Purchase this article with an account.
Mark Greenlee, Markus Siebertz, Katharina Rosengarth, Maka Malania, Tina Plank; fMRI activation of LGN and visual cortex under photopic, mesopic and scotopic luminance levels. Journal of Vision 2015;15(12):254. doi: 10.1167/15.12.254.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
We investigated whether the fMRI BOLD response in the visual pathway depends on the light adaptation level. Twelve normal-sighted participants (4 males, 8 females; age 21-41 years) with functional magnetic resonance imaging (fMRI) were measured under scotopic, mesopic and photopic luminance levels. The visual stimulation consisted of a 30-degree radial checkerboard stimulus flickering at 8 Hz. The stimuli were presented in a block design (12 s stimulation, 12 s baseline). Photopic, mesopic and scotopic luminance levels were achieved by applying 2 to 6 neutral density filters (transmission 13%) resulting in a maximal luminance of 43 (photopic), 0.73 (mesopic) or 0.01 (scotopic) cd/m2, respectively. Dark-adapted subjects reported a Purkinje-shift in perceived colors under mesopic conditions and the total absence of color perception under scotopic conditions. fMRI measurements were conducted using a 3T scanner (Siemens Allegra). Functional images were acquired with a T2*-weighted gradient echo planar imaging sequence (TR=2s, TE=30 ms, FA=90°) consisting of 34 transverse slices (voxel size = 2.5 x 2.5 x 2.5 mm; FoV=160 x 160 mm). Data analysis was performed with SPM8. Images were normalized to the Thalamus Atlas (Krauth et al., 2010, Neuroimage, 49, 2053-2062). ROI-analysis was conducted on the atlas-based magno (M) - and parvocellular (P) voxels of the LGN. A 2 (hemispheres) x 3 (luminance levels) x 2 ( M/P ROIs) repeated-measurements ANOVA was conducted on the percent signal changes in the BOLD signal for the LGN. Results show a significant main effect of luminance level (decreasing BOLD response with decreasing luminance; p< .001) and a significant interaction between luminance condition and ROI (M/P; p = .001). In agreement with an earlier study (Hadjikhani & Tootell, 2000, Human Brain Mapping, 9, 55–63), in retinotopically defined V1 we found no activation in the projection zone of the fovea for the scotopic luminance level.
Meeting abstract presented at VSS 2015
This PDF is available to Subscribers Only