The emerging clarity of the roles of gesture in communication and interventions for people with aphasia

This is an exciting time in the quest to understand the role of gesture in human communication. The special context of aphasia for the study of the interplay between gesture, speech, language and cognition has a small but important history. The early investigations of gesture type and frequency of production, and the clinical reports of the positive role of gesture production on language production for people with aphasia (e.g.,Skelly, Schinsky, Smith, & Fust, 1974), laid down a base from which many of the authors contributing to this special issue have worked. These early studies suggested that aphasia in general, and later aphasia type, impacts on gesture production, with some studies reporting negative views of gesture production. As the models of gesture, speech and language production were refined, studies examining gesture in aphasia became more sophisticated and revealing. Recently, there appears to be an exponential growth in interest in gesture and aphasia if counts of published studies over the past 5 as compared to the previous 15 years are indicative. Many of these researchers are motivated to study gesture within the context of aphasia to discover possible therapeutic options for restoring language function or compensating for language impairment. Others, however, are more theoretically motivated, by the special lens provided by aphasia on the interaction of speech, language, gesture and cognition.

OVERVIEW OF THE ISSUE

This special issue of Aphasiology presents groundbreaking empirical evidence from seven studies concerning several key questions in the field. The first article by de Ruiter and de Beer (2013) presents an erudite account of the main competing theories of gesture, speech and language interaction, setting the stage for three studies that follow (Cocks, Dipper, Pritchard, & Morgan, 2013; Hogrefe, Ziegler, Wiesmayer, & Goldenberg, 2013; Sekine, Rose, Foster, Attard, & Lanyon, 2013) examining gesture production in aphasia and the participant variables that impact on production patterns. Two studies then follow (Marshall et al., 2013;Rose, Raymer, Lanyon, & Attard, 2013) that examine gesture as a therapeutic modality for restoration of language function and communication compensation. The final study (Rogalsky et al., 2013) examines the brain–behaviour relationships that underpin gesture comprehension, challenging accounts of the role of mirror neurons in action comprehension.

GESTURE PRODUCTION PATTERNS IN APHASIA

The idea that aphasia type and severity might impact on gesture production is not new. Many previous studies have examined this concept, but to date small numbers of participants, a restricted range of coded gestures and the brevity of the language samples examined have limited the utility of their results. The three studies addressing gesture production patterns in this special issue address many of these prior limitations and go further to specify the role of semantic knowledge in gesture production. These are now summarised.

Gesture production patterns were examined in 10 health controls and a large group of 46 individuals with Broca’s (10), Wernicke’s (10), transcortical motor (6), conduction (10) and anomic (10) aphasia by Sekine et al. (2013). Twelve gesture types (gesticulations, emblems, pantomimes) were coded from conversational samples. Sekine et al. found people with aphasia produced more gestures per 100 words than controls, and those with Broca’s aphasia producing the highest rate, and the highest amount of meaning-laden gestures (pantomimes, emblems, iconics). Speech fluency showed a strong relationship with gesture type, such that there was a strong positive correlation between fluency and production of referential gestures and a strong negative correlation between fluency and production of concrete deicitcs, iconics, emblems and pantomimes. Regression analyses revealed that speech fluency accounted for 27% of the variance in the rate of production of meaning-laden gesture types, whereas neither overall aphasia severity nor the degree of word retrieval impairment significantly predicted gesture production patterns.

The notion that semantic knowledge is crucial for the production of iconic gestures is examined here by Cocks et al. (2013). Their study is large (N = 29 people with mild–moderate aphasia) by previous standards and as such is able to elegantly examine the relationship between iconic gesture production during fluent speech, as compared to speech containing word retrieval difficulties. Their results corroborate previous findings that people with aphasia produce more iconic gestures during periods of word retrieval than during fluent speech (Lanyon & Rose, 2009; Sekine et al., 2013; Sekine & Rose, in press). However, Cocks et al. go further to differentiate path, manner and shape outline production in these conditions as they relate to participants’ semantic knowledge of both actions and objects. The finding that people with strong semantics produce semantically rich manner gestures supports previous findings in people with severe aphasia that semantic knowledge impacts on the diversity of gesture production (Hogrefe, Ziegler, Weidinger, & Goldenberg, 2012). In particular, Cocks et al. provide evidence for the importance of strong semantic knowledge to produce iconic gesture during word retrieval difficulties, principally action semantics and gesture production during word retrieval difficulties for verbs.

