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Chapter 6 Update - March 2005
On butterflies and moths: exploring the role of the fusiform gyrus in … face perception
Various lines of research support the notion that we have a specialised brain region for processing
faces. Neurons in monkeys appear to be selectively responsive to faces, patients with prosopagnosia
are unable to recognise familiar faces (but can recognise other objects and can identify features of
faces such as their age and sex) and neuroimaging evidence suggests that one part of the brain is
more significantly activated than others when people view faces. This part is the fusiform gyrus,
also called fusiform face area (FFA).
This view may be too simplistic. For example, it has been argued that the FFA, rather than being
specialised for recognising faces specifically, is responsible for distinguishing between members of a
homogeneous class of objects (not just faces). An extension to this argument suggests that the FFA
is active when it distinguishes between members of object classes that we are expert in identifying.
Because we are very familiar with faces, and expert at recognising them, the FFA is, therefore,
active when we view faces. This argument also suggests, however, that expert identifiers should
activate the FFA when they view objects they are expert in recognising (and not just faces).
To test these various hypotheses, Rhodes et al (2004) set up two experiments in which people were
either trained or were not trained to recognise Lepidoptera (moths and butterflies). Brain activation
was monitored using fMRI while participants viewed faces and Lepidoptera. In the second
experiment, experts in identifying moths and butterflies passively watched examples of the species
while brain activity was recorded. If the FFA is active during expert discrimination, then it should
be just as active during face perception and Lepidoptera perception in experts.
The authors found no support for this hypothesis. In the first experiment, the FFA was more
significantly activated when people watched faces than Lepidoptera, regardless of whether people
had been trained to recognise examples of the species. In the second experiment, activation was
greater in the FFA when the butterfly experts watched faces than Lepidoptera. There was no overlap
in the areas activated by faces and moths and butterflies.
The results suggest that the FFA contains neurons that allow ‘individuation’ of (i.e., discrimination
between) faces.
Rhodes, G., Byatt, G., Michie, P.T. & Puce, A. (2004). Is the fusiform face area specialised for
faces, individuation, or expert individuation? Journal of Cognitive Neuroscience, 16, 2, 189-203.