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<\/p>\n\nSalk researchers discovered how the brain keeps track of similar but distinct memories. This microscope image shows neural activity in the dentate gyrus, a subsection of the hippocampus where distinct groups of cells were active during the learning episodes (green) and memory retrieval (red).\n<\/p>\n
Courtesy of Wei Deng, Salk Institute for Biological Studies\n<\/p>\n<\/div>\n
\n“Everyday, we have to remember subtle differences between how things are today, versus how they were yesterday – from where we parked our car to where we left our cellphone,” says Fred H. Gage<\/a>, senior author on the paper and the \nThe process of taking complex memories and converting them into representations that are less easily confused is known as pattern separation. Computational models of brain function suggest that the dentate gyrus helps us perform pattern separation of memories by activating different groups of neurons when an animal is in different environments.\n<\/p>\n \nHowever, previous laboratory studies found that in fact the same populations of neurons in the dentate gyrus are active in different environments, and that the way the cells distinguished new surroundings was by changing the rate at which they sent electrical impulses. This discrepancy between theoretical predictions and laboratory findings has perplexed neuroscientists and obscured our understanding of memory formation and retrieval.\n<\/p>\n \nTo explore this mystery more deeply, the Salk scientists compared the functioning of the mouse dentate gyrus and another region of the hippocampus, known as CA1, using laboratory techniques for tracking the activity of neurons at multiple time points.\n <\/p>\n \nFirst, the researchers took mice from their original chamber and placed them in a novel chamber to learn about a new environment (episode 1). Meanwhile, they recorded which hippocampal neurons were active as the animals responded to their new surroundings. Subsequently, the mice were either returned to that same novel chamber to measure memory recall or to a slightly modified chamber to measure discrimination (episode 2). The active neurons in episode 2 were also labeled in order to determine if the neurons activated in episode 1 were used in the same way for recall and for discrimination of small differences between environments.\n <\/p>\n \nWhen the researchers compared the neural activity during the two episodes, they found that the dentate gyrus and CA1 sub-regions functioned differently. In CA1, the same neurons that were active during the initial learning episode were also active when the mice retrieved the memories. In the dentate gyrus, however, distinct groups of cells were active during the learning episodes and retrieval. Also, exposing the mice to two subtly different environments activated two distinct groups of cells in the dentate gyrus.\n <\/p>\n \n“This finding supported the predictions of theoretical models that different groups of cells are activated during exposure to similar, but distinct, environments,” says Wei Deng, a Salk postdoctoral research and first author on the paper. “This contrasts with the findings of previous laboratory studies, possibly because they looked at different sub-populations of neurons in the dentate gyrus.”\n <\/p>\n \nThe Salk researchers’ findings suggest that recalling a memory-such as the location of missing keys-does not always involve reactivation of the same neurons that were active during encoding. More importantly, the results indicate that the dentate gyrus performs pattern separation by using distinct populations of cells to represent similar but non-identical memories.\n <\/p>\n \nThe findings help clarify the mechanisms that underpin memory formation and shed light on systems that are disrupted by injuries and diseases of the nervous system.\n <\/p>\n \nMark Mayford, of Scripps Institute Research Institute, also contributed to the research. The study was supported by the James S. McDonnell Foundation<\/a>, the Lookout Fund, the Instituto Kavli para el Cerebro y la Mente<\/a>, y el Institutos Nacionales de Salud<\/a> (Grants: MH-090258, NS-050217, AG-020938).\n <\/p>\n Acerca del Instituto Salk de Estudios Biol\u00f3gicos:<\/strong> \nLos logros del cuerpo docente han sido reconocidos con numerosos galardones, entre los que se incluyen premios Nobel y la pertenencia a la Academia Nacional de Ciencias. Fundado en 1960 por el Dr. Jonas Salk, pionero en la vacuna contra la poliomielitis, el Instituto es una organizaci\u00f3n independiente sin fines de lucro y un hito arquitect\u00f3nico.<\/p>","protected":false},"featured_media":0,"template":"","faculty":[76],"disease-research":[127,124],"class_list":["post-2413","disclosure","type-disclosure","status-publish","hentry","faculty-rusty-gage","disease-research-alzheimers-disease","disease-research-neuroscience-and-neurological-disorders"],"acf":[],"yoast_head":"\n
\nVi and John Adler Chair for Research on Age-Related Neurodegenerative Disease at Salk. “We found how the brain makes these distinctions, by storing separate ‘recordings’ of each environment in the dentate gyrus.”\n <\/p>\n
\nEl Instituto Salk de Estudios Biol\u00f3gicos es una de las instituciones de investigaci\u00f3n b\u00e1sica m\u00e1s destacadas del mundo, donde un cuerpo docente de prestigio internacional investiga cuestiones fundamentales de las ciencias de la vida en un entorno \u00fanico, colaborativo y creativo. Centrados tanto en el descubrimiento como en la formaci\u00f3n de las futuras generaciones de investigadores, los cient\u00edficos del Salk realizan contribuciones revolucionarias a nuestra comprensi\u00f3n del c\u00e1ncer, el envejecimiento, el Alzheimer, la diabetes y las enfermedades infecciosas mediante el estudio de la neurociencia, la gen\u00e9tica, la biolog\u00eda celular y vegetal, y otras disciplinas relacionadas.\n<\/p>\n