Lee HA, Lee SH. Hierarchy of direction-tuned motion adaptation in human visual cortex. J Neurophysiol 107: 2163-2184, 2012. First published January 4, 2012 doi:10.1152/jn.00923.2010.-Prolonged exposure to a single direction of motion alters perception of subsequent static or dynamic stimuli and induces substantial changes in behaviors of motion-sensitive neurons, but the origin of neural adaptation and neural correlates of perceptual consequences of motion adaptation in human brain remain unclear. Using functional magnetic resonance imaging, we measured motion adaptation tuning curves in a fine scale by probing changes in cortical activity after adaptation for a range of directions relative to the adapted direction. We found a clear dichotomy in tuning curve shape: cortical responses in early-tier visual areas reduced at around both the adapted and opposite direction, resulting in a bidirectional tuning curve, whereas response reduction in high-tier areas occurred only at around the adapted direction, resulting in a unidirectional tuning curve. We also found that the psychophysically measured adaptation tuning curves were unidirectional and best matched the cortical adaptation tuning curves in the middle temporal area (MT) and the medial superior temporal area (MST). Our findings are compatible with, but not limited to, an interpretation in which direct impacts of motion adaptation occur in both unidirectional and bidirectional units in early visual areas, but the perceptual consequences of motion adaptation are manifested in the population activity in MT and MST, which may inherit those direct impacts of adaptation from the directionally selective units. visual motion; visual cortex; direction selectivity; functional magnetic resonance imaging; V1; middle temporal area PROLONGED EXPOSURE TO A VISUAL pattern drifting in one direction alters perception of subsequently presented stimuli. Adaptation reduces the visibility of objects moving in the adapted direction (Raymond 1993;Tolhurst 1973), makes static or dynamic patterns appear to drift in the opposite direction (Mather et al. 1998), distorts the apparent speed of a moving stimulus (Stocker and Simoncelli 2009;Thompson 1981), or even shifts the perceived direction of motion away from the adapted direction (Levinson and Sekuler 1976).These profound alterations in perception suggest that adaptation has substantial impacts on the neural systems for processing motion stimuli. Indeed, there have been many attempts at uncovering neural consequences of motion adaptation. Although these studies have demonstrated that adaptation substantially modifies neural activities in retina (Barlow and Hill 1963) or visual areas in the cortex (Hammond et al. 1985;Huk et al. 2001;Petersen et al. 1985;Tolias et al. 2001), it has been quite challenging to single out a neural locus or mechanism for motion adaptation. Given the hierarchical and distributed nature of cortical motion processing, which has been supported by a body of anatomical (Felleman and van Essen 1991; Maunsell a...