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P1-7 Time frequency analysis of VEPs elicited by low spatial frequency and high reversal rate stimuli using complex demodulation method
S102 Amplitude, ratio of first harmonic (1F) and second harmonic (2F) components, and difference of those parameters between rectangular pattern and sinusoidal pattern were evaluated. Result: VEP amplitudes were gradually increased according to that the temporal frequency was increased from 6 to 12 Hz, and it was more remarkable for sinusoidal pattern. VEP amplitudes for both rectangular pattern and sinusoidal pattern obtained maximum value at the temporal frequencies of 10 12 Hz, and sinusoidal pattern was much larger. Characteristics of 1F and 2F component were also different between two patterns, especially for temporal frequency of 6 Hz. Discussion: VEP amplitude by the sinusoidal pattern was larger than that of rectangular pattern in the alpha frequency band. Detail analysis for relationship between VEP and posterior dominant alpha rhythm is required. Black-and-white shift in sinusoidal pattern was not so clear as compared with that in rectangular pattern. Those will be the reasons for difference of the characteristics on 1F and 2F components. P1-5 Depth-dependent changes in stereoscopic visual evoked potentials by dynamic random dot stereograms Y. Kasagi1 , I. Shimoyama1 , R. Okamoto1 , S. Yoshida1,2 1 Section for Human Neurophysiology, Research Center for Frontier Medical Engineering, Chiba University, Chiba, Japan, 2 Chiba Prefectural University of Health Sciences, Japan To examine the temporal and spacial properties of the human neuronal processing related to the binocular vision, we have studied and analyzed evoked Electroencephalograms (EEGs) as its transient responses to the stereoscopic visual stimulation. Four healthy volunteers with documented informed consent participated. EEGs were recorded at 19 sites with the balanced non-cephalic references. The signals were recorded with a band-pass filter between 0.5 and 100 Hz, and sampled at 1 KHz with 16-bit resolution. As the visual stimulation, we used dynamic random-dot stereogram (DRDS) movies which could extract the specific stereoscopic responses dissociated from the others like conventional VEPs. DRDS movies are composed of 30 frames per second of different random dot stereogram images, and displayed on a 55-inch digital light processing display 2.1 m distant viewed through a wireless electric liquid crystal shutter glasses which synchronize with switching rate (60 Hz) of the left/right visions, so that each pair of frame is recognized by the participants as a 3-dimensional (3D) checkerboard-like pattern with every adjacent square having different depths. These patterns appear and then disappear during one second, which lasts for tree minutes for one trial. Transient visual evoked potentials were obtained by averaging EEGs triggering at the time point of appearance for different depth difference between adjacent squares. Several common peaks were marked around latency 100 ms (positive), 200 ms (negative) and 300 ms (negative), each of which had different topography. The latency and/or voltage of these peaks changed according to the depth that the participants are supposed to recognize. These suggest that the human depth recognition entails quantitative changes in the neuronal activity of the visual pathway. P1-6 Extraction of M and P components of the visual evoked potential using pseudorandom stimulation with swept parameter technique K. Momose1 Faculty of Human Sciences, Waseda University, Saitama, Japan
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Objective: To develop a method of extract magnocellular (M) and parvocellular (P) components from VEP, the nonlinear system identification method using pseudorandom binary sequence (PRBS) stimulation combined with swept parameter technique was examined. Method: VEP elicited by luminance modulated sinusoidal gratings based on PRBS was recorded and their binary kernels were calculated as crosscorrelation between PRBS and VEP. To manipulate the magnitudes of M and P visual pathway responses in VEP, the spatial frequency of gratings were swept during the PRBS stimulation. VEP to this stimulation was recorded from 8 healthy participants and their binary kernels changes during the stimulation were evaluated. PRBS stimulation of 40950 ms period was repeated twice, and the spatial frequency was swept from 0.5 to 9 [c/deg] or 9 to 0.5 [c/deg] within the period. Results: Different waveforms of binary kernels obtained from the former and latter half of the PRBS stimulation were confirmed, and the waveforms were continuously changed during the stimulation. These changes were similar to those in previous studies which presented the
