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ANC Workshop: Charlie Nash and Mark van Rossum: Chair, Lukasz Romaszko

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What
  • ANC Workshop Talk
When Nov 29, 2016
from 11:00 AM to 12:00 PM
Where IF 4.31/4.33
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Mark van Rossum


"Ambiguity and bias in population coding of single- and multivariate stimuli"


Across the brain information is often coded in population codes with broad tuning curves, so that multiple neurons respond to a single stimulus and a single neuron will respond to multiple stimuli. While research has focused on variability in decoding population activity, decoding biases remain understudied despite their possible role in explaining psychophysical data. Here we show that biases readily emerge when multiple stimuli are coded simultaneously in a population. The estimates follow non-trivial distributions and strong correlations between the estimates can arise. These effects can be understood from the particular shape of the likelihood function, which we model as a Gaussian process. The results carry concrete predictions for behavioral experiments, and provide a novel interpretation of the tilt illusion.

 

Joint work with Sander Keemink

 

Charile Nash

"Generative models of part-structured 3D objects"

 

We introduce two generative models of part-segmented 3D objects: the shape variational auto-encoder (ShapeVAE) and the shape factor analyzer (ShapeFA).  These models describe a distribution over the co-existence of object parts, as well as over the continuous variability of the object surface, leveraging the part structure of 3D objects in their architecture. We demonstrate that while the ShapeFA slightly outperforms the ShapeVAE in terms of density estimation, the ShapeVAE produces better quality samples and is effective at completing partially obscured shapes.