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Experts quibble over brain regions involved in emotion and empathy

by  /  6 August 2008

Emotional self-awareness and empathy, two related qualities that those with autism often lack, are associated with activity in the anterior insula, a region of the brain thought to regulate feelings, researchers have found1.

The results, published in the June issue of Social Neuroscience, are at odds with other findings in the field, prompting some researchers to caution against overestimating the regionʼs importance in processing emotions.

Alexithymia (pronounced ey-lek-suh-THAHY-mee-uh) is a personality trait defined by difficulties with identifying, understanding or describing oneʼs own feelings2. In the past few years, researchers have discovered that alexithymia is a key factor in the inability of individuals with autism to relate to others.

First described by psychiatrist Peter Sifneos in 1973, alexithymia affects about half of all individuals with autism3 and about ten percent of the general population.

In the study, the researchers used functional magnetic resonance imaging to examine brain activity in 15 individuals with high-functioning autism or Asperger syndrome and 15 age-matched controls.

The researchers showed the study participants photos of unpleasant, neutral or pleasant objects and asked them to think about and rate their reactions to the images. The researchers then matched the brain activity during the tasks with performance scores on alexithymia questionnaires.

Individuals with higher scores on the alexithymia scale tend to have less activity in the anterior insula, a region known for its role in processing emotional experiences and conscious feelings, the researchers found. This was true in both individuals with autism and in controls.

Those with autism, but not controls, also have reduced activity in the medial prefrontal, temporal and precuneus brain areas ― regions of the brain thought to be responsible for attributing mental states to others.

“This is where we find the difference between the two groups,” says lead investigator Uta Frith, emeritus professor of cognitive development at the University College Londonʼs Institute of Cognitive Neuroscience.

Emotional clues:

Previous studies support the general notion that the same brain regions may be involved in processing both oneʼs own emotions and othersʼ emotions.

The new study is interesting because it helps tease apart the patterns of brain activation that are linked with alexithymia and autism, notes Yoshiya Moriguchi, cooperative research fellow in the department of psychosomatic research, National Institute of Mental Health in Tokyo, Japan. “I am really impressed by the [results],” he says.

Moriguchi has also shown that alexithymia is associated with lower activity in the prefrontal cortex, but he did not find any difference in the anterior insula4.

The discrepancy can be explained by the different tasks the studies used, Moriguchi says. In Moriguchiʼs study, researchers measured brain activation in people with alexithymia in response to images of human hands and feet in painful situations. Participants were asked to rate the intensity of pain they imagined the person in the photos might feel.

Those tasks focused on thinking of othersʼ emotions, whereas Frithʼs study focused on thinking of oneʼs own emotions, Moriguchi notes. “I think the difference is very interesting.”

Others caution that Frithʼs results are just one piece of a more complicated picture, noting that regions other than the anterior insula are involved in empathy and in processing oneʼs emotions.

“Itʼs hard to make sense of the paper by itself,” says Marcel Just, director for the Center for Cognitive Brain Imaging at Carnegie Mellon University in Pittsburgh.

In a study published on 3 July, Justʼs group showed that people with autism have impaired connectivity in the ‘theory of mindʼ network, which is thought to be responsible for understanding othersʼ intentions and thoughts5.

Justʼs team also found impaired interconnectivity between the frontal regions of the brain and posterior areas such as the parietal lobe during a variety of different tasks that test abilities ranging from social interaction to language processing and problem solving.

Those regions may include the anterior insula in some cases, Just says, but the weakened synchronization between brain areas is more important than activity in any one region.

“What you see in some of Frithʼs papers and mine is that no matter what the task, you get frontal-posterior under connectivity [in people with autism],” he says.

Negative response:

There is also more than one way to define and assess alexithymia, notes Richard Lane, a professor of psychiatry, psychology, and neuroscience at the University of Arizona.

Lane created an alexithymia scale, called LEAS, in the early 1990s which assesses emotional awareness by asking people to write down their feelings in response to specific vignettes.

He says the scale used in Frithʼs study, the TAS 20, is less appropriate for such studies because subjects who score high on the TAS 20 scale tend to report being depressed or anxious.

“Thatʼs important because [the researchers] are asking the subjects to process negative pictures,” Lane says. Instead, he says, they should consider factoring out such negative emotions statistically before linking alexithymia to brain activation.

Michael Lombardo, a doctoral student in Simon Baron-Cohenʼs lab at the University of Cambridge, says his work on imaging and alexithymia has so far generated results that are also contradictory to Frithʼs study.

He has found, for example, that different regions of the brain, including the superior temporal gyrus, but not the insula, are important when people with autism think about their own feelings. The study, presented in a May poster session at the International Meeting for Autism Research conference in London, examined brain activation in response to different tasks and questions on likes and dislikes.

“There are lots of ways to look at this self-awareness issue,” Lombardo says. “Whether biology will track onto those labels [of empathy and emotional self-awareness] is still an open question.”

Frithʼs group began working on alexithymia after Sylvie Berthoz joined the institute as a postdoctoral fellow. Berthoz had just completed an imaging study on people identified as having alexithymia and presented the work in a lab meeting. “I remember saying when I introduced [alexithymia] at the lab meeting, ‘You probably never heard this word, but you will, so you better learn how to pronounce it,ʼ” Frith recalls.

Frithʼs team is conducting a larger study examining empathy tasks and other tasks that are known to activate other emotional processing networks, this time in four distinct groups of individuals: people with autism, people with alexithymia, and people with both or neither. “Weʼre particularly interested in whether the [effects of the] tasks can be dissociated,” she says.


References:
  1. Silani G. et al. Soc. Neurosci. 3, 97-112 (2008) PubMed
  2. Sifneos P.E. Psychother. Psychosom. 22, 255-262 (1973) PubMed
  3. Hill E. et al. J. Autism Dev. Disord. 34, 229-35 (2004) PubMed
  4. Moriguchi Y. et al. Cereb. Cortex 17, 2223-2234 (2006) PubMed
  5. Kana R.K. et al. Soc. Neurosci. Online publication ahead of print Abstract
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