White BL., Berkes P. & Fiser J. (2010) Suppression of intrinsic cortical response variability is state- and stimulus-dependent, Frontiers in Systems Neuroscience. Conference Abstract: Computational and systems neuroscience, 2010.
Neural responses to identical sensory stimuli can be highly variable across trials, even in primary sensory areas of the cortex. This raises the question of how such areas reliably transmits sensory-evoked responses to guide appropriate behavior. Internally-generated, spontaneous activity, which is ubiquitous in the cortex, is a leading candidate for causing much of the observed […]
Galperin H., Bex P. & Fiser J. (2008) The relationship between local feature distributions and object recognition. VSS 2008, Journal of Vision 8 (6), 519-519 [Abstract]
We investigated the structure of image features that support human object recognition using a novel 2-AFC form coherence paradigm. Grayscale images of everyday objects were analyzed with a multi-scale bank of Gabor-wavelet filters whose responses defined the positions, orientations and phases of Gabor patches that were used to reconstruct a facsimile of the original image. […]
Lisitsyn D., Galperin H. & Fiser J. (2012) Linking eye fixation strategies to experience in visual statistical learning. VSS 2012, Journal of Vision 12 (9), 1005-1005 [Abstract]
Linking eye-movement to visual perception or to learning has been notoriously difficult due to the fact that the visual stimulus is either too simplified providing no insights to the true nature of learning or with too rich input, the process of learning becomes intractable. Visual statistical learning (VSL) provides an ideal framework for such studies […]
Berkes P., White B. & Fiser J. (2009) No evidence for active sparsification in the visual cortex. NIPS 2009, NIPS Conference Abstracts 108-116 [Abstract]
The proposal that cortical activity in the visual cortex is optimized for sparse neural activity is one of the most established ideas in computational neuroscience. However, direct experimental evidence for optimal sparse coding remains inconclusive, mostly due to the lack of reference values on which to judge the measured sparseness. Here we analyze neural responses […]
Galperin H., Bex P. & Fiser J. (2008) Local position representation for complex images. ECVP 2008, Perception 37, 47-47 [Abstract]
We examine how local position information of different complex scenes is represented in the visual system. A 2AFC paradigm was used to examine internal noise and sampling efficiency for three classes of stimuli: natural objects, fractal patterns and random circular patterns, all synthesized from the same set of Gabor wavelets. Each trial, a noiseless source […]
Janacsek K, Fiser J, & Nemeth D. (2012). What is the best time to acquire new skills: age-related differences in implicit sequence learning across lifespan. BCCCD 2012, Budapest, Hungary [Abstract]
Implicit skill learning underlies not only motor, but also cognitive and social skills. Nevertheless, the ontogenetic changes in humansʼ implicit learning abilities have not yet been comprehensively characterized. We investigated such learning across the life span, between 4-85 years of age with an implicit probabilistic sequence learning task, and we found that the difference in […]
Berkes P., Wood F. & Pillow J. (2009) Characterizing neural dependencies with copula models. NIPS 2009, NIPS Conference Abstracts 119-136
The coding of information by neural populations depends critically on the statistical dependencies between neuronal responses. However, there is no simple model that can simultaneously account for (1) marginal distributions over single-neuron spike counts that are discrete and non-negative; and (2) joint distributions over the responses of multiple neurons that are often strongly dependent. Here, […]
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 […]
MacKenzie K., Aslin RN. & Fiser J. (2012) Statistical learning of hierarchical visual structures by human infants. BCCCD 2012, Budapest, Hungary [Abstract]
Brandeis University University of Rochester Brandeis University, USA Human infants are known to implicitly learn statistical regularities of their sensory environment in various perceptual domains. Visual statistical leaning studies with adults have illustrated that this learning is highly sophisticated and well approximated by optimal probabilistic chunking of the unfamiliar hierarchical input into statistically stable segments […]
Berkes P., Orbán G., Lengyel M. & Fiser J. (2009) Neural evidence for statistically optimal inference and learning in the primary visual cortex. SFN 2009, Chicago, IL [Abstract]
How do we infer from sensation the state of the external world? Humans and animals have been shown to perform statistically optimal inference and learning during perception in the presence of noise and uncertainty in the presented stimuli. This points to a probabilistic representation of the sensory input, where evidence coming from sensation is optimally […]