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The effects of tDCS across the Spatial Frequencies and Orientations that comprise the Contrast Sensitivity Function

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The effects of tDCS across the Spatial Frequencies and Orientations that comprise the Contrast Sensitivity Function

Richard, Bruno, Johnson, Aaron P., Thompson, Benjamin and Hansen, Bruce (2015) The effects of tDCS across the Spatial Frequencies and Orientations that comprise the Contrast Sensitivity Function. Frontiers in Psychology: Perceptual Science, 6 (1784). pp. 1-14.

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Abstract

Transcranial Direct Current Stimulation (tDCS) has recently been employed in traditional psychophysical paradigms in an effort to measure direct manipulations on spatial frequency channel operations in the early visual system. However, the effects of tDCS on contrast sensitivity have only been measured at a single spatial frequency and orientation. Since contrast sensitivity is known to depend on spatial frequency and orientation, we ask how the effects of anodal and cathodal tDCS may vary according to these dimensions. We measured contrast sensitivity with sinusoidal gratings at four different spatial frequencies (0.5, 4, 8, and 12 cycles/°), two orientations (45° Oblique and Horizontal), and for two stimulus size conditions [fixed size (3°) and fixed period (1.5 cycles)]. Only contrast sensitivity measured with a 45° oblique grating with a spatial frequency of 8 cycles/° (period = 1.5 cycles) demonstrated clear polarity specific effects of tDCS, whereby cathodal tDCS increased and anodal tDCS decreased contrast sensitivity. Overall, effects of tDCS were largest for oblique stimuli presented at high spatial frequencies (i.e., 8 and 12 cycles/°), and were small or absent at lower spatial frequencies, other orientations and stimulus size. Thus, the impact of tDCS on contrast sensitivity, and therefore on spatial frequency channel operations, is opposite in direction to other behavioral effects of tDCS, and only measurable in stimuli that generally elicit lower contrast sensitivity (e.g., oblique gratings with period of 1.5 cycles at spatial frequencies above the peak of the contrast sensitivity function).

Divisions:Concordia University > Faculty of Arts and Science > Psychology
Item Type:Article
Refereed:Yes
Authors:Richard, Bruno and Johnson, Aaron P. and Thompson, Benjamin and Hansen, Bruce
Journal or Publication:Frontiers in Psychology: Perceptual Science
Date:27 November 2015
Funders:
  • NSERC
  • Concordia Open Access Author Fund
ID Code:980878
Deposited By: AARON JOHNSON
Deposited On:17 Feb 2016 20:25
Last Modified:18 Jan 2018 17:52
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