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Introduction

Overview

Aprosodia is a disorder characterized by impaired ability to express or comprehend affective or nonaffective tonal aspects of speech. Although this disorder is often the result of a cerebrovascular episode, emerging data suggest the possibility that prosodic disturbance may also be among the lasting sequelae to follow SARS-CoV-2 infection (65). A wide variety of neurologic or psychiatric disorders are associated with disturbances in prosody among pediatric and adult populations. In addition to providing information pertaining to the characteristics and classification of the aprosodias, the authors of this clinical article present information related to assessment, prognosis, and treatment of the disorder. Evidence regarding the neuroanatomy and theoretical underpinnings of aprosodia is presented, along with current knowledge on prevalence of the disorder (eg, manifestations across cultures and across the lifespan) and the evidence base for behavioral and nonbehavioral interventions to treat prosodic deficits in adults and children. This article has been updated to reflect the state-of-the-science on manifestations of aprosodia in atypical neurodevelopment and neurodegenerative processes (eg, autism spectrum disorder, attention deficit disorder, multiple sclerosis, and amyotrophic lateral sclerosis) and the manifestations of aprosodia in psychiatric disorders (eg, schizophrenia, bipolar disorder, and posttraumatic stress disorder). In addition to reports of aprosodia following SARS-CoV-2 infection, preliminary evidence of changes in affective prosody (71) and reduced affect recognition (156) following lockdown protocols in the COVID-19 global pandemic, perhaps related to the impact of prolonged social isolation, warrants discussion and has accelerated the need for better diagnosis and treatment of aprosodia.

Key points

• Aprosodia is a disorder characterized by impaired ability to express or comprehend prosody, the melodic aspects of speech.

• Aprosodia can result from brain injury, neurologic disorders, atypical neurodevelopment, and certain psychiatric conditions.

• Aprosodia is frequently described as arising from right-hemisphere neocortical damage, but can also occur with left-hemisphere damage and with subcortical damage.

• Aprosodia has varied manifestations. Prosodic dysfunction can be described at the level of functional communication (ie, impact on affective versus nonaffective speech) or at the level of acoustic processing (eg, deficits in perceiving or generating pitch, timing, or tempo).

Historical note and terminology

Monrad-Krohn described prosody as the melody of language (163). More specifically, prosody refers to the pitch, volume, rate, and tempo of speech (179) and conveys both affective and nonaffective information. Affective prosody communicates the emotional meaning of the utterance as well as the affective disposition of the speaker (32). Affective prosody thereby helps to convey whether the speaker is angry, happy, sad, and so forth. Ross and colleagues, who draw from Monrad-Krohns original classifications, further characterize affective prosody as a combination of emotional prosody, the insertion of emotion into speech, and what is termed intellectual prosody, or that which communicates the speakers attitudes that modify the meaning of speech, allowing the speaker to communicate affective attitudes such as earnestness or sarcasm (163; 212).

Nonaffective prosody communicates the linguistic and other nonaffective aspects of speech, thereby clarifying the syntactic structure and semantic intention of an utterance (222). For example, nonaffective prosody performs functions such as cueing the listener as to whether the utterance is a statement, question, or command and differentiates lexical meaning (eg, CON-vict vs. con-VICT). Nonaffective or linguistic prosody has been subcategorized as grammatical (eg, to distinguish word-class or convey phrase boundaries) or pragmatic in nature (eg, emphasizing a word in an utterance for clarification) (181; 246). According to Ross, nonaffective prosody can also be defined as including paralinguistic elements, such as grunts or sighs (termed inarticulate prosody), and dialectical or regional characteristics of speech that reflect a speakers geographic origins (212). Aprosodia is, therefore, a disorder in which an individual is unable to express or comprehend affective or nonaffective prosodic components of language.

Although the dominant hemisphere (most generally, the left hemisphere) is clearly responsible for most linguistic functions, to our knowledge, John Hughlings Jackson and François Baillarger were the first to suggest that the nondominant (most generally, the right) hemisphere might mediate some components of language and speech (10; 120; 1878-1879). This was based, in part, on observations that utterances of patients with aphasia with left-hemisphere lesions still contained affective intonation despite the patients lack of propositional speech (122). Borod and colleagues provide a review of this early literature (40). The idea that the nondominant hemisphere could mediate some components of language and speech was not systematically examined until nearly a century later when Heilman, Scholes, and Watson studied the comprehension of the affective components of speech in patients with unilateral temporoparietal lesions of either the left or right hemisphere (106). In this study, patients were presented with recordings of sentences and asked to identify either the speech content or emotional tone. Results indicated that both patient groups were able to identify the content of the sentence, but only the group with right-hemisphere temporoparietal lesions was unable to correctly identify the affective prosody. Soon after, it was demonstrated that the expression of affective prosody was impaired in patients with right-hemisphere damage for both posed (257; 235) and spontaneous (214; 38) conditions. Although subsequent research has shown affective and nonaffective prosodic impairments in the presence of both left- and right-hemisphere damage, these early studies helped establish that the nondominant hemisphere plays a significant role in the production and comprehension of speech. Contemporary research using fMRI supports these earlier findings; comparing hemispheric activation in a sample of neurologically healthy participants revealed preferential left frontotemporal activation for sentence comprehension and preferential right frontotemporal activation for emotional prosody (233). Additionally, Seydell-Greenwald and colleagues found that emotional prosody also evokes bilateral activation of the pars orbitalis, amygdala, and anterior insula (233).

Based on findings of patients with deficits in understanding or expressing affective prosody, Ross suggested that these deficits be called aprosodia (208). He also proposed that the classification of the aprosodias parallel the aphasias; this classification system is described in the Clinical Manifestations section.

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