Vol 7: Visual motion integration is mediated by directional ambiguities in local motion signals.Report as inadecuate



 Vol 7: Visual motion integration is mediated by directional ambiguities in local motion signals.


Vol 7: Visual motion integration is mediated by directional ambiguities in local motion signals. - Download this document for free, or read online. Document in PDF available to download.

Download or read this book online for free in PDF: Vol 7: Visual motion integration is mediated by directional ambiguities in local motion signals.
This article is from Frontiers in Computational Neuroscience, volume 7.AbstractThe output of primary visual cortex V1 is a piecemeal representation of the visual scene and the response of any one cell cannot unambiguously guide sensorimotor behavior. It remains unsolved how subsequent stages of cortical processing combine -pool- these early visual signals into a coherent representation. We Webb et al., 2007, 2011 have shown that responses of human observers on a pooling task employing broadband, random dot motion can be accurately predicted by decoding the maximum likelihood direction from a population of motion-sensitive neurons. Whereas Amano et al. 2009 found that the vector average velocity of arrays of narrowband, two-dimensional 2-d plaids predicts perceived global motion. To reconcile these different results, we designed two experiments in which we used 2-d noise textures moving behind spatially distributed apertures and measured the point of subjective equality between pairs of global noise textures. Textures in the standard stimulus moved rigidly in the same direction, whereas their directions in the comparison stimulus were sampled from a set of probability distributions. Human observers judged which noise texture had a more clockwise CW global direction. In agreement with Amano and colleagues, observers perceived global motion coincided with the vector average stimulus direction. To test if directional ambiguities in local motion signals governed perceived global direction, we manipulated the fidelity of the texture motion within each aperture. A proportion of the apertures contained texture that underwent rigid translation and the remainder contained dynamic temporally uncorrelated noise to create locally ambiguous motion. Perceived global motion matched the vector average when the majority of apertures contained rigid motion, but with increasing levels of dynamic noise shifted toward the maximum likelihood direction. A class of population decoders utilizing power-law non-linearities can accommodate this flexible pooling.



Author: Rocchi, Francesca; Ledgeway, Tim; Webb, Ben S.

Source: https://archive.org/



DOWNLOAD PDF




Related documents