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Stephanie Cox, Mark Bolding, Jason J Nichols; Activation of the brain in normal subjects in response to an ocular surface stimulus. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3949. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To assess the feasibility of mapping the central processing of corneal sensation in the brainstem using functional magnetic resonance imaging (fMRI).
Subjects were provided with an informed consent prior to participation and were included if they had a Symptom Assessment in Dry Eye questionnaire score less than 20 mm and no history of contact lens wear or ocular surgeries. A 3T Siemens Prisma MRI scanner was used for measurement of activation within the brain. A high resolution anatomical scan (MPRAGE, 0.8 mm isotropic voxels) as well as functional scans (TR = 3540 ms, 81 scans, 1.9 x 1.9 x 2.0 mm, full brain coverage) were performed. During the functional scans, the right eye was exposed to a stream of oxygen for 20 seconds, and then the stimulus was stopped for 20 seconds. This cycle was repeated for the duration of the scan. Data preprocessing included realignment, co-registration, and normalization. A contrast between the two conditions (with vs. without stimulus) was used to find areas of activation in each subject. Statistical Parametric Mapping (SPM12) with the spatially unbiased atlas template of the cerebellum and brainstem (SUIT) toolbox was used for imaging processing and analysis.
Two female subjects were recruited (ages: 27 and 46). These subjects showed increased activation within three areas of the brainstem whose positions correspond to the primary sensory nucleus, and the Vi/Vc complex and the Vc/C1 complex of the trigeminal nucleus (Figure 1).
fMRI assessment of ocular surface sensation in the brainstem is feasible and could provide a powerful tool to further investigate the neurological response of humans to a variety of ocular surface stimuli and how this response differs in a variety of ocular surface diseases.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
The areas of activation seen in the brainstem in red are (caudally to rostrally) the Vc/C1 complex of the trigeminal nucleus, the Vi/Vc complex of the trigeminal nucleus, and the primary sensory nucleus.
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