Orientation Discrimination and Contrast Detection Thresholds in Migraine for Cardinal and Oblique Angles

• Published in: Investigative ophthalmology & visual science Vol. 47; no. 12; pp. 5599 - 5604
• Main Authors: Tibber, Marc S, Guedes, Antonio, Shepherd, Alex J
• Format: Journal Article
• Language: English
• Published: Rockville, MD ARVO 01.12.2006; Association for Research in Vision and Ophtalmology
• Subjects: Adult; Biological and medical sciences; Contrast Sensitivity - physiology; Eye and associated structures. Visual pathways and centers. Vision; Female; Fundamental and applied biological sciences. Psychology; Humans; Male; Medical sciences; Middle Aged; Migraine with Aura - physiopathology; Migraine without Aura - physiopathology; Neurology; Orientation; Sensory Thresholds - physiology; Vascular diseases and vascular malformations of the nervous system; Vertebrates: nervous system and sense organs; Vision Disorders - physiopathology; Visual Cortex - physiopathology; Nervous system diseases; Migraine; Cardiovascular disease; Orientation; Cerebral disorder; Vascular disease; Discrimination; Pain; Angle; Central nervous system disease; Detection threshold; Ophthalmology; Contrast threshold; Cerebrovascular disease
• ISSN: 0146-0404; 1552-5783; 1552-5783
• DOI: 10.1167/iovs.06-0640

To determine whether orientation discrimination deficits in migraine, which have been found to depend on the spatial frequency of the stimulus, are due to precortical dysfunction or to abnormal patterns of orientation tuning at cortical loci. Further, to assess whether any cortical involvement is restricted to the striate cortex or whether higher cortical areas are also involved. Orientation-specific abnormalities would provide evidence of cortical dysfunction. Orientation-discrimination and contrast-detection thresholds were assessed at cardinal (0 degrees) and oblique (45 degrees) orientations using explicit lines defined by Gabor patches. To test for extrastriate dysfunction, participants made orientation judgments using virtual lines defined by two widely spaced circles. Migraine history, migraine triggers, and pattern sensitivity were also assessed. Twenty migraineurs (10 with visual aura, 10 without) and 20 control participants were tested. Orientation-discrimination thresholds were lower for discriminations made about the cardinal axis than for discriminations made about the oblique axis, a well-documented phenomenon known as the oblique effect. Relative to the control group, the migraine group exhibited orientation-specific sensitivity losses on explicit and virtual judgments. Orientation-discrimination thresholds about the oblique axis were significantly elevated in the migraine group. In contrast, the migraine and control groups' detection thresholds did not differ. These findings reflect abnormal function of striate and extrastriate cortex in migraine. In addition, the discrimination data are consistent with wider orientation-tuning curves for orientation-sensitive cells in migraine, whereas the detection data suggest peak sensitivity does not differ between the groups.