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

On the Existence of Shadow Prices

For utility maximization problems under proportional transaction costs, it has been observed that the original market with transaction costs can sometimes be replaced by a frictionless "shadow market" that yields the same optimal strategy and utility. However, the question of whether or not this indeed holds in generality has remained elusive so far. In this paper we present a counterexample which shows that shadow prices may fail to exist. On the other hand, we prove that short selling constraints are a sufficient condition to warrant their existence, even in very general multi-currency market models with possibly discontinuous bid-ask-spreads.Comment: 14 pages, 1 figure, to appear in "Finance and Stochastics

Impact of perioperative dexamethasone in the context of neurosurgical brain metastasis resection

BACKGROUND: Patients with brain metastases that undergo brain metastasis resection regularly receive perioperative dexamethasone. We sought to evaluate whether perioperative dexamethasone in brain metastases is linked to survival. METHODS: Retrospective data on perioperative dexamethasone dosage in resected brain metastasis patients at three hospital sites of the Charité from 2010-2022 were collected. Cut-off values for cumulative perioperative dexamethasone dose as a continuous predictor variable for survival were determined using maximally selected rank statistics. Patients were dichotomized based on determined cut-offs of cumulative dexamethasone (pre-operative: < 40 mg vs ≥40 mg; post-operative: < 180 mg vs ≥ 180 mg) and pre- and postoperative: < 281 mg vs ≥ 281 mg). Medical records included baseline demographic, radiological, histopathological and treatment-related characteristics. Based on cut-off values for dexamethasone downstream statistical analyses included Kaplan-Meier, Cox proportional hazards regression for overall survival with adjustment for potential confounders including age, gender, Karnofsky performance status and presence of extracranial metastasis via propensity score matching. RESULTS: 539 patients were included. Median follow-up time was 58,97 months. After adjusting for age, gender, Karnofsky performance status and presence of extracranial metastasis patients with higher cumulative perioperative dexamethasone (≥281 mg) showed shorter survival (HR: 1.47 (1.20-1.80, p<0.001) as compared to patients with lower cumulative doses (<281 mg). This effect remained significant after correction for patients that died within 2 months after resection and for patients with KPS below 50% and, independently from this approach performing propensity score matched-based analysis of the total cohort of patients, respectively. CONCLUSION: Cumulative perioperative dexamethasone is associated with decreased survival in the context of brain metastasis resection. Strict dosage, down taper or methods reducing corticosteroid dependency should be regularly evaluated in clinical practice in patients with brain metastases

Review Article: Cystic Degeneration/Spongiosis Hepatis in Rats

Cystic degeneration/spongiosis hepatis in rats has been proposed to be a preneoplastic and/or neoplastic lesion by some authors, because of its proliferative properties and persistent increased cell turnover rate in stop experiments using hepatocarcinogens , and the assumption that it can develop into a sarcoma. The neoplastic potential of cystic degeneration is questioned in this review article. Cystic degeneration, which appears to derive from altered Ito cells, does not have neoplastic histomorphologi c characteristics, although it may be composed of cells with an increased mitotic index. In this regard, persistent proliferation is also seen with other nonneoplastic lesions. Arguments are presented to show that the induced, probably extremely rare sarcoma that was associated with cystic degeneration most likely derives from the very rare induced spherical Ito-cell aggregate with an unusually high cellular turnover rate in rats treated with hepatocarcinogens , and not from cystic degeneration. Also, in none of 12 referenced standard oncogenicity studies with chemically induced cystic degeneration was the lesion associated with mesenchymal (Ito-cell) tumors. Consequently, evidence is lacking that cystic degeneration in rats should be classifi ed as a preneoplastic or neoplastic lesion. The 12 oncogenicity studies in rats with induced cystic degeneration showed a marked sex predilection, with males more likely to develop either spontaneous or chemically induced lesions. In these 12 studies, cystic degeneration was more often associated with hepatocellular hypertrophy or hepatotoxicity, rather than hepatocarcinogenicity. Thus, it is concluded that hepatocarcinogens induce cystic degeneration, not because they are carcinogenic, but because they have other effects on the liver, and that cystic degeneration may be a secondary/reparative change. Cystic degeneration in fi sh parallels the situation in rats in many respects, yet the existence of the lesion in other species, including man, is not as well supported. Based on the data presented in this review, spontaneous and induced cystic degeneration in rats and fi sh is not a preneoplastic or neoplastic lesion and risk assessment for man can be based on no-effect levels and safety margins, as for other nonneoplasti c adverse effects that have no counterpart in man. </jats:p