Forward modeling allows feedback control for fast reaching movements

“From a theoretical point of view, we can segregate feedback loops into three categories: (1) sensory feedback, in which the location of the hand is estimated on the basis of sensory information; ( 2 ) non-sensory feedback, in which the location of the hand is estimated on the basis of efferent information; and (3) int…”

“Although the distinction between open- and closed-loop control was traditionally seen as a dichotomy worth debating, researchers have increasingly realized that one is simply a special case of the othe”

“The description above integrates feedback from the motor periphery into motor cortical function, but visual feedback is also important for volitional motor contro”

“In this computational scheme, prediction (forward modeling) gives clear advantages in terms of compensation of noise and delay in sensory feedback, cancelation of self-generated stimuli, and better state estimation [189, 190].”

“For example, in the motor control literature, theorists have proposed that motor commands are fed into a simulation device, called a forward model, that runs in parallel with the actually executed movement (Desmurget & Grafton, 2000; Miall & Reckless, 2002; Wolpert & Flanagan, 2001).”

“In addition to the parietal cortex, the cerebellum has long been implicated in internal models of motor control, including within the speech domain 18,40,76–79 , and the cerebellum has been specifically implicated as being part of a forward model 80,81 .”

“Projections such as these, which predict the sensorimotor state resulting from a movement, are typically described as representing a forward model of the movement (e.g., Davidson & Wolpert, 2005; Desmurget & Grafton, 2000; Kawato, 1999; Miall & Wolpert, 1996).”

“Motor prediction, as instantiated by a forward model, is a key computational component that can alleviate this problem (Desmurget and Grafton, 2000; Miall et al., 1993; Wolpert and Kawato, 1998).”

“The concept of ‘internal models’ which predict future sensory input due to the agent’s own action is a key element of many related theoretical accounts: for example, the ‘corollary discharge hypothesis’ [7], predictive coding [8,9], and motor control theory [10,11].”

“…planning and control stages of action has a long history (cf. Fitts 1957; Keele & Posner 1968; Meyer et al. 1988; Woodworth 1899), the planning–control model has several features that make it unique among these and other models of motor control (e.g., Arbib 1981; Desmurget & Grafton 2000; Jeannerod”

“and after the action, sequences of events reflecting these outcomes are predicted through learning and forward modeling processes (141, 190, 584).”

“Therefore, errors signals play an important role to help the motor system smoothly correct movements (Desmurget and Grafton, 2000).”

“A better understanding of the sequence of selective pressures leading to these advantages will lead to an improved understanding of the functional role of a brain and its relationship to an information-rich environment.”

“…between a sensory event and a motor response severely limit the use of feedback control (Keele, Cohen, & Ivry, 1990), newer behavioral work reveals mechanisms based on the integration of motor commands into estimation of state that can largely mitigate these delays (Desmurget & Grafton, 2000).”

“…sensory and efference copy information may be integrated to allow for the on-line correction of motor errors as well as to generate a more accurate estimate of body posture (e.g., Desmurget & Grafton, 2000; Wolpert & Ghahramani, 2000; Desmurget et al., 1999; Wolpert, Ghahramani, & Jordan, 1995).”

“The presence of a spatially, temporally, and functionally specifi c coupling between frontal and occipito-parietal regions during motor simulations provides support and electrophysiological constraints to computational models of action control that postulates the presence of feed-forward predictive mechanisms requirin…”

“More important from our perspective, an internal model of the expected sensory consequences of the movement provides a reference against which early visual and proprioceptive feedback can be compared (e.g., Desmurget & Grafton, 2000).”

“Perturbingthe targetofareachingmovementinanunpredictabledirectionhas beenaproductiveparadigmforinvestigatingthemechanismsof on-linevisuomotorcorrections(Pelissonetal.,1986;Prablanc andMartin,1992;DesmurgetandGrafton,2000).”

“MIP neurons are also considered to be part of a neural network that detects movement errors or position changes of a target so that fast movement corrections can occur (Desmurget & Grafton, 2000; Kalaska et al. 2003).”

“Forward models make predictions about the behaviour of the motor system and its sensory consequences (Wolpert et al. 1995; Wolpert and Flanagan 2001; Desmurget and Grafton 2000).”

“The question of whether or not the human brain uses continuous visual feedback throughout reaching movements remains hotly debated (Desmurget and Grafton 2000).”

“Evidence for internal models in the brain has grown increasingly stronger (e.g., see Desmurget and Grafton 2000; Kawato 1999 for recent reviews).”

“of the cerebellum [7,12,13], and the cerebellum has been specifically linked to state estimation [14,15], possibly in conjunction with the superior parietal cortex [4,16–18].”

“Several studies suggest that the parietal cortex is important in activating and maintaining such internal model”

“Mappings that can sup - port useful on - line corrections of hand trajectory based on pe - ripheral vision ( Desmurget and Grafton , 2000 ) might develop and help to eliminate errors gradually ( inappropriate hand coor - dination patterns ) and thereby contribute to the learning .”