Posters relationship between M/P pathway responses and waveform of binary kernels obtained from conventional VEP measurement. The changes may reflect the M and P pathway contribution changes during the stimulation and depend on the spatial frequency sweeping. Conclusions: The suggested technique would be effective for studying and screening several eye and neurocognitive disorders which have been reported to relate with selective damage in M/P pathways. P1-7 Time frequency analysis of VEPs elicited by low spatial frequency and high reversal rate stimuli using complex demodulation method H. Yamazaki1,2 , Y. Kita1,3,4 , K. Yatabe1 , M. Inagaki1 National Institute of Mental Health, National Center of Neurology and Psychiatry, Tokyo, Japan, 2 International Medical Center of Japan, Kohnodai Hospital, Ichikawa, Japan, 3 Graduate School of Education, Tohoku University, Sendai, Japan, 4 Research Fellow of the Japan Society for the Promotion of Science, Tokyo, Japan
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Objective: Time frequency analysis of visual evoked potentials (VEPs) elicited by low spatial frequency, low contrast and high reversal rate stimuli was conducted through a complex demodulation (CD) method, which allows to describe particular frequency components of a time series as a function of time. Methods: Black and white sinusoidal gratings with spatial frequency of 0.27 c/deg were presented through CRT monitor. The contrast was 30%, mean luminance was 60 cd/m2 , viewing distance was 1.2m and the stimulus visual field extended 14.7º×11.2º. VEPs at Oz location by 80%contrast square gratings stimuli with spatial frequency of 4.3 c/deg were recorded in 3 healthy adults. Reversal rate from 15 to 2 rev/sec (step down method) were employed to investigate the temporal frequency characteristics for each stimuli. Evoked potential data were converted into text format and time frequency analysis was performed off-line by CD method (Trigger Event Viewer System, NoruPro Light System). Results: Low spatial and high temporal frequency sinusoidal visual stimuli produced clear and stable EPs in all subjects. And VEPs with high spatial frequency and high contrast stimuli were clearly recorded at any reversal rate. Through CD method, substantial amplitude of specific frequencies to each reversal rate was definitely obtained in the time series. Conclusion: Low spatial frequency, low contrast and high reversal rate stimuli i.e., M-stimuli are reported to be optimal to activate magnocellular visual processing system. However, the amplitudes of VEPs by M-stimuli were known to be smaller than those elicited by checkerboard pattern reversal VEPs. Since CD has a power to quantify the amplitude of specific oscillations, there is a possibility that magnocellular function will be selectively investigated in this method. P1-8 Retrieval-related facilitation of visual short-term memory by high motivation M. Sanada1 , K. Ikeda1 , K. Kimura1 , T. Hasegawa1 1 Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan Objective: Although it has been shown that motivation (e.g. monetary incentive) can enhance short-term memory (STM) capacity (Gilbert & Fiez, 2004), the underlying mechanisms of this effect are still largely unknown. STM can be decomposed into three core functional processes, that is, encoding, maintenance, and retrieval (Jonides et al., 2008). Recent progress in visual short-term memory (VSTM) research suggests that the first two of these are closely intertwined (Awh et al., 2006), so that the three processes can be reorganized into a dichotomic separation between encoding/maintenance and retrieval. Our objective is to investigate which of these two parts are more affected by motivational manipulation. Methods: We recorded ERP components (the contra-lateral delay activity; CDA, and the retrieval-related P3) during a change detection VSTM task. The CDA is elicited during the encoding/maintenance phase, and its amplitude correlates with the number of items stored in VSTM (Vogel et al., 2004). The retrieval-related P3 is observed during the change detection process, and supposedly reflects memory updating (Golob & Starr, 2004). Monetary incentives (100/30 monetary points) and memory array sizes (2/4) were manipulated. We predicted that (1) if motivation facilitates the encoding/maintenance functions, then the CDA will be enlarged, whereas (2) if motivation enhances the retrieval ability, the retrieval-related P3 will be augmented.
