Objective detection of the flicker fusion threshold with pupil diameter and visual evoked magnetic field
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1
National Institute of Advanced Industrial Science and Technology, Japan
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2
Ciba University, Singapore
Introduction: The progressive diminution of frequency of the flicker fusion threshold was observed in the process of the development of the fatigue stage[1]. The ordinal detection of the flicker fusion threshold was decided from the subjective judgment of the flickering state of visual stimulus and a response by pressing a button. This process was not free from the arbitrariness of human responses. Non-arbitrary detection of a flicker fusion threshold was investigated from differences in the responses of pupil diameter and the visual evoked magnetic field (VEF) for flickering visual stimulation with a frequency over or under the flicker fusion threshold. Methods: Exp.1: Two flickering visual stimulus durations with a frequency under or over 7.5Hz from the threshold were presented to subjects. There was a 3sec omission time between 10 sec of flicker durations. Pupil diameter was observed in periods of omission. Exp.2: Four flickering stimulus of 3sec duration with under or over 2.5Hz or 7.5Hz from the threshold were presented randomly to subjects. VEF of ON and OFF responses were averaged for four stimulus durations. Results and Discussion: Exp.1: Pupil diameter increments and decrements from base line were observed in the omission period for the process of adapting to dark or light environments. The pupil diameter increment was larger (F(1/11)=10.59, P=0.022) and decrement was smaller (F(1/11)=11.86, P=0.018) in the over 7.5Hz flickering condition than in the under 7.5Hz condition. There was no difference of diameter change from large to small for the two flickering condition (F(1/11)=0.21, P=0.665). Adaptation for a light environment was inhibited under the condition of flicker recognition. Exp.2: VEF was observed in the V1 area on the MEG channel with a maximum amplitude of the P100m component. Averaged waveforms of ON and OFF responses were examined for four flickering conditions. The amplitude of OFF responses increased with the increment of the frequency of flicker （F(3/39)=3.05, P=0.045）. The increment of frequency enhanced for the adaptation to the light environment, and provoked amplitude of VEF of OFF response. Conclusion: Differences in pupil diameter and OFF responses for VEF could show the frequency of the flicker fusion threshold in a non-arbitrary way.
References
1. Simon E and Enzer N (1941) Measurments of fusion frequency of flicker as a test of fatique of the central nervous system, J. Industr. Hyg. & Toxicol. 23:83-89
Conference:
Biomag 2010 - 17th International Conference on Biomagnetism , Dubrovnik, Croatia, 28 Mar - 1 Apr, 2010.
Presentation Type:
Poster Presentation
Topic:
Sensory Processing and Functional Connectivity
Citation:
Harada
N,
Iwaki
S and
Tonoike
M
(2010). Objective detection of the flicker fusion threshold with pupil diameter and visual evoked magnetic field.
Front. Neurosci.
Conference Abstract:
Biomag 2010 - 17th International Conference on Biomagnetism .
doi: 10.3389/conf.fnins.2010.06.00193
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Received:
29 Mar 2010;
Published Online:
29 Mar 2010.
*
Correspondence:
Nobuyoshi Harada, National Institute of Advanced Industrial Science and Technology, Ikeda, Osaka, Japan, n-harada@aist.go.jp