Facilitation of memory for extinction of drug-induced conditioned reward: role of amygdala and acetylcholine

These experiments examined the effects of posttrial peripheral and intra-amygdala injections of the cholinergic muscarinic receptor agonist oxotremorine on memory consolidation underlying extinction of amphetamine conditioned place preference (CPP) behavior. Male Long-Evans rats were initially trained and tested for an amphetamine (2 mg/kg) CPP. Rats were subsequently given limited extinction training, followed by immediate posttrial peripheral or intrabasolateral amygdala injections of oxotremorine. A second CPP test was then administered, and the amount of time spent in the previously amphetamine-paired and saline-paired apparatus compartments was recorded. Peripheral (0.07 or 0.01 mg/kg) or intra-amygdala (10 etag/0.5 microL) postextinction trial injections of oxotremorine facilitated CPP extinction. Oxotremorine injections that were delayed 2 h posttrial training did not enhance CPP extinction, indicating a time-dependent effect of the drug on memory consolidation processes. The findings indicate that memory consolidation for extinction of approach behavior to environmental stimuli previously paired with drug reward can be facilitated by posttrial peripheral or intrabasolateral amygdala administration of a cholinergic agonist.     

Amygdala and "emotional" modulation of the relative use of multiple memory systems

The basolateral amygdala modulates the cognitive and habit memory processes mediated by the hippocampus and caudate nucleus, respectively. The present experiments used a plus-maze task that can be acquired using either hippocampus-dependent "place" learning or caudate-dependent "response" learning to examine whether peripheral or intra-basolateral amygdala injection of anxiogenic drugs would bias rats towards the use of a particular memory system. In Experiment 1, adult male Long-Evans rats were trained to swim from the same start point to an escape platform located in a consistent goal arm, and received pre-training peripheral injections of the alpha(2)-adrenoceptor antagonists yohimbine (2.5 or 5.0 mg/kg), RS 79948-197 (0.05, 0.1, or 0.2 mg/kg), or vehicle. On a drug-free probe trial from a novel start point administered 24h following acquisition, vehicle treated rats predominantly displayed hippocampus-dependent place learning, whereas rats previously treated with yohimbine (2.5, 5.0 mg/kg) or RS 79948-197 (0.1 mg/kg) predominantly displayed caudate-dependent response learning. In Experiment 2, rats receiving pre-training intra-basolateral amygdala infusions of RS 79948-197 (0.1 microg/0.5 microl) also predominantly displayed response learning on a drug-free probe trial. The findings indicate (1) peripheral injections of anxiogenic drugs can influence the relative use of multiple memory systems in a manner that favors caudate-dependent habit learning over hippocampus-dependent cognitive learning, and (2) intra-basolateral amygdala infusion of anxiogenic drugs is sufficient to produce this modulatory influence of emotional state on the use of multiple memory systems.     

Post-training cyclooxygenase-2 (COX-2) inhibition impairs memory consolidation

Evidence indicates that prostanoids, such as prostaglandins, play a regulatory role in several forms of neural plasticity, including long-term potentiation, a cellular model for certain forms of learning and memory. In these experiments, the significance of the COX isoforms cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) in post-training memory processes was assessed. Adult male Long-Evans rats underwent an eight-trial (30-sec intertrial interval) training session on a hippocampus-dependent (hidden platform) or dorsal striatal–dependent (visible platform) tasks in a water maze. After the completion of training, rats received an intraperitoneal injection of the nonselective COX inhibitor indomethacin, the COX-1–specific inhibitor piroxicam, the COX-2–specific inhibitor N-[2-cyclohexyloxy-4-nitrophenyl]-methanesulfonamide (NS-398), vehicle (45% 2-hydroxypropyl-β-cyclodextrin in distilled water), or saline. On a two-trial retention test session 24 h later, latency to mount the escape platform was used as a measure of memory. In the hidden platform task, the retention test escape latencies of rats administered indomethacin (5 and 10 mg/kg) or NS-398 (2 and 5 mg/kg) were significantly higher than those of vehicle-treated rats, indicating an impairment in retention. Injections of indomethacin or NS-398 that were delayed 2 h post-training had no effect on retention. Post-training indomethacin or NS-398 had no influence on retention of the visible platform version of the water maze at any of the doses administered. Furthermore, selective inhibition of COX-1 via post-training piroxicam administration had no effect on retention of either task. These findings indicate that COX-2 is a required biochemical component mediating the consolidation of hippocampal-dependent memory.     

Striking Differences: The Impact of Moderate and High Trauma on Reading Achievement

This study explored the relationship between childhood traumatic exposure, such as violence and loss of a significant other, and reading achievement. With a sample of 163 urban elementary children (grades 2–5), the impact of traumatic events on 3 years of reading scores was examined. Results suggested that violence exposure had an adverse effect on reading scores and that there was a striking difference between students who experienced moderate exposure as compared to students with high exposure. However, both groups of students experienced a significant decrease in reading achievement. Discussion of these findings proposes an explanation for why reading achievement might be adversely affected by traumatic exposure and gives suggestions for teachers to utilize with those students identified as having been exposed to traumatic events.     

The Pursuit of College in Adulthood: Reclaiming Past Selves or Constructing New?

This study examines the identity processes that are implicated when adults return to college, including the possibility that they may be reclaiming past selves from adolescence or constructing new selves at this particular juncture. In this study, 70 nontraditional-aged community college students were surveyed about their educational pathways, with a focus on their career and educational plans and actions when finishing high school through the current time. In addition, a diverse subset (n = 14) was interviewed. Results suggested four identity processes, two that involved past career selves from adolescence when constructing future pursuits (reclaim past, reject past before constructing new) and two that did not (construct new, expand current). Participants with prior college experience as adolescents were more likely to report well-developed past selves, but they more frequently rejected rather than reclaimed due to lack of perceived feasibility. Future research involving adult identity development is discussed.     

Stereopsis from reversible and irreversible patterns

Eight subjects reported stereoscopic depth as a function of the magnitude and direction of disparity carried by a reversible grid or an irreversible solid surface. The former alternated between a diamond seen against a grating or a uniform rectangular grid pattern with stereoscopic depth reported only when the diamond was perceived. Depth was attenuated for the grid compared to the solid surface patterns. Disparity can be defined by perceptually extracted forms with depth present only when those forms are bounded by visible contours.