Forward modeling allows feedback control for fast reaching movements

“1 (Frith et al., 2000a, p. 1773; Kawato, 1999, see Desmurget and Grafton (2000), Wolpert and Ghahramani (2000) for reviews).”

“Earlier work suggests involvement of posterior parietal cortex in state estimation (Desmurget and Grafton, 2000; Wolpert et al., 1995), and transcranial magnetic stimulation of aIPS (Tunik et al., 2005) or cIPS (Desmurget et al., 1999) interferes with the ability to update motor plans based on…”

“During the movement execution stage, visual and proprioceptive feedback arising from the receptors is monitored, updated, and compared with the corollary discharge(4,5) so that the motor system can detect errors and correct them quickly to achieve optimal performance.(6) In most everyday situations, input from all sen…”

“The motor system may correct the execution-errors on-line using feedback control [37,38] or initiate explorative activity to learn the new environment.”

“Sensorimotor integration can be reliably assayed by measuring compensatory motor responses in the face of unpredictable perturbations, forcing subjects to update an ongoing action (Desmurget and Grafton, 2000).”

“This is thought to be achieved by way of a forward (predictive) model of the spatiotemporal and kinetic parameters of the impending movement, which is compared with incoming afferent signals (Desmurget & Grafton, 2000; Shadmehr & Krakeaur, 2008).”

“feedback [109, 128–131].”

“…on-line motor corrections in OA would then suggest a specific disruption of the visuo-proprioceptive comparison of target and hand locations (Vindras, 1998) or an impaired forward modelling of the hand trajectory used for on-line comparison to visual target location (Desmurget and Grafton, 2000).”

“There is growing evidence that skilled motor behavior relies on the ability of the brain to predict the outcome of volitional acts (Desmurget and Grafton, 2000; Flanagan et al., 2006).”

“Another important line of evidence concerns research on the function and neural mechanisms of “corollary discharge” or “reafference” signals, which are necessary for an organism to distinguish self-generated sensory changes from those not related to own action (Desmurget and Grafton 2000; Crapse and Sommer 2008).”

“This happens online, so feedback controllers are limited by the time delay required for sensory processing, which in the case of visual feedback is estimated to be between 100 to 300 ms (Barnett-Cowan and Harris, 2009; Brenner and Smeets, 2003; Desmurget and Grafton, 2000; Saunders and Knill, 2003, 2005).”

“Online corrections might reside on motor outflow (Desmurget and Grafton 2000) and/or on sensory information, such as retinal error (Blouin et al. 1995; Desmurget et al. 1999).”

“Most of these works studied the acquisition accuracy, which is presumably determined by the resolution of proprioception [37] and the acquisition speed, which is influenced by the reaction time of the proprioception [11].”

“…online guidance of the movement (Desmurget et al., 1999; Lee and Van Donkelaar, 2006; Wolpert et al., 1998; Karnath and Perenin, 2005; Grea et al., 2002), using a forward model to estimate the current state of the limb in gaze-centered coordinates (Desmurget and Grafton, 2000; Ariff et al., 2002).”

“Forward models deliver predictions that help interpret the sensory effects of one’s actions, or those of others (Blakemore, Wolpert, & Frith, 2002; Desmurget & Grafton, 2000; O’Regan & Noë, 2001; Wolpert & Flanagan, 2001).”

“We do not even know to what extent the brain really considers such issues (building forward models; Desmurget and Grafton 2000; Flanagan and Wing 1997; Ishikawa et al. 2016; Mehta and Schaal 2002; Wolpert and Flanagan 2001; Miall and Wolpert 1996; Wolpert et al. 1998) and to what extent near-optimal movements arise fr…”

“Here we directly contrast two synthetic populations where: (1) each unit has a uniform receptive field by virtue of being connected to one receptive element the same size as its receptive field and (2) each unit has subfields by virtue of being connected to a random number (2-64) of receptor elements (each 250 m in di…”

“, 2005) and possibly also by dynamical error signals computed by the PPC (Desmurget and Grafton, 2000).”

