In the present study we employed Conditional Granger Causality (CGC) and Coherence analysis to investigate whether visual motion-related information reaches the human middle temporal complex (hMT. +) directly from the Lateral Geniculate Nucleus (LGN) of the thalamus, by-passing the primary visual cortex (V1). Ten healthy human volunteers underwent brain scan examinations by functional magnetic resonance imaging (fMRI) during two optic flow experiments.In addition to the classical LGN-V1-hMT. + pathway, our results showed a significant direct influence of the blood oxygenation level dependent (BOLD) signal recorded in LGN over that in hMT+, not mediated by V1 activity, which strongly supports the existence of a bilateral pathway that connects LGN directly to hMT. + and serves visual motion processing. Furthermore, we evaluated the relative latencies among areas functionally connected in the processing of visual motion. Using LGN as a reference region, hMT. + exhibited a statistically significant earlier peak of activation as compared to V1.In conclusion, our findings suggest the co-existence of an alternative route that directly links LGN to hMT+, bypassing V1. This direct pathway may play a significant functional role for the faster detection of motion and may contribute to explain persistence of unconscious motion detection in individuals with severe destruction of primary visual cortex (blindsight).
|Autori:||Gaglianese A; Costagli M; Bernardi G; Ricciardi E; Pietrini P|
|Titolo:||Evidence of a direct influence between the thalamus and hMT+ independent of V1 in the human brain as measured by fMRI.|
|Anno del prodotto:||2012|
|Digital Object Identifier (DOI):||10.1016/j.neuroimage.2012.01.093|
|Appare nelle tipologie:||1.1 Articolo in rivista|