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Suied C.,Institute Of Recherche Biomedicale Des Armees | Agus T.R.,Queens University of Belfast | Thorpe S.J.,University Paul Sabatier | Mesgarani N.,University of California at San Francisco | Pressnitzer D.,CNRS Perceptual Systems Laboratory
Journal of the Acoustical Society of America | Year: 2014

Sounds such as the voice or musical instruments can be recognized on the basis of timbre alone. Here, sound recognition was investigated with severely reduced timbre cues. Short snippets of naturally recorded sounds were extracted from a large corpus. Listeners were asked to report a target category (e.g., sung voices) among other sounds (e.g., musical instruments). All sound categories covered the same pitch range, so the task had to be solved on timbre cues alone. The minimum duration for which performance was above chance was found to be short, on the order of a few milliseconds, with the best performance for voice targets. Performance was independent of pitch and was maintained when stimuli contained less than a full waveform cycle. Recognition was not generally better when the sound snippets were time-aligned with the sound onset compared to when they were extracted with a random starting time. Finally, performance did not depend on feedback or training, suggesting that the cues used by listeners in the artificial gating task were similar to those relevant for longer, more familiar sounds. The results show that timbre cues for sound recognition are available at a variety of time scales, including very short ones. © 2014 Acoustical Society of America. Source


Mamassian P.,CNRS Perceptual Systems Laboratory
Current Biology | Year: 2015

Young children use multiple cues to appreciate the three-dimensional structure of the world. A new study reveals that these cues are properly integrated only years later, thus showing that sensory development is protracted well into teenage years. © 2015 Elsevier Ltd. All rights reserved. Source


De Cheveigne A.,CNRS Perceptual Systems Laboratory | De Cheveigne A.,Mohammed V University | De Cheveigne A.,University College London | Parra L.C.,City College of New York
NeuroImage | Year: 2014

We review a simple yet versatile approach for the analysis of multichannel data, focusing in particular on brain signals measured with EEG, MEG, ECoG, LFP or optical imaging. Sensors are combined linearly with weights that are chosen to provide optimal signal-to-noise ratio. Signal and noise can be variably defined to match the specific need, e.g. reproducibility over trials, frequency content, or differences between stimulus conditions. We demonstrate how the method can be used to remove power line or cardiac interference, enhance stimulus-evoked or stimulus-induced activity, isolate narrow-band cortical activity, and so on. The approach involves decorrelating both the original and filtered data by joint diagonalization of their covariance matrices. We trace its origins; offer an easy-to-understand explanation; review a range of applications; and chart failure scenarios that might lead to misleading results, in particular due to overfitting. In addition to its flexibility and effectiveness, a major appeal of the method is that it is easy to understand. © 2014 Elsevier Inc. Source


Neri P.,CNRS Perceptual Systems Laboratory | Neri P.,Ecole Normale Superieure de Paris
PLoS Computational Biology | Year: 2015

It is generally acknowledged that biological vision presents nonlinear characteristics, yet linear filtering accounts of visual processing are ubiquitous. The template-matching operation implemented by the linear-nonlinear cascade (linear filter followed by static nonlinearity) is the most widely adopted computational tool in systems neuroscience. This simple model achieves remarkable explanatory power while retaining analytical tractability, potentially extending its reach to a wide range of systems and levels in sensory processing. The extent of its applicability to human behaviour, however, remains unclear. Because sensory stimuli possess multiple attributes (e.g. position, orientation, size), the issue of applicability may be asked by considering each attribute one at a time in relation to a family of linear-nonlinear models, or by considering all attributes collectively in relation to a specified implementation of the linear-nonlinear cascade. We demonstrate that human visual processing can operate under conditions that are indistinguishable from linear-nonlinear transduction with respect to substantially different stimulus attributes of a uniquely specified target signal with associated behavioural task. However, no specific implementation of a linear-nonlinear cascade is able to account for the entire collection of results across attributes; a satisfactory account at this level requires the introduction of a small gain-control circuit, resulting in a model that no longer belongs to the linear-nonlinear family. Our results inform and constrain efforts at obtaining and interpreting comprehensive characterizations of the human sensory process by demonstrating its inescapably nonlinear nature, even under conditions that have been painstakingly fine-tuned to facilitate template-matching behaviour and to produce results that, at some level of inspection, do conform to linear filtering predictions. They also suggest that compliance with linear transduction may be the targeted outcome of carefully crafted nonlinear circuits, rather than default behaviour exhibited by basic components. © 2015 Peter Neri. Source


Mamassian P.,CNRS Perceptual Systems Laboratory
Current Biology | Year: 2016

When we look straight at an object, it appears the same as when it is seen from the corner of our eye; however, this stability of visual appearance can collapse if inconspicuous object changes are introduced during eye movements. © 2016 Elsevier Ltd. Source

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