Spatial Frequency Affects The Neural Basis Of Chinese Character Recognition

The change of visual spatial frequency directly affects the recognition of visual word.Spatial frequency refers to the number of periods in which light and dark streaks occur repeatedly in a unit perspective.High spatial frequency refers to the sudden change of brightness(such as sharp edges),which supports the extraction of local features.Low spatial frequency refers to the gradual change of brightness,which contains more information about the contour(overall)of the image.Some studies have found that,compared with low spatial frequency,high spatial frequency has a greater influence on the brain area of primary language function(such as visual word form area)under the ventral pathway in visual word recognition.However,so far,no studies have focused on the neural basis of the influences of low spatial frequency on the dorsal pathway in visual word recognition,especially the influence of spatial frequency on the brain regions of higher-level language function in the dorsal pathway.This study used functional Near-Infrared Spectroscopy(fNIRS)explores the influence of different spatial frequency of visual word in dorsal pathway in particular brain regions with high-level language functions.By manipulating the word type and spatial frequency,and adopting a repeated measurement design of 3(real,pseudo and non-word)×3(high,low and normal spatial frequency),this study aim to investigate the influence of spatial frequency on the processing of different Chinese characters through the through the two factors of manipulation type and spatial frequency.Results found that the spatial frequency main effect brain regions included the left inferior temporal gyrus,the inferior occipital gyrus,and the occipital gyrus.The brain area with the main effect of the word type included the left inferior occipital gyrus and middle occipital gyrus.And the interaction effect mainly occurs in the dorsal pathway brain area,including the left middle frontal gyrus,superior frontal gyrus and middle occipital gyrus;Further simple effect analysis found that the word type effect of the interaction brain region mainly comes from the difference of blood oxygen concentration between real and pseudo word in low spatial frequency and normal spatial frequency,but there is no such differences among real,pseudo and non-word under high spatial frequency condition.The results indicate that the visual word types stimulus with low spatial frequency are mainly processed under the dorsal pathway,and the influence of low spatial frequency on Chinese character recognition extends to the higher language function brain regions,such as left middle frontal gyrus.In this study,the influence of spatial frequency on Chinese character recognition and its neural basis were found by systematically manipulating spatial frequency.The results provide direct evidence for language processing and its brain mechanism,greatly enrich and promote the theory of visual vocabulary recognition,and provide a new perspective and direction for language processing research.