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expression was either fearful or neutral. The results showed that the fMRI response to
fearful and neutral faces was not modulated by the focus of attention, consistent with
the view that the processing of emotional items does not require attention.
However, the opposite results came up later in another ERP study by Holmes and
Vuilleumier [1]. When faces were attended, a greater frontal positivity in response to
arrays containing fearful faces than the neutral faces. In contrast, when faces were
unattended, this emotional expression effect was completely eliminated. This study
demonstrates a strong attentional gating in the emotion processing.
The ERP result was supported by an fMRI research by Pessoa [6]. Participants
were instructed to focus on the gender of faces or on the orientation of the bars. A
Face in the centre and two bars at peripheral were presented simultaneously. The
participants' task was either to judge the gender of the face or to determine whether
the two bars had the same orientation. Thus the spatial attention was controlled on or
off the face. The bar-orientation task was made very difficult to consume most atten-
tional resources, leaving little resource to process the unattended faces. During the
gender task, fearful faces evoked stronger neural activity than neutral faces in a net-
work of brain regions including the fusiform gyrus, superior temporal sulcus, orbi-
tofrontal cortex and amygdala. Note that such different activation was only observed
in the gender task but not observed in the bar-orientation task.
Another study by Anderson[7]investigated this question by manipulating object-
based attention while keeping spatial attention constant. Double-exposure' images
that contained faces and buildings were used. Both of them were semi-transparent,
and subjects were instructed to make either a male/female judgment (attend to faces)
or an inside/outside judgment (attend to places). No effect of attention was observed
for the two expressions. Similar responses were evoked to both attended and unat-
tended fearful or neutral faces in the amygdala. However, an interesting effect was
observed with expressions of disgust, which evoked stronger signals in the amygdala
during unattended relative to attended conditions [8].
With only a few exceptions [9, 10, 11], studies on perception emotional expres-
sions were conducted using static faces as stimuli. However, neuroimaging studies
have revealed that the brain regions known to be implicated in the processing of facial
affect, such as the posterior superior temporal sulcus (pSTS), the amygdala and the
insula, respond more to dynamic than to static emotional expressions [12]. So it is
more appropriate, in research dealing with the recognition of real-life facial expres-
sions, to use dynamic stimuli [11].
The present study thus attempts to investigate the relationship between attention
and emotion. To do this we use a standardized set of dynamic facial expressions with
angry, happy and neutral emotions, which are presented either attended or unattended
as a result of manipulation of spatial attention.
2 Methods
2.1 Participants
Fifteen volunteers participated in the experiment. All the participants had normal or
corrected-to-normal vision. The participants received course credits or were paid
award for taking part in the study.
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