A central goal of visual neuroscience is to understand how the brain supports perception. A powerful approach to studying the relationship between brain function and perception is to study the processes in parallel during development. Visual function is poor in infants and emerges over different developmental trajectories depending on the type of visual function. The distinct developmental time courses for different functions provide a unique opportunity to directly evaluate the link between brain development and perception, provided there is a clear hypothesis about the neural underpinnings of the perceptual ability. We have identified such a connection between perception of natural scenes and visual forms, and areas V2 and V4 in the primate brain. We propose three interrelated sets of experiments to explore the links between the development of naturalistic texture sensitivity and the functional development of these visual areas. First, we will study psychophysical and non-invasive high-density evoked response measures of sensitivity to texture and form stimuli longitudinally in individual infant macaques, to elucidate the developmental time courses for this perceptual ability. We propose the hdEEG assay as an adjunct to the psychophysics which can bridge our results directly to human infants. Second, we will directly assess neurophysiologically the development of neural response properties and receptive field organization of area V2 and the specific responses of V2 neurons to the same natural and naturalistic texture stimuli. We will use both anesthetized and awake preparations to fully characterize this process. The awake recordings will be conducted in parallel with behavioral assays in the same individuals to directly correlate behavioral and neural development. Third, we will study the development of neural sensitivity of area V4 to natural scenes and their underlying statistical properties, as well as thir ability to differentially signal the structure of suitable form stimuli. These experiments will advance our understanding of the role of V2 and V4 in support of 1) perceptual organization abilities, such as scene segmentation, object recognition, and global form perception, 2) the cascade of information processing between primary visual cortex and downstream object processing areas such as IT, and 3) the limitations that neural development pose on the development of perception and cognition. Our greater goal is to elucidate the mechanisms by which the ventral stream processes form information and parses natural scenes.
Disorders of the visual nervous system are a major cause of visual disability: Damage to the primary visual cortex (area V1) causes a loss of vision over part or all of the visual field; damage to areas beyond V1 are associated with specific forms of visual loss such as akinetopsia (motion blindness) and agnosia (form blindness). Moreover, developmental disorders, such as Williams Syndrome, Autism, and Amblyopia, are characterized by visual perceptual and cognitive deficits that are poorly understood. Our research seeks to understand the organization and function of the ventral visual processing stream both because of its potential as a substrate for visual loss and developmental plasticity, and because it is a key part of the processing cascade by which sensory signals are transformed to form decisions, guide actions, and create enduring memories.
