A study done at the University of Glasgow by the Institute of Neuroscience and Psychology has uncovered some intriguing qualities of the human eye. Namely, the visual cortex in the brain that receives data from the eye and processes it. From the findings, it looks like it is processing auditory information too. The visual cortex actually uses auditory signals to anticipate the images that the eyes are going to see. The study, entitled, Decoding sound and imagery content in early visual cortex, was published in Current Biology.
Lars Muckli, the lead researcher on the project wrote in a press release that sounds can create automatic projections, mental images and visual imagery. He gives the example of being on a street and hearing a motorcycle coming. The expectation is to see a motorcycle rolling down the street. If a horse came along, that would be surprising.
The researchers executed five experiments for the study. They used functional Magnetic Resonance Imaging (fMRI) to help shed light on the important connection between the ears and the visual cortex. In one experiment, using 10 volunteers, the scientists instructed their blindfolded subjects to listen to three sounds, birdsongs, people talking and noisy traffic. With the use of a special algorithm, they were able to see the way the audio was being processed in the visual cortex activity of the brain. The researchers also conducted an experiment that activated the visual cortex of subjects through visualization with no auditory or visual prompting.
Muckli said that their research deepens the basic understandings regarding just how interconnected various regions of the brain really are. The processing of auditory input has not previously been associated with the early visual cortex. There is, however, some anatomical evidence for this interconnectedness found in monkeys. Muckli continued to say that this is the first study to show clearly that the relationship exists in humans.
In the future, the team would like to test exactly how the auditory input supports the processing of visual information. So far, the assumption is that it furnishes predictions to aide the visual system when focusing on events that are surprising, thereby granting an advantage for survival. They would like to also explore a greater variety of auditory input to discover just how precise the brain’s predictive coding can be.
The continued research could offer insights into health conditions that are of a mental nature like, autism spectrum disorder and schizophrenia. It could very well help in understanding more deeply how and why sensory perceptions are different for people who have these conditions. This project was a part of the five year study that is being funded by a consolidator grant, Brain reading of contextual feedback and predictions, from the European Research Council and the Biotechnology and Biological Sciences Research Council.
This research could also help to explain why so many autistic children seem to mix up their senses. They are often heard saying phrases such as, “Did you see that?” when they are talking about a noise, or “I heard a cat,” when they are referring to seeing the animal. Since Autism Spectrum Disorder is partly a neurologically affected condition, perhaps the interconnectedness now being discovered is somehow indistinguishable for individuals with autism. While the visual cortex is processing auditory signals, it is interesting to think how other parts of the brain associated with the senses may be interconnected.
By Stacy Lamy