Biomedical subjects

Pavel Jurák

Publications and source records attributed to Pavel Jurák.

5 recordsLinked to original sources

PubMed2006

Intracerebral recording of cortical activity related to self-paced voluntary movements: a Bereitschaftspotential and event-related desynchronization/synchronization. SEEG study.

To analyze the distribution of the cortical electrical activity related to self-paced voluntary movements, i.e. the movement-related readiness potentials (Bereitschaftspotential, BP) and the event-related desynchronization (ERD) and synchronization (ERS) of cortical rhythms using intracerebral recordings. EEG was recorded in 14 epilepsy surgery candidates during preoperative video-stereo-EEG monitoring. Subjects performed self-paced hand movements, with their right and left fingers in succession. EEG signals were obtained from a total of 501 contacts using depth electrodes located in primary and nonprimary cortical regions. In accordance with previous studies, BP was found consistently in the primary motor (M1) and somatosensory (S1) cortex, the supplementary motor area (SMA), and in a few recordings also in the cingulate cortex and in the dorsolateral prefrontal and premotor cortex. ERD and ERS of alpha and beta rhythms were also observed in these cortical regions. The distribution of contacts showing ERD or ERS was larger than the distribution of those showing BP. In contrast to BP, ERD and ERS frequently occurred in the lateral and mesial temporal cortex and the inferior parietal lobule. The number of contacts and cortical regions showing ERD and ERS and not BP suggests that the two electrophysiological phenomena are differently involved in the preparation and execution of simple voluntary movements. Substantial differences between BP and ERD in spatial distribution and the widespread topography of ERD/ERS in temporal and higher-order motor regions suggest that oscillatory cortical changes are coupled with cognitive processes supporting movement tasks, such as memory, time interval estimation, and attention.

Adolescent↗

PubMed2005

Intracerebral P3-like waveforms and the length of the stimulus-response interval in a visual oddball paradigm.

OBJECTIVE: This study investigated the possible linkage of intracerebrally recorded P3-like waveforms to the processes induced by stimulus perception or motor response formation. METHODS: Event-related potentials were recorded from 560 cerebral sites in 17 patients suffering from intractable epilepsy during visual oddball task. Potentials evoked by the target stimuli were sorted according to button-pressing response times, and the P3 waveform was analyzed both in stimulus-locked and response-locked averages, which were separately averaged for fast and slow responses. RESULTS: P3-like waveforms were identified in 180 sites in 17 patients. Three different types of P3-like waveforms, diffusely distributed within the brain, were found: (1) time-locked to the stimulus (30 sites in 11 patients); (2) time-locked to the motor response (52 sites in 13 patients); and (3) with ambiguous time relationship to stimulus and motor response (98 sites in 16 patients). CONCLUSIONS: The intracerebral P3-like waveform could represent different processes involved in performing active oddball tasks. Therefore, our results support the hypothesis that the P3 waveform registered by surface electrodes could be a heterogeneous phenomenon. SIGNIFICANCE: These results provide evidence that the P3 waveform is not only related to stimulus processing, which differs from what has been generally claimed in the literature.

Adult↗

PubMed2003

Variability of phase shift between blood pressure and heart rate fluctuations: a marker of short-term circulation control.

BACKGROUND: We postulated that the variability of the phase shift between blood pressure and heart rate fluctuation near the frequency of 0.10 Hz might be useful in assessing autonomic circulatory control. METHODS AND RESULTS: We tested this hypothesis in 4 groups of subjects: 28 young, healthy individuals; 13 elderly healthy individuals; 25 patients with coronary heart disease; and 19 patients with a planned or implanted cardioverter-defibrillator (ICD recipients). Data from 5 minutes of free breathing and at 2 different, controlled breathing frequencies (0.10 and 0.33 Hz) were used. Clear differences (P<0.001) in variability of phase were evident between the ICD recipients and all other groups. Furthermore, at a breathing frequency of 0.10 Hz, differences in baroreflex sensitivity (P<0.01) also became evident, even though these differences were not apparent at the 0.33-Hz breathing frequency. CONCLUSIONS: The frequency of 0.10 Hz represents a useful and potentially important one for controlled breathing, at which differences in blood pressure-RR interactions become evident. These interactions, whether computed as a variability of phase to define stability of the blood pressure-heart rate interaction or defined as the baroreflex sensitivity to define the gain in heart rate response to blood pressure changes, are significantly different in patients at risk for sudden arrhythmic death. In young versus older healthy individuals, only baroreflex gain is different, with the variability of phase being similar in both groups. These measurements of short-term circulatory control might help in risk stratification for sudden cardiac death.

Adult↗

PubMed2003

The effect of apomorphine administration on smooth pursuit ocular movements in early Parkinsonian patients.

Electrooculography (EOG) recordings in 21 L-DOPA-naive patients suffering from Parkinson's disease (PD) were made before and after apomorphine subcutaneous administration (ASA). The effect of apomorphine on smooth pursuit eye movements (SPEM) was studied. Age-matched healthy subjects, who underwent SPEM recordings without the ASA procedure, were examined in order to compare baseline SPEM. EOG recordings were used to compare the patient group and the control group, and to compare the SPEM before and after ASA within the patient group. Significant differences in SPEM were found between both groups, as well as in the SPEM before and after ASA. The theory that SPEM is disturbed in early PD patients was confirmed. The dopaminergic control of horizontal SPEM is supposed.

Adult↗

PubMed2002

Error processing--evidence from intracerebral ERP recordings.

Over the last decade, several authors have described an early negative (Ne) and a later positive (Pe) potential in scalp event-related potentials (ERPs) of incorrect choice reactions. The aim of the present study was to investigate the intracerebral origin and distribution of these potentials. Seven intractable epileptic patients participated in the study. A total of 231 sites in the frontal, temporal, and parietal lobes were investigated by means of depth electrodes. A standard visual oddball paradigm was performed, and electroencephalogram (EEG) epochs with correct and incorrect motor reactions were averaged independently. Prominent, mostly biphasic, ERP complexes resembling scalp Ne/Pe potentials were consistently observed in several cortical locations after incorrect trials. The most consistent findings were obtained from mesiotemporal structures; in addition to P3-like activity found after correct responses, an Ne/Pe complex was generally detected after incorrect trials. The Pe had a longer latency than the P3. Other generators of Ne/Pe-like potentials were located in different regions of the frontal lobe. The latency of the Ne was shortest in parietal, longer in temporal, and longest in frontal regions. Our findings firstly show that multiple cortical structures generate Ne and Pe. In addition to the rostral anterior cingulate cortex, the mesiotemporal and some prefrontal cortical sites seem to represent integral components of the brain's error-checking system. Secondly, the coupling of Ne and Pe to a complex suggests a common origin of Ne and Pe. Thirdly, the latency differences of the Ne across lobes suggest that the Ne is primarily elicited in posterior and temporal, and only later in frontal regions.

Adolescent↗