The role of the GABA(A) agonist muscimol on memory performance: reward contingencies determine the nature of the deficit

A matching-to-position (MTP) paradigm was altered to influence the type of associations a rat would use to solve the task. Our main behavioral manipulation was the application of the differential outcomes procedure (DOP). The DOP involves correlating each to-be-remembered event with a distinct reward condition. This procedure results in the development of unique reward expectancies that enhance and guide choice behavior. Such distinct reward expectancies are not formed when either a common or random assignment of reward is used (a non-differential outcomes procedure [NOP]). Intracerebroventricular infusions of the amnestic agent muscimol (GABA(A) agonist) or aCSF were delivered to male rats trained on a delayed MTP task that implemented either the DOP or the NOP. Muscimol impaired performance in a dose dependent fashion in both groups--but the nature of the deficit differed as a function of reinforcement contingencies. Rats trained with the DOP displayed a non-mnemonic delay-independent impairment: performance at all delay intervals was disrupted. In contrast, NOP-trained rats displayed a delay-dependent impairment demonstrating that muscimol can also have memory-disrupting effects. The difference in pattern of impairment appears to be a function of the associations formed during training and the type of cognitive strategies involved in maintaining behavior on a conditional delayed discrimination task when reinforcement contingencies are varied. Thus, these results demonstrate that increasing GABA(A) receptor activation impairs a range of associative and memory functions.     

The effects of hippocampal lesions on learning, memory, and reward expectancies

The hippocampus appears to be critical for the formation of certain types of memories. Hippocampal-lesioned animals fail to exhibit some spatial, contextual, and relational associations. After aspiration lesions of the hippocampus and/or cortex, male rats were allowed to recover for three weeks before being trained on a matching-to-position task. The matching-to-position task was altered to influence the type of cognitive strategies a subject would use to solve the task. The main behavioral manipulation was the reinforcement contingency assignment: Use of a differential outcomes procedure (DOP) or a nondifferential outcomes procedure (NOP). The DOP involves correlating each to-be-remembered event with a distinct reward condition via Pavlovian trace conditioning, whereas the NOP results in random reward contingency. We found that hippocampal lesions did retard learning the matching rule, regardless of the reinforcement contingency assignment. However, when delay intervals were added to the task memory performance of subjects with hippocampal lesions was dramatically impaired--if subjects were not trained with the DOP. When subjects were trained with the DOP, the hippocampal lesion had a marginal effect on delayed memory performance. These findings demonstrate two important points regarding lesions of the hippocampus: (1) hippocampal lesions have a minimal effect on the on the ability of rats to use reward information to solve a delayed discrimination task; (2) rats with hippocampal lesions have the ability to learn about reward information using Pavlovian trace conditioning procedures.     

Rimes are not necessarily favored by prereaders: evidence from meta- and epilinguistic phonological tasks

This article explores young children's facility in phonological awareness tasks requiring either the detection or the articulation of head, coda, onset, and rime subsyllabic units shared in word pairs. Data are reported from 70 nonreading children and 21 precocious readers attending preschools. Prereading children were able to articulate shared heads, codas, and onsets, although rimes rarely were articulated. Precocious readers were able to articulate shared rimes, but articulation performance was still most accurate for onsets and codas. Rimes and heads were equally accessible in the detection task and were identified more often than onsets and codas (nonreaders) and codas (readers). It is concluded that the articulation advantage for nonrime units cannot simply reflect early reading instruction. This disjoint pattern of phonological awareness in detection and production tasks does not support Goswami's phonological status hypothesis. Results may instead reflect quite distinct influences on epilinguistic and metalinguistic phonological development.     

An on-line investigation of lexical ambiguity processing in schizophrenia

The processing of lexical ambiguity in context was investigated in eight individuals with schizophrenia and a matched control group. Participants made speeded lexical decisions on the third word in auditory word triplets representing concordant (coin-bank-money), discordant (river-bank-money), neutral (day-bank-money), and unrelated (river-day-money) conditions. When the interstimulus interval (ISI) between the words was 100 ms, individuals with schizophrenia demonstrated priming consistent with selective, context-based lexical activation. At 1250 ms ISI, a pattern of nonselective meaning facilitation was obtained. These results suggest an attentional breakdown in the sustained inhibition of meanings on the basis of lexical context.     

In Search of the Neurobiological Underpinnings of the Differential Outcomes Effect

Correlating unique rewards with to-be-remembered events (the Differential Outcomes Procedure [DOP]) enhances learning and memory performance in a range of species. Recently, we have demonstrated that the DOP can be used to reduce or eliminate the learning and memory impairments associated with animal models of amnesia and dementia. This powerful phenomenon, the Differential Outcomes Effect (DOE), has led to the question: How does such a simple manipulation exert such dramatic influence on learning and memory performance? A revised two-process account of the DOE states that using the DOP results in the activation of reward expectancies through Pavlovian mechanisms. The use of unique reward expectancies alters the nature of cognitive processing used to solve discrimination tasks. The change in cognitive processing is represented by utilization of a different memory system than that commonly used to acquire and remember information when a Nondifferential Outcomes Procedure (NOP) is used. Using neurochemical manipulations, it has been demonstrated that different, potentially independent, brain systems modulate memory performance when subjects are trained with a NOP versus a DOP. This memory-based DOP/NOP distinction resembles other dissociative memory theories in which two psychological processes are purportedly served by distinct neurobiological mechanisms. In addition, such results have important ramifications for the treatment of memory disorders because they demonstrate that stimulus and behavioral manipulations, like drugs, can influence neurotransmitter functioning.     

