Degenerative disorders and cognitive-communication impairment

Although TBI is one of the most common etiologies associated with PFC dysfunction, any disruption of the structure or function of the PFC or related cortical/subcortical neural circuitry may affect cognition, leading to EF deficits and subsequent cognitive-communication disorders. The prefrontal cortex is highly interconnected with the rest of the brain underscoring how damage in many cortical and subcortical areas can lead to dysfunction of the PFC and deficits in EF (Figure 11-1). For example, illnesses that lead to dementia such Huntington’s disease (HD), Parkinson’s disease (PD), Alzheimer’s disease (AD), and frontotemporal lobar degeneration and its variants (e.g., frontotemporal dementia [FTD], primary progressive aphasia [PPA], and semantic dementia [SD]) can specifically impair prefrontal neural circuitry leading to impairments in cognition and communication (Miller & Cummings, 2007). Psychiatric disorders such as schizophrenia, major depression, bipolar disorder, and possibly obsessive-compulsive disorder can also have significant impact on EF related to dysfunction of the PFC with potential impacts related to communication and cognition (Miller & Cummings, 2007).

Difficulties with complex communication have been well documented with a number of non-aphasic disorders (e.g., AD, FTD, SD), primarily associated with the progressive deterioration of memory and EF skills in older adults (Ash, Moore, Antani, et al., 2006; Blair, Marczinski, Davis-Faroque, & Kertesz, 2007; Dijkstra, Bourgeois, Allen, & Burgio, 2004; Laine, Laakso, Vuorinen, & Rinne, 1998; Peelle & Grossman, 2008). As diseases such as AD, PPA, and FTD progress, there are measureable declines in basic language comprehension and production abilities, which can be documented via standardized aphasia batteries. These decrements in linguistic skills show different rates of decline (faster deterioration in PPA and FTD and slower deterioration in AD) but eventually reach similar overlapping profiles in disrupted language performance (Blair et al., 2007). In AD, deterioration of utterance level and inter-sentence cohesion may precede an inevitable decline in more complex discourse abilities such as maintaining thematic relevance and global measures of discourse cohesion (Dijkstra et al., 2004). Discourse assessments provide a sensitive measure of the cognitive-communicative decline in dementia, as persons with mild AD and mild cognitive impairment can demonstrate significant difficulties processing gist level in information in discourse (Chapman, Zientz, Weiner, et al., 2002). Although these changes in communication can appear subtle, the burden of dialogue can shift and differentially impact their communication partners (Dijkstra et al., 2004; Ripich, Vertes, Whitehouse, et al., 1991). However, certain disorders, such as the various manifestations of FTD, are known to have a greater relative impact on EF performance and can manifest in more pronounced changes in cognitive-communication disruptions.

Frontotemporal dementia is a degenerative neurocognitive disorder characterized by alterations in behavior and communication skills with relatively less pronounced deficits in memory processes (Ash et al., 2006; Blair et al., 2007; Peelle & Grossman, 2008). In general, decreased communication fluency, as well as word and sentence level linguistic difficulties, are known to exist in most manifestations of FTD and are associated with atrophic changes in the left inferior frontal gyrus, the left insula, and portions of the left superior temporal gyrus (Ash et al., 2006; Ash, Moore, Vesely, et al., 2009; Blair et al., 2007). However, a specific variant with exacerbated impairment with social functioning and EF difficulties can present without aphasic symptoms, and exemplifies how deteriorations in EF can impact cognitive-communication (Ash et al., 2006; Peelle & Grossman, 2008). Ash and colleagues (2006) have documented specific organizational deficits in this group, with a failure to connect ideas in discourse at both a local (sentence to sentence) and global (theme or gist) levels, throughout relatively simple narrative discourse productions. This pattern of the disintegration of discourse components is related to cortical atrophy in the right prefrontal and temporal lobes, thought to be the anatomical correlate of the disorder (Ash et al., 2006; Peelle & Grossman, 2008). Additionally, poorly integrated discourse may be the most prominent change in communication ability in FTD with social executive impairments and these deficits are significantly correlated to clinically oriented behavioral measures of EF (Ash et al., 2006; Peelle & Grossman, 2008). Similar findings of poorly integrated discourse components measured on local and global levels have also been seen in patients with corticobasal degeneration (CB) (Gross, Ash, McMillan, et al., 2010). Persons with CB experience deficits related to cortical and sub-cortical changes that manifest in frontal and parietal symptoms, including social and EF deficits as well as motor planning difficulties (Gross et al., 2010).