“As is well-known for the motor control domain, the feedback monitoring system functions to precisely correct movements when they are inaccurate by comparing the target position and the predicted movement end-position according to a copy of the movement command (efferent copy) and sensory inflow (Desmurget and Grafton,…”

“…versus altered (unpredicted) speech, but the observed localization of this effect did not fall squarely in auditory cortex but rather in what appears to be an auditory-motor integration area, area Spt (Desmurget & Grafton, 2000; Kawato, 1999; Wolpert, 1997;Wolpert, Ghahramani, & Jordan, 1995).”

“This skill necessitates the fast processing of sensory information about our body and the environment in order to continuously control our movement (Desmurget and Grafton 2000).”

“If there is a mismatch between them, an error signal is generated and corrective processes can be started— similar to action monitoring (see Rodrı́gues-Fornells et al., 2002; Desmurget & Grafton, 2000).”

“the balance between pre-planning and using sensory feedback to correct movement pattern (e.g. Desmurget and Grafton, 2000 ).”

“Email: bresciani@tuebingen.mpg.de When reaching for a target object, the afferent signals provided by different sensory channels are continuously processed to supervise the ongoing movement (Wolpert et al. 1995; Desmurget & Grafton, 2000).”

“In particular, the aIPS has been discussed as a flexible dynamic area capable of goal-dependent updating of actions in order to establish an internal action representation (cf., Desmurget and Grafton 2000).”

“…different theories have been proposed, distinguishing, for example, efference information that in turn predicts the location of a body part in action, the “forward model” [45,46], from the source of information regarding the body part position that is provided by feedback from sensory systems [47].”

“Feedforward, however, utilizes the information learned from past experience to control the body parts to reach a desired position, which allows the body to reach the desired position faster (Desmurget & Grafton, 2000).”

“A possible solution is to rely on a fast prediction of the expected feedback that could be provided by a forward model (Miall et al., 1993; Desmurget and Grafton, 2000).”

“This model receives a copy of the motor commands that is used to predict movement endpoint and to compare it with the target location, allowing for a quick updating of the motor command (for reviews see Desmurget and Grafton 2000; Khan et al. 2006).”

“…been postulated by Smith and Shadmehr (2000) who address the basal ganglia as to play an important role in this context, however, also posterior parietal cortex, cerebellum and motor cortices are discussed to contribute to an internal body model (Desmurget & Grafton, 2000; Decety & Grèzes, 1999).”

“For this control system to work, an estimation of the state of the body in space is needed: this state estimator appears to involve parietocerebellar loops (Desmurget et al., 1999; Desmurget & Grafton, 2000).”

“The present study investigated whether brain areas coding for specific motor parameters within motor control (Blakemore and Sirigu, 2003; Desmurget and Grafton, 2000) are also involved inmotor imagery.”

“, unfolding as a preprogrammed sequence of muscle contraction (Goodale et al., 1986; Desmurget and Grafton, 2000).”

“In doing so, internal models provide stability to the motor system in an uncertain environment (Desmurget and Grafton, 2000; Izawa and Shadmehr, 2011; Wolpert et al., 2011).”

“This model divides reaching into two components, an initial feedforward phase related to planning processes and a second feedback phase related to processes that mediate hand path corrections (15).”

“This suggests that the spatial computations underlying feedforward and feedback control might rely on sim- ilar processes and neuronal substrates (Desmurget and Grafton, 2000; Scott, 2004; Pruszynski et al., 2011).”

“Both forward and inverse models can be used in internal error-correcting loops (Desmurget and Grafton, 2000; Kawato, 1999).”

“The weakness of these models is the absence of online feedback control, which is necessary for the continuous updating of motor commands by internal and external feedback loops (Desmurget & Grafton, 2000; Todorov & Jordan, 2002; Saunders & Knill, 2004; Guigon et al ., 2008).”

“Several lines of research suggest that the sensorimotor transformations necessary for this type of online motor control depend on posterior parietal cortex (PPC; Desmurget & Grafton, 2000; Desmurget et al., 1999, 2001; Grea et al., 2002) and the cerebellum (Blakemore, Frith, & Wolpert, 2001; Miall, Reckess, & Imamizu,…”

“As different mechanisms have been suggested for planning vs. execution of a goal-directed movement (Desmurget and Grafton, 2000; Glover, 2002; Sabes, 2000), their neural implementation may also rely on distinct cortical regions.”

