Sensory information in perceptualmotor sequence l

Authors: Elger L Abrahamse Rob H J van der Lubbe Willem B Verwey

Publish Date: 2009/06/30

Volume: 197, Issue: 2, Pages: 175-183

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Abstract

Sequence learning in serial reaction time SRT tasks has been investigated mostly with unimodal stimulus presentation This approach disregards the possibility that sequence acquisition may be guided by multiple sources of sensory information simultaneously In the current study we trained participants in a SRT task with visual only tactile only or bimodal visual and tactile stimulus presentation Sequence performance for the bimodal and visual only training groups was similar while both performed better than the tactile only training group In a subsequent transfer phase participants from all three training groups were tested in conditions with visual tactile and bimodal stimulus presentation Sequence performance between the visual only and bimodal training groups again was highly similar across these identical stimulus conditions indicating that the addition of tactile stimuli did not benefit the bimodal training group Additionally comparing across identical stimulus conditions in the transfer phase showed that the lesser sequence performance from the tactile only group during training probably did not reflect a difference in sequence learning but rather just a difference in expression of the sequence knowledgeOne crucial aspect of motor performance is the ability to learn sequences of movements Typically motor sequence learning is studied using buttonpressing tasks such as the serial reaction time SRT task or the discrete sequence production DSP task in which participants are required to respond to single stimuli presented visually on a screen However in daily life we simultaneously encounter multiple sources of sensory information across different modalities1 Whereas the effect of bimodal congruent stimuli has been extensively explored with respect to trial by trial performance in simple and choice reaction time RT tasks eg Frens et al 1995 Giard and Peronnet 1999 Rowland and Stein 2007 far less is known about the impact of such stimulus pairs on sequence learning across trials In the current study we explored whether congruent and temporally synchronized visual and tactile stimuli enhance learning of a sequence of actions in an SRT taskIn its basic form the SRT task requires participants to respond fast and accurately by pressing the buttons corresponding to the locations of successively presented visual stimuli eg Nissen and Bullemer 1987 Unbeknownst to them however stimulus presentation is structured and reaction time RT decreases with practice To differentiate sequence learning from general practice effects a random block of stimuli is inserted at the end of the practice phase The cost in terms of RT and/or accuracy ie sequence effect of this random block relative to its surrounding sequence blocks serves as an index for sequence learning Often participants are unable to express their sequence knowledge in other ways than reflected by RT and accuracy scores and learning is said to partly have taken place implicitlyThe nature of the representation underlying implicit learning is still being debated Whereas responsebased learning is the dominant and best documented account in literature eg BischoffGrethe et al 2004 Grafton et al 1995 Nattkemper and Prinz 1997 Rüsseler and Rösler 2000 Willingham 1999 Willingham et al 2000 recently support is mounting also for sequence learning that involves stimulus features responseeffect learning eg Stöcker et al 2003 Ziessler and Nattkemper 2001 and perceptual location learning eg Deroost and Soetens 2006 Mayr 1996 Remillard 2003 This prompts investigation on the effects that different sensory environments have upon sequence learning eg Abrahamse et al 2008 Jiménez and Vázquez 2008 Robertson and PascualLeone 2001 Robertson et al 2001 Robertson and colleagues Robertson and PascualLeone 2001 Robertson et al 2001 recognized the fact that we are continuously surrounded by multiple sources of sensory information in the real world They explored sequence learning in an SRT task in which required responses were signaled through redundant position and color cues They reported that compared to either single cue condition position or color sequence learning was augmented with combined position and color cuesThe latter supports the notion that perceptualmotor skill acquisition can benefit from multiple sources of congruent information at least within the visual domain However it remains unclear whether these findings would extend to congruent stimuli presented through different sensory modalities It is known from simple detection and choice RT tasks that presenting congruent stimuli across modalities sometimes results in additive or even superadditive sensory interactions eg Miller and Ulrich 2003 Santangelo et al 2008 Stein and Meredith 1993 indicating that information from the different sensory sources gets integrated along the timecourse of SR processing This integration of bimodal stimuli has been found to occur both at early and later sensoryperceptual processing stages and seems to be conditional on the spatial proximity and/or temporal synchrony of the separate stimuli eg Atteveldt et al 2007 Harrington and Peck 1998 Helbig and Ernst 2007 TederSälejärvi et al 2005 Murray et al 2005 From the notion that sensory information plays a role in the formation of the representations underlying sequence learning eg Clegg 2005 Remillard 2003 one may expect that the enriched perceptual events that follow from integrated bimodal stimuli produce stronger sequence representations than those obtained with single stimuliRecently Abrahamse et al 2008 introduced a new version of the SRT task in which stimuli were presented tactilely to the fingers and learning was compared to the typical visual version of the SRT task Sequence learning was reliably observed for both stimulus conditions but it appeared to be better for the condition with visual stimuli In a subsequent transfer phase for both visual and tactile training groups we assessed transfer of sequence learning to the other modality It seemed that transfer was perfect from tactile to visual stimuli but only partial the other way around As we will elaborate on below though these findings deserve some closer inspection because of methodological issuesIn the current study we extended the study of Abrahamse et al 2008 by adding a condition in which congruent visual and tactile stimuli were presented simultaneously Hence participants were trained either with congruent visual and tactile stimuli bimodal training group with visual stimuli only visual only training group or tactile stimuli only tactile only training group This allowed us to investigate the employment by the cognitive system of redundant visual and tactile stimuli each of which has been shown to produce sequence learning when presented alone ie Abrahamse et al 2008 In a subsequent transfer phase transfer to all three stimulus conditions ie visual tactile and bimodal transfer test was assessed for each training group The transfer of sequence knowledge to new conditions is one of the major tools in exploring the nature of sequence learning Clegg et al 1998 Thus exploring whether sequence knowledge acquired in one stimulus condition could readily be applied to different stimulus conditions provides indications on the nature of the representation underlying sequence learning In this respect the transfer test to the initial training condition offered a clear baseline for transfer Additionally comparing across identical stimulus conditions at transfer allows controlling for effects of the training stimulus condition on just the expression of sequence knowledge It has been shown a number of times that sequence knowledge is better expressed under some experimental conditions than others eg Deroost et al 2009 Frensch et al 19982 Finally and closely related to the latter assessing performance across one or more identical stimulus conditions allows comparing performances with more or less similar baseline RTs thereby circumventing the debate of whether differences in baseline RTs should be considered in determining the amount of sequence learning some authors have chosen to normalize the data for baseline differences eg Robertson and PascualLeone 2001We would like to stress that for both the training and transfer phase our main interest was whether the bimodal training group would benefit from the addition of tactile stimuli in comparison to the visual only training group The bimodal training group was logically expected to show better sequence learning than the tactile only training group due to the availability of visual stimuli since visual stimuli have been shown to produce better sequence learning than tactile stimuli only Abrahamse et al 2008

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