Haptic Working Memory for Grasping: the Role of the Parietal Operculum

Abstract

We investigated how haptic information on object geometry is encoded in the parietal operculum (OP) and is used for guiding object-directed motor acts in humans. We tested the effects of conditioning single-pulse transcranial magnetic stimulation (spTMS) applied to the left OP on corticospinal excitability assessed by a test spTMS applied to the ipsilateral motor cortex (M1) 5 ms after conditioning spTMS. Participants explored the size of a graspable object visually or haptically and waited for a go-signal to grasp it in the dark. They received TMS during the delay phase. In a separate group of participants performing the same task, conditioning spTMS was applied to the ventral premotor cortex (vPM) 7 ms before test spTMS. Results showed that conditioning TMS over OP modulated M1 output according to the information on object size that had been acquired haptically but not visually. Vice versa, conditioning TMS over vPM modulated M1 output according to information on object size acquired by vision but not haptically. Moreover spTMS over OP produced a significant modulation of the upcoming reaching behavior only when the object had been explored haptically. We show that OP contains a haptic memory of objects' macrogeometry and the appropriate motor plan for grasping them.

Online repetitive transcranial magnetic stimulation (TMS) to the parietal operculum disrupts haptic memory for grasping

“…In general the present data together with our previous description of OP‐M1 connectivity [Maule et al, ] support the idea that part of the OP cortex plays a major role in motor behavior rather than being a purely sensory area. Data obtained in non‐human primates share a striking similarity with the present findings.…”

“…In a recent study we proved in the intact human, by means of dual‐coil TMS, the existence of short‐latency (5 ms) OP‐M1 interactions [Maule et al, ]. The spatial resolution of TMS, however, did not allow a clear distinction between stimulation of OP1 opposite to stimulation of OP4.…”

A modular theory of multisensory integration for motor control

“…From a Bayesian perspective, it can be argued that it is advantageous to maintain multiple representations of movement parameters, expressed in diverse reference frames, in order to optimize motor performance. Electrophysiological evidence also supports the notion that motor planning and execution is carried out in multiple reference frames in parallel, both across different regions of the brain and within a single cortical area (Buneo et al, 2002; Beurze et al, 2010; Buchholz et al, 2013; Maule et al, 2013; Reichenbach et al, 2014). At the behavioral level, the fully convergent model depicted in Figure 6A cannot predict certain experimentally observed characteristics of movement planning and execution.…”

Contribution of transcranial magnetic stimulation to assessment of brain connectivity and networks

“…This grasp-specific facilitation was also noted in the movement preparation period, in the specific muscle used in the upcoming grasp (Davare et al, 2009). Further work showed that stimulation over the parietal operculum affected grasp of an object in the dark when the object was known visually, but that stimulation over PMv affected grasp when the object was known haptically (Maule et al, 2015). A facilitatory net effect was found in a surround muscle not involved in the movement, occurring 100 ms before movement onset, which turned back to inhibition 50 ms later (Houdayer et al, 2012).…”