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37. Automatic detection of dominant rhythm and slow wave with short duration in automatic EEG interpretation system
Society Proceedings / Clinical Neurophysiology 123 (2012) e87–e100
video-EEG with electrodes placed 10–20 scalp-electrode position, and electoromyograms (EMGs) were simultaneously recorded from the bilateral deltoid muscles. In each ictal event, artifact-free segment of 5 s before and after EMG onset of spasm was selected to analyze the power spectrum by multiple band frequency analysis (MBFA). Each power spectrum of spasms in a series was averaged by triggering EMGs. Ictal 45–110 Hz HFOs preceding each PSs were captured in all patients, and they presented over the area around the lesions on MRI. The resection of the lesion including the area of HFOs stopped PSs in one patient. Incomplete resection of area of ictal HFOs in the other 2 patients remained PSs. The area of ictal HFOs by averaging on scalp EEG during PSs represented the epileptogenic zone. doi:10.1016/j.clinph.2012.02.034
34. Comparison between ictal DC shifts and high frequency oscillation (HFO) recorded from subdural electrodes in epilepsy— Kyoko Kanazawa, Riki Matsumoto, Hisaji Imamura, Masao Matsuhashi, Takeharu Kunieda, Nobuhiro Mikuni, Susumu Miyamoto, Ryosuke Takahashi, Akio Ikeda (Department of Neurology, Kyoto University, Kyoto, Japan) To assess clinical usefulness of ictal DC shifts and HFO for delineating epileptogenic zone, we analyzed the two recorded from subdural electrodes implanted in 12 patients with partial epilepsy [glioma (Gli) = 4, focal cortical dysplasia (FCD) = 8], and correlated them with pathology. Ictal DC shifts and HFO were recorded with band pass filter of 0.016–600 Hz and sampling rate of 2000 Hz. As the results: (1) Both ictal DC shifts and HFO occurred in 4 patients, only DC shifts in 4, and only HFO in 1. Three patients showed neither DC shifts nor HFO. Once ictal DC shifts or HFO occurred, occurrence rate was 64.1–100.0% and 31.0–100.0%, respectively. (2) DC shifts occurred in 75.0% and 50.0% in Gli and FCD patients, respectively, and HFO in 50.0% and 37.5% similarly. (3) In each individual patient, electrodes with ictal DC shifts and HFO were common. (4) Two Gli patients with both DC shifts and HFO had also FCD pathology, and longer duration of intractable epilepsy. We concluded that both DC shifts and HFO complementarily contributed to delineate epileptogenic zone, and the two possibly tended to occur in Gli with FCD pathology and longer disease duration. doi:10.1016/j.clinph.2012.02.035
35. Brain responses to morphing human face into monkey face— Emi Yamada, Katsuya Ogata, Tomokazu Urakawa, Shozo Tobimatsu (Kyushu University, Fukuoka, Japan) Humans are able to recognize their own faces better than those of other species (e.g., monkeys). However, the neural basis of such phenomenon remains unknown. To elucidate this issue, a 128-ch highdensity event-related potential were recorded in 13 healthy adults during viewing morphing faces. We used 7 types of morphing faces with different ratios of human (H)/monkey (M) (H/M: 9/1 (F1), 7/3 (F2), 6/4 (F3), 5/5 (F4), 4/6 (F5), 3/7 (F6) and 1/9 (F7)). These stimuli were presented for 500 ms. The mean luminance, contrast and spatial frequency were adjusted to avoid inter-stimulus physical variances among the stimuli. In all stimuli, N170 and the late positive (LP) component (400–600 ms) were elicited as the major components in the temporo-occipital regions. The decrease ratio of human face contributed to both small and prolonged N170. Its latency was along prolonged. The amplitude of LP component for F1 and F7 were larger than those of others. These findings suggest that (1) N170
e95
reflects species-specific face processing, and (2) the LP component processes the difference in clearness of face stimuli. Therefore, we conclude that the identification of species starts at around 170 ms, then detailed feature of faces are analyzed after 400 ms. doi:10.1016/j.clinph.2012.02.036
