Scientists have long studied why our brains choose to process only a small amount of information we come across in everyday life. Some information reaches our consciousness, while other information – although absorbed – takes a back seat. But a new study may shed light on why this happens.
Through using a common visual illusion, called “binocular rivalry,” researchers from the Centre for Integrative Neuroscience (CIN) at the University of Tübingen in Germany were able to pinpoint a significant difference between conscious and unconscious motion that is represented in the brain.
The researchers say that our eyes usually see the same image. The process of binocular rivalry occurs when each eye is shown a completely different image.
Through this process, the researchers explain, our brains are unable to decide which image to process, with our perception moving between the two images every few seconds. This means the images are “rivals” for our attention, taking turns to enter our consciousness.
Magnetic pulses ‘disrupt consciousness’
For their study, published in the journal Current Biology, the researchers tested an adapted version of the binocular rivalry approach on 11 participants.
The subjects were presented with a different image for each eye, but one image was moving while the other was still. The participants’ eye movements were monitored using an infrared eye tracker.
At the same time, the researchers applied magnetic pulses (transcranial magnetic stimulation) to the specific area of the participants’ brains that plays a part in visual motion in order to “disturb” this area.
The researchers found that the magnetic pulses that stimulated the motion area had no effect on the length of time that the moving image was perceived. However, they found that participants perceived the still image for longer.
Explaining this finding, the scientists say, that although the result was unexpected, administering magnetic pulses while the participants’ minds were unconsciously processing motion caused their minds to take longer to become conscious of the moving image.
However, they add that once participants did become aware of the moving image, magnetic pulses had no effect.
“This result suggests a substantial qualitative difference between the conscious and unconscious representation of motion.
Transcranial magnetic stimulation can easily weaken a suppressed representation and thus delay the time when it becomes dominant again. However, once motion becomes conscious, it is harder to disrupt.”