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Matthew Heath, David A. Westwood and Gordon Binsted

The goal of the present investigation was to explore the putative contributions of feedforward- and feedback-based processes in the control of memory-guided reaching movements. Participants (N = 4) completed an extensive number of reaching movements (2700) to 3 midline targets (20, 30, 40 cm) in 6 visual conditions: full-vision, open-loop, and four memory-guided conditions (0, 200, 400, and 600 ms of delay). To infer limb control, we used a regression technique to examine the within-trial correspondence between the spatial position of the limb at peak acceleration, peak velocity, peak deceleration, and the ultimate movement endpoint. A high degree of within-trial correspondence would suggest that the final position of the limb was largely specified prior to movement onset and not adjusted during the action (i.e., feedforward control); conversely, a low degree of within-trial correspondence would suggest that movements were modified during the reaching trajectory (i.e., feedback control). Full-vision reaches were found to be more accurate and less variable than open-loop and memory-guided reaches. Moreover, full-vision reaches demonstrated only modest within-trial correspondence between the spatial position of the limb at each kinematic marker and the ultimate movement endpoint, suggesting that reaching accuracy was achieved by adjusting the limb trajectory throughout the course of the action. Open-loop and memory-guided movements exhibited strong within-trial correspondence between final limb position and the position of the limb at peak velocity and peak deceleration. This strong correspondence indicates that the final position of the limb was largely determined by processes that occurred before the reach was initiated; errors in the planning process were not corrected during the course of the action. Thus, and contrary to our previous findings in a video-based aiming task, it appears that stored target information is not extensively (if at all) used to modify the trajectory of reaching movements to remembered targets in peripersonal space.

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Matthew Heath

This investigation tested the proposal that a “highly accurate” and temporally unstable stored target representation is available to the motor system for the online control of memory-guided reaches. Participants reached to a target that was: (a) visible during the response, (b) extinguished at movement onset, and (c) occluded for 0, 500, 1500 and 2,500 ms in advance of response cueing. Additionally, trials were performed with (i.e., limb visible) and without (i.e., limb occluded) vision of the reaching limb. Results showed that limb occluded trials undershot the target location in each target condition, and were characterized by a primarily offline mode of control. In contrast, limb visible trials showed a consistent level of endpoint accuracy for each target condition and elicited more online reaching corrections than limb occluded trials. It is therefore proposed that a reasonably accurate and temporally stable stored target representation can be combined with vision of the moving limb for the online control of memory-guided reaches.

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Olav Krigolson, Jon Bell, Courtney M. Kent, Matthew Heath and Clay B. Holroyd

We used the event-related potential (ERP) methodology to examine differences in neural processing between visually and memory-guided reaches. Consistent with previous findings (e.g., Westwood, Heath, & Roy, 2003), memory-guided reaches undershot veridical target location to a greater extent than their visually guided counterparts. Analysis of the ERP data revealed that memory-guided reaches were associated with reduced potentials over medial-frontal cortex at target presentation and following movement onset. Further, we found that the amplitudes of the potentials over medial-frontal cortex for visually and memory-guided reaches were significantly correlated with the peak accelerations and decelerations of the reaching movements. Our results suggest that memory-guided reaches are mediated by a motor plan that is generated while a target is visible, and then stored in memory until needed—a result counter to recent behavioral theories asserting that memory-guided reaches are planned just before movement onset via a stored, sensory-based target representation.

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K. Brownell, T. Rolheiser, M. Heath and G. Binsted

The authors examined if previously reported anatomical asymmetries between the upper (uVF) and lower visual fields (lVF) influence the preparation and control of visually and memory-guided reaching movements. To manipulate visual field, participants maintained their visual gaze on a cue position presented above or below the location of a target object, thus resulting in reaches completed in respective uVF and lVF of peripersonal. In Experiment 1, participants performed reaches to four targets with indices of difficulty ranging from 3.1 to 5.1 bits under five visualmemory conditions: full vision and memory-guided conditions entailing 0, 2, 5, and 10 s of delay. In Experiment 2, participants reached to the vertex of Müller-Lyer figures in 3 visual-memory conditions: full vision, and memory-guided conditions entailing 0, and 2 s of delay. In accord with duplex theories of vision (e.g., Milner & Goodale, 1992), it was hypothesized that the introduction of a visual delay and/or the introduction of context-dependent illusory structure would differentially bias the efficiency and effectiveness of uVF and lVF reaches. Although data displayed mixed supported for the existence of an lVF advantage for movement execution, neither the introduction of delay nor contextual illusions succeeded in differentiating visual fields. Thus, performance advantages for movements made in the lower visual field do not appear associated with preferential connections to parietal (i.e., dorsal-action) and temporal (i.e., ventral-perception) architectures.

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John de Grosbois and Luc Tremblay

Grosbois and Tremblay ( 2017 ) examined the performance of participants under blocked full-vision (FV), no-vision (NV), and memory-guided NV viewing conditions. Under the blocked condition presentation, participants were conceivably able to prepare their movements differently across conditions. The results

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Jennifer Campbell, Stephanie Rossit and Matthew Heath

.1080/00140138808966724 Goodale , M.A. ( 2011 ). Transforming vision into action . Vision Research, 51 , 1567 – 1587 . PubMed ID: 20691202 doi:10.1016/j.visres.2010.07.027 10.1016/j.visres.2010.07.027 Heath , M. ( 2005 ). Role of limb and target vision in the online control of memory-guided reaches . Motor Control

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Satyajit Ambike, Daniela Mattos, Vladimir Zatsiorsky and Mark Latash

. PubMed doi:10.1007/s00221-012-3253-y 10.1007/s00221-012-3253-y Heijnen , M.J. , Romine , N.L. , Stumpf , D.M. , & Rietdyk , S. ( 2014 ). Memory-guided obstacle crossing: More failures were observed for the trail limb versus lead limb . Experimental Brain Research, 232 , 2131 – 2142 . PubMed

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Moslem Bahmani, Jed A. Diekfuss, Robabeh Rostami, Nasim Ataee and Farhad Ghadiri

grasping and manual aiming tasks (see Glover, 2004 for a review). However, to examine memory-guided movements that require the performer to hold-target related information in working memory while fixating on another object (e.g., target and golf ball), there has been a proliferation of research exploring

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Chanel T. LoJacono, Ryan P. MacPherson, Nikita A. Kuznetsov, Louisa D. Raisbeck, Scott E. Ross and Christopher K. Rhea

). Memory-guided obstacle crossing: More failures were observed for the trail limb versus lead limb . Experimental Brain Research, 232 ( 7 ), 2131 – 2142 . PubMed doi:10.1007/s00221-014-3903-3 10.1007/s00221-014-3903-3 Holden , M.K. ( 2005 ). Virtual environments for motor rehabilitation: Review

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Greg Wood, Samuel J. Vine, Johnny Parr and Mark R. Wilson

, which could impair shooting performance ( Wood, Jordet, & Wilson, 2015 ). Similarly, using an internal representation of the dimensions of the goal to guide their shot is inefficient as previous research has suggested that “stored target information serving memory-guided action is susceptible to a