Cognitive and Neuroanatomic Accounts of Referential Communication in Focal Dementia

Abstract

The primary function of language is to communicate—that is, to make individuals reach a state of mutual understanding about a particular thought or idea. Accordingly, daily communication is truly a task of social coordination. Indeed, successful interactions require individuals to (1) track and adopt a partner’s perspective and (2) continuously shift between the numerous elements relevant to the exchange. Here, we use a referential communication task to study the contributions of perspective taking and executive function to effective communication in nonaphasic human patients with behavioral variant frontotemporal dementia (bvFTD). Similar to previous work, the task was to identify a target object, embedded among an array of competitors, for an interlocutor. Results indicate that bvFTD patients are impaired relative to control subjects in selecting the optimal, precise response. Neuropsychological testing related this performance to mental set shifting, but not to working memory or inhibition. Follow-up analyses indicated that some bvFTD patients perform equally well as control subjects, while a second, clinically matched patient group performs significantly worse. Importantly, the neuropsychological profiles of these subgroups differed only in set shifting. Finally, structural MRI analyses related patient impairment to gray matter disease in orbitofrontal, medial prefrontal, and dorsolateral prefrontal cortex, all regions previously implicated in social cognition and overlapping those related to set shifting. Complementary white matter analyses implicated uncinate fasciculus, which carries projections between orbitofrontal and temporal cortices. Together, these findings demonstrate that impaired referential communication in bvFTD is cognitively related to set shifting, and anatomically related to a social-executive network including prefrontal cortices and uncinate fasciculus.

Adapting to Changes in Communication: The Orbitofrontal Cortex in Language and Speech Processing

“…The overuse or insufficient use of adjectives is not encouraged. The demand in shifting their perspective to the interlocutor is manipulated such that the demand is increased because some feature dimensions that distinguish between targets and competitors are not available to the interlocutor and are private to the participants [ 7 ]. In this task, a target that cannot be distinguished in color from the competitor from the interlocutor’s side would increase the perspective shifting demand for the participant when they had to refer to an alternative disambiguated feature, such as shape and size, which was expected for both sides.…”

“…One traditional view, which sees language processing as driven by domain-specific operations, argues that the language function is supported by the left perisylvian network, and early research on the language connectome mainly focused on the arcuate fasciculus that connects Broca’s and Wernicke’s Areas. However, recent work has shown that neural networks beyond language processing may support language and speech tasks in a broader and more communicative sense, proposing an insufficient role of traditional language networks underlying the language tasks and that domain-general networks, or neural networks serving other cognitive functions, such as executive and social functions, play crucial roles in certain language functions [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ].…”

Speech and language impairments in behavioral variant frontotemporal dementia: A systematic review

“…In terms of discourse-level features, accuracy of the discourse (as judged through global organization, complexity or the ability to remain on topic) seems to be preserved when investigated with a global index (Gola et al, 2015;Mendez et al, 2014), but more finegrained examinations reveal impairments in accurately reporting events and precisely guiding communication (with insufficient or superfluous responses) (Ash et al, 2006;Healey et al, 2019;Healey et al, 2015). As for connectedness, even if measures of action or evaluation clauses and temporal organization revealed no difference (Gola et al, 2015), other studies revealed impairments in global connectedness, maintenance of a theme and discourse organization (Ash et al, 2006;Rousseaux et al, 2010).…”

Speech and language impairments in behavioral variant frontotemporal dementia: A systematic review

“…In terms of discourse-level features, accuracy of the discourse (as judged through global organization, complexity or the ability to remain on topic) seems to be preserved when investigated with a global index (Gola et al, 2015;Mendez et al, 2014), but more finegrained examinations reveal impairments in accurately reporting events and precisely guiding communication (with insufficient or superfluous responses) (Ash et al, 2006;Healey et al, 2019;Healey et al, 2015). As for connectedness, even if measures of action or evaluation clauses and temporal organization revealed no difference (Gola et al, 2015), other studies revealed impairments in global connectedness, maintenance of a theme and discourse organization (Ash et al, 2006;Rousseaux et al, 2010).…”