| |
Abstract:
Unlike the 'impoverished' visual stimuli used in many
cognitive paradigms, complex visual stimuli that more nearly
approximate 'real world' sensory experiences likely involve
different processing within the brain. Such stimuli are typified by
the pictures from the IAPS (International Affective Picture
System). These pictures are frequently sorted in a typology that
distinguishes between "neutral" and (some variant of) "emotional".
It has not been shown, however, that this typology is clearly
instantiated within the brain. The purpose of this study was to
examine the impact of these pictures more broadly on limbic
structures. An event-related fMRI experiment was performed on a
Siemens 1.5T magnet using pictures from the IAPS as stimuli, which
were sorted as "negative" vs. "neutral". Eighteen normal subjects
performed a simple cognitive task involving counting the number of
people in the picture. A voxel-based ANOVA and time-course analyses
at regions of significance were performed. "Neutral" and "negative"
pictures were indistinguishable in their impact on several brain
regions often presumed to be involved in emotional processing (e.g.
orbitofrontal and insular cortices), while having a quantitatively
different impact on others (e.g. medial prefrontal cortex,
amygdala, midbrain). Thus, we conclude that complex visual stimuli
(IAPS), regardless of "type", do have a significant impact
throughout limbic circuitry. However, differentiation between
picture "type" is reflected quantitatively within some limbic
structures.
|
