Scotopic center surround organization in 10-week-old infants
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1Department of Ophthalmology, Children's Hospital, Boston, MA.
Insights
Infant visual development shows larger receptive fields than adults, indicating immature spatial summation. This suggests a developing center-surround mechanism is crucial for infant vision.
Area of Science:
- Visual neuroscience
- Developmental psychology
- Ophthalmology
Background:
- Infant spatial summation critical areas are large, possibly due to immature receptive fields.
- Scotopic lateral interactions in adults are understood via Westheimer's paradigm.
- Infant scotopic receptive field organization requires investigation.
Purpose of the Study:
- To investigate scotopic receptive field organization in 10-week-old infants.
- To compare infant receptive field organization with adult data.
Main Methods:
- Modified Westheimer's paradigm for infant testing.
- Determined detection thresholds for probe flashes on varying background diameters.
- Tested 10-week-old infants and adults under scotopic conditions.
Main Results:
- Infant detection thresholds increased up to 3-3.5 degrees background diameter, then decreased.
- Adult detection thresholds increased up to ~0.75 degrees background diameter, then decreased.
- Infants exhibit larger excitatory central receptive fields than adults.
Conclusions:
- Infant visual system exhibits larger receptive fields compared to adults.
- A balanced center-surround receptive field mechanism is operative in infants.
- Immature receptive field organization underlies spatial summation differences in infants.
Abstract:
The large critical areas for complete spatial summation in infants may be due to immaturities of receptive field organization in both dark and light adapted scotopic conditions. Scotopic lateral excitatory/inhibitory interactions have been previously studied in adults using Westheimer's [(1965) Journal of Physiology, London, 181, 881-894] paradigm. We modified this paradigm to investigate scotopic receptive field organization in infants. Detection thresholds for probe flashes of constant diameter and duration presented on steady backgrounds of various diameters were determined for 10-week-old infants and adults. Infants' thresholds increased up to background diameters of 3 degrees to 3.5 degrees and then decreased at greater background diameters. Adults' thresholds increased for backgrounds up to about 0.75 degrees diameter and then decreased at greater background diameters. These results suggest that the excitatory, central receptive field size is larger in infants than adults, and that a balanced center-surround mechanism is operative.