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Miran Skrap

Publications and source records attributed to Miran Skrap.

9 recordsLinked to original sources
PubMed2005

Non-anaplastic pleomorphic xanthoastrocytoma with neuroradiological evidences of leptomeningeal dissemination.

CASE REPORT: A case of a non-anaplastic pleomorphic xanthoastrocytoma (PXA) presenting with leptomeningeal dissemination (LMD) affecting a 9-year-old girl is presented. DISCUSSION: The neoplasia in this young girl had the otherwise classical clinical features of PXA: the relatively advanced paediatric age of the patient, the seizures as presenting sign; the primary site in the temporal lobe; and the MRI findings of the partially solid and cystic superficial lesion. Only the tumour involvement of the chiasma and the infundibulus was a relatively unusual finding. In a 5-year period, the tumour underwent malignant transformation, bringing the child to death because of the primary tumour progression. However, the leptomeningeal deposits remained unchanged throughout the clinical course. CONCLUSION: To our knowledge, this is the first case of a non-anaplastic PXA presenting with disseminated disease. Thus, it was thought important to describe this case in order to add further information regarding the spectrum of the presenting clinical features of this rare neoplasm and the phenomenon of LMD of non-malignant glioma.

Astrocytoma↗
PubMed2005

Mental rotation in a patient with an implanted electrode grid in the motor cortex.

We investigated the effects of cortical stimulation on mental rotation tasks in a patient with an electrode array placed over his left primary motor cortex. The array was implanted to relieve chronic pain resulting from right brachial plexus damage. Tasks involving motor imagery were slowed down by cortical stimulation, whereas those involving visual imagery were not. When the patient performed the motor-imagery task, the interference effect on response times disappeared if the stimulator was switched off. We also probed two of the sites (anterior-lateral and posterior-medial position), and found that stimulation of the more anterior-lateral one consistently disrupted motor imagery.

Brain Injuries↗
PubMed2005

Better without (lateral) frontal cortex? Insight problems solved by frontal patients.

A recently proposed theory on frontal lobe functions claims that the prefrontal cortex, particularly its dorso-lateral aspect, is crucial in defining a set of responses suitable for a particular task, and biasing these for selection. This activity is carried out for virtually any kind of non-routine tasks, without distinction of content. The aim of this study is to test the prediction of Frith's 'sculpting the response space' hypothesis by means of an 'insight' problem-solving task, namely the matchstick arithmetic task. Starting from Knoblich et al.'s interpretation for the failure of healthy controls to solve the matchstick problem, and Frith's theory on the role of dorsolateral frontal cortex, we derived the counterintuitive prediction that patients with focal damage to the lateral frontal cortex should perform better than a group of healthy participants on this rather difficult task. We administered the matchstick task to 35 patients (aged 26-65 years) with a single focal brain lesion as determined by a CT or an MRI scan, and to 23 healthy participants (aged 34-62 years). The findings seemed in line with theoretical predictions. While only 43% of healthy participants could solve the most difficult matchstick problems ('type C'), 82% of lateral frontal patients did so (Fisher's exact test, P < 0.05). In conclusion, the combination of Frith's and Knoblich et al.'s theories was corroborated.

Adult↗
PubMed2005

Generation and recognition of abstract rules in different frontal lobe subgroups.

The Left Lateral cortex is known to have a role in inductive reasoning tasks. A more specific hypothesis on its role is that it is crucial in the generation of new abstract rules, rather than in the selection and implementation of a specific rule among a set of previously learned ones. Two new tests - the Generation of Hypotheses test and the Recognition of the Rule test - were administered to 46 patients with focal damage to the frontal cortex. Patients were divided in three frontal subgroups: Left Lateral, Right Lateral and Medial. On the basis of the new hypothesis, it was predicted that (i) the Left Lateral subgroup would fail in the Generation of Hypotheses test but would show spared performance on the Recognition of the Rule test and that (ii) the other frontal subgroups would perform normally on both tests. The findings on the Left Lateral and Right Lateral frontal subgroup were consistent with the predictions. This suggests that the Left Lateral frontal cortex is critical specifically for the generation of hypotheses in inductive reasoning. The Medial frontal subgroup, in contrast with our expectations, was impaired on Generation test; two hypotheses have been raised to explain this finding.

