Brain able to act through 'Mind's Eye'

Optical illusions are more than just those pictures in a book that helped me kill time on long road trips when I was a kid. They are fun, interesting ways to trick your brain. According to an article by Andy Henion, in Futurity, illusions can also help researchers try to figure out how your brain determines what to attend to and what to ignore. Since neural imaging was made possible, researchers have been attempting to ‘see’ what the brain is doing or at least where it is thinking. fMRI allows researchers to see a hemodynamic response to activity, signaling where the brain is active and where it is not. One downside to fMRI scanners is due to the nature of the test, it does not provide accurate temporal information.

Evidence for intentional control over attention is given by a simple study by Posner in 1980. He had subjects respond to the location of an image. Occasionally, the future location of the image would be hinted, greatly reducing reaction times. This lead most neuroscientists to infer that the frontal lobe, previously shown to work in spatial and goal oriented tasks and decisions, was responsible for spatial attention. Initial structural research done using MRI scanners and spatial perception seems to correlate activation in the fronto-parietal regions of the brain with a change in perception. However, because of the test’s inaccurate temporal information, it remained unclear whether fronto-parietal activation occurred before or after the change in perception. If activation occurs before a change in perception, it would indicate the activation is responsible for the change in perception. Conversely, if activation occurs after the change in perception, then it occurred as a response to the change.

Researchers at Michigan State University have found a way to isolate one possibility. By cleverly preventing subjects from becoming aware of when the change in perception occurred, they were able to reduce any possible effects from the noticing of the change in stimulus. Subjects looked at a monitor, with a small group of moving dots centered in front of each eye. The dots in front of each eye moved in random patterns that did not match each other, causing perceptual instability. Optical illusions, like the famous young woman / old lady picture or wine goblet / two faces, are other examples of perceptual instability. The instability caused perception to change back and forth, but, because the illusion was two non-identical sets of moving dots, it was hard to tell what was different in the chaos, causing subjects to effectively not perceive their own change in perception. This sounds scary, but it happens all the time. In all honestly, despite my best effort, I will find myself wondering about dinner or plans for the upcoming weekend in the middle of class! Distractions are normal, and attention can change rapidly, just ask any child. The researchers monitored subjects’ brains during these stealthy perceptual changes, and found a diminished BOLD effect in the fronto-parietal area of the brain. The lessened effect indicates lower activation in the frontal and parietal lobes.

Generally, the frontal and parietal lobes combine to form the ‘where pathway.’ It is the traditional area of activation for higher visuospatial cognition. The fact that there is a diminished response while the brain is able to change perception indicates that it is not responsible for changing visual perception, as has been considered. The paper discusses a possible theory that the cause of perceptual change must be elsewhere in the brain and suggests the occipital lobe and posterior temporal lobe as possible locations.

Article from Futurity: http://www.futurity.org/brain-vision-decisions-1019122/

Original Paper from Nature: http://www.nature.com/neuro/journal/vaop/ncurrent/full/nn.4130.html