1. Professors Oliver Braddick & Janette Atkinson 講演会:視覚発達研究の最前線  応用編

日時 9月15日(木) 10:30-12:00
場所 文学部新第7講義室

演題 Visual processing in developmental disorders: perinatal brain damage, Williams syndrome, and refractive screening. (発達障碍と視覚的情報処理: 周産期の脳損傷、ウィリアムズ症候群、および屈折異常診断)

概要 両教授は視覚メカニズムの解明という基礎科学的な側面だけではなく、視覚の障碍と脳科学的考察をつなぐ応用的研究でも高名である。今回は、出産前後の原因による脳損傷やウィリアムス症候群が視知覚に与える影響を脳内メカニズムとあわせて考察した研究や、眼の屈折異常に関して英国内で乳幼児に対して行った大規模なスクリーニングテストの実例などをご紹介いただく。両教授の研究は基礎研究が臨床応用に果たす役割、そして臨床例が基礎科学にもたらす貴重な知見、などの意味で基礎と応用がうまくバランスされた希有な例であり、視覚科学に限らず今後の心理学全般の研究の方向性についての示唆を与えてくれるものとなるだろう。

講演要旨 Because visual functions develop early in infancy, and involve a large part of the brain, they provide a unique ‘window’ on the developing human brain. We have used measures of visual cortical function in the first months of life, including orientation-specific evoked potentials and control of selective attention, to study children at risk of perinatal brain damage, either through adverse events when born at term or through very premature birth. These early cortical measures are found to be good predictors of later neurological outcome. Later, from 3-5 years, tests which measure childrens’ visual attention and the frontal control of visuospatial processing provide sensitive indicators of subtle impairments which are not usually apparent on conventional neurological and psychological testing. We have studied a large cohort of individuals with Williams syndrome (WS), a rare genetic disorder with a characteristic deficit of spatial cognition and relatively good production of language. Tests of global form and motion thresholds, and of visuo-motor control, support the idea that WS children and adults have a deficit of function in the dorsal relative to the ventral cortical stream. Other tests show deficits in the fronto-parietal systems that use spatial information for planning and executive control. However, the ‘dorsal stream vulnerability’ shown in measures of motion coherence thresholds is not unique to WS but is also evident in a wide range of neurodevelopmental disorders including individuals with autism, fragile x, dyslexia, hemiplegia, and perinatal brain damage with extremely premature births. In addition we have developed, photo and videorefractors, new, safe, non- invasive paediatric instruments to carry out screening on total infant populations and identified significant refractive errors (near and far sightedness and astigmatism) as precursors of common visual disorders such as strabismus and amblyopia. From these programmes , screening 9000 8-9 month old infants, we have found that high hyperopia predicts poor vision at 4 years, which ca be prevented in many cases by infant refractive correction with the wearing of glasses. This ‘hyperopic’ infant group also show a range of subtle but significant deficits in preschool and school entry visuo-motor, visuo-cognitive and attentional tests. We will discuss the two-way relationships between optical development and developing brain systems.  

2. Professors Oliver Braddick & Janette Atkinson 講演会:視覚発達研究の最前線 基礎編

日時 9月15日(木) 17:00-18:30
場所 学術情報メディアセンター201教室

演題 Local and global processing of form and motion: development and brain mechanisms. (形と動きについての局所的・大域的情報処理:発達過程と脳内機構)

概要 局所的な線分の傾きや動きの方向から大域的な形の知覚を得るための脳内の視覚情報処理様式について、最近の成果をもとにお話しいただく。乳幼児における心理実験および脳電位測定実験、また成人における心理および脳機能画像化(fMRI)実験の結果などから、脳内での形の知覚のメカニズムとその発達的な変化について総合的に議論していただく予定である。なお、この講演はSCSシステムを介して全国の視覚研究関係者に配信される。 

講演要旨 Visual areas beyond V1/V2 have large receptive fields which can integrate local information about contour orientation (shape) and motion direction to extract larger scale structure of the visual scene. The functions of these higher-level ‘ventral-’ and ‘dorsal-stream’ systems can be tested psychophysically through coherence thresholds for global form and global motion stimuli. Our functional brain imaging experiments show that global form and motion tests activate distinct, non-overlapping networks in extra-striate visual areas. We have investigated the early development of global processing in infants by behavioural testing and visual event-related potentials. These results show that, although local processing of contour orientation develops before that of motion direction in the first months of life, infants integrate local motion signals to detect global structure almost as soon as the local signals are available, whereas the integration of global form information develops more gradually. However, in middle childhood, form coherence thresholds attain adult levels more rapidly than for motion, and global motion thresholds are impaired in a wide range of neurodevelopmental disorders. This phenomenon of ‘dorsal stream vulnerability’ has been identified in individuals with genetic disorders of Williams syndrome, autism and fragile x, as well as in children who have suffered perinatal brain damage leading to hemiplegia, in those born extremely prematurely and in a subset of dyslexics.