Elsevier

NeuroImage

Volume 110, 15 April 2015, Pages 219-222
NeuroImage

Comments and Controversies
Orientation decoding: Sense in spirals?

https://doi.org/10.1016/j.neuroimage.2014.12.055Get rights and content

Highlights

  • •

    Decoding of spiral sense requires some form of orientation bias.

  • •

    Spirals of opposite sense cannot be decoded on the basis of radial bias.

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    Prior reports of unbiased decoding are due to inadvertent bias from digital filters.

Abstract

The orientation of a visual stimulus can be successfully decoded from the multivariate pattern of fMRI activity in human visual cortex. Whether this capacity requires coarse-scale orientation biases is controversial. We and others have advocated the use of spiral stimuli to eliminate a potential coarse-scale bias—the radial bias toward local orientations that are collinear with the centre of gaze—and hence narrow down the potential coarse-scale biases that could contribute to orientation decoding. The usefulness of this strategy is challenged by the computational simulations of Carlson (2014), who reported the ability to successfully decode spirals of opposite sense (opening clockwise or counter-clockwise) from the pooled output of purportedly unbiased orientation filters. Here, we elaborate the mathematical relationship between spirals of opposite sense to confirm that they cannot be discriminated on the basis of the pooled output of unbiased or radially biased orientation filters. We then demonstrate that Carlson's (2014) reported decoding ability is consistent with the presence of inadvertent biases in the set of orientation filters; biases introduced by their digital implementation and unrelated to the brain's processing of orientation. These analyses demonstrate that spirals must be processed with an orientation bias other than the radial bias for successful decoding of spiral sense.

Section snippets

Acknowledgment

Colin Clifford is supported by Australian Research Council Future Fellowship FT110100150.

References (36)

  • A. Alink et al.

    fMRI orientation decoding in V1 does not require global maps or globally coherent orientation stimuli

    Front. Psychol.

    (2013)
  • G.M. Boynton

    Imaging orientation selectivity: decoding conscious perception in V1

    Nat. Neurosci.

    (2005)
  • G.J. Brouwer et al.

    Decoding and reconstructing color from responses in human visual cortex

    J. Neurosci.

    (2009)
  • T.A. Carlson

    Orientation decoding in human visual cortex: new insights from an unbiased perspective

    J. Neurosci.

    (2014)
  • C.W.G. Clifford et al.

    Radial biases in the processing of motion and motion-defined contours by human visual cortex

    J. Neurophysiol.

    (2009)
  • C.W.G. Clifford et al.

    Are coarse-scale orientation maps really necessary for orientation decoding?

    J. Neurosci.

    (2011)
  • W. Freeman et al.

    The design and use of steerable filters

    IEEE Trans. Pattern. Anal. Mach. Intell.

    (1991)
  • J. Freeman et al.

    Orientation decoding depends on maps, not columns

    J. Neurosci.

    (2011)

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