Asymmetrical Body Perception: A Possible Role for Neural Body Representations

ABSTRACT— Perception of one's body is related not only to the physical appearance of the body, but also to the neural representation of the body. The brain contains many body maps that systematically differ between right- and left-handed people. In general, the cortical representations of the right arm and right hand tend to be of greater area in the left hemisphere than in the right hemisphere for right-handed people, whereas these cortical representations tend to be symmetrical across hemispheres for left-handers. We took advantage of these naturally occurring differences and examined perceived arm length in right- and left-handed people. When looking at each arm and hand individually, right-handed participants perceived their right arms and right hands to be longer than their left arms and left hands, whereas left-handed participants perceived both arms accurately. These experiments reveal a possible relationship between implicit body maps in the brain and conscious perception of the body.     

EFFECT OF REINFORCER MAGNITUDE ON PERFORMANCE MAINTAINED BY PROGRESSIVE‐RATIO SCHEDULES

This experiment examined the relationship between reinforcer magnitude and quantitative measures of performance on progressive‐ratio schedules. Fifteen rats were trained under a progressive‐ratio schedule in seven phases of the experiment in which the volume of a 0.6‐M sucrose solution reinforcer was varied within the range 6–300 μl. Overall response rates in successive ratios conformed to a bitonic equation derived from Killeen's (1994) Mathematical Principles of Reinforcement. The “specific activation” parameter, a, which is presumed to reflect the incentive value of the reinforcer, was a monotonically increasing function of reinforcer volume; the “response time” parameter, δ, which defines the minimum response time, increased as a function of reinforcer volume; the “currency” parameter, b, which is presumed to reflect the coupling of responses to the reinforcer, declined as a function of volume. Running response rate (response rate calculated after exclusion of the postreinforcement pause) decayed monotonically as a function of ratio size; the index of curvature of this function increased as a function of reinforcer volume. Postreinforcement pause increased as a function of ratio size. Estimates of a derived from overall response rates and postreinforcement pauses showed a modest positive correlation across conditions and between animals. Implications of the results for the quantification of reinforcer value and for the use of progressive‐ratio schedules in behavioral neuroscience are discussed.     

Gender differences in the relationships of cardiovascular symptoms and somatosensory amplification to mortality

Symptoms of angina and dyspnea predict coronary artery disease and death less well in women than in men. Greater somatosensory amplification - a psychosocial propensity to report symptoms of physical discomfort - may lead women to report relatively high levels of angina and dyspnea for reasons unrelated to coronary disease, reducing their associations with mortality. We assessed this hypothesis in a nationally representative survey of U.S. adults. When stratified by gender, angina and dyspnea significantly predicted mortality among men, but predicted it less well among women. After adjusting for amplification, cardiovascular symptoms did not predict mortality among women, but amplification was positively associated with mortality among older women.     

Determining risk in pediatric research with no prospect of direct benefit: time for a national consensus on the interpretation of federal regulations

United States federal regulations for pediatric research with no prospect of direct benefit restrict institutional review board (IRB) approval to procedures presenting: 1) no more than "minimal risk" ( section sign 45CFR46.404); or 2) no more than a "minor increase over minimal risk" if the research is commensurate with the subjects' previous or expected experiences and intended to gain vitally important information about the child's disorder or condition ( section sign 45CFR46.406) (DHHS 2001). During the 25 years since their adoption, these regulations have helped IRBs balance subject protections with the pursuit of scientific knowledge to advance children's welfare. At the same time, inconsistency in IRB application of these regulations to pediatric protocols has been widespread, in part because of the ambiguity of the regulatory language. During the past decade, three federally-charged committees have addressed these ambiguities: 1) the National Human Research Protections Advisory Committee (NHRPAC) (Washington, DC), 2) the Institute of Medicine (IOM) Committee on the Ethical Conduct of Clinical Research Involving Children (Washington, DC); and 3) the United States Department of Health and Human Services Secretary's Advisory Committee for Human Research Protections (SACHRP) (Washington, DC). The committees have reached similar conclusions on interpretation of language within regulations section sign section sign 45CFR46.404 and 406; these conclusions are remarkably consistent with recent international recommendations and those of the original National Commission for the Protection of Human Subjects of Biomedical and Behavioral Research (1977) report from which current regulations are based. Drawing on the committees' public reports, this article identifies the ethical issues posed by ambiguities in regulatory language, summarizes the committees' deliberations, and calls for a national consensus on recommended criteria.     

Individual differences in current events knowledge: Contributions of ability,personality, and interests

What accounts for individual differences in the sort of knowledge that people may draw on in everyday cognitive tasks, such as deciding whom to vote for in a presidential election, how to invest money in the stock market, or what team to bet on in a friendly wager? In a large sample of undergraduate students, we investigated correlates of individual differences in recently acquired knowledge of current events in domains such as politics, business, and sports. Structural equation modeling revealed two predictive pathways: one involving cognitive ability factors and the other involving two major nonability factors (personality and interests). The results of this study add to what is known about the sources of individual differences in knowledge and are interpreted in the context of theoretical conceptions of adult intelligence that emphasize the centrality and importance of knowledge (e.g., Ackerman, 1996; Cattell, 1971).     

