Studying Face Blindness Requires Naturalistic Emotional Stimuli

Face blindness is a condition that affects about 2% of the population’s
ability to do what many consider an effortless task – to recognize
faces of family, friends, and other acquaintances. A small number of
people find it difficult to identify the person with whom they are
meting or remembering people that they have previously met. Some, in
fact, cannot recognize the faces of spouses, children, or even
their own faces. To better understand developmental face disorders,
recent research on face blindness stresses the importance of using
emotional faces and bodies.

A study published in the open-access journal PLoS ONE
and researchers from the Netherlands and Massachusetts
Hospital discusses an interesting finding about how the brain
interprets face information. Beatrice de Gelder (Tilburg
University, Tilburg, The Netherlands) and colleagues demonstrate that
increased neural activity in the fusiform face area (FFA, the area of
the brain associated with face recognition) is associated with the
presence of emotional
information in the face. The researchers believe that this finding can
assist the design of new assessment and training programs. In addition,
the study reveals that people with face blindness do not have body and
face sensitive processes are that are as
categorically segregated, which suggests cortical specialization as a
potential cause of the disorder.

Faces offer information on a person’s gender, age,
emotion, familiarity, and attractiveness. Depending on the
context, these details can be called
upon and used either quite rapidly or after full recognition of facial
attributes, including a name. In order to evaluate face recognition
problems and to understand it neuro-functional basis and potential
deficits, the
contextual requirements and the task settings are very important.

De Gelder and colleagues used functional magnetic resonance imaging
(fMRI) to assess how well a group of individuals could process faces.
The participants all suffered developmental prosopagnosics;
that is, they reported life-long problems in recognizing people and
difficulties when meeting familiar people unexpectedly. These people
were compared with a control group that was matched for age, sex and
education level. The aim of the research was to find out how the neural
underpinnings of
face and body processing in prosopagnosia are changed by emotional
information in the face and the body. The participants received a
series of tests that assessed their ability to recognize objects and
faces, their perception, and their ability to match and memorize faces.

The analysis by De Gelder and colleagues revealed that the
developmental prosopagnosia group displayed a similar activation level
as the control group
in FFA for the emotional faces, but the developmental
prosopagnosia also displayed a lower activation in this area for
neutral faces. Therefore, there is a higher threshold for the
recognition of neutral faces in these prosopagnosics. Neutral faces are
believed to be more difficult because these faces
are more difficult stimuli than the other categories with which they
are usually compared.

Faces that are showing emotion contain an additional feature that
provides important communicative information and thus the emotional
stimuli trigger a higher level of
arousal. The researchers also observed that when prosopagnosics looked
at emotional faces, there were high activity levels in the amygdala –
the region of the brain that deals with emotional reactions – than when
looking at neutral ones.

The authors conclude that: “The results from the present study clearly
demonstrate the importance of emotional information in face processing
and urge (future imaging) studies to take the modulatory effect of
emotion into account, in order to further untangle the complex nature
of DP [developmental prosopagnosia].”

Neural Correlates of Perceiving Emotional Faces and Bodies in
Developmental Prosopagnosia: An Event-Related fMRI-Study
Van den Stock J, van de Riet WAC, Righart R, de Gelder B
PLoS ONE (2008). 3(9):e3195.
Here to View Article

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: Peter M Crosta