Motor imagery of locomotion with an additional load: actual load experience does not affect differences between physical and mental durations

Abstract

Motor imagery relies strongly on motor representations. Currently, it is widely accepted that both the imagery and execution of actions share the same neural representations (Jeannerod, Neuroimage 14:S103-S109, 2001). Comparing mental with actual movement durations opens a window through which to examine motor representations and how they relate to cognitive motor processes. The present experiment examined mental durations reported by participants standing upright who imagined walking either with or without an additional load while actually carrying or not carrying that same load. Results showed a robust effect of longer durations when imagining the additional load during mental walking, whereas physical walking with an additional load did not extend movement durations accordingly. However, experiencing an actual load during imagery did not influence mental durations substantially. This dissociation of load-related effects can be interpreted as being due to an interaction of motor processes and their cognitive representation along with a reduction in neural activity in vestibular and somatosensory areas during imagery of locomotion. It is argued that this effect might be specific to locomotion and not generalize to a broader range of movements.

Why is the Duration of Imagined Walking Underproduced? A dual-representation view on the mental imagery of locomotion

“…The first step of this investigation was to replicate the underproduction of imagined walking duration. Although multiple research groups independently found this pattern (Grechkin et al, 2010;Kunz et al, 2009;Munzert et al, 2015;Stevens, 2005), there are also studies in IMAGINED WALKING 7 which real and imagined walking times were comparable to each other (Bakker et al, 2007;Courtine et al, 2004;Fusco et al, 2014;Papaxanthis et al, 2002;Personnier et al, 2010;Schott & Munzert, 2007). Given this discrepancy in the literature, replication of the underproduction tendency would be crucial for the present study.…”

“…A number of studies have been carried out to investigate mental simulation of walking, and results from these studies are consistent with the general findings summarized above: In overt behavior, the time it IMAGINED WALKING 6 takes participants to imagine walking a given distance varies systematically as a function of the walked distance (and thus as a function of the time it takes them to physically walk the same distance; Bakker, de Lange, Stevens, Toni, & Bloem, 2007;Courtine, Papaxanthis, Gentili, & Pozzo, 2004;Decety, Jeannerod, & Prablanc, 1989;Fusco et al, 2014;Papaxanthis, Pozzo, Skoura, & Schieppati, 2002;Personnier, Kubicki, Laroche, & Papaxanthis, 2010;Plumert, Kearney, Cremer, & Recker, 2005;Saimpont, Malouin, Tousignant, & Jackson, 2012;Schott & Munzert, 2007); and in the brain, movement-related areas such as the premotor cortex, supplementary motor area, and cerebellum are commonly activated while participants perform real and imagined walking (Bakker et al, 2008;Hamacher et al, 2015;Hanakawa et al, 1999;Harada, Miyai, Suzuki, & Kubota, 2009;Jahn et al, 2004;la Fougère et al, 2010;Miyai et al, 2001;van der Meulen, Allali, Rieger, Assal, & Vuilleumier, 2014). However, one notable observation is that participants often underproduce imagined walking times relative to real walking times that they spend actually walking the same distances (Grechkin, Nguyen, Plumert, Cremer, & Kearney, 2010;Kunz et al, 2009;Munzert, Blischke, & Krüger, 2015;Stevens, 2005). The degree of underproduction can be substantial, making the imagined walking times as short as 59% of the corresponding real walking times (Stevens, 2005).…”

“…Thus, the groups differed not only in the task order but also in physical environments. Although the difference in the surroundings could have affected participants' visual perception of target distance (Lappin, Shelton, & Rieser, 2006), it was anticipated that effects of the environmental difference would not be critical because (a) the key comparison between real and imagined walking was done within-participant; and (b) temporal underproduction of imagined walking has been observed in multiple labs (Grechkin et al, 2010;Kunz et al, 2009;Munzert et al, 2015;Stevens, 2005).…”

“…A priori power analysis was conducted (with the G*Power 3 program; Faul, Erdfelder, Lang, & Buchner, 2007) using ηp 2 = .10 as an estimated size of the main effect of walking mode (real and imagined) on walking times. This estimate was based on effect sizes reported in the literature-for example, when Kunz et al (2009) and Munzert et al (2015) had each participant perform real and imagined walking without any additional manipulations during imagined walking trials, the effect sizes of walking mode ranged from .12 to .84. To derive a conservative estimate of required sample size for the present experiment, a moderate correlation IMAGINED WALKING 15 (r = .50) between real and imagined walking times was assumed.…”

Mu oscillations and motor imagery performance: A reflection of success, not ability

“…Motor imagery refers to the mental rehearsal of movement from the first-person perspective in the absence of overt motor action (Jeannerod 1995;Madan & Singhal, 2012;Munzert et al, 2015;Munzert et al, 2009). Indications that this cognitive strategy can facilitate motor skill acquisition and enhance motor performance have made it a popular research area in recent years, with particular interest being directed to possible applications in both athletic and clinical settings.…”