Original Research ARTICLE
Increased noise in cortico-cortical integration after mild TBI measured with the equivalent noise technique
- 1Ophthalmology and Vision Science Department, McGill Vision Research, McGill University, Canada
- 2Essilor (Singapore), Singapore
The bulk of deficits accompanying mild traumatic brain injury (mTBI) is understood in terms of cortical integration—mnemonic, attentional, and cognitive disturbances are believed to involve integrative action across brain regions. Independent of integrative disturbances, mTBI may increase cortical noise, and this has not been previously considered. High-level integrative deficits are exceedingly difficult to measure and model, motivating us to utilize a tightly-controlled task within an established quantitative model to separately estimate internal noise and integration efficiency. First, we utilized a contour integration task modelled as a cortical-integration process involving multiple adjacent cortical columns in early visual areas. Second, we estimated internal noise and integration efficiency using the linear amplifier model (LAM). Fifty-seven mTBI patients and 24 normal controls performed a 4AFC task where they had to identify a valid contour amongst three invalid contours. Thresholds for contour amplitude were measured adaptively across three levels of added external orientation noise. Using the LAM, we found that mTBI increased internal noise without affecting integration efficiency. mTBI also caused hemifield bias differences, and efficiency was related to a change of visual habits. Using a controlled task reflecting cortical integration within the equivalent noise framework empowered us to detect increased computational noise that may be at the heart of mTBI deficits. Our approach is highly sensitive and translatable to rehabilitative efforts for the mTBI population, while also implicating a novel hypothesis of mTBI effects on basic visual processing—namely that cortical integration is maintained at the cost of increased internal noise.
Keywords: Traumatic Brain Injury, internal noise, Efficiency, contour perception, Equivalent noise method, Cortical integration
Received: 06 Feb 2019;
Accepted: 02 Jul 2019.
Edited by:András Büki, University of Pécs, Hungary
Reviewed by:Eugene Golanov, Houston Methodist Hospital, United States
John K. Yue, University of California, San Francisco, United States
Copyright: © 2019 Ruiz, Baldwin, Spiegel, Hess and Farivar-Mohseni. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Ms. Tatiana Ruiz, McGill Vision Research, McGill University, Ophthalmology and Vision Science Department, Montréal, H3G 1A4, Canada, firstname.lastname@example.org