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The Barccsyn Seminar Cycle, funded by the SGR “Network Dynamics”, aims to invite researchers from abroad in computational and systems neuroscience to Barcelona. We are excited to hear about their own work, as well as to have them get to know the growing Barccsyn community. In this vein we encourage our invited speakers to spend enough time in Barcelona to visit several labs, ideally one day and a half.

next session

Date: Thursday, May 23rd, 2024
Time: 12h
Place: CRM – Pol 1

Speaker: Ralf Haefner (Rochester University)

Title: Behavioral and neural signatures of approximate inference during passive and active vision

Abstract: Perception requires the combination of uncertain sensory inputs with prior expectations. How such probabilistic computations might be implemented in the brain is a key question in systems neuroscience. Most of my talk will present recent work on temporal biases in evidence accumulation tasks. We found that approximate hierarchical inference results in a confirmation bias whose strength depends on the task in a predictable way. We verified our predictions using psychophysical experiments and showed that the proposed underlying mechanism – a positive feedback loop between decision-making and sensory areas – can reconcile a wide range of prior studies who differed in the biases they found. Next, we extended our work to the case of active sensing and showed that human eye-movements suffer from a similar confirmation bias as they collect information across the visual scene, again explainable by an approximate Bayesian observer. Interestingly, a neural signature of such computations include an increase in differential correlations with task learning in contradiction to classic feedforward models of noise correlations, a prediction we confirmed in monkey neurophysiology experiments.

Ralf Haefner

Ralf Haefner

Rochester University

Ralf joined the University of Rochester in 2014 and currently is Assistant Professor of Brain & Cognitive Sciences and Physics & Astronomy. Previously, he was a Visiting Research Fellow in the Department of Neurobiology at Harvard Medical School and the Swartz Fellow in the Sloan-Swartz Center for Theoretical Neurobiology at Brandeis University.  He earned his PhD from Oxford University in 1999.

Research Interests:

My primary scientific interest lies in understanding how the brain forms percepts and how it uses them to make decisions, especially in the visual domain. In particular, I am interested in how the brain’s perceptual beliefs about the outside world are represented by the responses of populations of cortical neurons. To that end I use tools from machine learning to construct mathematical models that aim to explain neural responses and behavior.

  • perceptual decision-making
  • probabilistic inference
  • selective attention
  • neural population encoding and decoding
  • depth perception/processing of binocular disparity

Date: Thursday, June 13th, 2024
Time: 10h
Place: Institut d’Estudis Catalans – IEC (Room Pi i Sunyer)




Alaa Ahmed

Alaa Ahmed

University of Colorado Boulde

Ahmed’s research focuses on understanding how the brain controls movement. She uses a neuroeconomic approach that combines techniques from neuroscience, economics, psychology and engineering to investigate the costs and constraints underlying human sensorimotor decision-making, learning, and control. Dr. Ahmed is the recipient of an NSF CAREER Award and a DARPA Young Faculty Award presented to “rising research stars in junior faculty positions at U.S. academic institutions”. Her work has been featured in Forbes, Wired, Time, PBS, and other national and international media outlets.
Research Interests: Biomechanics, Neural Control of Movement, Motor Learning and Decision Making, Neuroeconomics


Alex Hyafil | Centre de Recerca Matemàtica

Alex Roxin | Centre de Recerca Matemàtica

Klaus Wimmer | Centre de Recerca Matemàtica



For inquiries about this event please contact the Scientific Events Coordinator Ms. Núria Hernández at​​