No abstract

Visual evoked potentials (VEPs) were recorded to textures segregated by gradients in orientation or motion. Recordings were obtained in traumatic brain-injured (TBI) subjects and in normal controls. We analyzed both the low-level VEPs (llVEPs) evoked by homogenous stimuli, as well as the components associated with texture segregation (tsVEP) obtained through an appropriate linear combination. Our results suggest that the tsVEP, presumably higher up in the visual processing chain than the llVEP, is sensitive to TBI and can reveal further information as to the nature of possible information processing deficits after TBI. It could also help quantify cortical damage that is not revealed with more standard clinical tools.

There are important developmental changes occurring during infancy in visual cortical structures that underlie higher-order perceptual abilities. Using high-density electrophysiological recording techniques, the present study aimed to examine the development of visual mechanisms, during the first year of life, associated with texture segregation. Forty-two normal full term infants were tested at 1, 3, 6 or 12 months of age. Visual-evoked potentials to low-level stimuli varying in orientation (oriVEP) and higher-level textured stimuli (texVEP) were recorded from 128 scalp electrodes. Difference potentials were obtained to extract the VEP component associated specifically with texture segregation (tsVEP). Results show a clear developmental pattern regarding amplitude, latency and scalp distribution of tsVEP, which appears at around 3 months but does not reach maturity by 12 months of age. A reduction in latency is particularly evident between 3 and 6 months, whereas amplitude shows a gradual increase with a marked increment between 3 and 6 months for low-level orientation stimuli and between 6 and 12 months for higher-level textured stimuli. These developmental patterns are attributed to neural maturational processes such as myelination and synaptogenesis. The differential developmental rates can be explained by delayed maturational processes of brain regions involved in more complex visual processing.