All Publications


  • Dynamic Interaction between Reinforcement Learning and Attention in Multidimensional Environments. Neuron Leong, Y. C., Radulescu, A., Daniel, R., DeWoskin, V., Niv, Y. 2017; 93 (2): 451-463

    Abstract

    Little is known about the relationship between attention and learning during decision making. Using eye tracking and multivariate pattern analysis of fMRI data, we measured participants' dimensional attention as they performed a trial-and-error learning task in which only one of three stimulus dimensions was relevant for reward at any given time. Analysis of participants' choices revealed that attention biased both value computation during choice and value update during learning. Value signals in the ventromedial prefrontal cortex and prediction errors in the striatum were similarly biased by attention. In turn, participants' focus of attention was dynamically modulated by ongoing learning. Attentional switches across dimensions correlated with activity in a frontoparietal attention network, which showed enhanced connectivity with the ventromedial prefrontal cortex between switches. Our results suggest a bidirectional interaction between attention and learning: attention constrains learning to relevant dimensions of the environment, while we learn what to attend to via trial and error.

    View details for DOI 10.1016/j.neuron.2016.12.040

    View details for PubMedID 28103483

  • Shared memories reveal shared structure in neural activity across individuals NATURE NEUROSCIENCE Chen, J., Leong, Y. C., Honey, C. J., Yong, C. H., Norman, K. A., Hasson, U. 2017; 20 (1): 115-125

    Abstract

    Our lives revolve around sharing experiences and memories with others. When different people recount the same events, how similar are their underlying neural representations? Participants viewed a 50-min movie, then verbally described the events during functional MRI, producing unguided detailed descriptions lasting up to 40 min. As each person spoke, event-specific spatial patterns were reinstated in default-network, medial-temporal, and high-level visual areas. Individual event patterns were both highly discriminable from one another and similar among people, suggesting consistent spatial organization. In many high-order areas, patterns were more similar between people recalling the same event than between recall and perception, indicating systematic reshaping of percept into memory. These results reveal the existence of a common spatial organization for memories in high-level cortical areas, where encoded information is largely abstracted beyond sensory constraints, and that neural patterns during perception are altered systematically across people into shared memory representations for real-life events.

    View details for DOI 10.1038/nn.4450

    View details for Web of Science ID 000391085500019

    View details for PubMedID 27918531

  • Reinforcement Learning in Multidimensional Environments Relies on Attention Mechanisms JOURNAL OF NEUROSCIENCE Niv, Y., Daniel, R., Geana, A., Gershman, S. J., Leong, Y. C., Radulescu, A., Wilson, R. C. 2015; 35 (21): 8145-8157

    Abstract

    In recent years, ideas from the computational field of reinforcement learning have revolutionized the study of learning in the brain, famously providing new, precise theories of how dopamine affects learning in the basal ganglia. However, reinforcement learning algorithms are notorious for not scaling well to multidimensional environments, as is required for real-world learning. We hypothesized that the brain naturally reduces the dimensionality of real-world problems to only those dimensions that are relevant to predicting reward, and conducted an experiment to assess by what algorithms and with what neural mechanisms this "representation learning" process is realized in humans. Our results suggest that a bilateral attentional control network comprising the intraparietal sulcus, precuneus, and dorsolateral prefrontal cortex is involved in selecting what dimensions are relevant to the task at hand, effectively updating the task representation through trial and error. In this way, cortical attention mechanisms interact with learning in the basal ganglia to solve the "curse of dimensionality" in reinforcement learning.

    View details for DOI 10.1523/JNEUROSCI.2978-14.2015

    View details for Web of Science ID 000356673100010

    View details for PubMedID 26019331