All the participants underwent fMRI as part of their initial stroke evaluation and were given a series of tests designed to measure empathy. The tests included eight questions requiring inferences about the emotions of individuals appearing in short videotaped scenarios and two questions requiring inferences about the emotions of people in stories that were read to the patients. The patients were also administered the Interpersonal Reactivity Index, which is designed to evaluate various aspects of cognitive and affective empathy, as well as the prosody comprehension subtest of the Aprosodia Battery, which evaluates the ability to recognize emotions based on the tone of voice. The non-stroke patients' test scores were used to establish normative values by which the stroke patients were compared.
The researchers then looked to see if performance on the empathy tests correlated with the location of brain lesions in the stroke patients.
“There was a strong association between the presence of a lesion in one or more regions of interest in the network hypothesized to underlie affective empathy and impairments on our testes of affective empathy,” the researchers wrote. For instance, “of the 14 patients with impaired affective empathy, nine (64.3 percent) had lesions in one or more of the regions of interest.”
The researchers said the strongest associations involved infarcts in the temporal pole or the anterior insula. Lesions in the temporal parietal junction were not associated with poor performance on the empathy tests.
The study found that stroke patients who exhibited impaired empathy also lacked the ability to interpret the emotional meaning of a tone of voice. While older stroke patients were more likely to have impaired empathy than younger patients; sex, volume of infarct, and performance on tests for hemispatial neglect were not factors.
The researchers noted that the study had limitations, including the fact that it did not include patients with left hemisphere stroke. Nonetheless, when it comes to empathy, the “study provides converging evidence that areas identified as engaged in the task are indeed necessary for the task. Furthermore, the study indicates that one or more nucleus of the right thalamus also likely plays an important role in this network.”
Christopher M. Filley, MD, professor of neurology and psychiatry at the University of Colorado School of Medicine, said that while much of stroke research has been focused on more easily identified cognitive functions, such as language and memory, “the area of social cognition has been much harder to understand.”
He said it's not uncommon for family members of stroke patients to say that there has been a personality change for the worse.
“This loss of empathy can be very distressing and damaging to relationships, often completely disrupting family dynamics,” Dr. Filley told Neurology Today. What families need to understand is that the stroke patient isn't “willfully uncaring or malicious.”
David Gill, MD, a behavioral neurologist at Unity Rehabilitation and Neurology in Rochester, NY, said fMRI studies that attempt to pinpoint regions of the brain involved in abstract concepts, such as empathy or desire, are often viewed skeptically because the fact that an area of the brain “lights up” is not proof that the region is involved in the given activity.
Dr. Gill, who is a member of the Neurology Today editorial advisory board, said this latest study of stroke patients was interesting because it found that when those areas of the brain that had been previously identified in fMRI studies as being related to empathy were injured by stroke, empathy tended to be affected. But he cautioned against over-interpreting the significance of the results, saying that “empathy is a complicated concept and it is difficult to create tests to measure something so complicated. In addition, we do not know how to treat people who have poor empathy.”
Dr. Leigh said he is part of a research team at Johns Hopkins that is tracking stroke patients over time as they recover to study various aspects of cognitive function, including empathy. The team, headed by Argye Hillis, MD, has developed a clinical assessment scale to specifically identify deficits in empathy. The researchers hope that this type of assessment will eventually be incorporated into disability rating scales that are used as outcomes measures.
“We often don't focus on the kind of suffering a family goes through because their loved one no longer seems to care about their feelings,” Dr. Leigh said.
LINK UP FOR MORE INFORMATION:
•. Leigh R, Oishi K, Hsu J, et al. Acute lesions that impair affective empathy. Brain
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