Ana Branka Šefer

Ocular and Cervical Vestibular Evoked Myogenic Potentials in Patients With Multiple Sclerosis

Objectives: The aim of this study was to evaluate latencies and corrected p13-n23 cervical vestibular evoked myogenic potentials (cVEMP) and n10-p13 ocular vestibular evoked myogenic potentials (oVEMP) amplitudes in patients with relapsing remitting multiple sclerosis (MS). Methods: This was a prospective, case-control study. Thirty patients with MS and 15 healthy controls were included. Cervical vestibular evoked myogenic potentials and oVEMP in response to acoustic clicks of 1 ms duration at the intensity of 130 dB SPL and the stimulation frequency of 1 Hz were studied. Signals were divided in segments of 120 ms duration (20 ms before the stimulus and 100 ms after the stimulus) and averaged. Results: In MS group, there was significant latencies prolongation of all sternocleidomastoid responses (p13 and n23) and n10 response of the ocular muscles. The sternocleidomastoid p13-n23 normalized amplitude was significantly higher in MS patients. Prolonged latencies were found in 57% and conduction block in 7% of patients in at least one sternocleidomastoid response in the MS group. Prolonged latencies were found in 30% and conduction block in 40% of patients in at least one ocular response in the MS group. When cVEMP and oVEMP are combined, 80% had pathological finding. When correlating brainstem clinical, brainstem MRI, and cVEMP findings, there was no statistical significance (brainstem clinical vs. cVEMP P = 0.1; brainstem MRI vs. cVEMP P = 0.82). When correlating brainstem clinical, brainstem MRI and oVEMP findings, there was a statistical significant correlation between brainstem clinical versus oVEMP, P = 0.02, whereas there was no statistical significance between brainstem MRI versus oVEMP (P = 0.38). Conclusions: Combination of cVEMP and oVEMP in MS patients allows better estimation of brainstem lesions.

Movement Related Evoked Potentials in Parkinson’s Disease Patients and Healthy Controls

The aim of this study was to demonstrate the role of movement related evoked cortical potentials (MREP) in Parkinson’s disease (PD) diagnostics. The experiment consisted of repeated spontaneous thumb movements in a time interval of 5-10 s. There were two groups of subjects, PD patients and healthy controls. We observed shift in the latency of the beginning of MREP, the Bereitschaftpotential (BP), in patients with PD. The BP started earlier for healthy controls than for the PD patients when the PD patient’s affected hand movement was observed. The BP latency shift was observed for the affected hand, but the beginning of the BP was not influenced for the healthy hand. The later components of MREP were not significantly influenced. The PD patients group was diverse and in accordance with that the standard deviations of MREP components’ amplitudes for this group was much greater that for the controls group.

Influence of the set size and probe item affiliation in the Sternberg memory task on auditory event-related potentials

The purpose of this study is to examine cerebral dynamics that occur as a result of memorizing and retrieving information from working memory. A modified Stenberg memory task was performed. We recorded auditory eventrelated potentials evoked by the memory task. Subjects were healthy adults with no auditory impairments. During the Sternberg experiment, sets of two or four digits were acoustically presented to subjects. After the last item in the set, the target digit (probe) was presented. Subjects had to indicate whether the probe did (positive probe) or didn’t (negative probe) belong to the presented set by pressing appropriate buttons. According to the obtained results the reaction time increases with the increase of the memory set size. The activity in the period in which subjects rehearse the previously presented set is stronger expressed for the set consisted of two items. For the set of two digits the MPW appears earlier and its amplitude is greater than for the set of four digits. The amplitude of the major positive wave (MPW) is greater for the positive probe than for the negative probe, and the latency of the MPW evoked by the negative probe is greater than for the positive probe. Obtained results correspond to the presently accepted theory, but there are also interesting features for further research.

Movement related potentials in spontaneous and provoked thumb movement

In order to get better insight in the brain electrical activity generated during the preparatory and executive phases of body movement we recorded the movement related evoked potentials (MREP) in three different experimental conditions. First, in the voluntary movement, then in the condition where the movement was performed as a reaction to acoustical signal and finally, in the condition where two different tones where presented and the movement was made after the target one (choice reaction). In both cases the reaction time was also measured. The obtained results clearly showed that apparently equal movements where accompanied with different cerebral dynamics. The self paced movement preparatory phase, reflected in bereitschaft potential (BP) and negative slope potential (NS), lasts longer. The activity was located in the temporal brain region. In the executive phase motor potentials (MP) were generated in parietal region and also in temporal region where motor cortex areas are situated. In the second experiment preparatory phase was shorter. The activity was located in the frontal brain region in the first moment and after that it caught the hole left half of the brain. The bigger influence had executive phase with motor potentials (MP). The majority of activity was situated in the left temporal brain region where three the most conspicuous areas of activity were found. Amplitudes in this part were much higher then in the self paced movement. The results of the third experiment showed that reaction time was longer. This was visible from the moments of the activations of the same brain regions compared with their activations in the second experiment. Longer reaction time can be explained with the influence of the cognitive component that was needed because of the complexity of the task. In the third experiment amplitudes were even higher than in the second experiment.