Cerebellar tasks do not distinguish between children with developmental dyslexia and children with intellectual disability.

This paper explored the claim that only children with developmental dyslexia, whose reading ability is discrepant from their average general reasoning ability show specific deficits in motor tasks assessing cerebellar functioning (Fawcett et al., 2001, Cerebellar tests differentiate between groups of poor readers with and without IQ discrepancy. J. Learning Disabilities, 34, 119) and rapid serial naming (RAN, Wolf & Bowers, 1999, The double deficit hypothesis for the developmental dyslexias. J. Educ. Psychol., 91, 1). All available children between the ages of 11 and 14 were recruited from two special schools for children with either (a) formally-diagnosed intellectual disabilities (N = 18); or (b) formal diagnoses of developmental dyslexia (N = 25). These two groups of children did not differ on gender, age, pseudoword decoding abilities, or on 7 of 8 literacy measures, but did differ significantly, as expected on verbal and non-verbal reasoning tasks. Importantly, there were no deficits in bead threading ability or postural stability in the children with developmental dyslexia compared to the children with intellectual disabilities. There were also no between-group differences in rapid naming measures. The present results therefore provide no support for the claim that cerebellar deficits or RAN distinguish between children with dyslexia and children with intellectual disabilities that include reading.     

Are the salutogenic effects of social supports modified by income? A test of an "added value hypothesis".

Older adults (54 men, 113 women; M age = 69.5 years) were examined to test the hypothesis that social supports would be more salutogenic (health promoting) for persons with lower incomes than for persons with higher incomes. Interactions of income and social supports (mean of 3 emotional scales of the Interpersonal Support Evaluation List) at study entry predicted changes 15-18 months later in a cardiovascular composite (linear combination of high-density lipoproteins-mean arterial pressure; p < .05), and natural killer cell activity (p < .05). For both outcomes, emotional supports were salutogenic for persons with lower incomes (< or =$29,000/year), but not for persons with higher incomes (>$29,000/year). In contrast, interactions of the Tangible Support Scale with income did not occur. Persons with lower incomes may derive benefits from social supports that go beyond tangible assistance.     

Quantitative depictions of threatening phenomena in news reports. The scary world of frequency data

Two experiments addressed the question of whether news reports depicting base‐rate data indicative of increasing population size over time would assuage the apprehension and victimization risk associated with another news story depicting frequency increases in a threatening phenomenon during the same time period. Men exposed to the population data manifested lower levels of apprehension and victimization risk than men not exposed to such data, but women showed no reduction in either apprehension and victimization risk than men not exposed to such data, but women showed no reduction in either apprehension or victimization risk after exposure to population data. This interaction was replicated in both experiments. Experiment 2 demonstrated that the same interaction can be produced using base‐rate data other than that depicting population increases over time and that the effects of the base‐rate stories are not merely a product of distraction from the threatening story. Differences in apprehension levels, information processing styles, mathematical problems solving skill, and sex role response sets were considered as alternative explanations for the interaction.     

Increasing Middle School Students’ Life Satisfaction: Efficacy of a Positive Psychology Group Intervention

This study identified middle school students who were less than delighted with their lives (reported life satisfaction scores between 1 and 6 on a 7-point scale), and attempted to improve these students’ mental health via a 10-week group wellness-promotion intervention developed from prior applications of positive psychology research. Complete data at baseline, post-intervention, and 6-month follow-up was gathered from 55 sixth grade students who were randomly assigned to the intervention condition (n = 28) or wait-list control (n = 27). Repeated measures analyses of a propensity score matched sample of 40 participants indicated a significant group by time interaction for global life satisfaction from baseline to post-intervention. Specifically, life satisfaction of students in the intervention group increased significantly, while the control group declined during the same period (although this change was not statistically significant). The intervention group’s gains were maintained at follow-up, but were matched by similar gains for students in the control group. No effects of intervention group were identified in the indicators of affect or psychopathology. The improvements in life satisfaction evidenced by students in the intervention group during the first semester of middle school are important given the adjustment difficulties that often appear during this sensitive developmental period marked by biological and educational changes.     

Salience Not Status: How Category Labels Influence Feature Inference

Two main uses of categories are classification and feature inference, and category labels have been widely shown to play a dominant role in feature inference. However, the nature of this influence remains unclear, and we evaluate two contrasting hypotheses formalized as mathematical models: the label special‐mechanism hypothesis and the label super‐salience hypothesis. The special‐mechanism hypothesis is that category labels, unlike other features, trigger inference decision making in reference to the category prototypes. This results in a tendency for prototype‐compatible inferences because the labels trigger a special mechanism rather than because of any influences they have on similarity evaluation. The super‐salience hypothesis assumes that the large label influence is due to their high salience and corresponding impact on similarity without any need for a special mechanism. Application of the two models to a feature inference task based on a family resemblance category structure yields strong support for the label super‐salience hypothesis and in particular does not support the need for a special mechanism based on prototypes.