The development of the visual threat response in human infants

154 THE DEVELOPMENT OF THE VISUAL THREAT RESPONSE IN HUMAN INFANTS VAN HOF-VAN DUIN, J. AND MOHN, G. Department of Physiology I , Erasmus University Rotterdam, Medical School, P.O.Box 1738, 3000 DR Rotterdam, The Netherlands Whereas the eyeblink response to l i g h t or to glabella tap can be demonstrated in human infants from 28 weeks of gestation, eye closure in response to an approaching object (while avoiding t a c t i l e stimulation) only develops some weeks a f t e r the 40-week term (4, 6). The maturation of this visual component of the threat response was studied both in normal f u l l term infants and in infants born prematurely. In both groups of infants the response becomes positive between 10 to 16 weeks corrected age (age corrected for due date at 40 weeks gestation) i f early development was otherwise uncomplicated. In 17 out of 90 infants in whom perinatal conditions were abnormal, the development of the visual threat was delayed. The appearance of the visual threat response in normal infants coincides with a number of other developmental changes such as the beginning of symmetrical monocular optokinetic nystagmus, binocular depth perception, Vernier acuity and the expansion of the nasal visual f i e l d . I t has been suggested that the development of several of these functions is dependent on functional maturation of corticosubcortical pathways ( I , 3). Recent electrophysiological and behavioural studies in the monkey have emphasized the role of the posterior parietal cortex (area 7a) in the mediation of eyeblink responses to approaching objects (5); s u b c o r t i c a l l y , the superior c o l l i c u l u s and/or the pretectum are l i k e l y to be involved (2). The development of the visual threat in humans not only provides further evidence for the functional development of cortico-subcortical pathways, but also suggests that maturation of i n t r a c o r t i c a l pathways may play a role in the changes of visual behaviour occurring at 3 to 4 months corrected age in normal human infants. REFERENCES I. Atkinson, J . , Human Neurobiology, 3 (1984) 61-75. 2. Holstege, G., Tan, J . , Van Ham, J. and Bos, A., Brain Res., 311 (1984) 7-22. 3. Maurer, D. and Lewis, T.L., Canad. J. Psychol., 33 (1979) 232-252. 4. Peterson, L., Yonas, A. and Fisch, R.O., Infant Behav. Develop., 3 (1980) 155-165. 5. Shibutani, H., Sakata, H. and Hyvarinen, J . , Exp. Brain Res., 55 (1984) I-8. 6. White, B.L., Human Infant: Experience and Psychological Development. Englewood C l i f f s NJ: Prentice Hall, 1971.