The role of the lateral prefrontal cortex and anterior cingulate in stimulus–response association reversals

Many complex tasks require us to flexibly switch between behavioral rules, associations, and strategies. The prefrontal cerebral cortex is thought to be critical to the performance of such behaviors, although the relative contribution of different components of this structure and associated subcortical regions are not fully understood. We used functional magnetic resonance imaging to measure brain activity during a simple task which required repeated reversals of a rule linking a colored cue and a left/right motor response. Each trial comprised three discrete events separated by variable delay periods. A colored cue instructed which response was to be executed, followed by a go signal which told the subject to execute the response and a feedback instruction which indicated whether to ‘‘hold’’ or ‘‘f lip’’ the rule linking the colored cue and response. The design allowed us to determine which brain regions were recruited by the specific demands of preparing a rule contingent motor response, executing such a response, evaluating the significance of the feedback, and reconfiguring stimulus–response (SR) associations. The results indicate that an increase in neural activity occurs within the anterior cingulate gyrus under conditions in which SR associations are labile. In contrast, lateral frontal regions are activated by unlikely/unexpected perceptual events regardless of their significance for behavior. A network of subcortical structures, including the mediodorsal nucleus of the thalamus and striatum were the only regions showing activity that was exclusively correlated with the neurocognitive demands of reversing SR associations. We conclude that lateral frontal regions act to evaluate the behavioral significance of perceptual events, whereas medial frontal–thalamic circuits are involved in monitoring and reconfiguring SR associations when necessary

An fMRI investigation of moral cognition in healthcare decision making

This study used fMRI to investigate the neural substrates of moral cognition in health resource allocation decision problems. In particular, it investigated the cognitive and emotional processes that underpin utilitarian approaches to health care rationing such as Quality Adjusted Life Years (QALYs). Participants viewed hypothetical medical and nonmedical resource allocation scenarios which described equal or unequal allocation of resources to different groups. In addition, participants were assigned to 1 of 2 treatments in which they either did or did not receive advanced instructions about the principles of utilitarianism. In all cases, participants were asked to judged the proposed allocations as “fair” or “unfair.” More brain activity was observed within the superior parietal lobe, angular gyrus, middle temporal gyrus, and bilateral caudate nucleus when participants viewed scenarios depicting equal divisions of resources. Conversely, unequal resource divisions were associated with more activity in the inferior frontal gyrus and insula cortex. Furthermore, instructions about the principles of utilitarianism led to significant activation differences within the inferior frontal gyrus and the middle frontal gyrus. Significant differences in activity were also found within the inferior frontal cortex and anterior insula between medical and nonmedical scenarios. The implications for cognitive control mechanisms and the cognitive and neural bases of utilitarian ethical judgment are discussed

Analyticity of The Ground State Energy For Massless Nelson Models

We show that the ground state energy of the translationally invariant Nelson model, describing a particle coupled to a relativistic field of massless bosons, is an analytic function of the coupling constant and the total momentum. We derive an explicit expression for the ground state energy which is used to determine the effective mass.Comment: 33 pages, 1 figure, added a section on the calculation of the effective mas

Non-semisimple Lie algebras with Levi factor \frak{so}(3), \frak{sl}(2,R) and their invariants

We analyze the number N of functionally independent generalized Casimir invariants for non-semisimple Lie algebras \frak{s}\overrightarrow{% oplus}_{R}\frak{r} with Levi factors isomorphic to \frak{so}(3) and \frak{sl}(2,R) in dependence of the pair (R,\frak{r}) formed by a representation R of \frak{s} and a solvable Lie algebra \frak{r}. We show that for any dimension n >= 6 there exist Lie algebras \frak{s}\overrightarrow{\oplus}_{R}\frak{r} with non-trivial Levi decomposition such that N(\frak{s}% \overrightarrow{oplus}_{R}\frak{r}) = 0.Comment: 16 page

A Physicist's Proof of the Lagrange-Good Multivariable Inversion Formula

We provide yet another proof of the classical Lagrange-Good multivariable inversion formula using techniques of quantum field theory.Comment: 9 pages, 3 diagram

The role of the dominant versus the non-dominant hemisphere: an fMRI study of Aphasia recovery following stroke

