Fiser J., Bourjaily M., Chiu C. & Weliky M. (2006) Mapping different states in neural activity in the primary visual cortex of the awake ferret. SFN 2006, Atlanta, GA [Abstract]
There is a discrepancy between the generally accepted role of ongoing activity during visual development, where spontaneous firing is viewed as an important guiding activity indispensable for proper emergence of the visual structure, and during visual perception, where spontaneous neural activity is considered to be unwanted noise. This discrepancy stems from the presently dominant view […]
Orbán G., Lengyel M. & Fiser J. (2007) V1 activity as optimal Bayesian inference. COSYNE 2007, Salt Lake City, UT [Abstract]
Previous theoretical approaches relating neural activity in the primary visual cortex to formal computational goals that V1 might be optimized for focused mostly on the filter-like properties of cells or on related features such as contrast invariance. The key insights gained from these studies were that V1 neurons (simple cells, in particular) can be seen […]
Orbán G., Lengyel M. & Fiser J. (2007) Spontaneous activity in V1: a probabilistic framework. Sloan-Swartz Meeting of Theoretical Neurobiology 2007, San Diego, CA [Abstract]
In this talk, we focus on two puzzles coming from two lines of research. First, cortical neurons show high level of spontaneous activity. The role of this metabologically expensive and richly structured ongoing neural signal with strong stimulus independent variance is presently unknown. Second, previous theoretical approaches proposed that neural activity in the primary visual […]
Orbán G., Fiser J, Aslin RN. & Lengyel M. (2007) Do we develop visual representations based on pair-wise statistics of the visual scene? Sloan-Swartz Meeting of Theoretical Neurobiology 2007, San Diego, CA [Abstract]
The dominant view on how humans develop new visual representations is based on the paradigm of iterative associative learning. According to this account, new features are developed based on the strength of the pair-wise correlations between sub-elements, and complex features are learned by recursively associating already obtained features. In addition, Hebbian mechanisms of synaptic plasticity […]
White BL. & Fiser J (2007) The effect of anesthesia on neural activity in the primary visual cortex of the rat. SFN 2007, San Diego, CA [Abstract]
Much of what we know about visual processing in the brain is based on neural data collected in anesthetized animals assuming that the essential aspects of the computations are preserved under such conditions. However, recent findings support an alternative view on visual perception that puts a strong emphasis on the role of ongoing activity which […]
Galperin H., Bex P. & Fiser J. (2007) Human orientation sensitivity during object perception. VSS 2007, Journal of Vision 7 (9), 587-587 [Abstract]
The accurate representation of local contour orientation is crucial for object perception, yet little is known about how humans encode this information while viewing complex images. Using a novel image manipulation method, we assessed sensitivity to the local orientation structure of natural images of differing complexity. We found that the visual system involuntarily discounts substantial […]
MacKenzie K., Fortis-Santiago Y. & Fiser J. (2007) Integrating central and peripheral information during object categorization. VSS 2007, Journal of Vision 7 (9), 194-194 [Abstract]
Images presented at fixation provide more information to the visual system than images presented parafoveally. However, it is not clear whether it is more beneficial to receive the larger amount of information first in sequential categorical comparisons. Theories based on activation of mental sets, pure information content, or interference make different predictions on the likely […]
Cui M., Fontanini A., Katz DB. & Fiser J. (2008) Characterizing internal dynamic states and their emergence in the primary visual cortex of the awake ferret. SFN 2008, Washington, DC [Abstract]
According to recently emerging views on visual cortical processing, activity in the primary visual cortex is governed by dynamically changing internal states of the system modulated by the incoming information rather than being fully determined by the visual stimulus. We analyzed systematically the dynamical nature of these states and the conditions required for their emergence. […]
White BL. & Fiser J. (2008) The relationship between awake and anesthetized neural responses in the primary visual cortex of the rat. SFN 2008, Washington, DC [Abstract]
Much of what we know about visual processing in the brain is based on neural data collected in anesthetized animals assuming that the essential aspects of the computations are preserved under such conditions. However, recent findings support an alternative view that visual processing depends upon ongoing activity, which is significantly altered in anesthetized preparations. Therefore, […]
Galperin H., White BL. & Fiser J. (2008) Expectation of reward modulates responses in rat primary visual cortex. SFN 2008, Washington, DC [Abstract]
Classical views of information flow in primary visual cortex suggest that orientation information is encoded early in a feedforward architecture and passed to higher levels of cortex for further processing. More recent studies suggest that top-down information can modulate processing of even basic visual attributes. We investigated whether responses in primary visual cortex are modulated […]