Functional mapping of the magnocellular and parvocellular subdivisions of human LGN

Abstract

The magnocellular (M) and parvocellular (P) subdivisions of primate LGN are known to process complementary types of visual stimulus information, but a method for noninvasively defining these subdivisions in humans has proven elusive. As a result, the functional roles of these subdivisions in humans have not been investigated physiologically. To functionally map the M and P subdivisions of human LGN, we used high-resolution fMRI at high field (7T and 3T) together with a combination of spatial, temporal, luminance, and chromatic stimulus manipulations. We found that stimulus factors that differentially drive magnocellular and parvocellular neurons in primate LGN also elicit differential BOLD fMRI responses in human LGN and that these responses exhibit a spatial organization consistent with the known anatomical organization of the M and P subdivisions. In test-retest studies, the relative responses of individual voxels to M-type and P-type stimuli were reliable across scanning sessions on separate days and across sessions at different field strengths. The ability to functionally identify magnocellular and parvocellular regions of human LGN with fMRI opens possibilities for investigating the functions of these subdivisions in human visual perception, in patient populations with suspected abnormalities in one of these subdivisions, and in visual cortical processing streams arising from parallel thalamocortical pathways.

Differential hemispheric and visual stream contributions to ensemble coding of crowd emotion

“…In this pilot study, we used non-face stimuli, sinusoidal counter-phase flickering gratings biased to engaged the M-pathway (a low-luminance contrast, varying gray-on-gray grating with a low spatial frequency and 15 Hz flicker) and biasing P-pathway (an isoluminant, high color-contrast red-green grating with high spatial frequency with slow, 5 Hz flicker), following the method detailed in Denison et al 84 . These types of stimuli have been known to selectively bias M-pathway and P-pathway processing in previous studies using object, letter, scene, and face stimuli 44,45,50,84–87 . Although different types of stimuli and different cohorts of participants were employed, the localizer scans showed activations in foci adjacent to and overlapping with our ROIs including the bilateral IPS and SFG activated by M-pathway stimuli and the bilateral FG activated by P-pathway stimuli.…”

Altered visual perception near the hands: A critical review of attentional and neurophysiological models

“…P cells are responsible for virtually all colour processing. In a nutshell, M cells have high temporal acuity but poor spatial acuity, whereas P cells have high spatial acuity but poor temporal acuity (Denison et al, 2014;Derrington and Lennie, 1984;Legge, 1978;Livingstone and Hubel, 1988). In real-world vision, both M and P cells collaborate to create and update our dynamic conscious perception of objects and scenes.…”

Testing the generality of the zoom-lens model: Evidence for visual-pathway specific effects of attended-region size on perception

“…In other words, each M cell encodes information from a relatively large region of a visual scene, and across this region they process coarse spatial Bgist,^and their responses are sharp and precise across time. In technical terms, P cells are especially sensitive to rapid changes in luminance across space (i.e., high spatial frequencies) and slow changes in luminance across time (i.e., low temporal frequencies), whereas M cells are suited to processing slow changes in luminance across space (i.e., low spatial frequencies) and are sensitive to rapid changes in luminance across time (i.e., high temporal frequencies) (Denison, Vu, Yacoub, Feinberg, & Silver, 2014;Derrington & Lennie, 1984;Livingstone & Hubel, 1988;Schiller & Logothetis, 1990).…”