Failure to detect lies, sarcasm might warn dementia--study

Frontotemporal dementia, or Pick's disease, is a rare form of dementia that affects frontal and temporal lobes of brain. People suffering from this condition lose the ability to detect sarcasm or lies as compared to people who age normally, the researchers said.

"If somebody has strange behavior and they stop understanding things like sarcasm and lies, they should see a specialist who can make sure this is not the start of one of these diseases,” the Live Science quoted lead researcher Katherine Rankin, a neuropsychologist at the University of California, San Francisco, as saying.

Findings of the study can help diagnose patients with the condition and start treatment as early as possible.

175 people with dementia studied
For the study, Rankin and her postdoctoral fellow Tal Shany-Ur analyzed responses of 175 people, over half of whom had some form of neurodegeneration, watching a video of two people talking to each other.

At different spots, one person in video would tell lies or use sarcastic remarks. Participants were given verbal and non verbal cues to identify false or insincere statements.

In order to find a link between neurodegeneration and patients' detection inability, the researchers used MRI to form accurate brain maps of the study participants.

The researchers then compared their scores with the results of brain scans that measured loss of volume related to dementia.

The present study, titled 'Divergent Neuroanatomic Correlates of Sarcasm and Lie Comprehension in Neurodegenerative Disease,' is a part of UCSF Memory and Aging Center large scale study that uses people's emotional and social behavior for predicting, preventing, and diagnosing brain disorders.

Findings
Researchers found that healthy older adults could easily distinguish sarcasm in the speech. However, patients with frototemporal dementia had a hard time spotting lies, sarcasm, and truth.

Rankin, also a member of the UCSF Memory and Aging Center and the senior author of the study, said, “These patients cannot detect lies. This fact can help them be diagnosed earlier.”

"We wanted to know if we could use this test [to gain] a better idea of what disease the person has," she said.

"We have to find these people early," she said. "We want people to recognize that these social lapses are actually a disease -- parts of their brain are being eaten away."

A plausible explanation
Scientists believe that the ability to detect lies is centered in brain's frontal lobe, which degenerates in case of frontotemporal dementia due to accumulation of damaged proteins known as tau and death of neurons in that area.

This kind of social decline is most commonly found in people under 65, according to Rankin. Other signs of the disease could be dramatic changes in behavior and personality.

Dementia, in general, is a loss of brain function that affects memory, thinking, language, judgment, and behavior.

Because the frontal lobes play a significant role in complex, higher-order human behaviors, losing the ability to detect lies is only one of several ways the disease may manifest, the UCSF press release states.

Findings of the study were presented at the 63rd Annual Meeting of the American Academy of Neurology on April 14 in Hawaii.