Knudsen E I, Knudsen P F
Department of Neurobiology, Stanford University School of Medicine, California 94305-5401.
J Neurosci. 1990 Jan;10(1):222-32. doi: 10.1523/JNEUROSCI.10-01-00222.1990.
This study describes developmental changes in the capacity of owls to adjust sound localization in response to chronic prismatic displacement of the visual field and to recover accurate sound localization following the restoration of normal vision. Matched, binocular displacing prisms were mounted over the eyes of 19 barn owls (Tyto alba) beginning at ages ranging from 10 to 272 d. In nearly all cases, the visual field was shifted 23 degrees to the right. Sound localization was assessed on the basis of head orientations to sound sources, measured in a darkened sound chamber with a search coil system. Chronic exposure to a displaced visual field caused the owls to alter sound localization in the direction of the visual field displacement, thereby inducing a sound-localization error. The size of the sound-localization error that resulted depended on the age of the animal when prism experience began. Maximal errors of about 20 degrees were induced only when prism experience began by 21 d of age. As prism experience began at later ages, the magnitude of induced errors decreased. A bird that wore prisms beginning at 102 d of age, altered sound localization by only 6 degrees. An adult owl, when exposed chronically to a displaced visual field, altered sound localization by about 3 degrees. We refer to the early period in life when displaced vision induces exceptionally large sound-localization errors (relative to those induced in the adult) as a sensitive period. The capacity to recover accurate sound localization following restoration of normal vision was tested in 7 owls that had been raised wearing prisms. Four owls that had prisms removed by 182 d of age recovered accurate localization rapidly (over a period of weeks), whereas 3 owls that were older when the prisms were removed did not recover accurate localization when tested for up to 7 months after prism removal. Adjustment of sound localization slowed greatly or ceased at about 200 days of age, referred to here as the critical period for visual calibration of sound localization. Three owls were subjected repetitively to displacement of the visual field. An owl that adjusted sound localization to the left of normal during the sensitive period retained the capacity to adjust again to the left, but not to the right of normal, later in the critical period. The converse was true for an owl that adjusted sound localization to the right of normal during the sensitive period.(ABSTRACT TRUNCATED AT 400 WORDS)
本研究描述了猫头鹰在应对视野长期棱镜移位时调整声音定位的能力变化，以及恢复正常视力后恢复准确声音定位的能力变化。从10至272日龄不等的19只仓鸮（Tyto alba）的眼睛上安装了匹配的双眼移位棱镜。几乎在所有情况下，视野都向右偏移了23度。在一个黑暗的隔音室中，使用搜索线圈系统，根据头部对声源的定向来评估声音定位。长期暴露于移位的视野会使猫头鹰朝着视野移位的方向改变声音定位，从而产生声音定位误差。产生的声音定位误差大小取决于开始佩戴棱镜时动物的年龄。仅在21日龄之前开始佩戴棱镜时，才会产生约20度的最大误差。随着棱镜体验在更大年龄开始，诱导误差的幅度会减小。一只在102日龄开始佩戴棱镜的鸟，声音定位仅改变了6度。一只成年猫头鹰在长期暴露于移位的视野时，声音定位改变了约3度。我们将生命早期移位视力会引发异常大的声音定位误差（相对于成年时引发的误差）的时期称为敏感期。在7只从小佩戴棱镜长大的猫头鹰中测试了恢复正常视力后恢复准确声音定位的能力。4只在182日龄前摘除棱镜的猫头鹰迅速恢复了准确的定位（在数周内），而3只在摘除棱镜时年龄较大的猫头鹰在摘除棱镜后长达7个月的测试中未恢复准确的定位。声音定位的调整在约200日龄时大幅减慢或停止，在此称为声音定位视觉校准的关键期。对3只猫头鹰反复进行视野移位。一只在敏感期将声音定位调整到正常左侧的猫头鹰在关键期后期仍保留再次向左调整的能力，但不能调整到正常右侧。对于一只在敏感期将声音定位调整到正常右侧的猫头鹰，情况则相反。（摘要截选至400字）
