Neurological Basis of Charles Bonnet Syndrome

Article: A Brain Mechanism for 'Vision' in the Blind is Revealed
Source: Weizmann Institute of Science, via ScienceDaily  and Technology Networks
Published: January 7, 2021

The visual centers in those seeing a film or imagining as instructed had similar timing in their brain activity,
while those experiencing spontaneous hallucinations showed a gradual increase in slow fluctuations.

This is a very interesting study both for scientific and clinical reasons. The idea to investigate spontaneous "resting-state" fluctuations in the brain via patients with Charles Bonnet syndrome is excellent. These are patients who experience visual hallucinations, "phantom vision" if you will, after losing sight. Their eyes no longer send input to their brain, but these patients can still "see" with their intact visual cortex. Of note is the finding that brain wave activity reminiscent of slow spontaneous fluctuations emerged just before onset of the hallucination, indicating that the hallucinations were evoked internally and not from external stimuli. Limitations of the study include its small sample size of only five patients with Charles Bonnet syndrome. However, the news coverage of Charles Bonnet syndrome is an excellent opportunity to call attention to this condition. As you can imagine, hallucinations can be a frightening and isolating experience. So awareness of Charles Bonnet syndrome for both trainees and the public increases assurance if they encounter the situation.

My rating of this study: ⭐⭐

Hahamy A, Wilf M, Rosinl B, et al. "How do the blind ‘see’? The role of spontaneous brain activity in self-generated perception." Brain. 144(1):340–353. January 2021. https://doi.org/10.1093/brain/awaa384