Discourse Skills & Right Hemisphere Damage: A Literature Review

Introduction

Discourse is a necessary component of daily communication and interaction between individuals, functioning on multiple and often highly complex syntactical and semantic levels. Discourse, in the broadest sense, refers to the use of spoken or written language in a social context, but pertains moreover to the deep-coded levels of communication, at the inferential and even non-verbal levels. Discourse is a social and verbal as well as cognitive phenomenon and hence is multifaceted. Everyday functional communication demands the use of discourse, and such use is heavily reliant on the operation of the right brain hemisphere. Indeed, in most cases, when the right brain hemisphere is damaged, discourse skills are impaired in significant ways, varying according to the spectrum of how severely the patient’s right brain hemisphere is injured. This paper examines the cause and effect dynamics mediating this process (in relation to discourse), paying close attention to the distinctions between macro-structure and micro-structure.

Right Hemisphere Damage (RHD), Discourse Impairment

Right hemisphere damage (RHD) is an acquired disorder from the result of stroke or traumatic brain injury (TBI) (ASHA, 2020). RHD affects:

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• Semantic processing of words
• Discourse processing
• Prosody
• Pragmatics

However RHD rarely affects syntax, grammar, phonological processing and word retrieval (ASHA, 2020); nor does damage to the right hemisphere apparently translate to impairments to fundamental word and sentence processing (Klepousniotou & Baum, 2005). This would imply that the RH does not deal with such sub-unit elements of discourse; it is not involved with the precise permutations of internal discourse structure, per se. At any rate, there appear to be sizable and indeed vital differences in the functions fulfilled by different hemispheres. In consequence, different kinds of remedial approaches to distinct discourse impairments are presumably in order, focusing on the LH or RH accordingly. Other cognitive impairments, such as attention, memory and executive functioning, can also contribute toward interfering with the communication skills that a RHD patient is left with. All of these impairments impeded discourse skills in various ways. Research by Johns et al. (2008) suggests that the right hemisphere plays an important role in language processing, where it deals with information that is inferred or implied; and, moreover, in distinguishing, supporting or ruling out information which is relevant or irrelevant to the ongoing task. These are essential skills, it is clear, for subjects’ capacities to analyse the suitability of certain responses or utterances in a given situation; their discursive facility, that is.

In some cases, evidence suggests that damage to the right hemisphere affects the meaning maintenance function. One can point for example to work by Tompkins et al. (‎2008) investigating “whether RHD deficits in processing secondary and or distantly related meanings of words would extend the peripheral, weakly related semantic features of unambiguous nouns”. 28 adults with unilateral RHD and 38 adults without brain damage participated in the study. Subjects were presented with spoken statements concluding with an “unambiguous noun”, followed by a “spoken target phoneme string” (ibid). The stated targets included secondary semantic (weakly related) features that were incommensurate with the dominant mental images generally associated with the given noun. The purpose was to determine the extent of early activation or maintenance of activation for the above peripherals. The results found that both participant sets exhibited no maintenance activation for either type of feature (over a longer period of time). Further, RHD participants were less accurate than adults with no brain injury (during both test intervals). Extrapolating these findings, one can tentatively posit that the right hemisphere plays a critical role in activating semantic features that are less relevant to, or related with, their matched lexical items. That said, findings cannot be generalised (thus one cannot ascribe a definitive rule), on the basis of a single study. Indeed, as the researchers themselves make clear, further investigation is needed (in discourse comprehension for adults with RHD) to ensure that the above findings are verified in a scientifically rigorous manner.

Important distinctions may be established between the left and right hemispheres inasmuch as certain inferences can be drawn from subjects with damage to either side; inferences that point to discrete functions vis-à-vis discourse skills. So, evidence suggests that the right hemisphere operates no discourse model containing micro-structural information (Long & Baynes, 2002; Long et al., 2005; Prat et al., 2007). In this context, micro-structural information denotes “lexical elements governing discourse cohesion” and stands therefore in distinction to macro-structural information, which describes “the global aspects of discourse organisation” (Beeman & Chiarello, 2013, p. 298). Studies have shown that the RH plays a large role in such macro-structural features, facilitating a “big picture” (discursive) understanding for the subject, particularly in respect of the “ability to understand visual information, visual representations, and spatial relationships between objects” (Manasco, 2019, p. 36). This same spatial-visual register of comprehension is heavily in play in mediating the reception and interpretation of facial expressions, for example; thus it lends itself imperatively to non-verbal communication, which necessarily informs the verbal components of any discursive event in significant ways. As a result of this “big picture” macro-function, the RH is critical in enabling subjects to apprehend and follow the “main idea or theme” of any discursive interaction, seeing as such a connecting “theme” permits for the “various subcomponents of the story” to be arranged into “coherent” structure (Traxler, 2011, p. 224). Without the overarching structure to comprehend the purpose and intent of a discursive event, the subject is restricted in their ability to make sense of the discrete sections of the discourse in action. This is because damage to the RH works to impede “inference generation tasks and integration tasks”, leading, in turn, “to difficulties in generating macro-structures or thematic inferences”; put simply, it creates “problems in bridging gaps” (Kong, 2016, p. 219). To reiterate, then, RHD is markedly different from LHD in its identified impairments and, therefore, in the specific operations which may be inferred to work on the left or right hemispheres (in regard to discourse skill).

