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Biomedical subjects

P Hlustík

Publications and source records attributed to P Hlustík.

9 recordsLinked to original sources
PubMed2001

Somatotopy in human primary motor and somatosensory hand representations revisited.

High-resolution functional magnetic resonance imaging of healthy volunteers was used to study the functional anatomy of the human primary motor (M1) and somatosensory (S1) cortical hand representations during simple movements of thumb, little finger and wrist and a sequential movement of the middle three fingers. Rest served as a control state. The results demonstrated an orderly somatotopy in both M1 and S1, even though the cortical areas active with individual movements significantly overlapped. Moreover, the activation patterns in M1 and S1 differed in three aspects: (i) S1 activation was distributed into significantly more clusters than M1 and the primary cluster was smaller; (ii) the overlaps of areas active with different movements were significantly larger in M1 than in S1; (iii) the difference between the three-finger sequential movement and the single-finger movements was more pronounced in S1 than in M1. The sequence-activated S1 cortex was distributed into significantly more clusters. There was also a trend for a bigger volume difference between sequence and the single finger movements in S1 than M1. These data suggest that while the distributed character dominates in M1 and S1, a somatotopic arrangement exists for both M1 and S1 hand representations, with the S1 somatotopy being more discrete and segregated, in contrast to the more integrated and overlapping somatotopy in M1.

Adult↗
PubMed1998

Suppression of vascular artifacts in functional magnetic resonance images using MR angiograms.

This paper describes a method for processing functional magnetic resonance images that suppresses signal changes originating from macroscopic veins visible in acquired magnetic resonance angiograms. Finger tapping experiments were performed on a 1.5-T scanner and the response was evaluated with voxel-by-voxel cross-correlation of the time course with a sinusoid at the paradigm frequency. After applying a vascular mask to suppress signal changes under macroscopic vessels, the vascular and nonvascular subpopulations of the data were compared. By visual inspection, the method was found to remove extracortical activation while preserving activation in the parenchyma. The observed higher signal amplitudes and temporal phase lags of the vascular population agree with theoretical models and previous studies. A significant portion of negatively correlated voxels occurs adjacent to through-plane vessels. Finally, comparing the centers of mass of the activated area before and after vascular suppression showed significant shifts in some subjects.

Artifacts↗
PubMed1993

Advanced EMG techniques in diagnostics of spinal muscular atrophies and motor neuron disease--magnetic stimulation, single fiber EMG and macro EMG.

Motor neuron disease (MND) and spinal muscular atrophies (SMA) are difficult to diagnose with classical EMG methods because significant findings appear relatively late and both groups of diseases show neurogenic type of record differing only in a relatively greater amount of fasciculations and higher amplitude of motor unit potential (MUP) in MND compared with SMA. We examined 12 patients with MND-amyotrophic lateral sclerosis and 7 patients with SMA type III and IV according to Swash with advanced EMG techniques-magnetic stimulation, single fiber and macro EMG. With transcranial magnetic stimulation, a significant prolongation of cortical latency was found in MND (P < 0.0001 right hand and P < 0.0005 left hand) against SMA, where it was almost normal. With single fiber EMG, mean jitter was less markedly increased in MND (P < 0.05 against SMA) and fiber density was lower in MND (P < 0.005). With macro EMG, no significant difference was found in either macro amplitude or area. Macro fiber density was also lower in MND (P < 0.005). Advanced EMG techniques proved to differentiate clearly the III. (Kugelberg-Welander) and IV. (adult) type of SMA from MND-amyotrophic lateral sclerosis.

Adult↗
PubMed1992

Preliminary experimental experiences with xenotransplantations.

In our xenotransplantation experiments has been a major aim to induce specific tolerance. The results from the meeting of the donor's and the recipient's immunocompetent systems already in the period of embryonic development and/or the influence of methylprednisolone are described.

Animals↗
PubMed1992

Single fiber EMG in multiple sclerosis.

A group of 25 patients with sclerosis multiplex (SM) was examined by means of single fiber (SF) EMG. This group had the mean value of jitter 55.0 +/- 4.5 microseconds and fiber density (FD) 2.15 +/- 0.12. The findings of the patients with the first attack of illness and the findings of the patients with twenty-year duration are the same. A hypothesis is suggested that not only the peripheral neuron but also the CNS structures take part in the increase of jitter. The different results of stimulated single fiber (SSF) and SF EMG are discussed; the former reflects only the peripheral part of the nervous system due to peripheral stimulation. The higher levels of CNS cannot take part in it.

Adolescent↗
PubMed1992

Single fiber EMG in cerebrovascular stroke (CVS).

This paper gives previously unpublished data about fiber density (FD) and jitter in patients with CVS. The cluster of these values is very similar to that found in sclerosis multiplex (SM). There is a problem whether both clusters represents the same disorder of CNS compared with amyotrophic lateral sclerosis (ALS) or spinal muscular atrophy which have different values. Another problem is the participation of presumed central lesion on the increased jitter, the mechanism of which is still unknown.

Aged↗
PubMed1992

Tetanic syndrome and its examination.

The article presents a new electromyographic method; it describes the non-invasive examination of tetany with surface electrodes. This method is more sensitive than the classical needle technique and, moreover, the necessity to use expensive disposable needle electrodes is avoided.

Electromyography↗
PubMed1991

Histological and biochemical characteristics of kryoprotected embryonic nervous tissue for transplantation purpose.

In clinical and experimental conditions, a biochemical equipment and a histological image of a fresh embryonic nervous tissue and a tissue conserved by deep freezing for transplantation purposes were examined. By repeated examination of neurotransmitters, the contents of dopamine and serotonin were found unchanged by freezing. In a human embryo, serotonin predominates over dopamine, while in chicken embryos, used for xeno-transplantations, it is vice versa. As for the microscopic structure of nervous tissue, no influence of kryopreservation for 4 to 14 days was found.

Animals↗