The direct, not V1-mediated, functional influence between the thalamus and middle temporal complex in the human brain is modulated by the speed of visual motion. (22nd January 2015)

• Record Type: Journal Article
• Authors: Gaglianese, A.; Costagli, M.; Ueno, K.; Ricciardi, E.; Bernardi, G.; Pietrini, P.; Cheng, K.
• Is Part Of: Neuroscience. Volume 284(2015)
• Page Start: 833
• Page End: 844
• Publication Date: 2015-01-22
• Subjects: BOLD blood oxygenation level-dependent -- CGC Conditional Granger Causality -- EPI echo-planar imaging -- FM fast motion -- hMT+ middle temporal complex -- HRFs hemodynamic response functions -- LGN lateral geniculate nucleus -- ROI region of interest -- SM slow motion -- V1 primary visual cortex; Conditional Granger Causality -- fMRI -- hMT+ -- speeds -- thalamus -- visual motion; Neurochemistry -- Periodicals; Neurophysiology -- Periodicals; Neurology -- Periodicals; Neurochimie -- Périodiques; Neurophysiologie -- Périodiques; Neurochemistry; Neurophysiology; Electronic journals; Periodicals; Electronic journals; 612.8
• DOI: 10.1016/j.neuroscience.2014.10.042
• Languages: English
• ISSNs: 0306-4522

Abstract

Highlights: A direct pathway carrying motion information directly connects the thalamus with hMT+. fMRI connectivity shows that this route is recruited for slow- and fast-moving stimuli. Stimulus speed influences the connectivity of LGN with different divisions of hMT+. This may explain why MT and MST can still respond to motion despite V1 lesions. Abstract: The main visual pathway that conveys motion information to the middle temporal complex (hMT+) originates from the primary visual cortex (V1), which, in turn, receives spatial and temporal features of the perceived stimuli from the lateral geniculate nucleus (LGN). In addition, visual motion information reaches hMT+ directly from the thalamus, bypassing the V1, through a direct pathway. We aimed at elucidating whether this direct route between LGN and hMT+ represents a 'fast lane' reserved to high-speed motion, as proposed previously, or it is merely involved in processing motion information irrespective of speeds. We evaluated functional magnetic resonance imaging (fMRI) responses elicited by moving visual stimuli and applied connectivity analyses to investigate the effect of motion speed on the causal influence between LGN and hMT+, independent of V1, using the Conditional Granger Causality (CGC) in the presence of slow and fast visual stimuli. Our results showed that at least part of the visual motion information from LGN reaches hMT+, bypassing V1, in response to both slow and fast motion speeds of the perceived stimuli. We also investigated whether motion speeds have different effects on the connections between LGN and functional subdivisions within hMT+: direct connections between LGN and MT-proper carry mainly slow motion information, while connections between LGN and MST carry mainly fast motion information. The existence of a parallel pathway that connects the LGN directly to hMT+ in response to both slow and fast speeds may explain why MT and MST can still respond in the presence of V1 lesions.