title: Bias in magnitude estimation following left hemisphere injury.
abstract: There is a growing interest both in identifying the neural mechanisms of magnitude estimation and in identifying forms of bias that can explain aspects of behavioral syndromes like unilateral neglect. Magnitude estimation is associated with activation of temporo-parietal cortex in both cerebral hemispheres of normal subjects; however, it is unclear if and how left hemisphere lesions bias magnitude estimation because the infrequency of neglect and the presence of aphasia in these subjects confound examination. In contrast, we examined magnitude estimation using 12 different types of sensory stimuli that spanned five sensory domains in two patients with very different clinical presentations following unilateral left hemisphere stroke. One patient had neglect sub-acutely without aphasia. The other had aphasia chronically after a temporo-parietal lesion but not neglect. The neglect patient was re-examined 48 h after being treated with modafinil (Provigil) for decreased arousal. Both patients demonstrated bias in magnitude estimation relative to normal subjects (n=83). Alertness improved in the neglect patient after taking modafinil. His neglect also resolved and his magnitude estimates more closely resembled those of normal subjects. This is the first evidence, to our knowledge, that left hemisphere injury can bias magnitude estimation in a manner similar but not identical to that associated with right hemisphere injury.
authors.affiliation: Department of Neurobiology and Developmental Sciences, The University of Arkansas for Medical Sciences, United States.
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Woods
authors.forename: Mark
authors.initials: M
authors.lastname: Mennemeier
authors.forename: Edgar
authors.initials: E
authors.lastname: Garcia-Rill
authors.forename: Jay
authors.initials: J
authors.lastname: Meythaler
authors.forename: Victor W
authors.initials: VW
authors.lastname: Mark
authors.forename: George R
authors.initials: GR
authors.lastname: Jewel
authors.forename: Heather
authors.initials: H
authors.lastname: Murphy
mesh_terms: D000328:Adult; D001559:Benzhydryl Compounds / Q000627:therapeutic use; D015982:Bias; D001930:Brain Injuries / Q000473:pathology / Q000503:physiopathology*; D002540:Cerebral Cortex / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005500:Follow-Up Studies; D007839:Functional Laterality; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D000077408:Modafinil; D018696:Neuroprotective Agents / Q000627:therapeutic use; D010468:Perceptual Disorders / Q000188:drug therapy / Q000503:physiopathology*; D010812:Physical Stimulation / Q000379:methods; D012677:Sensation / Q000502:physiology*; D012684:Sensory Thresholds / Q000502:physiology
chemical_list: D001559:Benzhydryl Compounds; D018696:Neuroprotective Agents; D000077408:Modafinil