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Objective: To develop a method of extract magnocellular (M) and parvocellular (P) components from VEP, the nonlinear system identification method using pseudorandom binary sequence (PRBS) stimulation combined with swept parameter technique was examined. Method: VEP elicited by luminance modulated sinusoidal gratings based on PRBS was recorded and their binary kernels were calculated as crosscorrelation between PRBS and VEP. To manipulate the magnitudes of M and P visual pathway responses in VEP, the spatial frequency of gratings were swept during the PRBS stimulation. VEP to this stimulation was recorded from 8 healthy participants and their binary kernels changes during the stimulation were evaluated. PRBS stimulation of 40950 ms period was repeated twice, and the spatial frequency was swept from 0.5 to 9 [c/deg] or 9 to 0.5 [c/deg] within the period. Results: Different waveforms of binary kernels obtained from the former and latter half of the PRBS stimulation were confirmed, and the waveforms were continuously changed during the stimulation. These changes were similar to those in previous studies which presented the
Posters relationship between M/P pathway responses and waveform of binary kernels obtained from conventional VEP measurement. The changes may reflect the M and P pathway contribution changes during the stimulation and depend on the spatial frequency sweeping. Conclusions: The suggested technique would be effective for studying and screening several eye and neurocognitive disorders which have been reported to relate with selective damage in M/P pathways. P1-7 Time frequency analysis of VEPs elicited by low spatial frequency and high reversal rate stimuli using complex demodulation method H. Yamazaki1,2 , Y. Kita1,3,4 , K. Yatabe1 , M. Inagaki1 National Institute of Mental Health, National Center of Neurology and Psychiatry, Tokyo, Japan, 2 International Medical Center of Japan, Kohnodai Hospital, Ichikawa, Japan, 3 Graduate School of Education, Tohoku University, Sendai, Japan, 4 Research Fellow of the Japan Society for the Promotion of Science, Tokyo, Japan
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Objective: Time frequency analysis of visual evoked potentials (VEPs) elicited by low spatial frequency, low contrast and high reversal rate stimuli was conducted through a complex demodulation (CD) method, which allows to describe particular frequency components of a time series as a function of time. Methods: Black and white sinusoidal gratings with spatial frequency of 0.27 c/deg were presented through CRT monitor. The contrast was 30%, mean luminance was 60 cd/m2 , viewing distance was 1.2m and the stimulus visual field extended 14.7º×11.2º. VEPs at Oz location by 80%contrast square gratings stimuli with spatial frequency of 4.3 c/deg were recorded in 3 healthy adults. Reversal rate from 15 to 2 rev/sec (step down method) were employed to investigate the temporal frequency characteristics for each stimuli. Evoked potential data were converted into text format and time frequency analysis was performed off-line by CD method (Trigger Event Viewer System, NoruPro Light System). Results: Low spatial and high temporal frequency sinusoidal visual stimuli produced clear and stable EPs in all subjects. And VEPs with high spatial frequency and high contrast stimuli were clearly recorded at any reversal rate. Through CD method, substantial amplitude of specific frequencies to each reversal rate was definitely obtained in the time series. Conclusion: Low spatial frequency, low contrast and high reversal rate stimuli i.e., M-stimuli are reported to be optimal to activate magnocellular visual processing system. However, the amplitudes of VEPs by M-stimuli were known to be smaller than those elicited by checkerboard pattern reversal VEPs. Since CD has a power to quantify the amplitude of specific oscillations, there is a possibility that magnocellular function will be selectively investigated in this method. P1-8 Retrieval-related facilitation of visual short-term memory by high motivation M. Sanada1 , K. Ikeda1 , K. Kimura1 , T. Hasegawa1 1 Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan Objective: Although it has been shown that motivation (e.g. monetary incentive) can enhance short-term memory (STM) capacity (Gilbert & Fiez, 2004), the underlying mechanisms of this effect are still largely unknown. STM can be decomposed into three core functional processes, that is, encoding, maintenance, and retrieval (Jonides et al., 2008). Recent progress in visual short-term memory (VSTM) research suggests that the first two of these are closely intertwined (Awh et al., 2006), so that the three processes can be reorganized into a dichotomic separation between encoding/maintenance and retrieval. Our objective is to investigate which of these two parts are more affected by motivational manipulation. Methods: We recorded ERP components (the contra-lateral delay activity; CDA, and the retrieval-related P3) during a change detection VSTM task. The CDA is elicited during the encoding/maintenance phase, and its amplitude correlates with the number of items stored in VSTM (Vogel et al., 2004). The retrieval-related P3 is observed during the change detection process, and supposedly reflects memory updating (Golob & Starr, 2004). Monetary incentives (100/30 monetary points) and memory array sizes (2/4) were manipulated. We predicted that (1) if motivation facilitates the encoding/maintenance functions, then the CDA will be enlarged, whereas (2) if motivation enhances the retrieval ability, the retrieval-related P3 will be augmented.