36. ERP changes during simultaneous presentation of audio–visual stimuli—Taichi Hirayama, Hiroaki Shoji, Hisaki Ozaki (Ibaraki University, Mito, Japan) Audio–visual neural interaction was examined by using ERPs. EEGs were recorded from 19 locations. The vowels (/a/ or/i/) pronounced by a Japanese male or white-noise (/noise/) were used as auditory stimuli. Visually presented face pronouncing vowel ([a] or [i]) was used as visual stimulus. Auditory and visual stimuli were simultaneously presented in Audio–Visual condition (AV), i.e., (1) phonetically congruent (auditory:/a/, visual:[a]), (2) incongruent (auditory:/a/, visual:[i]), (3) deviant (auditory:/noise/, visual:[a]) stimulus pair was used. Crossmodal interaction was examined by subtracting ERP in auditory (A) or visual (V) condition from ERP in AV condition. Compared to unimodal auditory stimulus (A), residual auditory data (AV–V) in AV condition showed large N1 components at frontal area in all stimulus pair. This result might be related to an augmented attentional resource due to bimodal information. Compared to unimodal visual stimulus (V), residual visual data in ‘‘congruent’’ AV–A drove increased P1 component at occipital area. In visual modality, increased attentional resource might be selectively needed for congruent stimulus. Significantly decreased N170 component was observed only for female group in ‘‘congruent’’ AV–A. Since N170 component is considered to reflect coding of facial parts, this result might suggest suppression of neural face processing by female. doi:10.1016/j.clinph.2012.02.037
37. Automatic detection of dominant rhythm and slow wave with short duration in automatic EEG interpretation system—Shigeto Nishida, Takenao Sugi, Akio Ikeda, Takashi Nagamine, Hiroshi Shibasaki, Masatoshi Nakamura (Fukuoka Institute of Technology, Fukuoka, Japan) An automatic interpretation system for an awake background EEG has been developed by the authors, and gave satisfactory results. The detection of EEG components (dominant rhythm and slow wave) is important in this system. However, it is difficult to detect the EEG component, which appears in short time, because the EEG component is detected based on the power spectrum for the EEG data of 5 s in this system. In this study, a method for detecting the dominant rhythm and the slow wave with short duration by using AR (autoregressive) model is proposed. First, AR models are constructed for the EEG data of short period, and peak frequency and power of main component in short period are calculated from the poles of AR models. The dominant rhythm and the slow wave are detected by using these parameters. The proposed method was applied for EEG data, and brought satisfactory results. Furthermore, the proposed method can judge the ‘‘organization of dominant rhythm’’ and ‘‘rhythmicity of slow wave’’. By introducing the proposed method in the automatic EEG interpretation system, this system becomes more powerful for assisting the electroencephalographer for their EEG interpretation. doi:10.1016/j.clinph.2012.02.038
video-EEG with electrodes placed 10–20 scalp-electrode position, and electoromyograms (EMGs) were simultaneously recorded from the bilateral deltoid muscles. In each ictal event, artifact-free segment of 5 s before and after EMG onset of spasm was selected to analyze the power spectrum by multiple band frequency analysis (MBFA). Each power spectrum of spasms in a series was averaged by triggering EMGs. Ictal 45–110 Hz HFOs preceding each PSs were captured in all patients, and they presented over the area around the lesions on MRI. The resection of the lesion including the area of HFOs stopped PSs in one patient. Incomplete resection of area of ictal HFOs in the other 2 patients remained PSs. The area of ictal HFOs by averaging on scalp EEG during PSs represented the epileptogenic zone. doi:10.1016/j.clinph.2012.02.034
34. Comparison between ictal DC shifts and high frequency oscillation (HFO) recorded from subdural electrodes in epilepsy— Kyoko Kanazawa, Riki Matsumoto, Hisaji Imamura, Masao Matsuhashi, Takeharu Kunieda, Nobuhiro Mikuni, Susumu Miyamoto, Ryosuke Takahashi, Akio Ikeda (Department of Neurology, Kyoto University, Kyoto, Japan) To assess clinical usefulness of ictal DC shifts and HFO for delineating epileptogenic zone, we analyzed the two recorded from subdural electrodes implanted in 12 patients with partial epilepsy [glioma (Gli) = 4, focal cortical dysplasia (FCD) = 8], and correlated them with pathology. Ictal DC shifts and HFO were recorded with band pass filter of 0.016–600 Hz and sampling rate of 2000 Hz. As the results: (1) Both ictal DC shifts and HFO occurred in 4 patients, only DC shifts in 4, and only HFO in 1. Three patients showed neither DC shifts nor HFO. Once ictal DC shifts or HFO occurred, occurrence rate was 64.1–100.0% and 31.0–100.0%, respectively. (2) DC shifts occurred in 75.0% and 50.0% in Gli and FCD patients, respectively, and HFO in 50.0% and 37.5% similarly. (3) In each individual patient, electrodes with ictal DC shifts and HFO were common. (4) Two Gli patients with both DC shifts and HFO had also FCD pathology, and longer duration of intractable epilepsy. We concluded that both DC shifts and HFO complementarily contributed to delineate epileptogenic zone, and the two possibly tended to occur in Gli with FCD pathology and longer disease duration. doi:10.1016/j.clinph.2012.02.035
