The Jitter Spatial Frequency Sweep VEP: A new paradigm to study spatiotemporal development of pattern- and motion-processing mechanisms in human infants.

Abstract

We introduce a new VEP paradigm -the Jitter Spatial Frequency (JSF) Sweep VEP -that permits efficient mapping of the spatiotemporal tuning of the developmental motion asymmetry (DMA). Vertical sinewave gratings undergoing 90 o horizontal oscillatory displacements (6 or 10 Hz) were presented while their SF was swept over 2 to 5 octaves during each VEP trial. JSF sweep VEPs were recorded from 28 infants (8-43 weeks), and symmetric (second-harmonic, F2) and asymmetric (F1) components of the VEP were measured. JSF sweeps can provide four useful estimates: (1,2) the high-SF cutoff of F1 and F2 responses estimates the spatial resolution of direction-selective (DS) and non-DS mechanisms, respectively; (3) the low-SF cutoff for F1 estimate the SF-boundary between mature (F1 absent) and immature (F1 present) DS mechanisms; and (4) the F1 high-SF cutoff estimates the lower velocity limit of cortical DS cells. For 6 Hz, the low-SF F1 cutoffs increased two times faster than traditional (contrast-reversal) VEP grating acuity (0.5 vs ~0.25 octaves/month), and twice that of the high-SF F1 and F2 cutoffs. This implies that no single mechanism can account for the DMA at both low and high SFs. At 10 Hz, the DMA exhibited no significant development, consistent with slower maturation of DS mechanisms at higher ST frequencies. The F2 high-SF cutoffs were higher than F1 at both 6 and 10 Hz, suggesting higher spatial resolution for non-DS (pattern) vs DS (motion) mechanisms. Finally, the lower velocity limit of the DS mechanisms decreased from ~2 deg/sec at 8 weeks, to 0.75 deg/sec at 33 weeks, similar to analogous limits for direction-of-motion identification in adults (~0.5 -1 deg/sec), and close to prior VEP estimates in infants (0.6 deg/sec).

Effects of affective content and motivational context on neural gain functions during naturalistic scene perception

“…Across analyses, results showed small to moderate effects of content and context, and large effects of picture type (faces vs. naturalistic scenes) on the CRF. In line with previous sweep-ssVEP work (Friedl & Keil, 2020;Hamer & Norcia, 2009;Song & Keil, 2014), neural activity over occipital cortex increased with increasing stimulus contrast, plateauing just before the maximum contrast (90% Michelson) was reached. Stimuli with faces showed overall greater response amplitude than naturalistic scenes depicting people or animals.…”

“…This cross-validation analysis suggests that the response parameter is a valid estimate of neural mass activity, while also providing important information on the CRF. The sweep-ssVEP method varies the dimension of interest within each trial (Hamer & Norcia, 2009;Norcia et al, 2015). Compared with the classical approach (e.g., used in ERP studies) in which each step of the dimension (e.g., contrast, spatial frequency, luminance) is presented statically in a given trial, the sweep-ssVEP method dramatically reduces the number of trials needed for a robust signal.…”