Sequelae of Aggression in Acutely Suicidal Adolescents

The consequences of aggression on problem course and suicide risk were examined in 270 acutely suicidal adolescents (ages 12-17 years; 184 girls). Participants were assessed during psychiatric hospitalization (T1), 6-months post-hospitalization (T2), and 15 or more months post-hospitalization (T3). Study variables included self- and parent-reported aggression; self-reported internalizing symptoms, suicidal ideation, suicide attempt, and adverse events; and clinician-rated suicidal behavior. Aggression was not directly related to suicide attempt concurrently or prospectively. However, among more aggressive youth, internalizing symptoms were more predictive of T3 suicide attempt than among less aggressive youth. T1 aggression predicted aggressive incidents and the likelihood of incarceration prior to T3. Two-level hierarchical linear modeling indicated that self-reported aggression and internalizing problems were linked in terms of severity and rates of decline over time. Overall, parent-reported aggression was negatively associated with suicidal ideation. Findings highlight (a) the continuity and consequences of aggression, (b) a possible role of aggression in worsening suicide risk factors and potentiating suicide attempt, and (c) the importance of ongoing research on subtypes of suicidal adolescents.     

The role of left perisylvian cortical regions in spelling

In order to examine the role of left perisylvian cortex in spelling, 13 individuals with lesions in this area were administered a comprehensive spelling battery. Their spelling of regular words, irregular words, and nonwords was compared with that of individuals with extrasylvian damage involving left inferior temporo-occipital cortex and normal controls. Perisylvian patients demonstrated a lexicality effect, with nonwords spelled worse than real words. This pattern contrasts with the deficit in irregular word spelling, or regularity effect, observed in extrasylvian patients. These findings confirm that damage to left perisylvian cortex results in impaired phonological processing required for sublexical spelling. Further, degraded phonological input to orthographic selection typically results in additional deficits in real word spelling.     

The role of working memory in syntactic ambiguity resolution: a psychometric approach

In 2 studies, the authors used a combination of psychometric and experimental techniques to investigate the effects of domain-general and domain-specific working memory factors on offline decisions concerning attachment of an ambiguous relative clause. Both studies used English and Dutch stimuli presented to English- and Dutch-speaking participants, respectively. In Study 1, readers with low working memory spans were less likely to use recency strategies for disambiguation than were readers with high spans. This finding is inconsistent with predictions of locality- and resource-based accounts of attachment. Psychometric analyses showed that both domain-specific (verbal) and domain-general working memory accounted for the effect. Study 2 found support for the hypothesis that segmentation strategies imposed during silent reading can account for the counterintuitive relationship. Results suggest that readers with low spans have a greater tendency to break up large segments of text because of their limited working memory, leading to high attachment of the ambiguous relative clause.     

Modeling individual differences in working memory performance: a source activation account

Working memory resources are needed for processing and maintenance of information during cognitive tasks. Many models have been developed to capture the effects of limited working memory resources on performance. However, most of these models do not account for the finding that different individuals show different sensitivities to working memory demands, and none of the models predicts individual subjects' patterns of performance. We propose a computational model that accounts for differences in working memory capacity in terms of a quantity called source activation , which is used to maintain goal-relevant information in an available state. We apply this model to capture the working memory effects of individual subjects at a fine level of detail across two experiments. This, we argue, strengthens the interpretation of source activation as working memory capacity.     

Deep dyslexia in the two languages of an Arabic/French bilingual patient.

We present a single case study of an Arabic/French bilingual patient, ZT, who, at the age of 32, suffered a cerebral vascular accident that resulted in a massive infarct in the left peri-sylvian region. ZT's reading displays the characteristics of the deep dyslexia syndrome in both languages, that is, production of semantic, visual, and morphological errors, and concreteness effect in reading aloud and impossibility of reading nonwords. In the first part of this paper, using a three-route model of reading, we account for the patient's performance by positing functional lesions, which affect the non-lexical, the semantic lexical and the non-semantic lexical routes of reading. Phonological priming observed in a cross-language visual lexical decision task indicates that implicit assembled phonological recoding is possible. The above lesions and implicit nonword reading characterize the output form of deep dyslexia. However, error distribution reveals dissociations across languages (e.g. the semantic error rate is higher in French whereas translations are more frequent in the Arabic testing) that cannot be accounted for within a three-route model. In the second part, extensions to Plaut and Shallice's connectionist model (Cognitive Neuropsychology, 10 (5) (1993) 377) are proposed to account for the translinguistic errors observed. ZT's error distribution is compared to that obtained by Plaut and Shallice after lesions had been applied at different locations through the 40-60 network. The overall syndrome of deep dyslexia found in both languages is explained as resulting from lesions along the direct (O-->I) and output (S-->Ip, Ip-->P) pathways of reading. Lesions along the output pathway mostly affecting S-->Ip connections in French and Ip-->P connections in Arabic account for discrepancies in ZT's error pattern across tasks and languages. This case study demonstrates the superiority of a connectionist approach for predicting the error pattern in deep dyslexia.