From: joedees@bellsouth.net
Date: Fri Jul 19 2002 - 11:00:46 MDT
On 19 Jul 2002 at 10:44, Wade Smith wrote:
> http://news.bmn.com/news/story?day=020719&story=2&printerready=yes
>
> A cold-eyed analysis of hot objects
> 18 July 2002 20:30 GMT
>
> by Bea Perks, BioMedNet News
>
> Our brains do not allow us to observe an entire scene in one
> fell swoop; the visual system can only process a finite number
> of images at a time. So objects in our field of view must
> compete for attention either by being in sharp contrast (via
> so-called "bottom-up" processes, whereby lower brain regions
> inform higher regions); or by having "emotional valence" -
> eliciting an emotional response - that allows higher brain
> regions to inform lower regions of the image's emotional content.
>
> One question that has puzzled cognitive scientists is whether
> objects with emotional valence will always divert our attention
> from "neutral" objects.
>
> Now, Leslie Ungerleider, chief of the National Institute of
> Mental Health's Laboratory of Brain and Cognition in Bethesda,
> Maryland, has preliminary data to suggest that images with
> emotional valence still have to compete with neutral images for
> a share of the visual system's attentional resources. She
> presented her findings yesterday at the third biennial forum of
> the Federation of European Neuroscience Societies in Paris.
>
> Ungerleider set up a study in which subjects were shown an image
> of a face (either happy, fearful, or neutral), together with an
> image of two short bars in varying orientation.
>
> The study comprised two trials. In the first, the "attended"
> trial, subjects were asked to concentrate on ("attend" to) the
> image of the face and perform a gender discrimination test (is
> this face female or male?). In the second, or "unattended,"
> trial, subjects were asked to switch their attention to the bars
> and to perform an orientation test (are they oriented in the
> same way or not?).
>
> During the trials, the activity in different regions of the
> subjects' brains was monitored with fMRI.
>
> When Ungerleider analyzed the fMRI data for the amygdala, a
> brain region involved in processing information with emotional
> valence, she found, as expected, that there was greater activity
> in that region when subjects attended to the emotional images of
> faces compared with when they attended to the neutral images of
> bars.
>
> However, when subjects attended to the bars, the simultaneous
> appearance of a face image elicited a reduced activity in the
> amygdala. In other words, the neutral bars successfully competed
> for attention with the relatively emotional face. This result
> was the same regardless of the face's expression.
>
> "The valence effect was only impressive during attended trials,"
> said Ungerleider. "During the unattended trials, the valence
> effect is completely eliminated."
>
> She found a similar pattern for other brain regions, including
> the occipital (or visual) cortex and the superior temporal
> sulcus (another higher-order visual region.)
>
> "Stimuli that have emotional valence, like all neutral stimuli,
> must compete for these processing resources," said Ungerleider.
>
> "That's not to say that stimuli with emotional valence cannot
> bias competition in their own right," she added. "We think, for
> example, that fearful faces compared with neutral faces ... bias
> competition in [the former's] favor. However, if resources are
> depleted by a very difficult competing task, even the processing
> of emotional stimuli will not take place."
>
> The data were warmly received by delegates attending last
> night’s plenary session on Mechanisms of visual attention in the
> human brain. Ungerleider's work has made visual attention "the
> hottest topic in cognitive science," said session chair Jean
> Bullier, director of the CNRS Brain and Cognition Unit in
> Toulouse, France.
>
>
>
> This was distributed via the memetics list associated with the
> Journal of Memetics - Evolutionary Models of Information Transmission
> For information about the journal and the list (e.g. unsubscribing)
> see: http://www.cpm.mmu.ac.uk/jom-emit
>
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