### Abstract

Background: Line bisection errors in neglect are attributed to perceptual size distortions. In order to compare the two segments of the line to determine if they are equal, one might first estimate the location of a midpoint that defines the two line segments to be compared. Objectives: The authors attempted to determine whether estimating a line's midpoint can be dissociated from comparing the two segments of this line, and if so, what the relative contribution of each of these tasks is to the perceptual bias in neglect. Methods: The authors studied two patients with hemispatial neglect from right hemisphere lesions by asking them where bisection marks were placed on prebisected lines and whether the two adjacent line segments were equal. Results: There was a stronger bias judging the position of the bisecting marks ("where" determination) than comparing the size of two adjacent line segments. Conclusions: These results suggest that perceptual size distortion of line segments alone cannot explain the subjects' line bisection bias, but postperceptual deficits in "where" computations may better account for their errors locating the midpoint. "Where" determinations might require more attentional capacity, depend more heavily on viewer-centered allocation of attention, and be mediated by the right hemisphere's "where" dorsal stream. In contrast, comparing the length of two segments might be mediated by the left hemisphere's "what" ventral stream.

Original language | English (US) |
---|---|

Pages (from-to) | 1580-1584 |

Number of pages | 5 |

Journal | Neurology |

Volume | 59 |

Issue number | 10 |

State | Published - Nov 26 2002 |

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### ASJC Scopus subject areas

- Neuroscience(all)

### Cite this

*Neurology*,

*59*(10), 1580-1584.

**Is the middle between both halves? Midpoint location and segment size estimation in neglect.** / Riestra, Alonso R.; Womack, Kyle B.; Crucian, Gregory P.; Heilman, Kenneth M.

Research output: Contribution to journal › Article

*Neurology*, vol. 59, no. 10, pp. 1580-1584.

}

TY - JOUR

T1 - Is the middle between both halves? Midpoint location and segment size estimation in neglect

AU - Riestra, Alonso R.

AU - Womack, Kyle B.

AU - Crucian, Gregory P.

AU - Heilman, Kenneth M.

PY - 2002/11/26

Y1 - 2002/11/26

N2 - Background: Line bisection errors in neglect are attributed to perceptual size distortions. In order to compare the two segments of the line to determine if they are equal, one might first estimate the location of a midpoint that defines the two line segments to be compared. Objectives: The authors attempted to determine whether estimating a line's midpoint can be dissociated from comparing the two segments of this line, and if so, what the relative contribution of each of these tasks is to the perceptual bias in neglect. Methods: The authors studied two patients with hemispatial neglect from right hemisphere lesions by asking them where bisection marks were placed on prebisected lines and whether the two adjacent line segments were equal. Results: There was a stronger bias judging the position of the bisecting marks ("where" determination) than comparing the size of two adjacent line segments. Conclusions: These results suggest that perceptual size distortion of line segments alone cannot explain the subjects' line bisection bias, but postperceptual deficits in "where" computations may better account for their errors locating the midpoint. "Where" determinations might require more attentional capacity, depend more heavily on viewer-centered allocation of attention, and be mediated by the right hemisphere's "where" dorsal stream. In contrast, comparing the length of two segments might be mediated by the left hemisphere's "what" ventral stream.

AB - Background: Line bisection errors in neglect are attributed to perceptual size distortions. In order to compare the two segments of the line to determine if they are equal, one might first estimate the location of a midpoint that defines the two line segments to be compared. Objectives: The authors attempted to determine whether estimating a line's midpoint can be dissociated from comparing the two segments of this line, and if so, what the relative contribution of each of these tasks is to the perceptual bias in neglect. Methods: The authors studied two patients with hemispatial neglect from right hemisphere lesions by asking them where bisection marks were placed on prebisected lines and whether the two adjacent line segments were equal. Results: There was a stronger bias judging the position of the bisecting marks ("where" determination) than comparing the size of two adjacent line segments. Conclusions: These results suggest that perceptual size distortion of line segments alone cannot explain the subjects' line bisection bias, but postperceptual deficits in "where" computations may better account for their errors locating the midpoint. "Where" determinations might require more attentional capacity, depend more heavily on viewer-centered allocation of attention, and be mediated by the right hemisphere's "where" dorsal stream. In contrast, comparing the length of two segments might be mediated by the left hemisphere's "what" ventral stream.

UR - http://www.scopus.com/inward/record.url?scp=0037180466&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0037180466&partnerID=8YFLogxK

M3 - Article

C2 - 12451201

AN - SCOPUS:0037180466

VL - 59

SP - 1580

EP - 1584

JO - Neurology

JF - Neurology

SN - 0028-3878

IS - 10

ER -