Hogrefe et al. (2013) examined the amount of information 16 speakers with aphasia conveyed through gesture versus speech in two narration tasks where participants could speak or were silent. Although two participants conveyed more information through gesture than through spoken expression, not all participants were able to fully exploit gesture in the silent condition. Interestingly, participants’ scores on the pantomime-to-command test were the main predictor of the comprehensibility of their gestures. Hogrefe et al. then argue that the emphasis of distinctive features necessary for pantomimes to be comprehensible is deficient in individuals with aphasia and semantic memory deficits.

THE ELUSIVE “GESTURE FACILITATION” EFFECT: THERE’S MORE WORK TO DO!

Interestingly, considering the participants as a group, Cocks et al. found no difference in the number of resolved word retrieval difficulties that contained gesture versus the number of unresolved containing gesture, suggesting little effect of gesture production in word retrieval success. However, as has previously been reported (Lanyon & Rose, 2009), additional patho-linguistic parameters, such as the fidelity of phonological access and encoding mechanisms, may be important in understanding individual facilitation patterns, masked in group analysis. Recent work (Kroenke, Kraft, Regenbrecht, & Obrig, in press) examining word re-learning and its neural underpinnings in people with aphasia added further support to the idea first proposed by Rose et al. (Rose & Douglas, 2001; Rose, Douglas, & Matyas, 2002) that gesture may facilitate word retrieval for those with strong semantics but impaired phonological access. Larger scale and more detailed work is required to further delineate this idea, which has important implications for tailoring aphasia intervention.

GESTURE AS A THERAPEUTIC MODALITY IN APHASIA

A systematic review of the scientific evidence for the effects of symbolic and non-symbolic gesture training on aphasia was carried out by Rose et al. (2013). Twenty-three studies involving a total of 134 participants were analysed for scientific quality, and their results were synthesised. Eleven of the 19 single subject experimental designs achieved high quality scores. Gesture training alone led to non-significant effects on verbal production. Combined gesture and verbal training showed positive effects on verbalisation for over 50% of the participants, but there is limited advantage over verbal training alone, except for some individuals with aphasia. Significant gains in gesture production were reported only for trained gestures. Rose et al. argue for large-scale investigations in this field, which can handle analyses of response from subtypes of aphasia.

Marshall et al. (2013) report on their innovative computer-based gesture intervention tool “GeST”. Such innovation is vital to enable intensive intervention otherwise not achievable in health care systems with limited resources. It also opens opportunity to provide intervention to individuals living at distance from health care centres. By involving people with aphasia in the design of GeST from the outset, the resulting product has been well received by participants. Marshall et al. examine the feasibility of GeST in nine individuals with severe and persisting aphasia and investigate its impact on gesture production and spoken naming performance in a pre-post design. One impressive design feature concerns GeST’s ability to recognise participant’s gesture attempts and provide feedback on accurate productions. Gains were item specific and required regular therapist support.

THE NEURAL BASIS OF GESTURE COMPREHENSION

To investigate the neural basis of action understanding, Rogalsky, Raphel, Tomkovics, O’Grady, Damasio, Bellugi and Hickok carried out a lesion analysis of 21 sign language users with focal unilateral cortical lesions. In particular, they aimed to investigate the role of the mirror neuron system as compared to the temporal lobe ventral stream in gesture comprehension. In one task, participants had to comprehend individual signs, and in a second, signed commands. Left hemisphere lesions did not significantly affect single sign comprehension, while sentence sign comprehension deficits were associated with left temporal-parietal damage and not mirror system regions in the left frontal lobe. The results argue against the mirror system being critical in action understanding.

THE FUTURE

Taken together, the studies in this special issue advance our understanding of the role of gesture in people with aphasia, both in terms of natural adaptive behaviours and what may be possible in therapeutic contexts. The studies also provide evidence that helps to further specify models of gesture, speech and language interaction and the neural networks that underpin these behaviours. The field is ripe for further exploration. I believe within that the next decade research will provide a set of neural and behavioural patient characteristics that therapists will be able to use in clinical reasoning for specific gesture-based aphasia treatment prescription. I eagerly await that day!

Miranda Rose

School of Human Communication Sciences, La Trobe University, Melbourne,, Australia and Centre for Clinical Research Excellence in Aphasia Rehabilitation, Brisbane, Queensland,, Australia

Miranda L. Rose, Department of Human Communication Sciences, La Trobe University, Bundoora, VIC, 3086 [email protected]