Sub-cortical neurodegenerative disorders such as Parkinson’s disease and Huntington’s disease also provide evidence of measurable declines in cognitive-communication skills related to EF difficulties (Litvan, Frattali, & Duffy, 2005; Murray, 2000; Saldert, Fors, Stroberg, & Hartelius, 2010). Even during the early stages of HD, the comprehension of complex discourse can be impaired similar to persons who are in later stages of the disease progression (Murray & Stout, 1999; Saldert et al., 2010). Persons with HD generally demonstrate the ability to process main ideas during discourse comprehension but can be particularly challenged by detailed information and implied information, as well as the interpretation of figurative language (Chenery, Copland, & Murdoch, 2002; Murray & Stout, 1999). Additionally, persons with HD demonstrate large variations in a number of higher-level discourse comprehension skills such as the interpretation of metaphor and ambiguity in discourse (Saldert et al., 2010). Discourse production can also be compromised in PD and HD, leading to reduced output and decreased syntactic abilities, with shorter and less complex sentence constructions in discourse. Significantly less informative discourse has also been noted with an overall reduction of informational content and proportionally fewer informative utterances in simple discourse tasks produced by persons with HD (Murray, 2000).

But these phenomena are not strictly related to progressive disorders associated with aging and known neuropsychiatric pathology. College students who, by self-report, demonstrate characteristics of impulsive aggressive outbursts also show impairments of complex language function related to measureable EF deficits (Villemarette-Pittman, Stanford, & Greve, 2003). These appreciable differences in cognitive-communication skills indicate that planning of complex verbal output and organization of spoken communication were significantly difficult when compared to the communication of their peers. These behaviors were related to poor integration of information, the inclusion of inaccurate information, and awkward sequencing of information. These cognitive-communication challenges were significant even in the presence of intact basic language and other cognitive skills (Villemarette-Pittman et al., 2003).

Localized brain damage, aphasia, and executive function

Strokes and cerebrovascular disease in general can result in focal deficits such as hemiplegia/paresis and aphasia but also commonly result in cognitive deficits (Lesniak, Bak, Czepiel, et al., 2008; Zinn, Bosworth, Hoenig, & Swartzwelder, 2007). In a study of 200 consecutive admissions to a stroke unit, patients assessed with a broad cognitive battery (e.g., orientation, attention, gnosis, memory, praxis, visuospatial abilities, language, and EF) and re-assessed at 1 year after onset demonstrated that cognitive deficits were persistent in 72 percent of this population (Lesniak et al., 2008). Although the most common deficits noted were in the areas of attention and short-term memory, the presence of impaired EF in the second week after stroke emerged as the only predictor of functional recovery after 1 year (Lesniak et al., 2008). Similarly, Zinn and colleagues studied EF abilities in individuals with acute stroke and found that nearly 50 percent of their participants demonstrated impairments on measures of EF, and that such patients are at risk for failure to benefit fully from rehabilitation during the acute period and for several months following (Zinn et al., 2007).

Due to the common co-occurrence of aphasia and EF deficits following stroke, it is important to understand the unique and combinatorial impact on communication these deficits could have. Prescott and colleagues presented the Tower of Hanoi, a measure of complex problem solving, to individuals with aphasia and found that 30 percent of the group could not complete the task and those who did required significantly more time and moves to accomplish the task (Prescott, Gruber, Olsen, & Fuller, 1987). Glosser and Goodglass (1990) administered an EF battery to 22 individuals with left hemisphere brain damage and aphasia, to 19 with right hemisphere brain damage, and to 49 healthy controls. Results indicated that those individuals with left frontal lesions were significantly more impaired in EF than those with posterior or mixed lesions of the left hemisphere.

The relationship between cognitive abilities and specific communication treatment protocols has also been investigated. Individuals with aphasia who perform more poorly on assessments of non-verbal cognitive skills and measures of EF take longer to achieve performance criteria for context-based treatments (e.g., using compensatory communication strategies) and EF measures predicted communication performance at 6 months post treatment. Thus performance on the EF measures may be related to overall outcome, appropriateness of certain treatment types, and prescribed amount of treatment (Hinckley, Carr, & Patterson, 2001). This has also been demonstrated in investigations of cognitive flexibility with regard to the acquisition and use of varied symbols (i.e., alternate modes) for functional communication tasks. Persons with aphasia demonstrate the means to express concepts in an alternate mode; however, they can be persistent (i.e., preservative) in their attempts to use the verbal modality, albeit unsuccessfully. This suggests that cognitive flexibility, a component of EF, might be required for successfully using alternative modes communication (Purdy, Duffy, & Coelho, 1994). These relationships between EF and language also impact functional communication, defined as “the ability to receive or to convey a message, regardless of the mode, to communicate effectively and independently in a given natural environment” (Fridriksson, Nettles, Davis, et al., 2006, p. 402). Correlations between functional communication abilities and EF are reported to be significant, suggesting that for individuals with aphasia, communicative success is related to or dependent on the integrity of EF skills as well as linguistic competency (Fridriksson et al., 2006).

