The neural consequences of semantic richness: when more comes to mind, less activation is observed

Some concepts have richer semantic representations than others. That is, when considering the meaning of concepts, subjects generate more information (more features, more associates) for some concepts than for others. This variability in semantic richness influences responses in speeded tasks that involve semantic processing, such as lexical decision and semantic categorization tasks. It has been suggested that concepts with richer semantic representations build stronger attractors in semantic space, allowing faster settling of activation patterns and thus faster responding. Using event-related functional magnetic resonance imaging, we examined the neural activation associated with semantic richness by contrasting activation for words with high and low numbers of associates in a semantic categorization task. Results were consistent with faster semantic settling for words with richer representations: Words with a low number of semantic associates produced more activation than words with a high number of semantic associates in a number of regions, including left inferior frontal and inferior temporal gyri.     

Enriching the environment of alphaCaMKIIT286A mutant mice reveals that LTD occurs in memory processing but must be subsequently reversed by LTP

alphaCaMKII(T286A) mutant mice lack long-term potentiation (LTP) in the hippocampal CA1 region and are impaired in spatial learning. In situ hybridization confirms that the mutant mice show the same developmental expression of alphaCaMKII as their wild-type littermates. A simple hypothesis would suggest that if LTP is a substrate for learning, then enriching the environment should cause learning-dependent changes in wild-type mice that have LTP. Such changes would not be seen in LTP-deficient alphaCaMKII(T286A) mutants. Excitatory synaptic currents in CA1 neurons, recorded with patch clamp in brain slices, revealed that enrichment induces an increase in glutamate release probability and a decreased miniature current amplitude. Confocal microscopy also showed dendritic spine density to be reduced. However, contrary to the hypothesis above, these enrichment-induced changes occur only in the mutant mice and are not detectable in wild-type littermates. We suggest that enrichment induces alphaCaMKII-independent changes in both wild-type and mutant mice. Such changes may be subsequently reversed in wild-type animals via alphaCaMKII-dependent mechanisms, such as LTP. Reversal of plasticity has long been hypothesized to be essential for the hippocampus to maintain its role in memory processing. The inability to reverse plasticity in alphaCaMKII(T286A) mutant mice would then result in impairment of spatial learning.     

Estimates of the Validity and Utility of the Conners’ Continuous Performance Test in the Assessment of Inattentive and/or Hyperactive-Impulsive Behaviors in Children

This study evaluated the validity and classification utility of the Conners' Continuous Performance Test (CCPT) in the assessment of inattentive and hyperactive-impulsive behaviors in children. Significant, positive correlations between the CCPT parameters and behavioral ratings of ADHD behaviors were hypothesized. In addition, it was hypothesized that the CCPT parameters would perform better than a random test (chance) and show fair to moderate utility of classification across the different indices. Participants were 104 children between 6 and 12 years of age who were referred for evaluation of attention problems. The first hypothesis was not supported. There were no significant, positive correlations between the CCPT parameters and parent and teacher ratings of inattentive and hyperactive-impulsive behaviors. The second hypothesis was only partially supported. The CCPT Overall Index and the Omission Errors (84th percentile cutoff) performed better than a random test; however, the utility of the CCPT Overall Index only ranged from poor to slight. Receiver operating characteristic analyses showed the accuracy of the CCPT to be low. The implications and limitations of this study and future research directions are discussed.     

Coregulation of balance between children's prosocial approaches and acts of compliance: a pathway to mother-child cooperation?

Examined the free-field interaction of 32 mother-child dyads who volunteered to participate in a 1-hr home observation. Observers coded mother instructions, child compliance, and child prosocial approaches plus mothers' social attention as potential reinforcers for the children's compliance and social approaches. Herrnstein's matching law was used to analyze covariations between mothers' attention and the children's 2 responses. This analysis was followed by correlational and sequential probability analyses to determine linkages between these 2 child responses and the children's willingness to obey their mothers' instructions. Results showed consistent matching between mothers' social attention and the children's production of prosocial approaches and acts of compliance. An index of the proportions of these 2 responses also covaried with the children's compliance probabilities, and the prosocial approach component was the direct covariate. These findings are discussed within an interactional synchrony framework in which children's willingness to obey their mothers is influenced by opportunities for the dyad to engage each other in specific forms of social interaction.     

Commentary on high-performance computing and human vision II: Virtual reality and eyeball tracking

Visualization of scientific data that are not normally visible can be greatly enhanced by understanding human visual perception. Mars the Movie illustrated the use of stereo resolution for producing realistic vistas of the Mars surface. The real-time recording and analysis of eyeball-tracking data is another example of human vision research which benefits from high-performance computing. Currently the bottleneck is not in the hardware but in the available software to transform data efficiently.     

Psychometric Properties of the Right Wing Authoritarianism Scale in Black and White South African Students

Recently Taylor and Boeyens (1991) showed that the South African Personality Questionnaire has inadequate internal consistency and factorial validity for use in the black population. This paper reports a study supporting their conclusion that scales developed with data from a white sample do not hold together psychometrically or conceptually when used with a black sample. In a sample of white students, Altemeyer's Right Wing Authoritarianism scale, initially developed in Canada, had an acceptable alpha of 0.83, but there was an unacceptable alpha of 0.43 in a black student sample. Item and factor analysis showed that for the black sample there was little structure and that the scale was effectively a set of heterogenous items. This paper presents a detailed discussion of the item and factor analyses and shows how certain items have different connotations for whites and blacks as a result of their different political and cultural histories. Although cultural differences in conservatism can be observed by looking at individual items, a comparison between black and white individuals on the higher order construct of Authoritarianism cannot be made. It is concluded that basic conceptual work based on the phenomenology of the concept being measured needs to precede the psychometric development of scales for use in the black community.