Epilepsy and Behaviour: A Literature Review

1. Epilepsy and Behaviour:A Literature Review Amir Omidvarnia Nov. 23, 2009

2. 1.Perceptual Flexibility After Frontal or Temporal Lobectomy (1994) • The study is completely behavioural. • 31 patients who had undergone focal cortical surgery were compared with 10 control subjects. • Authors wanted to know if there is any difference between Right and Left Frontal lobes in ‘shift visual perspective’ ability. • Result: Right Frontal lobe has an important role in the ability to shift visual perspective.

3. 1.Perceptual Flexibility After Frontal or Temporal Lobectomy (1994) • An example of stimulation cards: Subjects were requested to identify two objects in this picture (an Inuit or a facing to the left human)

4. 2.Effects of epilepsy on recognition memory (1994) • This study is related to the effects of temporal and temporal plus extra-temporal epilepsies on recognition memory performance. • Two groups of patients were involved: in patients with unilateral temporal lobe epilepsy and in patients with combined temporal and extra-temporal (frontal or parietal) epileptogenic foci. • A two-part learning and recognition task was used, 40 verbalizable pictures for the first task and 80 ones for the second task.

5. 2.Effects of epilepsy on recognition memory (1994) • Characteristics of ‘Old/New’ ERP signals such as N400 or P600 components have been studied. • ERPs have been recorded from 4 depth electrodes in hippocampal region. • Both ERP characteristics and behavioural results have been analysed. • Result: Frontal and Parietal regions contribute in hippocampal ERP modulation.

6. 3.Effects of Left and Right TLE on interval timing performance (1999) • 10 patients with Left TLE and 9 patients with Right TLE along with a 14 individuals control group have been involved. • Temporal reproduction task: subjects have been requested to re-produce visual stimulus duration. • Temporal discrimination task: subjects have been requested to discriminate ‘SHORT’ and ‘LONG’ stimuli.

7. 3.Effects of Left and Right TLE on interval timing performance (1999) • Psychophysics functions have been obtained and some behavioural information have been extracted (such as Weber fractions etc). • The authors have used statistical analysis methods for their conclusions. • Result: Performance of the Left and Right TLE patients are different on these tasks.

8. 4.Effects of medial TL lesions on recognition memory (2000) • 13 Left TLE, 16 Right TLE and 13 normal subjects were involved. • ERP signals were recorded using seven surface electrodes (Pz, Cz, Fz, T5, T6, C3 and C4) according to 10-20 standard. • ‘Old/New’ effect was studied using a continuous verbal recognition memory task regarding ‘inter-item lag’ parameter (time distance between words).

9. 4.Effects of medial TL lesions on recognition memory (2000) • While behavioural results don’t show any difference between patients and control group, ERP characteristics reflect some differences between them. • Result: ERP waveform of Left TLE patients are pretty different with Right TLE’s and control group. Therefore, medial temporal structures play a role in ‘Old/New’ effect projected on the scalp.

10. 5.Contribution of frontal cortex in auditory stimulus changes (2001) • A case study: study on the role of prefrontal cortex in auditory processing in a 6-year-old girl with three different types of epileptic seizures • The authors wanted to see if there is any contribution of ERP signals directly recorded from frontal cortex (N1 and MMN components) by changes in non-phonetic and phonetic sounds. • Three bilateral sub-dural electrode strips have been used for ERP signal recording.

11. 5.Contribution of frontal cortex in auditory stimulus changes (2001) • Three types of auditory tasks have been adopted: random sequences of standard tones, deviant tones or complex sound such as phone ring, standard syllables and vibratory stimuli (I think the former is not an auditory task). • Result: Right Lateral prefrontal cortex is related to early stages of processing repeating sounds and sound changes.

12. 6.Temporal lobe epilepsy and verbal memory (2002) • 42 unilateral TLE patients • The authors wanted to know about the relationship between the performance of verbal memory tests and temporal lobe structures (medial temporal lobe are thought to be related to explicit memory and neocortical regions are responsible for perceptual and conceptual implicit memory). • two groups of tasks have been applied.

13. 6.Temporal lobe epilepsy and verbal memory (2002) • For implicit memory test, word identification and word generation tasks have been used. For explicit memory test, word recognition and recall tasks have been adopted. • Only behavioural analysis has been reported and. • Result: performance of TLE patients in implicit memory test was similar to the control group, while they have shown lower performance in explicit memory test rather than normal persons.

14. 7.Involvement of visual pathways in the processing of non-provocative visual stimuli (2007) • 15 photosensitive patients with local-PPR, 15 photosensitive patients with propagating-PPR and 17 PPR-negative have been involved. • The authors wanted to investigate the level of involvement of magnocellular and parvocellular pathways in the processing of non-provocative visual stimuli. • Checkerboard visual stimulus with different spatial frequencies has been adopted.

15. 7.Involvement of visual pathways in the processing of non-provocative visual stimuli (2007) • VEP signals have been recorded through 21 surface electrodes. • Morphological characteristics of VEP waveforms (N75-P100 and P100-N135 components) have been studied. • Result: local-PPR individuals had normal VEP amplitudes, while propagating-PPR subjects showed an increase in N-75-P100 and P100-N135 components. The result show that local-PPR and propagating-PPR are pathophysiologically distinct from each other.

