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You might have come across stereographic Images like the one shown below (found here):
What happens in your brain when you observe the dinosaur? (as you put your face on the image by touching your nose and then slowly withdrawing from the image.)
Is this perception a particular trick that my eye performs or is it processing the visual data in an alternative way?
Is the effect of this percept measurable by an EEG?
The source I have quoted below gives an example of the following stenographic image:-
Is this perception a particular trick that my eye performs or is it processing the visual data in an alternative way?
Stereograms can be viewed as three-dimensional images by providing two side-by-side views of a three-dimensional scene, rendered from slightly different viewpoints. Stereoscopes facilitate focusing of the eyes depths other than the surface of a two-dimensional stereogram image, allowing the two separate images to overlap in the center of the field of vision (Kimmel, 2002). Once the correct depth is achieved, it may seem to the viewer as if the two images are different due to the horizontal retinal disparities. Then the two images can fuse into a coherent three- dimensional percept where horizontal disparities in the images provide important depth cues.
Is the effect of this percept measurable by an EEG?
Autostereograms have been used in recent research to investigate three-dimensional depth perception. These efforts have improved understanding of the various visual cues involved in forming three-dimensional percepts, perceiving motion in depth, attention- switching in the depth of field, and the neural correlates of forming and maintaining a unified three-dimensional structure in awareness.
Revonsuo and colleagues (Revonsuo, et al., 1997) used neural synchronization to investigate the neural correlates of three-dimensional percept formations. They confirmed that autostereoscopic perception is primarily mediated by right parieto-temporal activity. Their research indicated a region of synchrony spanning portions of the right temporal, parietal and occipital lobes, with maximum power in the gamma (36-44Hz) frequency range. Also employing electroencephalogram (EEG) recording, Burgess, Rehman, and Williams (2003) located particular brain regions, including the left frontal (F7) and the right and midline occipital (Oz, O2) clusters, exhibiting functional clustering during autostereoscopic perception. Overall, neural complexity was highest with the most functional clustering of responses during observer awareness of the three-dimensional object. Additional clustering analyses revealed functional clusters of scalp recordings in the aforementioned areas that correlated with both phases of three-dimensional perception (search to three-dimensional and three-dimensional maintenance).
Sources
Autostereograms and Autostereoscopic Perception
Authors: Leslie Blaha, Christopher Honey, and Eric Nichols
Date: October 31, 2005
Burgess, A.P., Rehman, J., & Williams, J.D. (2003). Changes in neural complexity during the perception of three-dimensional images using random dot stereograms. International Journal of Psychophysiology, 48, 35-42.
Kimmel, R. (2002). Three-dimensional shape reconstruction from autostereograms and stereo. Journal of Visual Communication and Image Representation, 13, 324-333.
