Reaching for and grasping an object seems a continuous process, yet somatosensory signals undergo dramatic state changes near the time of object contact. Tactile afferents start conveying contact forces, while on-going proprioceptive signals are altered as hand shape stops changing. How cortex maintains object identity in the presence of changing, multi-modal signals remains unknown. We quantified object-specific information in neurons of the primary motor cortex (M1) and somatosensory areas 3a, 3b/1, and 2 in male macaque monkeys. Surprisingly, despite the decrease in activity in each area immediately after contact, object identity information increased across sensorimotor cortex, particularly in purely cutaneous areas 3b/1, but also in multi-modal area 2. Uniquely among sensorimotor areas, object-specific information was present in M1 and 3a throughout grasp, although identity was encoded differently before and after contact. These shifts highlight the profound change in the complex coding of object identity in the sensorimotor cortex during grasp.
Yan et al. (Sat,) studied this question.