Adult↗
PubMed2005

Specific impairments of rule induction in different frontal lobe subgroups.

The neural correlates of inductive reasoning are still poorly understood. In order to explore them, we administered a revised version of the Brixton test, a rule attainment task, to a group of 40 patients with a focal frontal brain lesion of mixed aetiology and to 43 control subjects. To interpret an impairment on the test as suggesting an inductive reasoning deficit a number of alternative hypotheses need first to be considered, namely whether the Brixton impairment could be explained by: (i) a working memory deficit; (ii) a monitoring deficit; (iii) a difficulty in applying an already induced rule; (iv) greater impulsivity. The patients with left lateral (LL) frontal lesions were significantly impaired on the Brixton test; more importantly they were the only group in which none of the alternative hypotheses we explored proved able to explain the flawed performance. In sharp contrast, right lateral lesion patients did not make significantly more errors on the Brixton test than controls, but they produced three times more capture errors (a sign of impaired monitoring processes). The results were interpreted as suggesting functional dissociations between inductive reasoning, monitoring and working memory and a localisation of key processes for induction in left lateral frontal cortex and in right lateral cortex for monitoring and checking.

Adult↗
PubMed2003

Visuomotor deficits and fast recovery after area V6A lesion in monkeys.

In order to study the involvement of area V6A in visually guided behavior, restricted lesions to the anterior bank of the parieto-occipital sulcus (POs) were made in two adult Cercopithecus aethiops monkeys, trained in visuomotor tests. Beside the known clinical signs of parietal deficit (abnormal posture of the arm contralateral to the most recent lesion and reluctance to use it), misreaching was evident soon after surgery and disappeared quickly. Uncertainties in a landmark test and prolonged response times to the pressing of light-buttons lasted for a few weeks and 1 month, respectively. As suggested by previous anatomical and physiological data, these findings confirm the role of the POs region in the execution of reaching movements. Moreover, they also demonstrate that following lesion, locally networked areas can rapidly adjust in order to re-establish pre-lesional behavior. These adjustments take place well before that any anatomical changes may occur.

Animals↗
PubMed2002

Effects of lesions to area V6A in monkeys.

In order to assess the role played by area V6A in visuomotor control, two adult green monkeys ( Cercopithecus aethiops) were subjected to small, bilateral lesions in the anterior bank of the parieto-occipital sulcus. Before and after the lesions, monkeys were tested for naturally designed reaching, grasping and picking-up pieces of food from various positions on a plate and from a differently oriented narrow slit. All movements were recorded with closed circuit TV and analysed offline on a single-photogram basis for defective reaching and wrist orientation. V6A lesions provoked parietal weakness, reluctance to move, and specific deficits in reaching, wrist orientation and grasping. Recovery from the observed deficits was rapid, even after a second, contralateral lesion was given, creating a bilateral lesion. Thus, together with previous anatomical and electrophysiological data, these results directly support the hypothesis that area V6A is part of the network involved in the control of reaching movements and wrist orientation.

Animals↗
PubMedDate not supplied

Proteomic studies on low- and high-grade human brain astrocytomas.

Human brain astrocytomas range from the indolent low-grade to the highly infiltrating and aggressive high-grade form, also known as glioblastoma multiforme. The extensive heterogeneity of astrocytic tumors complicates their pathological classification. In this study, we compared the protein pattern of low-grade fibrillary astrocytomas to that of glioblastoma multiforme by 2D electrophoresis. The level of most proteins remains unchanged between the different grade tumors and only few differences are reproducibly observable. Fifteen differentially expressed proteins, as well as seventy conserved spots, were identified by mass spectrometry. Western and immnunohistochemical analysis confirmed the differential expression of the identified proteins. These data provide an initial reference map for brain gliomas. Among the proteins more highly expressed in glioblastoma multiforme, we found peroxiredoxin 1 and 6, the transcription factor BTF3, and alpha-B-crystallin, whereas protein disulfide isomerase A3, the catalytic subunit of the cAMP-dependent protein kinase, and the glial fibrillary acidic protein are increased in low-grade astrocytomas. Our findings contribute to deepening our knowledge of the factors that characterize this class of tumors and, at the same time, can be applied toward the development of novel molecular biomakers potentially useful for an accurate classification of the grade of astrocytomas.

Astrocytoma↗