Study on information processing of the human visual system

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The information processing of the human visual pathways was studied by using electrophysiological and psychophysical methods.Following results were obtained. 1)Contrast sensitivity function (CSF) in normal aging and patients with visual disorders: Decreased CSF in aged people at high spatial frequencies was found. There was a high correlation between abnormal CSF and abnormal VEP in patients with optic neuritis. Deterioration of CSF was observed in patients with epilepsy treated with polypharmacy. These results indicate the usefulness of CSF in assessing the visual function. 2)Electroretinogram (ERG) and visual evoked potential (VEP) in normal subjects and patients with visual dysfunction: ERGs to uniform-field stimulation are different from those to patten-reversal stimulation, indicating that the former originates from the pre-ganglionic cells and the latter from the ganglion cells in the retina. Stimulus parameters of VEPs such as luminance, contrast, check size and temporal frequency were very important to determine the VEP responses. Frontal negativity of VEPs (N100) may be generated in the frontal lobe as a indicator of visual attention. Temporal frequency deficit in patients with dementia of Alzheimer type was found by steady-state flash VEPs. By using isoluminant chromatic sinusoidal gratings and apparent motion display, it is possible to stimulate the parallel visual pathways. 3)Binocular vision and visual discrimination in normal subjects: Binocular vision was assessed by random dot stereograms in normal subjects and event-related potentials to visual discrimination was recorded. But the further studies are required to clarity their significance.