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SUMMARY:Topographic processing of numerosity in the human brain - Dr. B. M
 . Harvey\, University of Utrecht
DTSTART:20131211T130000Z
DTEND:20131211T140000Z
UID:TALK47829@talks.cam.ac.uk
CONTACT:John Mollon
DESCRIPTION:Numerosity\, the set size of a group of visually-presented ite
 ms\, is processed by association cortex\, but certain aspects mirror prope
 rties of primary senses (Dehaene\, 1997\; Burr and Ross\, 2008). Sensory c
 ortices contain topographic maps reflecting the structure of sensory organ
 s such as the retina\, cochlea or skin. Is the cortical representation and
  processing of numerosity organized topographically\, even though no senso
 ry organ has a numerical structure? Using high-field fMRI (7T) and custom-
 built model-based analysis that captures numerosity tuning (Dumoulin and W
 andell\, 2008)\, we describe neural populations tuned to small numerositie
 s in human posterior parietal cortex. These neural populations are organiz
 ed topographically\, forming a numerosity map where preferred numerosity i
 ncreases from medial to lateral cortex. This numerosity map is robust to c
 hanges in low-level stimulus features\, although numerosity-tuning propert
 ies do vary with stimulus features. Furthermore\, the cortical surface are
 a devoted to specific numerosities (cortical magnification factor) decreas
 es with increasing numerosity\, and the tuning width increases with prefer
 red numerosity. These organizational properties mirror key features of sen
 sory and motor topographic maps. This extends topographic principles to re
 presentation of higher-order cognitive processing in association cortex\, 
 supports the analogy between numerosity and primary senses\, and demonstra
 tes that topographic structures can emerge within the brain.
LOCATION:Kenneth Craik Room\, Craik-Marshall Building\, Downing Site
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