Hippocampus. Of course, its a school for those river horses that are on the endangered species list.
Seriously. The hippocampus is a part of the brain located inside the temporal lobe (humans have two hippocampi, one in each side of the brain). It forms a part of the limbic system and plays a part in memory and navigation. The name derives from its curved shape, which slightly resembles a seahorse (Greek: hippocampus).
In Alzheimer's disease, the hippocampus becomes one of the first regions of the brain to suffer damage; memory problems and disorientation appear amongst the first symptoms. Damage to the hippocampus can also result from oxygen starvation (anoxia) and encephalitis.
Role in General Memory
Psychologists and neuroscientists dispute the precise role of the hippocampus, but, in general, agree that it has an essential role in the formation of new memories about experienced events (episodic or autobiographical memory). Some researchers prefer to consider the hippocampus as part of a larger medial temporal lobe memory system responsible for general declarative memory (memories that can be explicitly verbalized).
Some evidence supports the idea that, although these forms of memory often last a lifetime, the hippocampus ceases to play a crucial role in the retention of the memory after a period of consolidation. Damage to the hippocampus usually results in profound difficulties in forming new memories (anterograde amnesia), and normally also affects access to memories prior to the damage (retrograde amnesia). Damage to the hippocampus does not affect some aspects of memory, such as the ability to learn new skills (playing a musical instrument, for example), suggesting that such abilities depend on a different type of memory (procedural memory) and different brain regions.
Role in Spatial Memory and Navigation
Some evidence implicates the hippocampus in storing and processing spatial information. Studies in rats have shown that neurons in the hippocampus have spatial firing fields. These cells are called place cells. Some cells fire when the animal finds itself in a particular location, regardless of direction of travel, while most are at least partially sensitive to head direction and direction of travel. In rats, some cells, termed splitter cells, may alter their firing depending on the animal's recent past (retrospective) or expected future (prospective). Different cells fire at different locations, so that, by looking at the firing of the cells alone, it becomes possible to tell where the animal is. Place cells have now been seen in humans involved in finding their way around in a virtual reality town. The findings resulted from research with individuals that had electrodes implanted in their brains as a diagnostic part of surgical treatment for serious epilepsy.
The discovery of place cells led to the idea that the hippocampus might act as a cognitive map - a neural representation of the layout of the environment. Recent evidence has cast doubt on this perspective, indicating that the hippocampus might be crucial for more fundamental processes within navigation. Regardless, studies with animals have shown that an intact hippocampus is required for simple spatial memory tasks (for instance, finding the way back to a hidden goal).
Without a fully-functional hippocampus, humans may not successfully remember the places they have been to and how to get where they are going. Researchers believe that the hippocampus plays a particularly important role in finding shortcuts and new routes between familiar places. Some people exhibit more skill at this sort of navigation than do others, and brain imaging shows that these individuals have more active hippocampi when navigating.
Does this mean that women in general do not have fully-developed hippocampi? Okay, okay, put that frying pan down.
London's taxi drivers must learn a large number of places and know the most direct routes between them (they have to pass a strict test, The Knowledge, before being licensed to drive the famous black cabs). A study at University College London showed that part of the hippocampus is larger in taxi drivers than in the general public, and that more-experienced drivers have bigger hippocampi. Whether having a bigger hippocampus helps an individual to become a cab driver or finding shortcuts for a living makes an individual's hippocampus grow is yet to be explained.
New York taxi drivers, in the meantime, have been proven to have large hippocampi, but are fairly empty. In fact, the comedian Jerry Seinfeld has mostly stated that to qualify as a NYC Taxi Driver, you merely need to have a face.
Why all this discourse on hippocampi, you ask? Well, it started with this article on BBC about Duke Nukem and memory.
Studies of the brain using the video game Duke Nukem have shown how sleep affects long-term memory. The Belgian team used MRI scans to see how volunteers stored spatial information from the game. Sleep-deprived gamers recalled information from a different part of the brain to those who slept.
"If you move to a new town, you have to think about where you are going," said Pierre Orban of Liege University in Belgium, one of the authors on the paper. "But with time, once you know the city, you don't have to think about your route anymore."
This automatic behaviour may be enhanced by sleep, the researchers believe. It mimics patterns of memory formation seen when a task is repeated. The work also explains how the brain is able to file and store this information.
Scans showed that the hippocampus, an area of the brain known to be involved in memory and direction, was most active when the gamers had to retrieve memories to reach their destination.
The volunteers were then split into two groups: those that were allowed a good night's sleep and those that were not. Over the next two nights, both groups were allowed to sleep.
Volunteers were then asked to play the game again, navigating the streets between two landmarks as quickly as possible while the scientists watched their brain activity with MRI. The closer a gamer got to the final landmark, the better the score. The researchers found that the group who had slept recalled information from an area of the brain known as the striatum.
Storing these memories allowed them to make automatic decisions about the direction they had to travel. Sleep-deprived gamers, who still relied on the hippocampus, had to think harder about their virtual navigation. "If you have slept, you use a means of navigation that is less thoughtful," Mr Orban told the BBC News website. "You somehow know that you have to turn left, or right or carry straight on." This work shows that sleep promotes memory reorganization from the hippocampus to the striatum.
Moral Lesson: "Make Sure You Get Lots of Sleep Breaks When Finishing That New PS2 First Person Shooter", or better yet, "The Game Will Still Be There When You Wake Up."
-
selected texts from BBC News Service and Wikipedia
No comments:
Post a Comment