The cognitive demands on cooperation in social dilemmas: an fMRI study.

This study uses fMRI to investigate the cognitive demands of decision-making in two types of cooperation games: a prisoner's dilemma (PD) eliciting a temptation to free-ride, leading to a dominant, self-interested response, and a stag hunt (SH) that has no dominant response but offers pay-off incentives that make mutual cooperation collectively beneficial but risky. Consequently, the PD poses greater conflict between self- and collective interest, greater demands for computational reasoning to derive the optimal solution, and greater demands for mentalizing to infer the intentions of others. Consistent with these differences between the two games, the results indicate that the PD is associated with increased activity in the anterior cingulate gyrus, prefrontal cortex, parietal lobe, and temporoparietal junction. With less conflict, the demands for computation and mentalizing are reduced in the SH, and cooperation levels increase dramatically. The differences in brain activation elicited by the different incentive structures of the PD and the SH appear to be independent of individual differences in revealed social preferences.

Developmental dyslexia and widespread activation across the cerebellar hemispheres.

Developmental dyslexia is the most common learning disability in school-aged children with an estimated incidence of five to ten percent. The cause and pathophysiological substrate of this developmental disorder is unclear. Recently, a possible involvement of the cerebellum in the pathogenesis of dyslexia has been postulated. In this study, 15 dyslexic children and 7 age-matched control subjects were investigated by means of functional neuroimaging (fMRI) using a noun-verb association paradigm. Comparison of activation patterns between dyslexic and control subjects revealed distinct and significant differences in cerebral and cerebellar activation. Control subjects showed bilaterally well-defined and focal activation patterns in the frontal and parietal lobes and the posterior regions of the cerebellar hemispheres. The dyslexic children, however, presented widespread and diffuse activations on the cerebral and cerebellar level. Cerebral activations were found in frontal, parietal, temporal and occipital regions. Activations in the cerebellum were found predominantly in the cerebellar cortex, including Crus I, Crus II, hemispheric lobule VI, VII and vermal lobules I, II, III, IV and VII. This preliminary study is the first to reveal a significant difference in cerebellar functioning between dyslexic children and controls during a semantic association task. As a result, we propose a new hypothesis regarding the pathophysiological mechanisms of developmental dyslexia. Given the sites of activation in the cerebellum in the dyslexic group, a defect of the intra-cerebellar distribution of activity is suspected, suggesting a disorder of the processing or transfer of information within the cerebellar cortex.

FMRI findings in an aphasic patient with reversed cerebral dominance for language.

An 80-year-old right-handed woman with no history of brain damage or familial strain of left-handedness acutely developed aphasia associated with a left hemiparesis following a right hemisphere stroke. Brain MRI showed a posterior insular ischemic infarction extending to the temporo-parietal region of the right hemisphere. Severe overall language disruption (global aphasia) in the acute phase of the stroke rapidly evolved into conduction aphasia, characterized by a neurolinguistic profile of disproportionately severe repetition deficits and markedly distorted phonological skills. In the lesion phase of the stroke, a functional MRI study using a word repetition task was conducted which revealed a consistent pattern of right hemisphere activations. For the first time, right hemisphere language dominance is demonstrated by fMRI in a clear instance of crossed aphasia in a dextral.

Sports-related acute and chronic avulsion injuries in children and adolescents with special emphasis on tennis.

Acute and chronic sports-related muscle and tendon injuries are not infrequent in youngsters. In particular, the physis is prone to trauma as it constitutes the weakest part of the immature skeleton. The type of sports activity determines the location of the lesion. Most commonly, apophyses of the hip and pelvis are subject to avulsion. The purpose of this paper is to give a short overview of the pathogenesis, location, prevalence and imaging characteristics of acute and chronic avulsion injuries in the immature skeleton, with special emphasis on tennis-related injuries. Tennis-related injuries particularly involve apophyses of the ischial tuberosity, the anterior inferior or superior iliac spine and the iliac crest.