Investigation of the behavioural and cognitive effects of epilepsy in adults

1. Investigation of the behavioural and cognitive effects of epilepsy in adults Amir Omidvarnia Andrew Bagshaw Harriet Allen

2. Outline • Introduction • Some definitions • Tasks

3. Introduction • Epilepsy may affect behaviour and cognition in the patients. • Several factors can play role in the impairments such as the location of the seizure foci (e.g. TLE, OLE etc), seizure type, duration of epilepsy.

4. Introduction • A potential way to investigate the effects of epilepsy on behaviour, cognition and perception is to compare the performance of participants without epilepsy with groups of patients with foci in different brain regions on well chosen attentional or behavioural tasks.

5. Outline of the research • Six behavioural, attentional and cognitive tasks have been piloted to investigate the effects of epilepsy on visual cognition, language functioning and memory processing. • These tasks can be used to record ERP (Event-Related Potential) signals or fMRI data of the participants.

6. What is Evoked-Related Potential (ERP) Signal?

7. ERP signals • An evoked potential (or "evoked response") is an electrical potential recorded from the nervous system of a human or other animal following presentation of a stimulus, as distinct from spontaneous potentials as detected by EEG or EMG (Wikipedia).

8. ERP Signals • There are several kinds of ERP signals such as Visual Evoked Potentials (VEPs), Auditory evoked Potentials (AEPs) etc. • The general waveform of the ERP signals depends on the stimuli which are presented to the subject.

9. Pattern Reversal VEP

10. Flash VEP

11. Tasks

12. Checkerboard Task • Checkerboard stimulus produces pattern Reversal VEPs which is a standard PR VEP waveform in all VEP studies.

13. Vertical Grating Task • We developed a vertical grating task to investigate the dependency of EEG gamma frequency and amplitude with epilepsy.

14. Language Task • This task has been used to explore a potential non-invasive approach for pre-surgical evaluation of language lateralization in epilepsy surgeries.

15. N-Back Task • The same as the language task, this task may be used for pre-surgical evaluation of working memory functionality.

16. Suppression task • This task is useful for evaluation of centre-surround antagonism in receptive fields of photoreceptor cells of the retina. This effect is necessary for edge detection and contrast enhancement.

17. Orientation Discrimination Task • Using this task, we can compare the ability of global orientation processing in early visual processing system (V1 area) between control subjects and people with epilepsy.

18. Behavioural Measurements • Reaction time • Success rate • False alarm • Psychometric functions (depend on the tasks)

19. EEG recording • EEG markers are sent to the recording software through the parallel port. • Accurate timing is very important. • VEP trials should be averaged to be ready for further analysis

20. For Future... • EEG recording for both control group and patients group • Recording of the EEG signals and fMRI data simultaneously (EEG-fMRI data)

21. Thanks for your patience