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My laboratory studies striate and extrastriate areas of visual cortex in monkeys that have been trained to perform sophisticated visuo-motor tasks. Extracellular activity on single and multiple neurons is related to behavioral performance while the animals perform these tasks. These studies will be complemented by a direct study of neuronal populations using both intrinsic optical imaging techniques as well as functional magnetic resonance. One line of study involves studying the neuronal basis of perceptual learning in the cerebral cortex. Monkeys are trained for many months to perform a difficult visual discrimination task and the potential physiological correlates of the trained behavioral improvement are studied (Ghose et al, 2002).
The second area of research addresses how strategies acquired during the course of training affect neuronal signals and visual performance. Although animals are sensitive to task timing and form temporal representations automatically there has been very little study of how timing strategies affect visual processing. Although there is evidence that task timing directly affects visual responses (Ghose and Maunsell, 2002) it is unclear how universal these affects are. It is also possible that behavioral strategies alter the relationship between individual neuronal activity and the performance of the animal. Because such strategies are automatically formed during any repetitive task, characterizing the effects of such strategies is critical for understanding the neuronal basis of perception and decision making.
Current projects in this area involve simultaneous measurements of neuronal activity and behavior in a challenging task whose demands vary over time in a consistent manner. As with the perceptual learning project, a key aspect of the strategy project is the modeling how the signals from individual neurons are integrated and interpreted to form a percept and ultimately guide behavior.
Ghose, G.M. and Harrison, I.T. Temporal precision of neuronal information in a rapid perceptual judgment. J Neurophysiol, 101:1480-1493,2009.
Ghose, G.M. and Maunsell, J.H. Spatial summation can explain the attentional modulation of neuronal responses to multiple stimuli in area V4. J Neurosci, 28(19):5115-26,2008.
Yoshor, D, Ghose, G.M., Bosking W.H., Sun P.,and Maunsell J.H. Spatial attention does not strongly modulate neuronal responses in early human visual cortex.. J Neurosci, 27(48):13205-9,2007.
Yoshor, D, Bosking, W.H., Ghose, G.M., and Maunsell J.H. Receptive fields in human visual cortex mapped with surface electrodes. Cereb Cortex, 17(10):2293-302,2007.
Ghose, G. Strategies optimize the detection of motion transients. J Vision, 6(4):429-440, 2006.
Ghose, G. Learning in mammalian sensory cortex. Current Opinion Neurobiol, 14(4):513-518, 2004.
Ghose, G. and J. Maunsell. Attentional modulation in visual cortex depends on task timing. Nature, 419(6907):616-20, 2002.
Ghose, G., T. Yang and J. Maunsell. Physiological correlates of perceptual learning in monkey v1 and v2. J Neurophysiol, 87(4):1867-88, 2002.
Ghose, G. and J. Maunsell. Specialized representations in visual cortex: a role for binding?. Neuron, 24(1):79-85, 111-25, 1999.
DeAngelis, G., G. Ghose, I. Ohzawa and R. Freeman. Functional micro-organization of primary visual cortex: receptive field analysis of nearby neurons. J Neurosci, 19(10):4046-64, 1999.
Maunsell, J., G. Ghose, J. Assad, C. McAdams, C. Boudreau and B. Noerager. Visual response latencies of magnocellular and parvocellular LGN neurons in macaque monkeys.. Vis Neurosci, 16(1):1-14, 1999.
Ghose, G. and R. Freeman. Oscillatory discharge in the visual system: does it have a functional role? J Neurophysiol, 68(5):1558-74, 1992.
Ghose, G. and D. Ts'o. Form processing modules in primate area V4. J Neurophysiol, 77(4):2191-6, 1997.
Ghose, G. and R. Freeman. Intracortical connections are not required for oscillatory activity in the visual cortex. Vis Neurosci, 14(6):963R-979R, 1997.
Ghose, G., I. Ohzawa and R. Freeman. A flexible PC-based physiological monitor for animal experiments. J Neurosci Methods, 62(1-2):7-13, 1995.
Ghose, G., R. Freeman and I. Ohzawa. Local intracortical connections in the cat's visual cortex: postnatal development and plasticity. J Neurophysiol, 72(3):1290-303, 1994.
Ghose, G., I. Ohzawa and R. Freeman. Receptive-field maps of correlated discharge between pairs of neurons in the cat's visual cortex. J Neurophysiol, 71(1):330-46, 1994.