Magnetoencephalographic (MEG) response properties associated with capacity-limited sensory gating resources during more/less estimation judgements: Case of the disappearing magnetic dipole in right posterior parietal cortex (rPPC) under the cloak of surround masking.
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1
Swinburne University of Technology, Brain and Psychological Sciences Research Centre, Australia
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2
Swinburne University of Technology, Centre for Human Psychopharmacology , Australia
The elimination of redundant visual input is influenced by a number of factors including modifications in attentional and sensory load. One way to induce such capacity limits over sensory gating resources is through surround masking, a psycho-physical procedure well documented to have deleterious effects upon discrimination of the physical properties of visual perception, such as brightness intensity and differences in contrast. Previous primate neurophysiology literature suggests that high sensory load induced by surround masking, has a regulatory effect upon the inhibitory segments of receptive fields in lateral geniculate nucleus and V1. This 'swamping' of inhibitory resources reduces the visual systems capacity to filter out irrelevant sensory information, resulting in perceptual ambiguity and signal noisiness. We used the Elekta Neuromag (vector view 306) system to observe the electromagnetic (MEG) signature during more/less discrimination judgements of randomly drifting dots, enveloped by either a high (95%) or low (25%) contrast annulus. Essentially, event related fields (ERFs) in the presence of a low-contrast surround were featured by a focused magnetic dipole in rPPC approximately 285-309ms post-stimulus onset.This putative number estimation judgement dipole in rPPC was significantly attenuated (and almost absent in one observer) within the same time-window in the presence of the high-contrast surround. However, the high-contrast surround only appeared to delay this response by approximately 40-60ms and not completely eliminate it. These findings cast a new light on some prevailing notions on the origins of developmental dyscalculia (DD) - arithmetical learning disorder. These findings suggest that DD may be related to poor sensory-gating or inhibitory resources, influenced at a perceptual level, and not just at the cognitive/high-order level of neural organization.
Keywords:
Dyscalculia,
Magnetoencephalography,
inhibition,
Estimation judgements,
Gating resources,
Perceptual-sets,
Sensory-load,
Surround-masking
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:
Jastrzebski
N,
Crewther
D and
Woods
W
(2015). Magnetoencephalographic (MEG) response properties associated with capacity-limited sensory gating resources during more/less estimation judgements: Case of the disappearing magnetic dipole in right posterior parietal cortex (rPPC) under the cloak of surround masking..
Conference Abstract:
XII International Conference on Cognitive Neuroscience (ICON-XII).
doi: 10.3389/conf.fnhum.2015.217.00307
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Received:
19 Feb 2015;
Published Online:
24 Apr 2015.
*
Correspondence:
Ms. Nicola Jastrzebski, Swinburne University of Technology, Brain and Psychological Sciences Research Centre, Melbourne, Australia, nicolajastrzebski@gmail.com
Prof. David Crewther, Swinburne University of Technology, Centre for Human Psychopharmacology, Melbourne, Australia, dcrewther@swin.edu.au
Dr. William Woods, Swinburne University of Technology, Brain and Psychological Sciences Research Centre, Melbourne, Australia, wwoods@swin.edu.au