High-level Adaptation Effects
Neuronal adaptation can be regarded as a mechanism by which perceptual processing is constantly re-calibrated as a result of specific characteristics of incoming stimuli. Adaptation has been demonstrated in the form of perceptual illusions or aftereffects. The first written record of this is ascribed to Aristotle, who observed that, following prolonged fixation of the downward motion of a waterfall, a static visual scene appears to move upward. In this “waterfall illusion” or, more generally, the “motion aftereffect”, a stationary stimulus appears to move in opposite direction to that of a previously fixated continuous visual motion. Perceptual adaptation is thought to result from the selective habituation after prolonged firing of neuronal populations that code specific stimulus attributes, a phenomenon sometimes referred to as the “psychologist´s microelectrode”, as it can provide valuable insight into the neural fine tuning to special stimulus attributes in visual perception. However, while adaptation to simple stimulus attributes such as motion or colour has been known for literally hundreds of years, a striking novel discovery within the last couple of years is that adaptation is also of central importance for how humans perceive complex visual stimuli. Adaptation to male faces, for example, has been found to bias the subsequent perception of androgynous faces towards female gender. Similar adaptation effects have been observed for one of the most important visual social signals: Human eye gaze. Jenkins et al. (2006) found that adaptation to gaze into one direction virtually eliminated participants’ ability to perceive smaller gaze deviations into the same direction. With our project, we aim at a deeper understanding of high-level adaptation effects. We are interested into several aspects of high-level adaptation effects such as the interrelationship of similarity of adaptation and test stimulus, the longevity of adaptation effects, the neural correlates of adaptation as investigated with EEG or fMRI, and the potential links between perceptual adaptation and neuronal repetition suppression.