Figure 1

Experimental design. (A) Schematic of the experiment. Central to the design is a compliant cylindrical manipulandum composed of a soft polymer envelope which is internally pressurized from a hydraulic air compressor. The monkey sits in a custom-made chair and reaches for the manipulandum through an opening in a transparent window. Multichannel signals are collected simultaneously from a pair of microelectrode arrays (MEAs in S1 and M1) and transmitted wirelessly to nearby neural signal processing electronics. (B) Time course of the task. Top: Graphical representation of task flow. The task flow is separated into four stages: Movement Planning (Yellow rectangular panel), Movement, i.e. arm/hand reach (Pink panel), Touch and Grasp (Green panel), and Steady State squeeze (Blue panel). The solid red line represents trial averaged time varying pressure inside the manipulandum as the monkey first grasps and then squeezes the manipulandum to reach a steady-state. In addition to this ‘NORMAL’ task, the dashed black line shows schematically an abrupt elevation in the internal pneumatic pressure of the manipulandum introduced during the steady state, labeled as the ‘SURPRISE EVENT’ the onset of which was randomly timed from 2–5 s after the onset of Touch. The two blue horizontal lines define the target pressure range within which the monkey must maintain the force of hand squeeze in steady state to complete a successful trial. (C) Schematic of the approximate cortical location of the implanted intracortical MEAs. CS central sulcus, IPS intraparietal sulcus, M1 primary motor cortex, S1 primary somatosensory cortex.