The rise and fall of priming: how visual exposure shapes cortical representations of objects.
Cerebral Cortex. 2005-02-16; 15(11): 1655-1665
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1. Cereb Cortex. 2005 Nov;15(11):1655-65. Epub 2005 Feb 16.
The rise and fall of priming: how visual exposure shapes cortical representations
Zago L(1), Fenske MJ, Aminoff E, Bar M.
(1)Martinos Imaging Center at MGH, Harvard Medical School, 149 Thirteenth Street,
Charlestown, MA 02129, USA.
How does the amount of time for which we see an object influence the nature and
content of its cortical representation? To address this question, we varied the
duration of initial exposure to visual objects and then measured functional
magnetic resonance imaging (fMRI) signal and behavioral performance during a
subsequent repeated presentation of these objects. We report a novel
‘rise-and-fall’ pattern relating exposure duration and the corresponding
magnitude of fMRI cortical signal. Compared with novel objects, repeated objects
elicited maximal cortical response reduction when initially presented for 250 ms.
Counter-intuitively, initially seeing an object for a longer duration
significantly reduced the magnitude of this effect. This ‘rise-and-fall’ pattern
was also evident for the corresponding behavioral priming. To account for these
findings, we propose that the earlier interval of an exposure to a visual
stimulus results in a fine-tuning of the cortical response, while additional
exposure promotes selection of a subset of key features for continued
representation. These two independent mechanisms complement each other in shaping
object representations with experience.
PMID: 15716471 [Indexed for MEDLINE]