“It is important to emphasize that the feedback controller integrates both afferent (sensory) and efferent signals (Desmurget & Grafton, 2000; Wolpert, Ghahramani, & Jordan, 1995; Wolpert, Miall, & Kawato, 1998).”

“Optimal movement control likely reflects a combination of both feedback and feedforward processes (cf. Desmurget and Grafton, 2000).”

“Such models have been used to describe reaching movements or planning of movement trajectories using Kalman filters and Bayesian statistics for optimal state estimation (Desmurget and Grafton, 2000; Kawato, 1999; Sabes, 2000; Simon, 2006).”

“For the time being, the ‘‘desired trajectory’’ approach seems to be too restricted for general-purpose motor control and planning in dynamically changing environments, as needed in every biological motor system, and some biological evidence has been accumulated that completely preplanned desired trajectories may not e…”

“These measures are made 100 ms after movement onset, before feedback can affect the action (Desmurget and Grafton, 2000).”

“Such a model can also be used to improve closed-loop control: sensory feedback can be predicted in advance—before it is actually received—and control action can be adapted (see, e.g., [74]).”

“It is clear that movement trajectories also depend on visual feedback (for reviews, see Connolly and Goodale, 1999; Desmurget and Grafton, 2000).”

“This function is highly reliant on the integrity of the parietal lobe and is an example of the establishment of an internal representation of an action, also referred to as an internal model by some investigators (Desmurget and Grafton, 2000; Sirigu et al., 1996; Wolpert et al., 1998).”

“Comparators are common in the neurobiology of motor control literature (for reviews, see Desmurget & Grafton, 2000; Kawato, 1999; Wolpert & Ghahramani, 2000).”

“During physical training, the estimated state of the motor system can refine future motor commands by generating an internal training signal that modifies plastic neural processes (Desmurget and Grafton 2000; Kawato 1999; Wolpert et al. 1995).”

“For instance, in [Desmurget and Grafton 2000] the authors propose an hybrid model for goal-directed movements in which both control schemes are integrated as a single control process.”

“This so-called forward model (Desmurget & Grafton, 2000; Jordan & Rumelhart, 1992; Kawato, 1999; Miall & Wolpert, 1996), similar to the conflict-based model, uses the information generated by the production system (in this case, the motor system) for error detection rather than relying on the…”

“Using similar ideas as in feed-forward motor control models (Desmurget & Grafton 2000), this interface could allow the creation of an internal efference copy of the possible representation of the articulated word, which might be very useful to the language processing system for prediction purposes.”

“The role of forward models in control is twofold: eliminating sensory processing delays [59,93] and mediating inverse model learning for establishing a feedforward control strategy [14].”

“Functionally, it has been suggested that a major role of PPC in movement guidance is to determine whether and to what extent the current motor response is inadequate (Desmurget et al., 1999a; Desmurget and Grafton, 2000).”

“Deconinck et al(52) suggest that motor imagery in children with developmental coordination disorder may be based on poor forward feedback, which relies more on the cerebellum than on the parietal lobe.(58) It is possible that a broad network of regions associated with visuospatial processing is affected by development…”

“For example, a deviation of the motor efference copy and/or the proprioceptive and sensory feedback from predictions made in forward models of the action (Desmurget and Grafton, 2000) can indicate that the entire action is going to fail.”

“To avoid such delays and blind periods, the brain must derive a predictive representation of visual space from brief visual glimpses and copies of motor commands (Ariff et al. 2002, Desmurget & Grafton 2000, Mehta & Schaal 2002, Wolpert & Ghahramani 2000).”

“Rapid online control of movement cannot rely completely on slow sensory feedback but instead must make continuous adjustments to motor commands based on a best estimate of the current and future states of the effector (7, 8).”

“This mechanism compares an internal goal with the predicted consequences of the ongoing movement, made available through the efference copy (Shadmehr and Mussa-Ivaldi, 1994; Wolpert et al., 1995; Desmurget and Grafton, 2000) (see Fig.”

“…past motor commands and delayed sensory feedback (Flanagan et al., 2003, Blakemore et al., 1999; Duhamel et al., 1992; Jordan and Rumelhart, 1992; Wolpert and Miall, 1996; Bhushan and Shadmehr, 1999; Desmurget and Grafton, 2000; Ariff et al., 2002; Mehta and Schaal, 2002; Sommer and Wurtz, 2002).”

“To monitor the performance of a reach, the brain needs to predict the consequences of its motor commands prior to their execution (Wolpert 1997; Desmurget and Grafton 2000).”

“Indeed, they do not have the same causal history nor do they have the same epistemic status.”

“The area proposed here as homologous to monkey MIP is virtually identical to a location previously shown to be involved in the modification of unfolding reaching plans on the basis of sensory feedback (Desmurget et al., 1999; Desmurget and Grafton, 2000).”

“Participants successfully correct their hand paths to the updated target location with latencies as short as 110 msec (Desmurget and Grafton, 2000).”

