Memory holds important functions in the human brain. Through experiences, it shapes our identities and guides our decisions, but what happens if neurodegenerative diseases like Alzheimer's strip away some of these memories? The hippocampus aids in both short and long-term memory. Disruptions in the hippocampal functions can lead to difficulty remembering personal experiences in the early stage of Alzheimer's. Recent research has discovered that memories are not fully lost; they are merely inaccessible due to impairments in retrieval.
Optogenetics is a tool Dr. Stephanie Grella used in her study, Artificially enhancing and suppressing hippocampus-mediated memories, to activate fear and reward memories in mice. It uses genetically modified cells to express light-sensitive proteins, and can induce context-specific behaviors. This demonstrates that forgotten memories could be brought back into consciousness by activating specific neural cells. This research paper focused on the dorsal and ventral hippocampus, each having different functions. The dorsal hippocampus codes for spatial and contextual information, while the ventral hippocampus codes for emotional responses. By tagging neurons along the dorsoventral area, the study revealed that fear could either be suppressed or enhanced depending on the region activated.
Optogenetics has also been used in another research regarding therapy for Alzheimer's disease. In the article Optogenetics: implications for Alzheimer’s disease research and therapy, researchers explore how optogenetics could be used to restore cognitive function and slow neurodegeneration in Alzheimer's patients. One major protein that is associated with Alzheimer's is amyloid-beta, which disrupts brain function and causes memory loss. By using optogenetics, researchers have discovered that memories are simply inaccessible in Alzheimer's patients, not lost due to the build up of amyloid-beta.
Though this study is groundbreaking, using optogenetics as a treatment for Alzheimer’s and other neurodegenerative diseases faces many challenges. Delivering light deep into the brain is difficult, and scientists need to develop safe ways to introduce light-sensitive proteins into human neurons. Ethical concerns and long-term effects must also be studied. This could open up new opportunities for more research and perhaps find an effective treatment for neurodegenerative diseases.
References:
(1)Chen, B. K.; Murawski, N. J.; Cincotta, C.; McKissick, O.; Finkelstein, A.; Hamidi, A. B.; Merfeld, E.; Doucette, E.; Grella, S. L.; Shpokayte, M.; Zaki, Y.; Fortin, A.; Ramirez, S. Artificially Enhancing and Suppressing Hippocampus-Mediated Memories. Current Biology 2019, 29 (11), 1885-1894.e4. https://doi.org/10.1016/j.cub.2019.04.065.
(2)Mirzayi, P.; Shobeiri, P.; Kalantari, A.; Perry, G.; Rezaei, N. Optogenetics: Implications for Alzheimer’s Disease Research and Therapy. Molecular Brain 2022, 15 (1). https://doi.org/10.1186/s13041-022-00905-y.
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