the rats reached adulthood. Locomotor hyperactivity was completely dependent on the strain of the offspring. In contrast, social behavior was primarily determined by the strain of the mother, while attentional orienting behavior was influenced by both the strain of the offspring and the strain of the dam. Anxiety-related behavior was influenced by an interaction between offspring and dam strain. © 2015 Wiley Periodicals, Inc. Dev Psychobiol 57: 226-236, 2015. [ABSTRACT FROM AUTHOR]

ABSTRACT The retrosplenial cortex (RSC) has an important role in contextual learning and memory. While the majority of experiments have focused on the physical context, the present study asked whether the RSC is involved in processing the temporal context. Rats were trained in a temporal discrimination procedure where the duration of the intertrial interval (ITI) signaled whether or not the next tone conditioned stimulus would be paired with food pellet reinforcement. When the tone was presented after a 16-min ITI it was reinforced, but when it was presented after a 4-min ITI it was not. Rats demonstrated successful discrimination in this procedure by responding more to the tone on reinforced trials than on non-reinforced trials. Pre-training electrolytic lesions of the RSC attenuated acquisition of the temporal discrimination. The results are the first to demonstrate a role for the RSC in processing temporal information and in turn extend the role of the RSC beyond the physical context to now include the temporal context. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The hippocampus plays a central role in spatial and contextual learning and memory, however relatively little is known about the specific contributions of parahippocampal structures that interface with the hippocampus. The postsubiculum (PoSub) is reciprocally connected with a number of hippocampal, parahippocampal and subcortical structures that are involved in spatial learning and memory. In addition, behavioral data suggest that PoSub is needed for optimal performance during tests of spatial memory. Together, these data suggest that PoSub plays a prominent role in spatial navigation. Currently it is unknown whether the PoSub is needed for other forms of learning and memory that also require the formation of associations among multiple environmental stimuli. To address this gap in the literature we investigated the role of PoSub in Pavlovian fear conditioning. In Experiment 1 male rats received either lesions of PoSub or Sham surgery prior to training in a classical fear conditioning procedure. On the training day a tone was paired with foot shock three times. Conditioned fear to the training context was evaluated 24 hr later by placing rats back into theconditioning chamber without presenting any tones or shocks. Auditory fear was assessed on the third day by presenting the auditory stimulus in a novel environment (no shock). PoSub-lesioned rats exhibited impaired acquisition of the conditioned fear response as well as impaired expression of contextual and auditory fear conditioning. In Experiment 2, PoSub lesions were made 1 day after training to specifically assess the role of PoSub in fear memory. No deficits in the expression of contextual fear were observed, but freezing to the tone was significantly reduced in PoSub-lesioned rats compared to shams. Together, these results indicate that PoSub is necessary for normal acquisition of conditioned fear, and that PoSub contributes to the expression of auditory but not contextual fear memory. © 2011 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The present study examined the effects of exercising (voluntary wheel running) during adolescence on attentional function in male and female spontaneously hypertensive rats (SHRs), a commonly used animal model of attention-deficit/hyperactivity disorder (ADHD). Once rats reached adulthood, they received one session in which a light was presented 12 times but not reinforced, followed by training sessions in which the light was paired with a food reward. Male and female SHRs that had access to running wheels exhibited levels of unconditioned orienting behavior that were similar to Wistar-Kyoto rats (normo-active control) while SHRs that did not have access to running wheels exhibited higher levels of unconditioned orienting behavior. When the light was later paired with food there were no differences between the groups of male rats, but exercising female SHRs exhibited a decrease in conditioned food cup behavior. Consistent with their established phenotype, SHR rats exhibited more locomotor activity during an open field exploration session than WKY rats, but there was no relationship between orienting behavior and locomotor activity. Together these data suggest that physical exercise during adolescence can benefit attentional capabilities. © 2011 Wiley Periodicals, Inc. Dev Psychobiol 53:383-390, 2011. [ABSTRACT FROM AUTHOR]

Changes in how well a conditioned stimulus (CS) predicts future events can alter the amount of attention paid to that cue. For example, the unexpected violation of a previously established relationship between a CS and another stimulus can increase attentional processing and subsequent conditioning to that cue [ J.M. Pearce & G. Hall (1980) Psych. Rev., 106, 532–552]. Previous lesion studies have implicated the central nucleus of the amygdala (CN) and basal forebrain corticopetal cholinergic system in mediating surprise-induced changes in attention. Here, expression of the immediate-early gene c-fos was used to determine which cortical targets of the basal forebrain cholinergic system are activated during an increase in attentional processing. Consistent with previous studies, increased Fos expression was observed in the posterior parietal cortex (PPC) when a visual stimulus no longer reliably predicted occurrence of a tone. Similar results were observed in the secondary auditory cortex; however, there were no significant changes in Fos expression in other auditory or visual cortices or in other cortical association areas that have been implicated in attentional function (frontal, cingulate or retrosplenial cortex). These findings support the notion that the PPC is the primary cortical component of a neural system mediating incremental changes in attention. In addition, an increase in Fos-positive cells was detected in the substantia innominata/nucleus basalis and the CN at the time of surprise. An opposite pattern of results was observed in the basal lateral nucleus of the amygdala, providing evidence for different stimulus-processing mechanisms in regions of the amygdala. [ABSTRACT FROM AUTHOR]