“…associated with a coarse motor plan, while somatosensory input fine-tunes a particular implementation of the movement (there are many degrees of freedom) on a more local level given the current context (Desmurget & Grafton, 2000), which can vary with limb position, loads, fatigue and other factors.”

“Because it is well recognized that motor commands are continuously updated by internal feedback loops (review in Desmurget and Grafton 2000), it has been suggested that on-line control of movement is also optimal in the theoretical sense (optimal feedback control; Bryson and Ho 1975; Hoff and Arbib…”

“…model relates the prepared motor commands to the sensory signals of the actual state of the effectors to predict the sensorimotor state that will result from the action; the estimated and actual sensorimotor states can be compared to refine future motor commands (Desmurget and Grafton, 2000).”

“These findings are also consistent with evidence that the earliest part of the motor output signal is only an approximation of the exact motor command needed to successfully perform an action (Desmurget and Grafton 2000; Ghilardi et al. 1995; Gordon et al. 1994; Karst and Hasan 1991a,b; Massey et al. 1991; Soechting a…”

“This conjunction of inputs is consistent with the role of PML/Crus IIp PC strips in visual and proprioceptive guidance of reaching, and possibly coordination of arm/eye/head movement (Stein and Glickstein 1992; Desmurget and Grafton 2000; Miall et al. 2001).”

“This raises the possibility that non-visual cues, such as efferent information (Desmurget & Grafton, 2000) or proprioception, may have been used to correct movements.”

“Another function related to the control of action is erasing stimuli produced e.g. by the body of the agent (Desmurget and Grafton, 2000).”

“The process of matching the final position of one’s limbs with an intended movement is achieved through a comparison process between the predicted sensory consequences of the action and the actual sensory feedback (Desmurget and Grafton, 2000; Wolpert and Ghahramani, 2000).”

“…the debate between the narrative-based and comparator-based approaches with the following tentative assumption: narrative-based approaches are likely to prove most viable with respect to agentive judgments, whereas comparator-based approaches are likely to prove most viable with respect to…”

“The specific timing of these differences could offer some information regarding the temporal pattern of the use of visual feedback during a reach-to-grasp movement, a point still open to debate (Desmurget and Grafton 2000).”

“These action representations are believed to be generated in anterior cerebellar lobules I–V (Desmurget and Grafton, 2000; Molinari et al., 2002; Daskalakis et al., 2004).”

“Predictive behaviour can be achieved through internal models (Miall et al. 1987; Wolpert et al. 1995; Desmurget & Grafton, 2000; Wolpert & Flanagan, 2001; Glasauer, 2003).”

“…internal models are used by the nervous system for estimating sensory variables and for optimal motor control (Wolpert et al., 1995a; Kawato, 1999; Desmurget and Grafton, 2000; Mehta and Schaal, 2002; Todorov, 2004; Saunders and Knill, 2005), but very little is known about the neural…”

“…and (multiple) schema(s), composed of inverse and forward models, inside the dotted square. this loops parallels the external feedback loop and supports states and inputs estimation and fast corrective command (Desmurget and Grafton, 2000) via feedback prediction (the part in gray inside the loop).”

“One key aspect is the role of visual feedback – it is often critical to be able to assess and update the relative movements, distances, and masses of objects in the visual environment in order to anticipate the appropriate forces required for a successful motor plan (Desmurget and Grafton, 2000).”

“Target representation cannot explain an MFR during nonreaching movement Nevertheless, it could be argued that a separate representation of target location within the sensorimotor system (Goodale et al., 1986; Prablanc and Martin, 1992; Pisella et al., 1998, 2000; Day and Lyon, 2000; Desmurget and Grafton, 2000; Brouwe…”

“…might not result from a ‘direct-matching’ between observing and acting, but may result from the representation of the final goal of the action, which gives rise to a prediction of the sequence of movements and sensory consequences involved in its achievement (e.g. Desmurget and Grafton, 2000).”

“Correction of movement and thus improvement of performance likely occurred primarily by means of feed-forward control (Desmurget and Grafton 2000).”

“One of these models, the internal forward model, estimates the sensory consequences (i.e. predicted sensory consequences) of the ensuing movements based on the copy of this motor command (Desmurget & Grafton, 2000; Wolpert & Ghahramani, 2000 for reviews).”

“Several lines of research suggest that movements, including speech, are planned and then “supervised” by systems that monitor and compare internally and externally generated feedback [5, 6].”

“…(Doya, 1999; Kawato, 1999; Miall and Wolpert, 1996; Wolpert et al., 1995), visuomotor control (Mehta and Schaal, 2002), imagery (Jeannerod, 2001; Kosslyn, 1994), stabilization of perception (Haarmeier et al., 2001), and the realization of fast reaching movements (Desmurget and Grafton, 2000).”

“Indeed, it has been proposed that this region might contain an internal model used for conscious monitoring of voluntary actions (Sirigu et al., 1996, 2004; Desmurget and Grafton, 2000; Farrer et al., 2008).”

“Feedback and feedforward mechanisms may be best understood in terms of human motor control, which is thought to involve both processes (Desmurget and Grafton 2000).”