Online gain update for manual following response accompanied by gaze shift during arm reaching

Abstract

To capture objects by hand, online motor corrections are required to compensate for self-body movements. Recent studies have shown that background visual motion, usually caused by body movement, plays a significant role in such online corrections. Visual motion applied during a reaching movement induces a rapid and automatic manual following response (MFR) in the direction of the visual motion. Importantly, the MFR amplitude is modulated by the gaze direction relative to the reach target location (i.e., foveal or peripheral reaching). That is, the brain specifies the adequate visuomotor gain for an online controller based on gaze-reach coordination. However, the time or state point at which the brain specifies this visuomotor gain remains unclear. More specifically, does the gain change occur even during the execution of reaching? In the present study, we measured MFR amplitudes during a task in which the participant performed a saccadic eye movement that altered the gaze-reach coordination during reaching. The results indicate that the MFR amplitude immediately after the saccade termination changed according to the new gaze-reach coordination, suggesting a flexible online updating of the MFR gain during reaching. An additional experiment showed that this gain updating mostly started before the saccade terminated. Therefore, the MFR gain updating process would be triggered by an ocular command related to saccade planning or execution based on forthcoming changes in the gaze-reach coordination. Our findings suggest that the brain flexibly updates the visuomotor gain for an online controller even during reaching movements based on continuous monitoring of the gaze-reach coordination.

Rapid visuomotor feedback gains are tuned to the task dynamics

“…The absence of any evidence of gain scaling for visuomotor responses contrasts with the results for the manual following response, or MFR ( Abekawa and Gomi 2015 ; Gomi et al 2006 ; Saijo et al 2005 ). It has been shown that the MFR exhibits stronger responses when the limb is loaded ( Saijo et al 2005 ), similar to the gain scaling of stretch reflex responses.…”

“…Feedback corrections to errors during reaching can arise through both muscle stretch-dependent motor responses (stretch reflexes) ( Bennett 1994 ; Kurtzer et al 2009 ; Nashed et al 2014 ) and rapid visuomotor responses responding to shifts in the visual location of the hand ( Franklin and Wolpert 2008 ; Sarlegna et al 2003 ; Saunders and Knill 2003 ), the target ( Brenner and Smeets 1997 ; Day and Lyon 2000 ; Goodale et al 1986 ; Hayashi et al 2016 ; Oostwoud Wijdenes et al 2011), or the visual background ( Abekawa and Gomi 2015 ; Saijo et al 2005 ). These visuomotor responses are involuntary in nature ( Day and Lyon 2000 ; Franklin and Wolpert 2008 ; Gomi 2008 ), with loop delays to force production on the order of 150 ms ( Franklin et al 2016 ).…”

Gain control in the sensorimotor system

“…In addition to visual perturbation of the target or hand position, visual background motion caused by one's own body movement can also induce online corrections in the direction of visual motion, a phenomenon called the manual following response. A recent study probed the visuomotor gains of these manual following responses during a midreach saccadic eye movement, finding that gain modulation occurs rapidly during the saccade to coordinate gaze and reach in a predictive manner [49].…”

Modulations of stretch reflex by altering visuomotor contexts

“…Though earlier studies have demonstrated a task-dependent regulation of the arm muscle stretch reflex in response to the size ( Yang et al, 2011 ) or position ( Mutha et al, 2008 ) of the visual goal, the effect of visual target uncertainty on the stretch reflex has not been investigated. Furthermore, previous studies have shown that uncertainty in the visual target induced by visual noise ( Izawa and Shadmehr, 2008 ) or dynamic location updates ( Dimitriou et al, 2013 ; Abekawa and Gomi, 2015 ) affects the online corrective visuomotor response. However, it remains unclear whether uncertainty in the visual target affects the gain of the quick feedback control evoked by sensory inputs in different modalities.…”