Relative timing of initial striate and extrastriate visual cortical activations using human Magnetic Evoked Fields
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1
Swinburne University of Technology, Centre for Human Psychopharmacology, Australia
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2
Swinburne University of Technology, Australia
While most multifocal evoked response studies using temporally random stimulation have concentrated on mapping the visual field, analysis of cortical nonlinearities can provide information of the contribution of magnocellular [M] and parvocellular [P] afferent streams. The temporal structure is predictive of autistic tendency (1, 2), and is likely to provide insight into other conditions showing perceptual anomalies, eg dyslexia. An m-sequence multifocal system developed using a VPixx/DataPixx combination for magnetoencephalographic (MEG) studies. Eleven normal young adults were recorded using an Elekta TRIUX MEG. Visual stimuli comprised a 9 patch dartboard stimulus with either low (24%) or high (96%) temporal contrast diffuse patches. Triggers designed to take account of the current frame condition or in relation to frame stimulus history enabled first and second order Wiener kernel analysis (3). Sensor space analysis of the foveal patch showed qualitative similarity with cortical VEP recordings. Analysis of gain, saturation and latency, showed that the first slice of the second order response (K2.1) was already saturated at 24% contrast indicative of M-pathway input, while the major waveform of the second slice of the second order response (K2.2), with 30ms longer latency, grew strongly with contrast, without saturation (indicative of P-input). Minimum norm estimates of cortical source localization show evidence of both V1 and extrastriate activation at the earliest latencies (around 40ms). The early activation of extrastriate cortex, contemporaneous with activation in striate cortex gives credence to the timing possibilities for feedback from the early dorsal stream to inform object processing through aspects such as figure/ground segmentation in human.
1. B. L. Jackson et al., (2013) PLoS One 8, e66797.
2. A. Sutherland, D. P. Crewther, (2010) Brain 133, 2089.
3. A. Klistorner, D. P. Crewther, S. G. Crewther, (1997) Vision Res 37, 2161.
Keywords:
MEG,
extrastriate cortex,
nonlinear,
Magnocellular,
Parvocellular
Conference:
XII International Conference on Cognitive Neuroscience (ICON-XII), Brisbane, Queensland, Australia, 27 Jul - 31 Jul, 2014.
Presentation Type:
Poster
Topic:
Sensation and Perception
Citation:
Crewther
D,
Brown
A and
Hugrass
L
(2015). Relative timing of initial striate and extrastriate visual cortical activations using human Magnetic Evoked Fields.
Conference Abstract:
XII International Conference on Cognitive Neuroscience (ICON-XII).
doi: 10.3389/conf.fnhum.2015.217.00185
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Received:
19 Feb 2015;
Published Online:
24 Apr 2015.
*
Correspondence:
Prof. David Crewther, Swinburne University of Technology, Centre for Human Psychopharmacology, Melbourne, Australia, crewtherdp@me.com