By examining how human brains process faces and other facial features, researchers have found that the brains of humans can recognise faces from other humans even when those faces are inanimate.
The researchers are also finding that the same brain regions that processes other forms of face recognition can also process other forms too.
Their results are published today in the journal PLOS ONE.
The researchers used functional magnetic resonance imaging (fMRI) to study the brains in 15 healthy volunteers, including five who had suffered from a severe form of autism.
They found that those with autism-related facial abnormalities showed evidence of being able to distinguish faces from those of non-autistic controls.
They were able to recognise faces of people with autism, as well, but only when those people were inanimate objects.
The findings suggest that the brain might be able to identify faces even when faces are made out of other objects.
“We found that there were differences in brain activation for faces of the same person and people who are in a similar social situation, such as a social interaction,” said the study’s lead author, John Cavanagh, from the University of California, Berkeley.
“For example, when we look at faces of strangers, we are less likely to recognise their faces even though they are identical to ours.”
The researchers found that people with autistic traits tended to have more abnormal activity in the amygdala, a brain area involved in emotion.
They are also found to have higher activity in regions of the brain linked to empathy and compassion, which is linked to feelings of compassion and understanding.
The amygdala is particularly important in helping people recognise faces because of the way it helps us process other people’s emotions, said co-author Mark Sperling, a neuroscientist at Stanford University.
“It helps us to remember faces and their attributes, so we can recognise other people,” he said.
In the study, the researchers scanned the brains, recording electrical activity in both the left and right amygdala.
This allows the scientists to study how the brains respond to different types of faces.
The results showed that the left amygdala, which helps regulate emotions, had an activation pattern similar to that of the other parts of the right hemisphere.
But the left amygdaloid was also significantly more active in people with other autism spectrum conditions, including autism, schizophrenia, and depression.
This pattern, said Spering, indicates that the amygdala is more active when we are in situations involving others.
The right amygdala, however, was less active in these individuals.
The amygdala’s response patterns are similar to those of the cortex, the part of the cerebral cortex that processes language.
The authors found that this finding was related to the fact that people who had autism-spectrum conditions showed greater activation in a region of the amygdala linked to emotional processing, which they called the amygdala-to-the-cortex region.
The left amygdala is linked with emotion processing and understanding, and the right amygdala is involved in emotions.
The differences in activity between the two areas were consistent across the participants, and were also found when looking at the faces.
“This is a really good example of how this is happening,” said co–author Robert Meehan, a professor of neuroscience at Johns Hopkins University.
The team’s results, however were not perfect.
They had difficulty identifying which of the 15 volunteers were autistics and which were not, as the volunteers tended to be older and with more severe autism symptoms.
This could explain why their brains were not responding as well to faces when the people in the study were in a different social situation.
But this was not a problem for people with normal facial features.
“When people with very mild autism are in the presence of another person, their amygdala- to-the–cortex response patterns seem to be identical,” said Meehart.
The research also found that, in contrast to the normal people, people with severe autism showed less activation in the right frontal lobe of the brains.
This may be because people with mild autism have a smaller amygdala, while people with moderate or severe autism show more.
This suggests that the right prefrontal lobe of people has a bigger role in processing emotion than other areas, the team believes.
“There is a possibility that these areas might be involved in higher-order processing of emotional states,” said Sargent, who is now working on a study looking at how people with a history of other types of disorders might respond to faces.
“We need to look at the whole brain in a lot more detail to understand how our brains react to other people.”