August 2014
Volume 14, Issue 10
Free
Vision Sciences Society Annual Meeting Abstract  |   August 2014
Temporal structure of Human Magnetic Evoked Fields to Colour, Form and Motion
Author Affiliations
  • David Crewther
    Centre for Human Psychopharmacology, Swinburne University of Technology
Journal of Vision August 2014, Vol.14, 984. doi:10.1167/14.10.984
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      David Crewther; Temporal structure of Human Magnetic Evoked Fields to Colour, Form and Motion. Journal of Vision 2014;14(10):984. doi: 10.1167/14.10.984.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

The temporal structure of responses to colour, form and motion stimuli are little studied. Here, we have extended VEP studies of colour and form response to magnetoencephalography (MEG). Seven participants (young adult) observed a projected dartboard comprising 9 patches with red/grey or blue/grey stimuli, presented either as diffuse surface colours or as a radial pattern. Each stimulus was presented at 5 levels of desaturation levels (100%, 75%, 50%, 25%, 0%) with constant luminance contrast (30%), using pseudo-random binary m-sequences (VPixx/DataPixx). Five minute recordings on the 306 sensor Elekta Triux MEG system were made using a 60 Hz frame rate. A motion/stationary pattern of white dots on black was used to extract motion onset fields. Wiener kernel analysis of the first-order K1 and the first two slices of the second-order kernel (K2.1, K2.2) revealed that the surface colour responses were largely found in the second order, while the pattern based colour responses were mainly found in first order. The surface colour K2.1 response showed strong saturation dependence for both red and blue desaturation series, while for exactly the same stimulus colours, pattern evoked K1 responses were hardly dependent on saturation (Blue Surface: Rsq=.23, p = .03; Blue Form: Rsq=.07, p=.26; Red Surface: Rsq=.23, p = .03; Red Form: Rsq=.14, p=.11). Motion onset evoked responses were characterized by peak field latencies of 95, 116 ms. Minimum norm source localization of the surface versus pattern evoked fields revealed peak activations in calcarine and lingual gyrus as well as early activation of the intra-parietal sulcus. The vastly different temporal structure, timing of peak fields and saturation dependence supports the notion that different neural populations subserve surface and form colour contributions.

Meeting abstract presented at VSS 2014

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