“…previous studies that have suggested that on presentation of a target the initial hand movement is planned on the basis of retinal coordinates and following foveation the hand movement is updated using ocular-proprioception (Desmurget and Grafton 2000; Fisk and Goodale 1985; Prablanc et al. 1979).”

“that this error signal is generated mainly by the discrepancy between the predicted visual consequences of movement command elaborated by a forward model and the actual visual sensory estimates (see [2] for review).”

“the effects of delays [5, 6], such as delay compensatory mechanisms based on forward models [8] and predictive mechanisms based on the concept of an internal inverse model [9], or combinations thereof [10–12].”

“control, may be temporally overlapping [40–42].”

“These peripheral inhibitory processes may thus participate, downstream of the motor plan, in the online adaptive control of movements that is becoming well documented (e.g., Desmurget and Grafton 2000).”

“For example, the relatively slow reaching movements performed by monkeys that last 100s of milliseconds are likely to be dependent on internal models acquired in advance rather than online sensory feedback control (Desmurget and Grafton, 2000).”

“In order to fit with human behavior [4], we proposed to change the weights of the two components of the DMP system, to obtain a predominantly feedforward control policy at an earlier phase of the motion (not disturbed by the goal-attractor) and a predominantly visual feedback control towards the end of the motion, as…”

“Indeed, previous neuroimaging, neurophysiology, and neurobehavioral investigations demonstrate that IPL, PMv, and the prefrontal cortex are involved in the online control of action [Desmurget and Grafton, 2000; Filimon, 2010; Grafton, 2010].”

“In recent years advancements have been made in understanding the neural and computational basis of pointing and reaching movements that are directed at visual targets (for reviews see for example Desmurget et al., 1998; Lacquaniti and Caminiti, 1998; Kawato, 1999; Desmurget and Grafton, 2000; Todorov, 2004; Buneo and…”

“On-line corrections can be observed early in a movement, suggesting they rely on an internal model of expected plant dynamics (Kawato, 1999; Desmurget and Grafton, 2000).”

“This timing is similar to that used by Verstynen and Sabes (2011) and reflects the feedforward phase of the movement (Elliott et al., 2001), before feedback mechanisms can affect cursor trajectory (Desmurget and Grafton, 2000).”

“Inverse models (which map kinematic trajectories to motor commands) have been hypothesized to play a role in the planning and execution of movement, while forward models (from motor commands to kinematic trajectories) have been proposed to provide internal feedback signals that expedite movement error estimation [35,3…”

“Current theoretical models of limb movement control generally include such predictive efference copy signals (e.g., Desmurget & Grafton, 2000).”

“These peripheral inhibitory processes may thus participate, downstream of the motor plan, in the online adaptive control of movements that is becoming well documented (e.g., Desmurget and Grafton 2000).”

“To explain such seamless responses, theories of limb motor control have emphasized the predictive or anticipatory nature of the planning process (Desmurget and Grafton, 2000; Diedrichsen et al., 2010).”

“Despite these striking successes, it appears difficult to hypothesize that motor control is purely an openloop process (Desmurget and Grafton 2000).”

“The emulation theory is built around the idea that the brains of organisms construct and maintain internal models, or emulators, of many of the processes with which it interacts, including its body and environment (Ito 1970; Desmurget and Grafton 2000; for more references see Grush 2004a,b).”

“Finally, the patient needs to have a relatively intact action-monitoring system to be aware of the abnormal movements as they are occurring.”

“Since movements in our task lasted about 300 ms (until movement reversal), and the minimal time for visual feedback to influence ongoing movements has been estimated at ~120 ms (Paillard 1996; Desmurget and Grafton 2000), a role for visual feedback cannot be excluded.”

“During overt action, such predictions may allow the actor to filter out predicted sensations (e.g., Reichenbach et al., 2014) or to correct for movement errors before they happen (e.g., Desmurget & Grafton, 2000; Shadmehr et al., 2010).”