A common stochastic accumulator with effector-dependent noise can explain eye-hand coordination

Abstract

The computational architecture that enables the flexible coupling between otherwise independent eye and hand effector systems is not understood. By using a drift diffusion framework, in which variability of the reaction time (RT) distribution scales with mean RT, we tested the ability of a common stochastic accumulator to explain eye-hand coordination. Using a combination of behavior, computational modeling and electromyography, we show how a single stochastic accumulator to threshold, followed by noisy effector-dependent delays, explains eye-hand RT distributions and their correlation, while an alternate independent, interactive eye and hand accumulator model does not. Interestingly, the common accumulator model did not explain the RT distributions of the same subjects when they made eye and hand movements in isolation. Taken together, these data suggest that a dedicated circuit underlies coordinated eye-hand planning.

A common control signal and a ballistic stage can explain the control of coordinated eye-hand movements

“…1), which is a modified version of a double-step paradigm with a countermanding signal incorporated in it. This data set was also used in two earlier published papers to test the common command hypothesis, which is the starting premise of the present work (Gopal et al 2015;Gopal and Murthy 2015). Visual cues (isoluminant colored squares), which subtended a visual angle of 1°, were used as targets in no-step trials (60%) and step trials (40%), which were randomly interleaved ( Fig.…”

“…In addition, these movements were not natural reaching movements but involved the use of button presses and joysticks instead. However, in previous work we have shown that when eye-hand RT correlation is strong, combined eye and hand movements appear to engage a common motor command, which is qualitatively distinct from planning of eye and hand movements made in isolation (Gopal et al 2015;Gopal and Murthy 2015). Here we test whether effector-specific multiple control signals or a single control signal is recruited to control coordinated eye-hand movements.…”

“…An acrylic sheet was kept in the same plane as that of the virtual image of the monitor, constraining the pointing hand movement on the same virtual plane. A schematic of the setup used is shown in a previously published paper (Gopal et al 2015).…”

“…Given these model constraints, the strength of the mean growth rate ( GO ) and the standard deviation of the noise ( GO ) were optimized by scanning a range of parameters (0.001-0.1) that can produce behaviorally relevant RT distributions with RTs that range from 1 ms to 1,000 ms. The details of the Monte Carlo simulations are given in Gopal et al (2015). We used a common command model to simulate the GO process of coordinated eye hand movements (Gopal et al 2015;Gopal and Murthy 2015).…”

“…The details of the Monte Carlo simulations are given in Gopal et al (2015). We used a common command model to simulate the GO process of coordinated eye hand movements (Gopal et al 2015;Gopal and Murthy 2015). The common eye-hand GO accumulator was modeled with Eq.…”