Parsing a perceptual decision in a sequence of moments of thought

MARTÍN GRAZIANO; PABLO POLOSECKI; DIEGO SHALOM; MARIANO SIGMAN

Huerta Grande, Córdoba (Argentina)

Congreso; IRCN First Joint Meeting of the Argentine Society for Neurosciences (SAN) and the Argentine Workshop in Neurosciences (TAN); 2009

<!-- /* Font Definitions */ @font-face {font-family:"DejaVu Sans"; mso-font-charset:0; mso-generic-font-family:auto; mso-font-pitch:variable; mso-font-signature:0 0 0 0 0 0;} @font-face {font-family:"Nimbus Roman No9 L"; mso-font-alt:"Times New Roman"; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:0 0 0 0 0 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:none; mso-hyphenate:none; font-size:12.0pt; font-family:"Nimbus Roman No9 L"; mso-fareast-font-family:"DejaVu Sans"; mso-bidi-font-family:"Times New Roman"; mso-font-kerning:.5pt;} @page Section1 {size:595.25pt 841.85pt; margin:2.0cm 2.0cm 2.0cm 2.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1; mso-footnote-position:beneath-text;} --> Theoretical, computational and experimental studies have converged to a model of decision making in which sensory evidence is stochastically integrated to a threshold, implementing a shift from an analog to a discrete form of computation. Understanding how this process can be chained and sequenced - as virtually all real-life tasks involve a sequence of decisions - remains an open question in neuroscience. We reasoned that incorporating a virtual continuum of possible behavioral outcomes in a simple decision task- a fundamental ingredient of real-life decision making – should result in a progressive sequential approximation to the correct response.  We used real-time tracking of motor action in a decision task, as a measure of cognitive states reflecting an internal decision process. We found that response trajectories were spontaneously segmented in a discrete sequence of explorations separated by brief stops (about 200 ms) – which remained unconscious to the participants. The characteristics of these stops were indicative of a decision process - a “moment of thought”: their duration correlated with the difficulty of the decision and with the efficiency of the subsequent exploration. Our findings suggest that simple navigation in an abstract space involves a discrete sequence of explorations and stops and, moreover, that these stops reveal a fingerprint of moments of thoughts. We design an EEG study to further evaluate these results and to find neurophysiological correlates of these stops.