Development of contrast normalization mechanisms during childhood and adolescence.
Contrast sensitivity is regulated by neural mechanisms that flexibly adjust responsiveness to optimize stimulus encoding across different environments. Here we studied the developmental status of gain control mechanisms in school-age children (5-17years) and adults using a visual masking paradigm. A variable contrast, spatially random 2-D noise test pattern was masked by the presence of a superimposed independent noise pattern presented at 0, 12 and 40% contrast. Frequency-tagged steady state visual evoked potentials were used to separately record responses to the test (5.14Hz) and the mask (7.2Hz). By incrementally increasing the test contrast we measured contrast response functions for each mask contrast. The unmasked contrast response functions were largely similar in shape across age, but peak amplitude was higher in the children. Masking shifted the contrast response function rightward on the contrast axis in both the adults and older children, elevating contrast thresholds by a similar factor across age. However, in younger children, masking resulted in a change in the slope of the contrast response function. These findings suggest that immaturity in the contrast normalization process persists until approximately 11years of age.
Department of Psychology, Stanford University, Stanford, CA, United States; Stanford Autism Center at Packard Children's Hospital, Department of Psychiatry, School of Medicine, Stanford University, Stanford, CA, United States. Electronic address: fpei@stanford.edu.
Francesca
F
Pei
Department of Psychology, Stanford University, Stanford, CA, United States; Department of Neuroscience, Psychology, Pharmacology and Child Health, University of Florence, Italy.
Stefano
S
Baldassi
Department of Neurology, University of Washington, Seattle, WA, United States.
Jeffrey J
JJ
Tsai
Department of Psychology, Stanford University, Stanford, CA, United States.
Holly E
HE
Gerhard
Department of Psychology, Stanford University, Stanford, CA, United States.
Anthony M
AM
Norcia
D000293:Adolescent; D002648:Child; D002657:Child Development / Q000502:physiology*; D002675:Child, Preschool; D015350:Contrast Sensitivity / Q000502:physiology*; D005074:Evoked Potentials, Visual / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010470:Perceptual Masking / Q000502:physiology; D012684:Sensory Thresholds / Q000502:physiology; D014793:Visual Cortex / Q000502:physiology
Contrast normalization mechanisms; Contrast sensitivity; Gain control; VEP; Visual development