ARTICLE IN BRIEF
Right hemisphere stroke patients who had lesions in certain regions, particularly the temporal pole or anterior insula, were more likely to do poorly on tests designed to measure the ability to recognize and make inferences about what another person is feeling.
A new study of acute ischemic stroke patients provides added insight into what regions of the brain are involved in a critical component of human interactions — empathy.
The study found that right hemisphere stroke patients who had lesions in certain regions, particularly the temporal pole or anterior insula, were more likely to do poorly on tests designed to measure the ability to recognize and make inferences about what another person is feeling.
Previous brain imaging studies had identified a number of distinct neural networks that seem to be actively engaged during empathy. This new study builds on those findings by demonstrating that so-called affective empathy can be impaired when there is stroke damage to such regions of the brain.
The study, published in the August issue of the journal Brain, does not have any immediate clinical application, but it may help explain why there can be changes in a person's interpersonal skills following a stroke. Families of stroke patients sometimes report that their loved one seems uncaring or uninterested in what they are experiencing. That lack of empathy can cause hurt feelings and damage relationships.
“There is a lot of attention paid to treatment and prevention of stroke,” said Richard Leigh, MD, the study's lead author and assistant professor of neurology and radiology at Johns Hopkins University, told Neurology Today. “But there are a lot of people out there who have already had strokes and we need to better understand how they recover from a stroke.”
Previous studies using functional magnetic resonance imaging (fMRI) have found that affective empathy engages distinct neural networks in specific regions of the brain — including the prefrontal cortex, orbitofrontal gyrus, anterior insula, anterior cingulate cortex, temporal pole, amygdala, and temporoparietal junction. But the fact that certain regions of the brain are activated on MRI during a given task, such as empathy, does not mean that those areas are critical to the task, the researchers noted.
To further explore the neural underpinnings of empathy, Dr. Leigh and colleagues at Johns Hopkins compared 27 patients with acute right hemisphere ischemic stroke with 24 control patients who had a transient ischemic attack but were neurologically intact. The stroke patients ranged in age from 26 to 75, with an average age of 54.5. One third of them were women.
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
© 2013 American Academy of Neurology
•. A Neurology Today
interview with Marcus Raichle, a pioneer in the PET to view changes in brain activity and neurobiological correlates of human behavior: http://bit.ly/1eoJN18
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