35. Brain responses to morphing human face into monkey face— Emi Yamada, Katsuya Ogata, Tomokazu Urakawa, Shozo Tobimatsu (Kyushu University, Fukuoka, Japan) Humans are able to recognize their own faces better than those of other species (e.g., monkeys). However, the neural basis of such phenomenon remains unknown. To elucidate this issue, a 128-ch highdensity event-related potential were recorded in 13 healthy adults during viewing morphing faces. We used 7 types of morphing faces with different ratios of human (H)/monkey (M) (H/M: 9/1 (F1), 7/3 (F2), 6/4 (F3), 5/5 (F4), 4/6 (F5), 3/7 (F6) and 1/9 (F7)). These stimuli were presented for 500 ms. The mean luminance, contrast and spatial frequency were adjusted to avoid inter-stimulus physical variances among the stimuli. In all stimuli, N170 and the late positive (LP) component (400–600 ms) were elicited as the major components in the temporo-occipital regions. The decrease ratio of human face contributed to both small and prolonged N170. Its latency was along prolonged. The amplitude of LP component for F1 and F7 were larger than those of others. These findings suggest that (1) N170
e95
reflects species-specific face processing, and (2) the LP component processes the difference in clearness of face stimuli. Therefore, we conclude that the identification of species starts at around 170 ms, then detailed feature of faces are analyzed after 400 ms. doi:10.1016/j.clinph.2012.02.036
36. ERP changes during simultaneous presentation of audio–visual stimuli—Taichi Hirayama, Hiroaki Shoji, Hisaki Ozaki (Ibaraki University, Mito, Japan) Audio–visual neural interaction was examined by using ERPs. EEGs were recorded from 19 locations. The vowels (/a/ or/i/) pronounced by a Japanese male or white-noise (/noise/) were used as auditory stimuli. Visually presented face pronouncing vowel ([a] or [i]) was used as visual stimulus. Auditory and visual stimuli were simultaneously presented in Audio–Visual condition (AV), i.e., (1) phonetically congruent (auditory:/a/, visual:[a]), (2) incongruent (auditory:/a/, visual:[i]), (3) deviant (auditory:/noise/, visual:[a]) stimulus pair was used. Crossmodal interaction was examined by subtracting ERP in auditory (A) or visual (V) condition from ERP in AV condition. Compared to unimodal auditory stimulus (A), residual auditory data (AV–V) in AV condition showed large N1 components at frontal area in all stimulus pair. This result might be related to an augmented attentional resource due to bimodal information. Compared to unimodal visual stimulus (V), residual visual data in ‘‘congruent’’ AV–A drove increased P1 component at occipital area. In visual modality, increased attentional resource might be selectively needed for congruent stimulus. Significantly decreased N170 component was observed only for female group in ‘‘congruent’’ AV–A. Since N170 component is considered to reflect coding of facial parts, this result might suggest suppression of neural face processing by female. doi:10.1016/j.clinph.2012.02.037
37. Automatic detection of dominant rhythm and slow wave with short duration in automatic EEG interpretation system—Shigeto Nishida, Takenao Sugi, Akio Ikeda, Takashi Nagamine, Hiroshi Shibasaki, Masatoshi Nakamura (Fukuoka Institute of Technology, Fukuoka, Japan) An automatic interpretation system for an awake background EEG has been developed by the authors, and gave satisfactory results. The detection of EEG components (dominant rhythm and slow wave) is important in this system. However, it is difficult to detect the EEG component, which appears in short time, because the EEG component is detected based on the power spectrum for the EEG data of 5 s in this system. In this study, a method for detecting the dominant rhythm and the slow wave with short duration by using AR (autoregressive) model is proposed. First, AR models are constructed for the EEG data of short period, and peak frequency and power of main component in short period are calculated from the poles of AR models. The dominant rhythm and the slow wave are detected by using these parameters. The proposed method was applied for EEG data, and brought satisfactory results. Furthermore, the proposed method can judge the ‘‘organization of dominant rhythm’’ and ‘‘rhythmicity of slow wave’’. By introducing the proposed method in the automatic EEG interpretation system, this system becomes more powerful for assisting the electroencephalographer for their EEG interpretation. doi:10.1016/j.clinph.2012.02.038