So, there is an evident dynamic of left/right dominance when it comes to the various components of discourse and structural mechanics at work. Indeed, “patients with unilateral RHD rarely exhibit [any] micro-structural deficiencies” (Johns et al., 2008). In clear contrast, LHD correlates directly with micro-structural impairments. For example, while LHD patients exhibit no problem in identifying a “pictorial representation of the sentence ‘The butcher weighed the meat’, they often have difficulty selecting the correct pictorial representation of sentences, such as, ‘The fireman weighed the policeman’” (Johns et al., 2008). What separates the two phrases, here, is the centrality in the latter sentence of micro-structural information which allows the subject to organise the precise semantic intent of what is being said, especially insofar as determining syntactic agency (who is the agent, who is the patient). This is because the LHD subject demonstrates impairment in sorting the syntactical data that clarifies that “the policeman is the object of fireman’s (the agent’s) action, and not vice versa” (Johns et al., 2008). Subjects who have RHD, however, do not demonstrate the same problem in distinguishing syntactic agency, because their micro-structural capacity is not, the evidence indicates, likewise damaged. In contrast to this, much experimental research suggests that RHD patients may “experience difficulty when macro-structural considerations are required to successfully comprehend discourse” (Ibid). Breaking this down, the issue is that, without fully functional macro-structure capability, it is very difficult for the RHD subject to put together the many smaller component parts of discourse so as to form a coherent and intelligible whole from the discourse.

Scholars have identified the right cerebral hemisphere as a possible locus of control for gesture. The assessment and rehabilitation research aims to:

1. Describe male non‐brain‐damaged (NBD) speakers’ gesture-use in the context of spontaneous discourse.
2. Compare the gesture production patterns of five individual males with right cerebral hemisphere damage (RHD) with the NBD group’s pattern of performance.

A study by Cocks et al. (2007) looked at gesture rates and the variation of fundamental frequency, examining these metrics in the context of four speaking conditions: “a personal narrative; two procedural narratives; two emotional narratives; and three comic book descriptions”. The intention of using these specific “discourse stimuli” was to employ “highly emotional versus neutral content” (ibid). All the gestures that were made were recorded in order to be digitally analysed by means of the McNeill (1992) Classifying System. The NBD group exhibited a greater frequency of immediate physical reaction (higher rates of body beats and head movement) when presented with discourse samples deemed to possess emotionally charged elements. In contrast, the RHD participants demonstrated a lack of consistency in their gesture-use across the different discourse genres. Broadly speaking, this finding is in keeping with the research by Johns et al. (2008) - though, it would depend upon the specific kinds of (macro or micro) structures being engaged (by the texts), which shaped the inference processes for accessing the meaning of the texts in question. At any rate, the majority of the RHD participants demonstrated lower non‐body‐focused gesture-rates. Significantly, and adding weight to the supposed “big picture” macro-function of the RH, this group exhibited fewer gestures in response to the emotionally charged discourse samples. However, it should be noted that there were no systematic patterns in the results of RHD participants in visuospatial ability, variations in fundamental frequency of speech, or body‐focused gestures. On this basis, one might reasonably posit that varying degrees of RHD equate to different levels of macro-structural impairment or that such impairment manifests in non-homogenous ways.

McNeill’s (1992) growth point theory supported a profitable platform for interpreting the reduction in the overall frequency of gesture-use that was evident in the RHD participants. Nevertheless, this fact alone cannot make up for the results observed during monitored interaction of participants engaging with the emotive texts. Indeed, the pattern revealed in relation to the RHD participants advances a challenge for theoretical work in this area. That is, the outcomes suggest that the analysis of gesture-use is fundamental for a more in-depth understanding of the expressive communication impairments that are related to acquired neurogenic impairment (Cocks et al., 2007). Indeed, this takes us back to the above-outlined issue regarding non-verbal aspects of communication. Subtle aspects of gesture apparently serve as indices of particular inference processes, arguably working in some cases as cues of, and for, the comprehension of discourse. On this analysis, gesture in itself might be deemed an at least note-worthy element of discourse skill – comprising, as it does, an imperative framing device for the ordering of semantic and syntactic information. Put in simple terms, gesture may plausibly be considered as playing some role in the embodiment processes that accompany discursive comprehension.

Patients with RHD manifest communication deficits, such as difficulties processing prosody, discourse, and understanding the nuances of distinct social contexts. In the above-mentioned study, participants with RHD and LHD were compared and analysed according to specific scientific frameworks. Participants were asked to respond to cartoon stimuli, and thus were, so to speak, “manipulated”, using fixed parameters that were (as far as was possible) set and controlled so to elicit formulaic responses. The intention was to create a consistent research environment that would yield consistent experiment conditions by removing as many variables as possible. Results showed that RHD participants’ responses were notably less appropriate than the control groups were. In addition, the RHD group responded in less typical ways than the control group and the participants with LHD. Specifically, the RHD group yielded fewer instances of formulaic expressions than the control group did. However, this difference was only a trend and cannot, without further investigation, be taken as indicative of any broader empirical event. Accordingly, the “pattern of performance across participant groups was not influenced by how constrained or formulaic the social situation was” (Baldo et al., 2015). These findings cast new critical light on the right and left hemispheres’ roles in social processing and communication; they also suggest that there is a possibility for the treatment of social communication deficits in patients with RHD. On this basis, further research is needed into the many aspects of discourse skill, especially such as delivers experimental data on the interplay between various aspects of left and right macro/microstructure – thus to provide researchers with a more comprehensive picture of the complex inter-dynamics at play.

Works Cited

1. ASHA. (2020). Right Hemisphere Brain Damage (RHD). Retrieved 6 January 2020, from https://www.asha.org/public/speech/disorders/Right-Hemisphere-Brain-Damage/.
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