16. 7.Involvement of visual pathways in the processing of non-provocative visual stimuli (2007) • Result: spatial frequency doesn’t have any effect on the results. In other words, increment in VEP amplitude is independent from spatial frequency.

17. 8.déjà vu (2008) • A case study: a 39-yaer-old male with TLE who has persistent sensation of déjà vu. • It is thought that ‘familiar elements’ for the perceived stimulus are the main reason of déjà vu. But this subject whose sensations of déjà vu persist long enough for him to shift his perceptual focus a number of times during the experience, spontaneously reports that these shifts make no difference to the sensation experienced.

18. 8.déjà vu (2008) • No specific behavioural task has been used in this study. • There is not any analytical results in the paper. • Conclusion: it seems that ‘familiar elements’ in perceptual stimuli are not the main cause of déjà vu. Déjà vu is probably the result of a cognitive feeling produced of the erroneous activation of neural familiarity circuits such as the parahippocampal gyrus which persist as long as this activation persists.

19. 9.Epileptic seizure prediction with a mental simulation task (2008) • 2 Right TLE patients, a Left frontotemporal patient and an IGE patient were involved. • The authors have suggested that the dependency of the performance of a specific task during preictal phase may reflect changes in brain state hours before seizure onset. • Two tasks have been used: observation or execution of a movement and mental simulation of a movement. The movement can be biological or non-biological.

20. 9.Epileptic seizure prediction with a mental simulation task (2008) • All subjects were regularly contacted in a 29 day period. They have been requested to do these tasks every day at the same time. Also they were required to indicate accurately the day, hour, and behavioural situation in which seizures occurred. • Mean Proportional Error (MPE) criteria were calculated for each subject and their correlations with seizure onsets were studied. • Result: a phase dependency in Right TLE patients could be observed.

21. 10.MT+ lesions and contralateral motion processing (2008) • Both right and left MT+ regions are involved in motion processing, but it is not clear which of them is more important. • A 19-year-old Left temporal-occipital lobe epilepsy patient who would complain that something was ‘wrong’ with his vision. His left MT+ region was impaired during his seizure evolution period. • Three tasks were used: full-field motion detection task, hemifield motion attention task and hemifield picture identification.

22. 10.MT+ lesions and contralateral motion processing (2008) • EEG signals and MRI images have been recorded for monitoring active regions of the subject during each task. • Only behavioural results of the patient with other normal persons in control group have been compared. • Result: left MT+ region is necessary for normal motion processing.

23. 10.MT+ lesions and contralateral motion processing (2008)

24. 11.VEP signals for diagnosis of photosensitivity instead of PPR (2008) • Normally, subjects are stimulated by some specific stimuli such as stroboscopic light stimulus until a PPR occurs. • In this paper, the authors have suggested that VEP signals can be used effectively for diagnosis of PSE instead of PPR. • 15 PSE patients and 7 normal subjects have been selected.

25. 11.VEP signals for diagnosis of photosensitivity instead of PPR (2008) • VEP signals have been recorded with visual stimuli that did not provoke PPR such as flashing light stimulus. • 18 different features have been extracted from their VEP signals and classified with several statistical classifiers. • A frequency term and a goodness of fit term to a particular template were able to predict about the photosensitivity of the subject.

26. 11.VEP signals for diagnosis of photosensitivity instead of PPR (2008) • Result: VEP signals have some information about PSE.

27. 12.Temporal lobe epilepsy does not impair visual perception (2008) • 25 TLE subjects and 27 control subjects have been involved. • Luminance discrimination and frequency discrimination stimuli have been tested on TLE patients. • Any difference between the performance of patients and control subjects have not been observed on studied tasks.

28. 12.Temporal lobe epilepsy does not impair visual perception (2008) • Only behavioural data have been analysed. • Result: TLE does not have any effect on visual perception.

29. 13.VEP indices of cortical lateral interactions in epilepsy treatments (2009) • 38 patients who used AEDs (tiagabine, topiramate, felbamate and gabapentin) have been compared with control group. • The fundamental and 2nd-harmonic components of the VEP steady-state responses were adopted to extract Indices which can reflect facilitatory (FI) and suppressive (SI) cortical interactions. • Two studies have been carried out. The first one has been concentrated on the impacts of AEDs on SI and FI.

30. 13.VEP indices of cortical lateral interactions in epilepsy treatments (2009) • The second one has been concentrated on the impacts of neurostimulation therapy on epileptic patients under chronic vagus nerve stimulation (VNS) treatment. • Windmill/Dartborad, checkerboard and another Delphi-based stimulus were used for activating VEP steady state responses. • Result: VEP’s can be used as a criterion reflecting cortical lateral interactions and medication-specific changes in them.

31. 14.Comparison of motor cortical excitability in focal and generalized epileptic patients (2009) • 25 patients (FE and IGE) and 20 normal subjects were studied. EMG signals were used. • Motor cortical inhibition and facilitation regarding changes in Stimulus Intensity (SI) were measured in the shape of Stimulus-Response curves. • S-R curves were compared with TMS measures such as CSP, MT and ICF. • Result: motor cortical inhibition in IGE patients is less effective the FE patients.