The human brain is an incredible work of art that never ceases to puzzle doctors and researchers worldwide. A recent case study published in the journal, Proceedings of the National Academy of Science, has provided valuable insight into the complexities of the brain.
Since 2010 Michael McCloskey and his team of researchers at John Hopkins University have been closely working with a man only known as R.F.S, to better understand his brain’s inability to recognize numbers from 2 to 9.
In 2010, the then 60-year-old engineering geologist suffered an acute neurological event that caused headaches, amnesia and, temporary loss of vision. A few months later he started experiencing difficulty walking, muscle spasms, difficult perceiving written digits and in May 2011 he was diagnosed with corticobasal syndrome. MRI scans showed parietal atrophy, and, cerebral, midbrain, and cerebellar volume loss.
By August 2011, R.F.S was completely unable to name or draw the digits 2 to 9 and was only able to perceive them as black scribbles, that looked different each time he looked at them. Surprisingly, however, he had no difficulty naming or copying the digits 0 and 1 which researchers believe could be due to their simple shape and close resemblance to letters.
He had no issues with letter recognition, visual picture naming, copying simple shapes, and naming typographical symbols (e.g., #, $, +). His digit metamorphopsia was only limited to Arabic digit identification and he faced no difficulty in reading and comprehending number words and Roman numerals, and hence was able to use these alternate forms to perform calculations.
Using electroencephalography (EEG), the researchers monitored R.F. S’s brain activity while he carried out various tasks. When he was shown a face with a number on it, he was completely unable to perceive the number or the face, but his EEG showed his brain was responding just as if he was looking normally at a face. Similarly, when he was shown numbers and letters embedded together, he wasn’t able to perceive the letter or digit as anything other than “spaghetti”, yet his EEG showed evidence of neural processing.
It is hard to pinpoint where exactly in the brain lies the problem. R.F.S’s bizarre condition gives evidence to the fact that perception and awareness are two separate things. While the brain may be able to identify a face, letter, or a digit, there is an additional level of neural processing required for visual awareness of the item.
Schubert, T. M., Rothlein, D., Brothers, T., Coderre, E. L., Ledoux, K., Gordon, B., & Mccloskey, M. (2020). Lack of awareness despite complex visual processing: Evidence from event-related potentials in a case of selective metamorphopsia. Proceedings of the National Academy of Sciences, 202000424. doi:10.1073/pnas.2000424117