Ivan Rektor

13-PARAFAC decomposition of evoked potentials in patients treated by STN DBS

The effect of STN DBS (Deep Brain Stimulation of Subthalamic Nucleus) on the somatomotor network may differ from the effects on the cognitive networks ( Rektor et al., 2015 ). Thus, we acquired high-density (HD) scalp EEG data from 10 Parkinson’s disease patients with STN DBS during DBS ON and OFF state while performing 3-stimulus visual oddball task and we employed blind 3-way decomposition method called PARAFAC. We performed PARAFAC on 3-way data array ( Morup et al., 2008 ) composed by preprocessed averaged trials from all patients, both states (DBS ON/OFF) and all stimulus types. The resulting estimated PARAFAC components have 3 signatures - topography, time series and trial strength loadings for particular averaged trials. Finally, we compared loadings between trial types during both states by Wilcoxon test. PARAFAC revealed evoked activity which showed significant difference between loadings of frequent and target stimuli in the DBS ON state and no difference in DBS OFF. We transformed the topography of the component into the source space, which points to areas of the fronto-parietal attention network. PARAFAC decomposition of evoked potentials seems to be a helpful exploratory tool for HD EEG data. Our results also support a hypothesis that the DBS improves not only motor control but also affects cognitive networks. Acknowledgement: The research was supported by AZV grant 16-33798A and by CF MAFIL of CEITEC (supported by the CzechBI large RI project LM2015062, MEYS CR).

04-Local synchrony in EEG as a marker of epileptogenic zone

Approximately a 1/3 of epileptic patients suffer from pharmacoresistant epilepsy. The surgery is often the only possible treatment, which brings a need for finding epileptogenic zone. The task is intricate in non-lesional patients in whom magnetic resonance imaging is uninformative. Our goal is to find a set of non-invasive imaging methods that would find the epileptogenic zone. We show first results with Local Synchrony (LS) method, that evaluates functional connectivity between cortical areas in short distances. We acquired high-density electroencephalography (HD-EEG) data from a set of 25 healthy control subjects (HC) and from a set of epileptic patients. We computed the Corrected Imaginary Coherence (CIC) in source space among all possible pairs of adjacent solution points. The CIC image from each patient was compared with the HC images to reveal regions with increased LS. We performed the analysis for 5 patients. In one patient, the revealed regions matched the neurologist’s opinion based on clinical evaluation. In others, increased LS showed regions that might be potential candidates for epileptogenic zone according to clinical evaluation. The evaluation of LS seems to be a useful method that might bring valuable information in the stage of finding the epileptogenic zone in epilepsy patients. Acknowledgement This study was supported by the project 17-32292A of the Czech Health Research Council and We also acknowledge the core facility MAFIL of CEITEC supported by the Czech-BioImaging large RI project (LM2015062 funded by MEYS CR).

44. Dealing with noise in psychophysiological interaction analysis

Background In some fields of fMRI data analysis, it is apparent that a correct methodology is crucial to achieving meaningful results. This paper provides a first quantitative evaluation of the effects of different preprocessing and noise filtration strategies on the psychophysiological interactions (PPI) – method for analysis of fMRI data ( Friston et al., 1997 ), where noise management is not yet established. Materials and methods To assess these effects, both real fMRI data and simulated fMRI data were used. Two regions of interest (ROIs) were chosen for the PPI analysis on the basis of their engagement during the task. PPI terms were computed and used in a general linear model (GLM); group-level analyses followed. This first-level PPI analysis pipeline was performed for 32 different preprocessing and analysis settings, which included either data filtration with RETROICOR ( Glover et al., 2000 ) or no such filtration; different filtration of the ROI “seed” signal with a nuisance data-driven time series; and the involvement of these data-driven time series in the subsequent PPI GLM analysis ( Weissenbacher et al., 2009 ). The extent of the statistically significant results was quantified at the group level using simple descriptive statistics. Conclusion We conclude that different approaches for dealing with noise in PPI analysis yield appreciably different results. We definitely recommend the usage of RETROICOR. Filtering the ROI signal with data-driven signals and adding these signals to the GLM for assessing the PPI effects is apparently influential, but it is not clear whether their usage improves results in all cases.

P807: Basal ganglia in temporal lobe epilepsy – SEEG and fMRI studies

fusion on PASL-MRI that were adjacent to their lesions. Six patients showed normal findings or hypoperfusion on inter-ictal PASL-MRI in areas where CBF increased during peri-ictal states. Three patients showed epileptic abnormalities on EEG in regions that were almost concordant with areas showing hyperperfusion on PASL-MRI. Although 5 patients showed hyperintense areas on DWI, the remaining 5 patients failed to show hyperintense areas where PASL-MRI showed hyperperfusions. Conclusion: Although this study included a small sample size, PASL-MRI revealed significant changes in inter-ictal or peri-ictal states in patients with LRE and lesions. Thus, PASL-MRI is useful for identifying an epileptic focus.

