A central goal of sensory neuroscience is to understand the neural code in sensory cortical areas to the point where, by monitoring neural responses in a subject engaged in a perceptual task, one could read, in real time, the content of the neural representation and account for the subject's perceptual capabilities. The overarching goal of the proposed research is to understand the nature of the neural code in primate V1. Specifically, we will focus on the neural code in two important perceptual tasks, pattern discrimination and contour grouping.
In Aim 1 we will test the hypothesis that, in addition to representing stimuli by the activity of a small subset of highly selective neurons, V1 representation relies on the large-scale pattern of spatial variations in neural population responses across the retinotopic map. Specifically, we recently discovered a novel topographic signal in V1, reflecting the spatial representation of the stimulus's luminance modulations (LM) in V1's retinotopic map. We also documented a similar retinotopic signal reflecting the global pattern of the stimulus' contrast modulations (CM). By monitoring neural responses at the retinotopic and columnar scales as monkeys perform a threshold orientation discrimination task, we will test the hypothesis that the retinotopic LM and CM signals contribute to visual perception.
In Aim 2 we will examine the contribution of primate V1 to perceptual grouping - the process of grouping together disparate visual elements that belong to the same object. Specifically, we will test the hypothesis that mechanisms involving configuration-specific lateral interactions in V1 play a key role in this process, and initiate the grouping by linking together pairs of elements that are likely to belong to the same object. To test this hypothesis, we will monitor neural population responses in V1 of monkeys as they perform a challenging and naturalistic perceptual grouping task. In addition, these experiments will be used to determine the rules by which responses to local image elements combine to form a spatiotemporal pattern of population activity in primate V1. Overall, the proposed experiments are likely to provide important and unique insights into the neural mechanisms that mediate cortical sensory processing.
The overarching goal of the proposed research is to understand the nature of the neural code that is employed in the primate primary visual cortex (V1) in order to represent visual stimuli. Specifically, we will test the hypothesis that, in additon to representing stimuli by the activity of a small subset of highly selective neurons, V1 representation relies on the large-scale pattern of spatial variations in neural population responses across V1's topographic maps. In addition, we will examine the role of V1 in grouping together elements that belong to the same visual object and segregating them from elements belonging to other objects or to the background. Together, these projects will contribute to our understanding of the neural mechanisms underlying sensory perception.
|Seidemann, Eyal; Chen, Yuzhi; Bai, Yoon et al. (2016) Calcium imaging with genetically encoded indicators in behaving primates. Elife 5:|
|Yang, Zhiyong; Heeger, David J; Blake, Randolph et al. (2015) Long-range traveling waves of activity triggered by local dichoptic stimulation in V1 of behaving monkeys. J Neurophysiol 113:277-94|
|Tan, Andrew Y Y; Chen, Yuzhi; Scholl, Benjamin et al. (2014) Sensory stimulation shifts visual cortex from synchronous to asynchronous states. Nature 509:226-9|
|Michel, Melchi M; Chen, Yuzhi; Geisler, Wilson S et al. (2013) An illusion predicted by V1 population activity implicates cortical topography in shape perception. Nat Neurosci 16:1477-83|
|Chen, Yuzhi; Palmer, Chris R; Seidemann, Eyal (2012) The relationship between voltage-sensitive dye imaging signals and spiking activity of neural populations in primate V1. J Neurophysiol 107:3281-95|
|Palmer, Chris R; Chen, Yuzhi; Seidemann, Eyal (2012) Uniform spatial spread of population activity in primate parafoveal V1. J Neurophysiol 107:1857-67|
|Chen, Yuzhi; Seidemann, Eyal (2012) Attentional modulations related to spatial gating but not to allocation of limited resources in primate V1. Neuron 74:557-66|
|Sit, Yiu Fai; Chen, Yuzhi; Geisler, Wilson S et al. (2009) Complex dynamics of V1 population responses explained by a simple gain-control model. Neuron 64:943-56|
|Chen, Yuzhi; Geisler, Wilson S; Seidemann, Eyal (2008) Optimal temporal decoding of neural population responses in a reaction-time visual detection task. J Neurophysiol 99:1366-79|
|Palmer, Chris; Cheng, Shao-Ying; Seidemann, Eyal (2007) Linking neuronal and behavioral performance in a reaction-time visual detection task. J Neurosci 27:8122-37|
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