RESUMO
Near-infrared spectroscopy has been used to record oxygenation changes in the visual cortex of 4 month old infants. Our in-house topography system, with 30 channels and 3 different source-detector separations, recorded changes in the concentration of oxy-, deoxy- and total haemoglobin (HbO2, HHb and HbT) in response to visual stimuli (face, scrambled visual noise and cartoons as rest). The aim of this work was to demonstrate the capability of the system to spatially localize functional activation and study the possibility of depth discrimination in the haemodynamic response. The group data show both face stimulation and visual noise stimulation induced significant increases in HbO2 from rest, but the increase in HbO2 with face stimulation was not significantly different from that seen with visual noise stimulation. The face stimuli induced increases in HbO2 were spread across a greater area across all depths than visual noise induced changes. In results from a single subject there was a significant increase of HbO2 in the inferior area of the visual cortex in response to both types of stimuli, and a larger number of channels (source-detector pairs) showed HbO2 increase to face stimuli, especially at the greatest depth. Activation maps were obtained using 3D reconstruction methods on multi source-detector separation optical topography data.
Assuntos
Velocidade do Fluxo Sanguíneo/fisiologia , Mapeamento Encefálico/métodos , Circulação Cerebrovascular/fisiologia , Potenciais Evocados Visuais/fisiologia , Face , Reconhecimento Visual de Modelos/fisiologia , Córtex Visual/fisiologia , Feminino , Humanos , Lactente , Masculino , Córtex Visual/irrigação sanguíneaRESUMO
The spike potential is a sharply timed positivity which precedes eye movements in adults, and is thought to indicate cortical planning of saccades. While the spike potential is observed under most conditions in adults, it has not been reported in young infants. In the present study we shed light on the ontogeny of the spike potential by demonstrating for the first time its existence in a group of older infants (12 months). This result is consistent with a relatively delayed onset of cortical control over saccades during development.