Chronically increased Gsalpha signaling disrupts associative and spatial learning

The cAMP/PKA pathway plays a critical role in learning and memory systems in animals ranging from mice to Drosophila to Aplysia. Studies of olfactory learning in Drosophila suggest that altered expression of either positive or negative regulators of the cAMP/PKA signaling pathway beyond a certain optimum range may be deleterious. Here we provide genetic evidence of the behavioral and physiological effects of increased signaling through the cAMP/PKA pathway in mice. We have generated transgenic mice in which the expression of a constitutively active form of Gsalpha (Gsalpha* Q227L), the G protein that stimulates adenylyl cyclase activity, is driven in neurons within the forebrain by the promoter from the CaMKIIalpha gene. Despite significantly increased adenylyl cyclase activity, Gsalpha* transgenic mice exhibit PKA-dependent decreases in levels of cAMP due to a compensatory up-regulation in phosphodiesterase activity. Interestingly, Gsalpha* transgenic mice also exhibit enhanced basal synaptic transmission. Consistent with a role for the cAMP/PKA pathway in learning and memory, Gsalpha* transgenic mice show impairments in spatial learning in the Morris water maze and in contextual and cued fear conditioning tasks. The learning deficits observed in these transgenic mice suggest that associative and spatial learning requires regulated Gsalpha protein signaling, much as does olfactory learning in Drosophila.     

The effects of age and task context on Stroop task performance

In this study, we investigated the impact of age and task context on Stroop task performance, using error scores, response latencies, and process dissociation estimates (e.g., Lindsay & Jacoby, 1994). Across three experiments, the findings showed that although older adults were able to evaluate Stroop task demands and modify their representations of task context in response to this knowledge, they were less able to maintain and update these representations on a trial-by-trial basis in tasks with high stimulus uncertainty or ambiguity. Moreover, although there was no age-related decline in the ability to modulate print color information, older adults were consistently less able to control the activation of conflicting word information. Together, these findings suggest that whereas age differences in the Stroop task may be magnified under conditions that promote transient failures to maintain task context, the primary source of these differences seems to be a more enduring decline in the efficiency of processes that are responsible for suppressing the activation of irrelevant lexical information.     

Dynamic averaging and foraging decisions in horses (Equus callabus)

The variability of most environments taxes foraging decisions by increasing the uncertainty of the information available. One solution to the problem is to use dynamic averaging, as do some granivores and carnivores. Arguably, the same strategy could be useful for grazing herbivores, even though their food renews and is more homogeneously distributed. Horses (Equus callabus) were given choices between variable patches after short or long delays. When patch information was current, horses returned to the patch that was recently best, whereas those without current information matched choices to the long-term average values of the patches. These results demonstrate that a grazing species uses dynamic averaging and indicate that, like granivores and carnivores, they can use temporal weighting to optimize foraging decisions.     

Effects of repetition and response deadline on associative recognition in young and older adults

The present study examined the joint effects of repetition and response deadline on associative recognition in older adults. Young and older adults studied lists of unrelated word pairs, half presented once (weak pairs) and half presented four times (strong pairs). Test lists contained old (intact) pairs, pairs consisting of old words that had been studied with other partners (rearranged lures), and unstudied pairs (new lures), and participants were asked to respond "old" only to intact pairs. In Experiment 1, participants were tested with both short and long deadlines. In Experiment 2, the tests were unpaced. In both experiments, repetition increased hit rates for young and older adults. Young adults tested with a long deadline showed reduced (Experiment 1) or invariant (Experiment 2) false alarms to rearranged lures when word pairs were studied more often. Young adults tested with a short deadline and older adults tested under all conditions had increased false alarm rates forstrong rearranged pairs. Implications of these results for theories of associative recognition and cognitive aging are explored.     

Hypnosis and clinical pain

Hypnosis has been demonstrated to reduce analogue pain, and studies on the mechanisms of laboratory pain reduction have provided useful applications to clinical populations. Studies showing central nervous system activity during hypnotic procedures offer preliminary information concerning possible physiological mechanisms of hypnotic analgesia. Randomized controlled studies with clinical populations indicate that hypnosis has a reliable and significant impact on acute procedural pain and chronic pain conditions. Methodological issues of this body of research are discussed, as are methods to better integrate hypnosis into comprehensive pain treatment.     

Cross Talk Between Native and Second Languages: Partial Activation of an Irrelevant Lexicon

Bilingualism provides a unique opportunity for exploring hypotheses about how the human brain encodes language. For example, the "input switch" theory states that bilinguals can deactivate one language module while using the other. A new measure of spoken language comprehension, headband-mounted eyetracking, allows a firm test of this theory. When given spoken instructions to pick up an object, in a monolingual session, late bilinguals looked briefly at a distractor object whose name in the irrelevant language was initially phonetically similar to the spoken word more often than they looked at a control distractor object. This result indicates some overlap between the two languages in bilinguals, and provides support for parallel, interactive accounts of spoken word recognition in general.     

Neuronal unit activity in the abducens nucleus during classical conditioning of the nictitating membrane response in the rabbit (Oryctolagus cuniculus).

Neuronal unit activity was recorded from the abducens (6th nerve) nucleus, the "final common path," during classical conditioning of the nictitating membrane (NM) response in the rabbit, with the use of a tone conditioned stimulus, an air puff unconditioned stimulus (UCS), 250-msec interstimulus interval, and 60-sec intertrial interval. Animals were given 2 days of conditioning training (104 trials in eight blocks per day) and 1 day of extinction. Control animals were given comparable periods of stimulus presentations, explicitly unpaired. Activity of small clusters of units--"multiple unit" recording--was compared with the amplitude-time course of the NM response. Between-blocks comparisons of neural and behavioral responses indicated an essentially perfect correlation during acquisition of the conditioned response (Day 1, r = .99; Day 2, r = .98) and a slightly lower correlation during extinction (r = .93) for the conditioning animals. Within-blocks comparisons indicated a close correspondence between the histograms of unit activity and the amplitude-time course of the NM response for the conditioning animals in all phase of training and for the control animals in the UCS trial blocks.     

Children's perception of media-portrayed sex roles

The immediate impact on preschool and elementary school children of a televised presentation in which the traditional sex roles of physician and nurse were reversed was examined. After viewing a videotape of a male nurse and a female physician, subjects were asked to identify photographs or names of the physician and nurse. Preschool, first-, and fourth-grade children selected male names or pictures for the physician and female names or pictures for the nurse, thereby reversing genders. Their immediate recall appeared strongly influenced by their stereotypes rather than by the film they had just viewed. Seventh-grade children correctly identified the names of the physician and nurse.The authors wish to thank Dr. Edward F. Meydrech, Assistant Professor, Department of Preventive Medicine and Chief of the Division of Biostatistics, University of Mississippi Medical Center, for his invaluable assistance in the analysis of the data.