Contextual modulation in human visual areas
Hiroshi Ban, Hiroki Yamamoto, Masaki Fukunaga, Asuka Nakagoshi, Masahiro Umeda, Chuzo Tanaka, and Yoshimichi Ejima
When it comes to visual processing, a complex scene, once viewed, is broken into pieces, sent to the contralateral hemisphere, and put back together by higher processing centers. This week, Ban et al. explore the role that the early stage of processing in the primary visual area (V1) has in putting a complex visual scene back together again. The authors presented subjects with quarter arc patterns located in one quadrant of the visual field. Using functional magnetic resonance imaging, regions of interest (ROI) in contralateral V1 were activated by quarter arcs in each quadrant. Activity in the ROI for one quadrant was enhanced when a complete circle was presented compared to the arc alone. Interestingly, the response was strongest when two arcs were presented in diagonal (interfield) rather than adjacent (intrafield) quadrants, perhaps best suggesting a complete circle. The authors argue that this phenomenon, called contextual modulation, involves feedback to V1 from higher centers.
Revisiting the direct and indirect striatal pathways
Agnes Nadjar, Jonathan M. Brotchie, Celine Guigoni, Qin Li, Shao-Bo Zhou, Gui-Jie Wang, Paula Ravenscroft, Franois Georges, Alan R. Crossman, and Erwan Bezard
Striatal neurons are often grouped by their projection targets. Neurons of the "direct" pathway innervate the internal segment of the globus pallidus (GPi), express the D1 dopamine receptor, and corelease dynorphin and substance P with GABA, whereas "indirect" pathway neurons t
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