The ultimate goal of aphasia therapy is to improve an individual’s ability to communicate within real world contexts (i.e., in unpredictable settings with fluctuating conditions and demands). Successful everyday communication requires goal-oriented behavior and flexible problem solving, which characterize EF (Helm-Estabrooks, 2002). Additionally, second to language, EF was the aspect of cognition that was most vulnerable to the effects of brain damage associated with aphasia (Helm-Estabrooks, 2002). Therefore, it is not possible to predict a person’s communicative success in everyday contexts on the basis of nonlinguistic cognitive skills or language performance alone. Thus, the implications of EF impairments for the management of individuals with aphasia must also been considered.

Overall, it is apparent that there is a complex relationship between nonlinguistic cognitive abilities, including EF, and language performance in persons with aphasia. These changes in cognitive abilities are prevalent in persons with aphasia and should be assessed separately. In particular, EF may play an important role in determining the success of various language and communication interventions and functional communication outcomes in persons with aphasia. Finally, for some individuals with aphasia, treatment of various aspects of cognition such as impaired EF may be an important consideration in conjunction with traditional linguistic-based and communication-based interventions.

Knowledge structure, executive function, and discourse

In the most general sense, cognitive control and EF are manifest in the ability to perform in adaptive and responsive ways to novel or complex situations, and are necessary for appropriate cognition, emotional regulation, and social abilities such as communication (Lezak, Howieson, & Loring, 2004). Abstracting EF to fundamental elements reveals behaviors that are goal-directed, are achieved through the coordination of thought and action, are necessary for processing information, and are required for acting in a purposeful and appropriate manner (Grafman, 2006a; Miller & Wallis, 2009; Wood & Grafman, 2003). Communication can be seen as behavior (or as a particular set of behaviors) that is goal-directed for the purpose of exchanging information. Communication requires cognitive control for coordinating and organizing information (e.g., decoding many levels of input, linguistic ability, situational knowledge, pragmatic factors, performance, self-monitoring, etc.) via knowledge frameworks.

A number of theoretical explanations have been proposed to account for the information processing and knowledge representation utilized by the PFC, which enable us to engage in non-routine, complex activities and perform complicated tasks, including discourse (Gilbert & Burgess, 2008; Wood & Grafman, 2003; Wood, Knutson, & Grafman, 2005). This includes non-routinized, socially appropriate communication behaviors. Examples of such everyday behaviors include relating a story of a past event for the entertainment of others, explaining the steps necessary to complete a task, creating a message to persuade the opinion of others, and so on. Current models of EF involve top-down driven processes (organization, pragmatics, content selection, behavioral efficiency) that interact with more automatic cognitive processes (e.g., attention, speech motor control, linguistic processing) in response to specific task demands to attain relevant goals (Gilbert & Burgess, 2008). For example, your goal in reading this chapter (i.e., discourse processing) might be to gain general knowledge about the relationship between EF disorders and their impact on communication. Similarly, your goal may also include short-term gains in extracting the necessary knowledge to pass an exam/course, or, more long-term, to improve your knowledge base in working with persons with cognitive-communication disorders. Either way, how you read the words will not change and is related to over-learned processes of word and text level decoding and semantic and syntactic processing for reading comprehension. However, when the reading objective presents itself (e.g., a conscious goal like preparation for an upcoming exam), you employ EF abilities related specifically to achieving the objective. The process for attending to or extracting particular themes of information for storage or memorization will be driven by your particular objectives. You may deploy a specific strategy such as outlining information, extracting key words, writing out definitions in your own words, or delineating general themes and sub-themes.

