Frontal Lobes Are What Make Us Human
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STUDY PINPOINTS REGION IN FRONTAL LOBES AS 'ESSENCE'
OF WHAT MAKES US HUMAN
Baycrest Center for Geriatric Care/EurekAlert!
January 31, 2001
Toronto, CANADA -- A new study has found the strongest evidence yet that
what sets humans apart from other primates may be found in the brain's
frontal lobes, particularly in an area the size of a "billiard ball" called
the right prefrontal cortex.
Dr. Donald Stuss, one of the world's experts on the frontal lobes, led the
study at The Rotman Research Institute, part of Baycrest Centre for
Geriatric Care, and affiliated with the University of Toronto. The findings
are published in the February 2001 issue of the international journal BRAIN
and the subject of the lead editorial.
Understanding the mental processes of others -- mentalizing -- is the basis
of our socialization and what makes us human. It gives rise to our capacity
to feel empathy, sympathy, understand humor and when others are being
ironic, sarcastic or even deceptive. It's a "theory of mind" that has been
associated with the frontal lobes, but until now scientists have had
difficulty demonstrating this ability to specific regions of the brain.
What is exciting about this study, according to Dr. Timothy Shallice of the
Institute of Cognitive Neuroscience at University College London, is that
the Rotman study came at this challenge with two different testing methods
and both generated similar compelling evidence to show that these higher
cognitive functions in humans are "localizable" to a specific region within
the frontal lobes. Dr. Shallice wrote the lead editorial in BRAIN.
Dr. Stuss and his research colleagues tested patients who had damage to
various parts of the frontal lobes, and other areas of the brain as well.
The selective impairment in only some patients provided the ability to
precisely localize those regions that are necessary when specific
mentalizing tasks are performed. Co-authors on the paper with Dr. Stuss, who
is director of The Rotman Research Institute at Baycrest, were Dr. Gordon
Gallup, Department of Psychology, State University of New York at Albany;
and Dr. Michael Alexander, Memory Disorders Research Centre at Boston
University and Department of Neurology, Harvard University.
"In our study, we've shown that the frontal lobes were the most critical
region for visual perspective taking, and the inferior medial prefrontal
region, particularly for the right, for detecting deception," says Dr.
Stuss. Visual perspective taking is the ability to empathize or identify
with the experience of another person.
It has long been known that some patients with frontal lobe damage have
significantly changed personalities. What is important about the study is
that it helps families, friends and caregivers of the patient to appreciate
and understand a very important reason why this occurs. This deficit in
mentalizing can affect social cognition which is important in everyday human
interactions. For example, patients with damage in the specific frontal area
are often less empathetic and sympathetic, and they miss social cues which
lead to inappropriate judgements.
In the study, 32 adults with lesions in frontal and non-frontal brain
regions, most commonly as a result of stroke, and a control group of 14
healthy adults, underwent two seemingly very simple tests. Both tasks
required participants to guess which coffee cup a ball was hidden under.
Participants sat across a table from the experimenter and a table curtain
was used on some occasions to conceal which cup the experimenter hid the
ball under. The participant was asked to point to the correct cup.
In the first test -- visual perspective taking -- participants had to
reflect on their own experience to understand and interpret the experience
of others. For example, the participants either saw the ball being hidden
under a particular cup with the curtain open, or were told that the ball was
being hidden when the curtain was closed and they could not see anything.
Then two assistants joined the task; one sat beside the experimenter, and
one beside the participant. The table curtain was drawn this time,
concealing which cup the ball was placed under. When the participant had to
guess where the ball was hidden, the assistants 'helped' by moving beside
the examiner and each pointed to a different cup. Participants needed to
realize that one of the assistants had not been in a position to see where
the ball was hidden (because they were sitting beside the participant who
themselves could not see where the ball was hidden). Frontal lesion subjects
had a much higher error rate on the task and it appeared that the 'right'
frontal lobe was most critical. While the small number of right frontal
subjects (4) makes this only a suggestion, it is still a striking finding,
says Dr. Stuss.
In the second test on deception, an assistant sat at the table beside the
experimenter and always pointed to a cup where the ball was NOT hidden.
Participants had to infer that the assistant was trying to deceive them.
Those with right inferior medial prefrontal damage had difficulty catching
on to the ruse and were the most frequently deceived.
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