1. The Uncertainty Accumulation model.
The Uncertainty Accumulation model. (A) Direction choices result from accumulation of sensory evidence within trials (gray lines are example single trial trajectories, and black line shows mean accumulation rate, μd= kC). A direction choice is made when accumulated evidence (sensory decision variable, vd) reaches a bound (±Bd) or by the sign of vd when the motion stimulus ends. (B) (Lower) The probability density of vd for a rightward motion strength (6.4% coherence). (Upper) The probability of reaching the upper (rightward) bound, P(+Bd), over time. (C) (Lower) Expected direction choice accuracy, A, for different vd and decision time given the decision rule and stimulus set. (Upper) Expected accuracy as a function of decision time when the positive bound is crossed. (D) Switch evidence of a negative feedback [log[1/(1-Â)]; Materials and Methods] for different motion strength and duration. Switch evidence grows with motion strength and stimulus duration due to gradual drift of vd away from 0. The dashed line indicates a fixed switch bound, Be. (E) Example trial sequence and how accumulated switch evidence (switch decision variable, ve) drives switches in environment choice. (Upper) The sequence of environments (lines) and subject’s choices (circles) resulting in positive (filled) or negative (open) feedback. Color indicates motion strength. (Lower) Changes in ve across trials. Subjects switch when ve exceeds the switch bound. For simplicity, we illustrate a fixed Be (but see text for switch urgency).
Braden A. Purcell, and Roozbeh Kiani PNAS 2016;113:31:E4531-E4540
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