Baby steps: investigating the development of perceptual-motor couplings in infancy

There are cells in our motor cortex that fire both when we perform and when we observe similar actions. It has been suggested that these perceptual-motor couplings in the brain develop through associative learning during correlated sensorimotor experience. Although studies with adult participants have provided support for this hypothesis, there is no direct evidence that associative learning also underlies the initial formation of perceptual–motor couplings in the developing brain. With the present study we addressed this question by manipulating infants’ opportunities to associate the visual and motor representation of a novel action, and by investigating how this influenced their sensorimotor cortex activation when they observed this action performed by others. Pre-walking 7–9-month-old infants performed stepping movements on an infant treadmill while they either observed their own real-time leg movements (Contingent group) or the previously recorded leg movements of another infant (Non-contingent control group). Infants in a second control group did not perform any steps and only received visual experience with the stepping actions. Before and after the training period we measured infants’ sensorimotor alpha suppression, as an index of sensorimotor cortex activation, while they watched videos of other infants’ stepping actions. While we did not find greater sensorimotor alpha suppression following training in the Contingent group as a whole, we nevertheless found that the strength of the visuomotor contingency experienced during training predicted the amount of sensorimotor alpha suppression at post-test in this group. We did not find any effects of motor experience alone. These results suggest that the development of perceptual–motor couplings in the infant brain is likely to be supported by associative learning during correlated visuomotor experience

Prevalence and characteristics of erectile dysfunction in black and mixed race primary care populations of the Cape Flats and Helderberg Basin area of the Western Cape, South Africa

Objective: To estimate the prevalence of erectile dysfunction (ED) among users of primary care in a Black and Mixed Race urban population in the Western Cape, and to describe any associated health and psychosocial factors. Design: Cross-sectional survey by interviewer administered questionnaire. Setting: Two primary care medical centres, 40km apart, in Cape Town metropolitan area. Serve different ethnic groups, with no cross-contamination between them. Study period: March-June 1999 Patients: 833 Males (35-70 years old) attending these health centres for primary care. Systematic selection of all attendees. Main outcome measures: Prevalence of ED and presence of associated health and psychosocial factors. Describe patient demographics, physical attributes, sexual relationships. Results: Results of 730 males with current sexual partners: Mean ages 48 years (SD:7 years) all; 46 years (SD:9 years) Black group; 51 years (SD: 9 years) Mixed Race group. All degrees of ED prevalence: All 77.1% (95% CI: 74.0-80.2), Black 76.4% (95% CI: 71.8-80.4) and Mixed Race 77.7% (95% CI: 72.8-82.0). Significantly associated diseases: hypertension, diabetes, gastrointestinal and heart disease. Alcohol consumption (younger patients), smoking (older patients) significantly related to ED. Males with ED: more sexual partners than males without ED. More than 90% choose primary care physician/ generalist as primary ED care-giver. Conclusions: ED is very common in both study groups. Primary care workers must be prepared to manage associated risk factors and health implications. ED sufferers in this population may also be at higher risk for sexually transmitted diseases due to multiple sexual partners. (SA Fam Pract 2003;45(1):14-20) Keywords: erectile dysfunction, impotence, prevalence, black

A case of multiple myeloma presemnting clinically as a solitary tumour of the skull

No Abstrac

A feral family on our doorstep

A family was discovered living in isolation in the Free State region of South Africa. Certain members of this family, (the mother and three sons and a daughter) displayed primitive and ape-like behaviour, prompting the local and international press to refer to them as a feral family. The affected members of the family are presented as a case study describing how the family became isolated, their response to outside intervention and eventually how the family was “discovered”. Clinical presentations are also documented as well as the therapeutic interventions used. After evaluation, the affected members of the family were shown to have various degrees of mental retardation. The words ‘feral' and ‘neglect' are defined and certain similar documented cases of feral children discovered previously in other regions are mentioned. The etiology of the condition is explored, discussing the effects of the environment on various aspects of neural development in children, especially referring to the lack of neuro-stimulation and other insults to the brain during the critical phase of brain plasticity. Cognitive deficits, poor mastery of language and decrease in brain size are often found in feral children. The role of a child's genetic predisposition and a paucity of environmental stimulation is also explained in the article. South African Psychiatry Review Vol. 9(4) 2006: 231-23

Generation and detection of very high frequency acoustic waves in solids Final report

Techniques for generation and detection of very high frequency acoustic waves in solid

Relaxations of the satisfiability problem using semidefinite programming

We derive a semidefinite relaxation of the satisfiability (SAT) problem and discuss its strength. We give both the primal and dual formulation of the relaxation. The primal formulation is an eigenvalue optimization problem, while the dual formulation is a semidefinite feasibility problem. It is shown that using the relaxation, the notorious pigeon hole and mutilated chessboard problems are solved in polynomial time. As a byproduct we find a new `sandwich' theorem that is similar to Lov'asz' famous $vartheta$-function. Furthermore, using the semidefinite relaxation 2SAT problems are solved. By adding an objective function to the dual formulation, a specific class of polynomially solvable 3SAT instances can be identified. We conclude with discussing how the relaxation can be used to solve more general SAT problems and some empirical observations

Statistics of matrix elements of local operators in integrable models

We study the statistics of matrix elements of local operators in the basis of energy eigenstates in a paradigmatic integrable many-particle quantum theory, the Lieb-Liniger model of bosons with repulsive delta-function interaction. Using methods of quantum integrability we determine the scaling of matrix elements with system size. As a consequence of the extensive number of conservation laws the structure of matrix elements is fundamentally different from, and much more intricate than, the predictions of the eigenstate thermalization hypothesis for generic models. We uncover an interesting connection between this structure for local operators in interacting integrable models, and the one for local operators that are not local with respect to the elementary excitations in free theories. We find that typical off-diagonal matrix elements $\langle\boldsymbol{\mu}|O|\boldsymbol{\lambda}\rangle$ in the same macro-state scale as $\exp(-c^{ O}L\ln(L)-LM^{O}_{\boldsymbol{\mu},\boldsymbol{\lambda}})$ where the probability distribution function for $M^{O}_{\boldsymbol{\mu},\boldsymbol{\lambda}}$ are well described by Fr\'echet distributions and $c^{O}$ depends only on macro-state information. In contrast, typical off-diagonal matrix elements between two different macro-states scale as $\exp(-d^{ O}L^2)$, where $d^{O}$ depends only on macro-state information. Diagonal matrix elements depend only on macro-state information up to finite-size corrections.Comment: 30 pages, 40 figure