Sarcasm Center Found In Brain's White Matter, Explaining Stroke Victims' Language Gap

In the aftermath of a stroke, many of the sufferer’s faculties with language, both in speaking and listening, are prone to dysfunction. A new study suggests sarcasm is one of those faculties, and it has distinct neurological roots in the white matter of the brain.

“Failure to recognize sarcasm can lead to important miscommunications,” wrote the authors, of Johns Hopkins University, in the study’s abstract. “Few previous studies have identified brain lesions associated with impaired recognition of sarcasm.” To better understand the difficulties in communicating with stroke victims, the researchers wanted to investigate which areas of the brain suffered the most. Their findings may give families some insight into interacting with loved ones who have experienced stroke.

Led by Dr. Argye Hillis, a neurology professor in the JHU School of Medicine, a group of scientists put 24 stroke victims in an MRI scanner. They looked specifically at eight tracts in the brain — areas that governed people’s ability to pick up on the complex changes in pitch, stress, and tone found in sarcastic remarks and that ferry those signals to other parts in the brain. Each subject listened to 40 sentences and determined which were sincere and which were sarcastic.

Results showed damage to the brain’s right sagittal stratum. “That’s a big white matter tract that connects some of the frontal and temporal regions to the thalamus, which is an area very important for getting information from auditory areas to the cortex for processing,” Hillis told. People with lesions in this area were able to identify only 22 percent of the sarcastic sentences, compared with 50 percent of people without damage to the area. According to Hillis, roughly 90 percent of the general public can distinguish between sarcastic and sincere statements.

Families of stroke victims stand a lot to gain from the findings. Sarcasm can be fun when it’s taken in jest, but it may come across as cold and callous when taken at face-value. Stroke victims may interpret a harmless remark as deeply offensive, Hillis says, all because certain parts of their brain weren’t communicating with one another.

“Don’t expect them to recognize your emotion from your tone of voice or your facial expression,” she said. “Just tell them how you feel.” The same goes for people undergoing counseling, as emotions may be difficult to vocalize. People that seem apathetic or indifferent may actually care a great deal; their brain just doesn’t allow them to show it.

Scientists typically don’t try to repair these lesions directly, Hillis said. Instead, future investigations will gauge the potential for restoring the lost sarcasm detection abilities. “There are some therapies speech pathologists have used, but there have only been very small studies,” she said. “We’re trying to find out if there are treatments that can improve things like sarcasm or understanding different emotions from tone of voice and facial expression.”

Source: Davisa C, Oishi K, Faria A, et al. White matter tracts critical for recognition of sarcasm.Neurocase. 2015.
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