P8.16 Neural cross-talk during discrimination of odds

Functional connectivity (FC) is crucial for cognition. Thus finding ways of increasing FC may facilitate improved cognitive performance. Our previous research demonstrates increased FC following Quadrato Motor training (QMT); a complex whole body movement technique performed in response to verbal commands; in female college students. Increased FC, specifically enlarged fronto-parietal alpha and temporal theta coherence, was accompanied by improved creativity and reaction time. However, while FC changes following motor training may be gender dependent, no research examined this issue. Therefore, the current study was aimed at examining gender dependent FC changes following motor training. 12 participants were tested (6 males) for FC changes following QMT. Electrophysiological changes were examined using a within-subject design, examining alpha and theta power and coherence. Cognitive performance was assessed using the Alternate Uses and Embedded Figures (EFT) tasks. Our main result was a distinct electrophysiological difference between females and males following QMT training; which mainly concerned significant decreased theta power and increased coherence in the female group. In addition, change in theta power was positively correlated with change in cognitive flexibility and negatively correlated with change in EFT in the female group; and positively correlated with change in EFT in the male group. Interestingly, increased cognitive flexibility following training was correlated with increased coherence in both genders. In conclusion, motor training has a differential effect on FC depending on gender and task context.

P5-24 Involvement of the subthalamic nucleus and globus pallidus internus in orientation and attention

disease (PD). In addition to motor symptoms, the patients with PD have been reported to show sensory processing deficits. Little has been reported on the effect of STN-DBS for sensory symptoms (especially temperature sensation and pain) in PD. The aim of this study is to quantitatively assess the effects of STN-DBS on temperature sensation and pain in PD by quantitative sensory testing. Methods: Participants were 17 patients with PD who underwent bilateral STN-DBS in Osaka University Hospital between 2001 and 2009 and 13 healthy controls. We assessed thermal thresholds for cold and warm and pain thresholds in the patients with PD in ‘DBS-ON’ and ‘DBS-OFF’ condition and in healthy controls by means of thermal quantitative sensory testing. Results: The cold sense and warm sense thresholds of the patients in ‘DBS-ON’ were significantly lower than those in ‘DBS-OFF’. And the cold sense and warm sense thresholds of the healthy controls ware significantly lower compared with those in ‘DBS-OFF’ of the patients with PD. On the other hand, the pain thresholds for cold and heat did not significantly differ between ‘DBS-ON’ and ‘DBS-OFF’. Conclusions: This finding suggested that temperature sensation of the patients with PD was disturbed compared with that of healthy controls, and STN-DBS could improve temperature sensation in the patients with PD. There are few reports about the effect and mechanisms of STN-DBS for temperature sensation. Therefore, we will report and discuss this result with consideration from literatures.

S13-2 Basal ganglia (BG) recording in epilepsy

Objective: The preictal, ictal and postictal oscillations in the BG (BG) were analyzed. The human BG did not generate specific epileptic EEG activity, neither interictal nor ictal (Rektor et al., 2002). Methods: Five epilepsy surgery candidates with temporal lobe epilepsy had depth electrodes implanted in the amygdalo-hippocampal complex (AH), temporal, cingulate, prefrontal and orbitofrontal cortices. All patients had diagonal electrodes targeted in hippocampus with contacts in BG, four patients in putamen and one in pallidum and caudate. The time frequency analysis, the power spectral analysis, the spectral coherence and correlation in time domain were used for analysis of EEG. Results: 1. Significant frequency components of 2 10 Hz were constantly observed in BG. In the other structures it appeared less constantly than in BG. The frequency of this component was reduced during seizures in BG. 2. There was a significant increase of power spectral density across all structures in all frequency ranges during epileptic seizures. Number of seizures with significant spectral power increase was highest in BG. 3. In the pre-ictal period, the coherency between oscillations in the putamen and AH, the cingulate and the pallidum/caudate were significant. Significant coupling between oscillations in the BG activity and in the AH were displayed during seizures. The relationship between the epileptic activity in BG and other studied structures was less significant. 4. The changes in the BG were consistent while the seizure activity spread over the cortex and partially persisted after the clinical seizure ended. They were inconsistent in the first period after the seizure onset. Conclusion: The BG most likely cannot generate seizures but the BG circuits might influence the cortical epileptic activity, via their feed-back pathways to the cortex. An inhibitory role of BG during temporal lobe seizures is suggested. Supported by Research Project MSM0021622404

P5-14 Time-frequency and spectral analysis of auditory executive event-related potentials in subthalamic nucleus

In our present work we have noted clear 8-10 Hz activity related to auditory ERPs. It is important to observe whether such an activity can be replicated in higher number of patients. We have not observed such an activity recorded from the globus pallidum internum in a patient with generalised dystonia (we do not report these results here). We also observed the major activation in frequency of 20 Hz and more in direct relation to P3-like potentials. Here, the correspondent changes were present in latencies of P3 potentials in standard and modified protocols.