Eye movements as a readout of sensorimotor decision processes

Abstract

Real-world tasks, such as avoiding obstacles, require a sequence of interdependent decisions to 1 reach accurate motor outcomes. Yet, most studies on primate decision making involve simple one-2 step choices. Here we investigate how sensorimotor decisions develop over time. In a go/no-go 3 interception task human observers (n=42) judged whether a briefly-presented moving target would 4 pass (interception required) or miss (no hand movement required) a strike box while their eye and 5 hand movements were recorded. Go/no-go decision formation had to occur within the first few 6 hundred milliseconds to allow time-critical interception. We found that the earliest time point at 7 which eye movements started to differentiate decision outcome (go vs. no-go) coincided with hand 8 movement onset. Moreover, eye movements were related to different stages of decision making. 9 Whereas higher eye velocity during smooth pursuit initiation (prior to "whether" decision) was 10 related to higher go/no-go decision accuracy, faster pursuit maintenance was associated with 11 accurate interception timing ("when" decision). These results indicate that pursuit initiation and 12 maintenance are continuously linked to ongoing sensorimotor decision formation. 13 interception New and NoteworthyIn this study we show that human eye movements are a continuous and sensitive indicator of go/no-16 go decision processes. We link different stages of decision formation to distinct oculomotor events 17 during the open-loop vs. closed-loop phase of pursuit eye movements. Critically, the earliest time 18 point at which eye movements started to differentiate decision outcomes coincided with hand 19 movement onset, suggesting shared sensorimotor processing in the eye and hand movement 20 systems. These results emphasize the potential of studying naturally occurring eye movements as 21 a continuous read-out of cognitive processes. 22 Eye movements as readout of sensorimotor decisions 3 Eye movements as a readout of sensorimotor decision processesPerceptual decisions in real-world scenarios often require a sequence of interdependent decisions. 23 For example, when a pedestrian steps onto a bike lane, an approaching cyclist has to decide 24 whether to stop or to veer around the obstacle. Depending on the initial decision outcome the 25 cyclist then has to decide how hard to brake or in which direction to swerve. Dynamically-evolving 26 decision processes have been studied in ecologically-inspired tasks, such as spatial navigation in 27 rodents (Harvey et al., 2012; Krumin et al., 2018; Pfeiffer and Foster, 2013) or during visual search 28 and foraging in human observers (Diamond et al., 2017; Najemnik and Geisler, 2005; Yoon et al., 29 2018). Yet, the time course of visually-guided sequential decisions in simple movement tasks is 30 relatively unexplored. This study probes decision-making processes using a speeded manual 31 go/no-go interception task. We investigate continuous eye movements during two-stage perceptual 32 decisions as a ...