Brain complexity: memory in hippocampus: GPS (Introduction)

by David Turell , Wednesday, July 13, 2016, 15:08 (2834 days ago) @ David Turell

It turns out we have a GPS in the hippocampus, but that makes sense if the hippocampus deals in memory it must deal in geographic memories as we map out our surroundings:-http://www.pnas.org/content/113/28/7900.full-"In recent years, research on mammalian navigation has focused on the role of the hippocampus, a banana-shaped structure known to be integral to episodic memory and spatial information processing. The hippocampus's primary output, a region called CA1, is known to be divided into superficial and deep layers. Now, using two-photon imaging in mice, researchers at Columbia University in New York have found these layers have distinct functions: superficial-layer neurons encode more-stable maps, whereas deep-layer brain cells better represent goal-oriented navigation, according to a study published last week (July 7) in Neuron.-***-"Losonczy, Danielson, and colleagues used two-photon calcium imaging to measure neural activity in the superficial and deep sublayers of hippocampal area CA1 in mice while the animals performed either “random foraging” or “goal-oriented learning” tasks. Two-photon imaging “is an extremely powerful method, because it allows us and others to look at the activity of not just a single cell, but of a relatively large population of neurons in hippocampal CA1,” Danielson explained. -***-“'What's particularly impressive to me in the study is that the anatomy in the hippocampus segregates two aspects of memory”—a stable map of the environment, and a representation of new goals or targets, neuroscientist Howard Eichenbaum of Boston University, who was not involved in the work, told The Scientist.-"It's a bit like Google Maps on your phone, Eichenbaum explained: the plot of your environment with a dot for your location is the stable map, whereas the target address and directions for getting there comprise the goal-oriented system.-***-"Compared with rodents, humans have a much larger CA1 area, and a much larger ratio of cortex association areas to hippocampus. Extending the findings to humans and other primates “would require a systematic study comparing their [hippocampus] anatomy and structure with their performance” in a navigation task, Danielson said.-"Perhaps one of the best studies of human navigation ability is the 2006 London taxi driver study. Researchers from University College London conducted structural MRI scans of London cab drivers and bus drivers, controlling for individuals' driving experience and stress levels. Compared with the bus drivers, the cab drivers had a higher volume of grey matter in their mid-posterior hippocampi, and a lower volume in their anterior hippocampi. The more years of experience the cabbies had, the greater the grey matter differences, the researchers found."-Comment: As usual our brain is built to help us. The two layers cover spatial memory and travel intent. Note this is a direct cell study, not fMRI.