Toward a Standardized Procedure for Delineating MT and MST within the Human Middle Temporal Complex
Poster No:
2078
Submission Type:
Abstract Submission
Authors:
Rania Ezzo1, Puti Wen1, Marisa Carrasco2, Bas Rokers1, Jonathan Winawer2
Institutions:
1New York University Abu Dhabi, Abu Dhabi, Abu Dhabi, 2New York University, New York, NY
First Author:
Co-Author(s):
Introduction:
Two adjacent regions on the lateral temporal lobe of macaque monkeys, the middle temporal (MT) and medial superior temporal (MST) areas, play critical but distinct roles in visual motion processing. Studying homologs of these maps in humans is important for understanding the neural computations of motion perception. Using fMRI, Deyoe et al (1996) identified "hMT+" in humans, a large motion-selective region likely containing multiple visual motion areas, including MT and MST. Subsequently, distinct retinotopic maps were identified within the hMT+ complex, including the presumed homologs of MT and MST (Huk et al., 2002; Amano et al. 2009, Kolster et al., 2010). Nonetheless, many fMRI studies of visual motion continue to localize hMT+ rather than the two separate maps due to several challenges: These maps vary in size, position and shape across individuals and hemispheres; they are small, exhibit relatively coarse retinotopy, and are situated in a cortical sulcus, which can compromise the quality of retinotopic maps. Our overall aim is to develop a standardized procedure to identify the MT/MST maps in humans using fMRI. Here we took a step toward this goal by assessing MT/MST map quality in each individual observer in a new fMRI dataset.
Methods:
For 13 participants, we collected a high-resolution anatomical scan, 2-6 motion localizer scans and 12 retinotopic mapping scans (up to 12.2° eccentricity). The motion localizer consisted of alternating blocks of static and moving black and white dots. The retinotopic stimuli were adapted from Benson et al. (2018): a carrier pattern, composed of objects overlaid on 1/f noise, was windowed within bar-, wedge- or ring-apertures. The apertures swept out positions in the visual field in discrete 1-s steps. To increase fMRI signal quality within cortical motion regions, the carrier pattern alternately zoomed in and out within constant-size apertures.
We located hMT+ as the posterior lateral temporal region showing greater signal for moving than static dots in the motion localizer. Then, using the retinotopy data, we modeled each voxels' population Receptive Field (pRF) position (x, y) and size (σ) using vistasoft (https://github.com/vistalab/vistasoft). To delineate MT and MST, we used the following pRF criteria: (1) polar angle values reverse (lower to upper to lower meridian) in the posterior to anterior direction where the upper vertical meridian is at the shared MT/MST boundary; and (2) the eccentricity gradient of foveal-to-peripheral representations follows a ventral to dorsal direction.
We located hMT+ as the posterior lateral temporal region showing greater signal for moving than static dots in the motion localizer. Then, using the retinotopy data, we modeled each voxels' population Receptive Field (pRF) position (x, y) and size (σ) using vistasoft (https://github.com/vistalab/vistasoft). To delineate MT and MST, we used the following pRF criteria: (1) polar angle values reverse (lower to upper to lower meridian) in the posterior to anterior direction where the upper vertical meridian is at the shared MT/MST boundary; and (2) the eccentricity gradient of foveal-to-peripheral representations follows a ventral to dorsal direction.
Results:
The hMT+ motion-related activity was located in the inferior temporal sulcus, and MT/MST shared a foveal confluence distinct from that of the primary visual cortex, consistent with previous findings (Wandell et al. 2009). An eccentricity gradient was present in MT and MST for 22/26 hemispheres (13/13 observers); both regions were typically elongated along this gradient which ran roughly ventral to dorsal (Fig 1). Polar angle values reversed from lower to upper to lower visual field, and ran approximately posterior to anterior directions for 21/26 hemispheres (12/13 observers). Unlike V1 to V3, polar angle and eccentricity gradients were not orthogonal (Fig 1).
Conclusions:
MT and MST retinotopic maps can be obtained reliably in most hemispheres using our acquisition and analysis procedures. We have collected a similar dataset in 40 subjects (NYU database) and will use this dataset to quantify the precision of map delineation across multiple independent researchers, who each manually draw boundaries for both areas in each participant. Standardizing the identification of MT/MST will facilitate studying the neural computations involved in human visual motion processing in each of these regions.
Modeling and Analysis Methods:
Activation (eg. BOLD task-fMRI)
Segmentation and Parcellation 2
Neuroanatomy, Physiology, Metabolism and Neurotransmission:
Cortical Anatomy and Brain Mapping
Perception, Attention and Motor Behavior:
Perception: Visual 1
Keywords:
Cortex
Cross-Species Homologues
FUNCTIONAL MRI
Perception
Segmentation
Vision
Other - Retinotopy
1|2Indicates the priority used for review
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Provide references using APA citation style.
Benson, N.C. et al. (2018). The Human Connectome Project 7 Tesla retinotopy dataset: Description and population receptive field analysis. Journal of vision, 18(13), 23-23.
DeYoe, E.A. et al. (1996). Mapping striate and extrastriate visual areas in human cerebral cortex. Proceedings of the National Academy of Sciences, 93(6), 2382-2386.
Huk, A.C. et al. (2002). Retinotopy and functional subdivision of human areas MT and MST. Journal of Neuroscience, 22(16), 7195-7205.
Kolster, H. et al. (2010). The retinotopic organization of the human middle temporal area MT/V5 and its cortical neighbors. Journal of Neuroscience, 30(29), 9801-9820.
Wandell, B.A. et al. (2009). Visual cortex in humans. Encyclopedia of neuroscience, 10, 251-257.