Optimal feedback control and the long-latency stretch response

Abstract

There has traditionally been a separation between voluntary control processes and the fast feedback responses which follow mechanical perturbations (i.e., stretch "reflexes"). However, a recent theory of motor control, based on optimal control, suggests that voluntary motor behavior involves the sophisticated manipulation of sensory feedback. We have recently proposed that one implication of this theory is that the long-latency stretch "reflex", like voluntary control, should support a rich assortment of behaviors because these two processes are intimately linked through shared neural circuitry including primary motor cortex. In this review, we first describe the basic principles of optimal feedback control related to voluntary motor behavior. We then explore the functional properties of upper-limb stretch responses, with a focus on how the sophistication of the long-latency stretch response rivals voluntary control. And last, we describe the neural circuitry that underlies the long-latency stretch response and detail the evidence that primary motor cortex participates in sophisticated feedback responses to mechanical perturbations.

Early compensatory and anticipatory postural adjustments following anterior cruciate ligament reconstruction

“…Conversely, almost all the latencies of the knee extensor and flexor muscles recorded in patients with ACLR fell above either 50 or 100 ms (VL: 90,9 %; RF: 90,9 %; BF: 93,9 %) and may then be considered long-latency 13 reflexes or voluntary responses (Pruszynski and Scott 2012;Valle et al 2013). Such a difference between patients with ACLR and healthy participants might be due to surgery-related neural adaptations of either peripheral or central origin, or to a combination of both.…”

“…Such a difference between patients with ACLR and healthy participants might be due to surgery-related neural adaptations of either peripheral or central origin, or to a combination of both. An efficient reaction to unexpected postural perturbations would depend on a feedback control system where an error signal, which is carried by sensory afferences, is processed to restore a given set point (Marsden et al 1983;Matthews 1991;Pruszynski and Scott 2012;Petersen et al 1998). Muscle spindles and joint receptors should be the main sources of sensory signals informing the brain on the onset of leg fall.…”

“…Since long-loop circuits are involved, this process can take place, thus allowing the sensory signal to be specifically associated to the task and the motor response to be adapted instantaneously to the actual circumstances (Lewis et al 2006;Kurtzer et al 2008;Pruszynski and Scott 2012;Pruszynski et al 2011;Casabona et al 2012;Valle et al 2013).…”

Identification of connectivity in human motor control: exciting the afferent pathways

“…The measures of afferent pathway connectivity presented in this thesis are valuable in this context as sensory feedback and sensorimotor integration are vital for motor function (Scott, 2004;Pruszynski and Scott, 2012). Showing the feasibility of obtaining PCC and the StrEP early after stroke opens the possibility to record afferent pathway connectivity after stroke in a longitudinal study design following stroke survivors throughout motor function recovery process.…”

“…The short latency response is generally thought to be mediated by a monosynaptic reflex pathway. The origin of the long latency reflex is more complex, several pathways may contribute to this reflex including a transcortical pathway (MacKinnon et al, 2000;Spieser et al, 2010;Pruszynski and Scott, 2012) 6 Stretch evoked potentials in normal subjects and after stroke Cross correlation coefficients [-] aff. side [μV] aff.…”