It has been suggested that the PFC is responsible for information consolidation (e.g., discourse processing) through the activation of unique stores of knowledge called structured event complexes (SECs) (Figure 11-2) (Grafman, 1995; Grafman & Litvan, 1999; Partiot, Grafman, Sadato, et al., 1996; Sirigu, Cohen, Zalla, et al., 1998; Sirigu, Zalla, Pillon, et al., 1995; Wood & Grafman, 2003; Wood et al., 2005). These SECs are believed to be goal oriented, sequentially structured, thematic, and rule governed. Structured event complex information is thought to be stored as cognitive frameworks that are used to guide information processing and are encoded and retrieved as complete episodes (described below) and stored in the PFC (Wood & Grafman, 2003).

Structured event complex knowledge is used to encode and retrieve hierarchical sequences related to everyday life activities that are activated during information processing (Grafman, 2006a; 2006b; Krueger, Moll, Zahn, et al., 2007; Wood & Grafman, 2003; Wood et al., 2005). Examples of everyday events sequences are commonly occurring behaviors and can include anything from the routine and mundane (e.g., verbalizing the steps necessary for making the morning coffee) to novel cognitively challenging behaviors (e.g., writing out the information necessary to plan a dinner party for 100 guests), to the transcendent (e.g., discussing career goals and maintaining progress toward these goals over a 30-year span). This knowledge may include sequences such as activating previously learned information necessary for planning, organization, sub-goal routines, acting on plans, analysis of performance, and updating plans based on success of the SEC (Grafman, 2006b; Hewitt, Evans, & Dritschel, 2006). In this sense, goal-directed communication activities (e.g., relating personal information in the form of a narrative, comprehending the thoughts and feelings of others during a conversation) could be conceptualized as rule-governed frameworks for information processing that are employed to guide the comprehension and production of discourse communication. These frameworks are learned through repeated exposures to communicative situations that follow general patterns (i.e., organizational structure) and may include a number of important contextual factors (e.g., pragmatic rules, time constraints, etc.). For example, discourse in the form of fictional narratives are often comprised of a goal-directed episode made up of story grammar components that are considered to be one type of SEC (e.g., comprehension, production, memory encoding, event recall) (Grafman & Krueger, 2008; Rumelhart, 1975; Stein & Glenn, 1979; Krueger et al.; Wood et al., 2005). Because of the rich content, predictable organizational structure, and linguistic processing demands involved in discourse tasks, the analysis of discourse has become an important means for understanding cognitive-communication disorders.

Analysis of discourse

The clinical examination of discourse has become a useful tool for studying communication skills in healthy children and adults, as well as in persons with acquired impairments subsequent to traumatic brain injury, stroke, and dementia (Arkin & Mahendra, 2001; Ash et al., 2006; Brookshire, Chapman, Song, & Levin, 2000; Coelho, 2007; Lehman Blake, 2006; Mar, 2004; McCabe & Bliss, 2006; Stemmer, 1999). Natural communication requires language processing beyond individual words or isolated sentences with the integration of smaller units of language into a coherent exchange of information (Gordon, 1993). Discourse encompasses a number of identifiable sub-genres (e.g., conversation, debate, picture description, story narrative, etc.), each with unique structure that defines and shapes the message components and their associations (Coelho et al., 2005; Fayol & Lemaire, 1993). The comprehension and production of discourse message represents complex behavior, which includes linguistic interpretation, organizational structure, and pragmatic rules. Since many levels of knowledge are necessary to construct a discourse, a number of methods of analysis have been devised to investigate these naturalistic communication acts (e.g., analysis of content, syntactic structure, cohesion, narrative structure, pragmatic behavior, etc.) (Table 11-1) (Cherney, Shadden, & Coelho, 1998; Mar, 2004).

Table 11-1

Levels of Discourse and Analyses

Levels of Discourse Investigation

Examples of Analyses

Word Level

Informational content Information efficiency/lexical productivity (e.g., words per minute) Reference & pronoun use Word-finding behavior Only gold members can continue reading. Log In or Register to continue Share this: Click to share on Twitter (Opens in new window) Click to share on Facebook (Opens in new window) Related Related posts: The cognition of language and communication The effects of aging on language and communication The role of memory in language and communication Management of acquired language disorders associated with attentional impairment Language and communication disorders associated with attentional deficits Attention: architecture and process Stay updated, free articles. Join our Telegram channel Join Tags: Cognition and Aquired Language Disorders An Information Procession Jan 6, 2017 | Posted by admin in PSYCHOLOGY | Comments Off on Communication following executive dysfunction Full access? Get Clinical Tree Get Clinical Tree app for offline access Get Clinical Tree app for offline access