Prefrontal persistent activity during the delay of spatial working memory tasks is thought to maintain spatial location in memory. A 'bump attractor' computational model can account for this physiology and its relationship to behavior. However, direct experimental evidence linking parameters of prefrontal firing to the memory report in individual trials is lacking, and, to date, no demonstration exists that bump attractor dynamics underlies spatial working memory. We analyzed monkey data and found model-derived predictive relationships between the variability of prefrontal activity in the delay and the fine details of recalled spatial location, as evident in trial-to-trial imprecise oculomotor responses. Our results support a diffusing bump representation for spatial working memory instantiated in persistent prefrontal activity. These findings reinforce persistent activity as a basis for spatial working memory, provide evidence for a continuous prefrontal representation of memorized space and offer experimental support for bump attractor dynamics mediating cognitive tasks in the cortex.
Bibliographical noteFunding Information:
We thank M. Goldman, J. de la Rocha and A. Roxin for fruitful discussions. We wish to acknowledge the late P. Goldman-Rakic, in whose laboratory experimental data were collected. This work was funded by the Ministry of Economy and Competitiveness of Spain, the European Regional Development Fund (Ref: BFU2009-09537) and by the National Science Foundation (NSF PHY11-25915 and DMS-0847749). K.W. acknowledges funding from the German Research Foundation (research fellowship Wi 3767/1-1). D.Q.N. was supported by the Generalitat de Catalunya (PIV-DGR 2010 program). C.C. received support from the Tab Williams Family Endowment. The work was carried out at the Esther Koplowitz Centre and partly at the Kavli Institute for Theoretical Physics, and at the Centre de Recerca Matemàtica.