Detecting sarcasm from paralinguistic cues: anatomic and cognitive correlates in neurodegenerative disease

Abstract

While sarcasm can be conveyed solely through contextual cues such as counterfactual or echoic statements, face-to-face sarcastic speech may be characterized by specific paralinguistic features that alert the listener to interpret the utterance as ironic or critical, even in the absence of contextual information. We investigated the neuroanatomy underlying failure to understand sarcasm from dynamic vocal and facial paralinguistic cues. Ninety subjects (20 frontotemporal dementia, 11 semantic dementia [SemD], 4 progressive non-fluent aphasia, 27 Alzheimer's disease, 6 corticobasal degeneration, 9 progressive supranuclear palsy, 13 healthy older controls) were tested using the Social Inference - Minimal subtest of The Awareness of Social Inference Test (TASIT). Subjects watched brief videos depicting sincere or sarcastic communication and answered yes-no questions about the speaker's intended meaning. All groups interpreted Sincere (SIN) items normally, and only the SemD group was impaired on the Simple Sarcasm (SSR) condition. Patients failing the SSR performed more poorly on dynamic emotion recognition tasks and had more neuropsychiatric disturbances, but had better verbal and visuospatial working memory than patients who comprehended sarcasm. Voxel-based morphometry analysis of SSR scores in SPM5 demonstrated that poorer sarcasm comprehension was predicted by smaller volume in bilateral posterior parahippocampi (PHc), temporal poles, and R medial frontal pole (pFWE<0.05). This study provides lesion data suggesting that the PHc may be involved in recognizing a paralinguistic speech profile as abnormal, leading to interpretive processing by the temporal poles and right medial frontal pole that identifies the social context as sarcastic, and recognizes the speaker's paradoxical intentions.

Figure 1

Bar graph representing the performance of each diagnostic group on both the Sincere (SIN) condition and the Simple Sarcasm (SSR) condition of the TASIT. No group differed significantly from healthy older control subjects on SIN, but the Semantic Dementia group performed significantly worse on SSR. Error bars represent ±1 SD from the mean.

Figure 2

Design matrices and transparent axial views of SPM5 “glass brain” representing results of main effect analysis (controlling for Sincere condition score, MMSE, age, sex, and TIV) and shared effect analysis (additionally controlling for confounding effects of diagnostic group) examining the relationship between of Simple Sarcasm (SSR) condition and gray matter volume (results shown corrected at pFWE<0.05). Shadowed regions represent regions where atrophy significantly correlated with poorer performance on the SSR task.

Figure 3

Results of main effects analysis (green) and shared effect analysis (yellow) of Simple Sarcasm (SSR) condition score, superimposed on sagittal (x = 28, x = 46), coronal (y = −16), and axial (z = 18, z = −22) slices of an averaged template brain (SPM5: t1.nii). Green colored areas represent regions where atrophy significantly correlated with poorer performance on the SSR task, controlling for sincere score, MMSE, age, sex, and TIV. Yellow colored areas represent regions remaining significant when diagnostic group membership was added into the design matrix, indicating regions that showed a significant relationship to sarcasm interpretation in more than one diagnostic group. Results are shown at a corrected level of significance (pFWE < 0.05) using the T-score range shown at the bottom right.