Background: Speech production is one of the most frequently affected cognitive functions following stroke; however, the neural mechanisms underlying the recovery of speech function are still incompletely understood. Aims: The current study aims to address the differential contributions of the dominant and non-dominant hemispheres in recovery from aphasia following stroke by comparing data from four stroke patients and 12 control participants to assess the patterns of activation during speech production tasks during functional magnetic resonance imaging (fMRI) scanning. Methods & Procedures: Four chronic stroke patients (three left-hemisphere lesion and one right-hemisphere lesion) diagnosed with Broca’s aphasia at the acute phase, but now recovered to near normal speech ability, were tested on speech production tasks (phonemic fluency, categorical fluency and picture naming) whilst undergoing fMRI. These patients were compared with 12 healthy controls undergoing the same procedure. Outcomes & Results: Individual subject analysis showed activation peaks in perilesional areas in three out of four patients. This included one patient with right-hemisphere lesion, who also showed predominant perilesional activation. Group analysis of control participants showed predominately left-hemisphere activation, but not exclusively so. Laterality indexes were calculated and showed predominant left-hemisphere lateralisation in the control group (LI = 0.4). Three out of the four patients showed speech lateralised to the same hemisphere as their lesion and the fourth patient showed speech lateralised to the opposite hemisphere to their lesion. Different speech production tasks resulted in varying lateralisation indices (LIs) within participants. Conclusions: The data suggest that perilesional areas support recovery of speech in the chronic phase post-stroke regardless of the site of the lesion. The study has implications for the understanding of functional recovery as well as for the paradigms used in fMRI to localise speech production areas. Specifically, a variety of speech tasks are required to elicit activation that is representative of the range of cortical involvement in speech in healthy adults and that also allows for accurate reporting of the extent of recovery experienced in patients

Casimir invariants for the complete family of quasi-simple orthogonal algebras

A complete choice of generators of the center of the enveloping algebras of real quasi-simple Lie algebras of orthogonal type, for arbitrary dimension, is obtained in a unified setting. The results simultaneously include the well known polynomial invariants of the pseudo-orthogonal algebras $so(p,q)$, as well as the Casimirs for many non-simple algebras such as the inhomogeneous $iso(p,q)$, the Newton-Hooke and Galilei type, etc., which are obtained by contraction(s) starting from the simple algebras $so(p,q)$. The dimension of the center of the enveloping algebra of a quasi-simple orthogonal algebra turns out to be the same as for the simple $so(p,q)$ algebras from which they come by contraction. The structure of the higher order invariants is given in a convenient "pyramidal" manner, in terms of certain sets of "Pauli-Lubanski" elements in the enveloping algebras. As an example showing this approach at work, the scheme is applied to recovering the Casimirs for the (3+1) kinematical algebras. Some prospects on the relevance of these results for the study of expansions are also given.Comment: 19 pages, LaTe

Uncommon cause of small bowel obstruction - gallstone ileus: a case report

Gallstone ileus is an uncommon cause of small bowel obstruction. We present a case of small intestinal obstruction owing to a large gallstone in lower ileum in a 65 years old man. The diagnosis was made by computed tomography

A solitary primary subcutaneous hydatid cyst in the abdominal wall of a 70-year-old woman: a case report

<p>Abstract</p> <p>Introduction</p> <p>A solitary primary hydatid cyst in the subcutaneous abdominal wall is an exceptional entity, even in countries where the <it>Echinococcus </it>infestation is endemic.</p> <p>Case presentation</p> <p>We report a case of a 70-year-old Caucasian woman who presented to our hospital with a subcutaneous mass in the para-umbilical area with a non-specific clinical presentation. The diagnosis of subcutaneous hydatid cyst was suspected on the basis of radiological findings. A complete surgical resection of the mass was performed and the patient had an uneventful post-operative recovery. The histopathology confirmed the suspected diagnosis.</p> <p>Conclusion</p> <p>Hydatid cyst should be considered in the differential diagnosis of every subcutaneous cystic mass, especially in regions where the disease is endemic. The best treatment is the total excision of the cyst with an intact wall.</p

A giant peritoneal simple mesothelial cyst: a case report

<p>Abstract</p> <p>Introduction</p> <p>A peritoneal simple mesothelial cyst is a very rare mesenteric cyst of mesothelial origin. The size of this lesion usually ranges between a few centimeters and 10 cm. It is usually asymptomatic, but occasionally presents with various, non-specific symptoms, which makes correct pre-operative diagnosis difficult. We present a case of a giant peritoneal simple mesothelial cyst that was successfully managed by complete surgical excision which is the treatment of choice.</p> <p>Case presentation</p> <p>A 21-year-old Caucasian Moroccan woman with vague abdominal discomfort and associated distention, during the previous 2 years, without other symptoms, presented to our hospital. Her past medical history was unremarkable. On physical examination, a mobile, painless and relatively hard abdominal mass was palpated. The laboratory examination and abdominal radiograph were unremarkable. Abdominal radiologic imaging showed a cystic mass of 35 × 20 × 10 cm that occupied the entire anterior and right abdominal cavity. Radical excision of the cyst was performed by midline laparotomy without any damage to the adjacent abdominal organs. The histopathological diagnosis was simple mesothelial cyst. The postoperative course was uneventful with no recurrence.</p> <p>Conclusion</p> <p><b>A </b>peritoneal simple mesothelial cyst is a quite rare abdominal tumor, that must always be considered in differential diagnosis of pelvic cystic lesions and other mesenteric cysts. The treatment of choice is the complete surgical excision of the cyst.</p