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 […]
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. […]
Orbán G., Berkes P., Lengyel M. & Fiser J. (2008) Looking for hallmarks of generative models in the visual cortex. COSYNE 2008, Salt Lake Ctiy, UT [Abstract]
A recently emerging computational framework of the visual cortex assumes that it implements a generative model of (natural) visual input. According to this view, the visual cortex implicitly embodies a statistical model of how external causes (the latent variables of the model) combine to form the visual input (the observed variables of the model). Given […]
Orbán G., Berkes P., Lengyel M. & Fiser J. (2008) Relating evoked and spontaneous cortical activities in a generative modeling framework. Sloan-Swartz Meeting of Theoretical Neurobiology 2008, Princeton, NJ [Abstract]
Recently we proposed a computational framework in which we assumed that the visual cortex implicitly implements a generative model of the natural visual environment and performs its functions such as recognition and discrimination by inferring the underlying external causes of the visual input. In the present work, we test this framework by relating synthetic and […]
Berkes P., Wood F. & Pillow J. (2008) Modeling neural dependencies with Poisson copulas. Bernstein Symposium 2008, Munich, Germany [Abstract]
The coding of information by neural populations depends critically on the statistical dependencies between neuronal responses. At the moment, however, we lack of a simple model that can simultaneously account for (1) marginal distributions over single-neuron spike counts that are typically close to Poisson; and (2) joint distributions over the responses of multiple neurons that […]
Fiser J., Orbán G. & Lengyel M. (2008) Linking implicit chunk learning and the capacity of working memory. VSS 2008, Journal of Vision 8 (6), 213-213 [Abstract]
Classical studies of the capacity of working memory have posited a fix limit for the maximum number of items human can store temporarily in their memory, such as 7-2 or 4-1. More recent results showed that when the stored items are viewed as complex multi-dimensional objects capacity can be increased and conversely, when distinctiveness of […]
MacKenzie K. & Fiser J. (2008) Sensitivity of implicit visual rule-learning to the saliency of the stimuli. VSS 2008, Journal of Vision 8 (6), 474-474 [Abstract]
Human infants have been shown to implicitly learn rules, such as the repetition of ABB or ABA patterns, regardless of the identity of the participating items, both with sequential information during language development and with simultaneously presented visual patterns. However, in these studies the ABB or ABA patterns were defined by the identity of the […]
Berkes P., Orbán G., Lengyel M. & Fiser J. (2009) Matching spontaneous and evoked activity in v1: a hallmark of probabilistic inference. COSYNE 2009, Frontiers in Systems Neuroscience Conference Abstract: Computational and systems neuroscience [Abstract]
Neural responses in the visual cortex of awake animals are highly variable, display substantial spontaneous activity even when no visual stimuli are being processed, and the variability in both evoked activity (EA) and spontaneous activity (SA) is strongly structured. However, most theories of visual cortical function remain mute about the possible computational roles and consequences […]
Fiser J., Orbán G., Lengyel M. & Aslin R. (2009) Coarse-to-fine learning in scene perception: Bayes trumps Hebb. VSS 2009, Journal of Vision 9 (8), 865-865 [Abstract]
Recent studies suggest that the coherent structures learned from multi-element visual scenes and represented in human memory can be best captured by Bayesian model comparison rather than by traditional iterative pair-wise associative learning. These two learning mechanisms are polar opposites in how their internal representation emerges. The Bayesian method favors the simplest model until additional […]
Cui M., Orban G., Lengyel M. & Fiser J. (2009) What eye-movements tell us about online learning of the structure of scenes. VSS 2009, Journal of Vision 9 (8), 389-389 [Abstract]
We have recently proposed that representations of novel multi-element visual displays learned and stored in visual long-term memory encode the independent chunks of the underlying structure of the scenes (Orban et al. 2008 PNAS). Here we tested the hypothesis that this internal representation guides eye movement as subjects explore such displays in a memory task. […]