A Review of Motion and Orientation Processing in Migraine

Abstract

Visual tests can be used as noninvasive tools to test models of the pathophysiology underlying neurological conditions, such as migraine. They may also be used to track changes in performance that vary with the migraine cycle or can track the efficacy of prophylactic treatments. This article reviews the literature on performance differences on two visual tasks, global motion discrimination and orientation, which, of the many visual tasks that have been used to compare differences between migraine and control groups, have yielded the most consistent patterns of group differences. The implications for understanding the underlying pathophysiology in migraine are discussed, but the main focus is on bringing together disparate areas of research and suggesting those that can reveal practical uses of visual tests to treat and manage migraine.

Keywords: migraine; motion processing; orientation processing.

Figure 1

An example of the displays used for motion discrimination tasks, using motion coherence (A–C) and equivalent noise (D–F) paradigms. In both tasks, the participant must classify the signal direction (or average signal direction) as right or left of vertical. In the motion coherence paradigm, external noise was added to the stimulus by assigning a subset of dot random directions. In the equivalent noise paradigm, external noise was added to the stimulus by increasing the standard deviation of motion directions displayed by the noise dots. In A–C, directions of signal motion are indicated by white arrows; directions of noise motion are indicated by black arrows. (In the actual experiment all signal and noise elements were comprised of white dots. Noise dots are shown in black for illustration purposes only.) Associated signal and noise probability distribution functions are presented alongside each example display; in these, the reference direction is denoted by a dotted black line and the signal probability density function is denoted by a solid black line. Adapted from Tibber et al. [32].

Figure 2

An example of the displays used to assess prolonged motion after-effects in migraine. Adapted from Shepherd [10,11].

Figure 3

An example of the displays used to assess the oblique effect using gratings. In one condition the reference grating (“Ref”) is vertical and the test grating is oriented slightly clockwise or counter-clockwise to vertical. Thresholds for reliable discrimination can be determined. In a second condition, the reference is oriented at 45 degrees from vertical and orientation thresholds are again determined. Adapted from Tibber et al. [24].

Figure 4

An example of the displays used to assess the oblique effect using virtual lines. As in Figure 3, in one condition the reference grating (“Ref”) is vertical and the test grating is oriented slightly clockwise or counter-clockwise to vertical. Thresholds for reliable discrimination can be determined. As in Figure 3, in the second condition, the reference is oriented at 45 degrees from vertical and orientation thresholds are again determined. Adapted from Tibber et al. [24].