Vase or face? When presented with the well known optical illusion in which we see either a vase or the faces of two people, what we observe depends on the patterns of neural activity going on in our brains.
“In this example, whether you see faces or vases depends entirely on changes that occur in your brain, since the image always stays exactly the same,” said John Serences, a UC Irvine cognitive neuroscientist.
In a recent study published in the Journal of Neuroscience, Serences and co-author Geoffrey Boynton, associate professor at the University of Washington, found that when viewing ambiguous images such as optical illusions, patterns of neural activity within specific brain regions systematically change as perception changes. More importantly, they found that patterns of neural activity in some brain regions were very similar when observers were presented with comparable ambiguous and unambiguous images.
“The fact that some brain areas show the same pattern of activity when we view a real image and when we interpret an ambiguous image in the same way implicates these regions in creating the conscious experience of the object that is being viewed,” Serences said.
Findings from their study may further contribute to scientists’ understanding of disorders such as dyslexia – a case in which individuals are thought to suffer from deficiencies in processing motion – by providing information about the functional role that specific brain regions play in motion perception.
Using functional magnetic resonance imaging (fMRI), researchers measured patterns of neural activity in the middle temporal (MT) region of the brain – an area associated with motion perception – under two different scenarios.
In the first, participants were asked to view objects moving only in one direction and to identify the direction in which the objects were moving (left or right). They were then presented with objects in which the direction of motion was ambiguous, or undefined, and asked to identify the main direction of motion.
The pattern of neural activity in the MT region was highly similar when an observer viewed real motion moving to the left and when they thought they saw the ambiguously moving objects moving to the left.
“The close correspondence between the pattern of activation in MT and what the observer reports seeing suggests that this region of your brain plays an important role in generating conscious experience of the world around you,” says Serences.
This study was funded by the National Institute of Health.