Cerebral Cortex Advance Access originally published online on September 1, 2006
Cerebral Cortex 2007 17(7):1561-1569; doi:10.1093/cercor/bhl067
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Functional Anatomy and Interaction of Fast and Slow Visual Pathways in Macaque Monkeys
1 Cognitive Neuroscience and Schizophrenia Program, Nathan S. Kline Institute, Orangeburg, NY 10962, USA, 2 Institute for Psychology, Hungarian Academy of Sciences, Budapest, 1394 Hungary, 3 Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA, 4 Department of Psychiatry, New York University Medical Center, New York, NY 10016, USA, 5 Department of Psychiatry, Columbia College of Physicians and Surgeons, New York, NY 10032, USA
Address correspondence to Charles E. Schroeder, PhD, Cognitive Neuroscience and Schizophrenia Program, Nathan S. Kline Institute for Psychiatric Research, 140 Old Orangeburg Road, Orangeburg, NY 10962, USA. Email: schrod{at}nki.rfmh.org.
We measured the timing, areal distribution, and laminar profile of fast, wavelength-insensitive and slower, wavelength-sensitive responses in V1 and extrastriate areas, using laminar current-source density analysis in awake macaque monkeys. There were 3 main findings. 1) We confirmed previously reported significant ventral–dorsal stream latency lags at the level of V4 (V4 mean = 38.7 ms vs. middle temporal mean = 26.9 ms) and inferotemporal cortex (IT mean = 43.4 ms vs. dorsal bank of the superior temporal sulcus mean = 33.9 ms). 2) We found that wavelength-sensitive inputs in areas V1, V4, and IT lagged the wavelength-insensitive responses by significant margins; this lag increased over successive levels of the system. 3) We found that laminar activation profiles in V4 and IT were inconsistent with "feedforward" input through the ascending ventral cortical pathway; the likely alternative input routes include both lateral inputs from the dorsal stream and direct inputs from nonspecific thalamic neurons. These findings support a "Framing" Model of ventral stream visual processing in which rapidly conducted inputs, mediated by one or more accessory pathways, modulate the processing of more slowly conducted feedforward inputs.
Key Words: current source density • dorsal stream • response latency • timing • ventral stream • wavelength sensitivity
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