Quantity Determination and the Distance Effect with Letters, Numbers, and Shapes: A Functional MR Imaging Study of Number Processing
Robert K. Fulbrighta,
Stephanie C. Mansona,
Pawel Skudlarskia,
Cheryl M. Lacadiea and
John C. Goreb
a Section of Neuroradiology, Department of Radiology, Yale University School of Medicine, New Haven, CT
b Institute of Imaging Science, Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville TN
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FIG 1. Reaction times when subjects identified stimuli (control task) and ordered letters, numbers, and shapes. A distance effect ( , P < .05) was seen with numbers and shapes, as subjects were faster ordering far numbers (OFN) compared with near numbers (ONN), and far shapes (OFS) compared with near shapes (ONS). No statistically significance difference was seen between near letters (ONL) and far letters (OFL). IFL indicates identify far letters; INL, identify near letters; IFN, identify far numbers; INN, identify near numbers; IFS, identify far shapes; INS, identify near shapes.
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FIG 2. Accuracy of subjects during the identify and order tasks. The identify task (control) resulted in near 100% accuracy irrespective of stimulus type. Subjects were less accurate when ordering letters compared with ordering numbers and shapes. IFL indicates identify far letters; INL, identify near letters; IFN, identify far numbers; INN, identify near numbers; IFS, identify far shapes; INS, identify near shapes; OFL, order far letters; ONL, order near letters; OFN, order far numbers; ONN, order near numbers; OFS, order far shapes; and ONS, order near shapes.
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FIG 3. Regional brain activation when subjects judged the order of letters, numbers, or shapes. The images represent group composite activation maps comparing order trials with identify trials within a particular stimulus type. The red-yellow scale indicates brain regions that were more active in the order trials than in the identify trials (P = .001). The blue-purple scale represents brain regions that were active in the identify trials than in the order trials (P = .001). Rows a–e indicate the section position along the z axis of the Talairach atlas system (40, 32, 24, 12, and 4, respectively). The legend for activation is as follows: sfg indicates superior frontal gyrus; acg, anterior cingulate gyrus; mfg, middle frontal gyrus; prcg, precentral gyrus; ips, intraparietal sulcus; ifg, inferior frontal gyrus; pcu, precuneus; smg, supramarginal gyrus; sog, superior occipital gyrus; cu, cuneus; ins, insula; bg, basal ganglia; c, caudate nucleus; stg, superior temporal gyrus; mtg, middle temporal gyrus; cf, calcarine fissure; mog, middle occipital gyrus; lg, lingual gyrus; R, right; L, left.
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FIG 4. Group composite maps compare the three stimulus types (see Methods). The red-yellow scale indicates brain regions that were more active (P = .001) when letters were compared with shapes (L vs S, column 1), when letters were compared with numbers (L vs N, column 2), or when numbers were compared with shapes (N vs S, column 3). The blue-purple scale represents brain regions that were active (P = .001) when shapes were compared with letters (column 1), when numbers were compared with letters (column 2), or when shapes were compared with numbers (column 3). Rows a–e indicate the section position along the z axis of the Talairach atlas system (40, 32, 24, 12, and 4, respectively). The legend for activation is as follows: mfg indicates middle frontal gyrus; acg, anterior cingulate gyrus; prcg, precentral gyrus; ips, intraparietal sulcus; sfg, superior frontal gyrus; ifg, inferior frontal gyrus; c, caudate nucleus; sog, superior occipital gyrus; ins, insula; bg, basal ganglia; stg, superior temporal gyrus; R, right; L, left.
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FIG 5. Group composite maps indicate brain activation when the near order trials were compared with the far order trials for letters, numbers, and shapes. The red-yellow scale indicates brain regions that were more active (P = .05) in near trials, and the blue-purple scale represents brain regions that were active (P = .05) in the far trials. Rows a–d indicate the section position along the z axis of the Talairach atlas system (32, 24, 12, and 4, respectively). The legend for activation is as follows: mfg indicates middle frontal gyrus; ifg, inferior frontal gyrus; ips, intraparietal sulcus; sfg, superior frontal gyrus; smg, supramarginal gyrus; pcu, precuneus; c, caudate nucleus; ins, insula; acg, anterior cingulate gyrus; bg, basal ganglia; t, thalamus; cf, calcarine fissure; mog, middle occipital gyrus; mtg, middle temporal gyrus; stg, superior temporal gyrus; R, right; L, left.
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