 | This Neuroanatomy needs attention from an expert in Neuroscience. The specific problem is: Creating a page for new publication on speed cells.(August 2015) |
Speed cells are neurons whose firing rates depend on an animal's speed through its environment. Together with place cells, grid cells, boundary cells, and head direction cells, they form a part of a larger set of neurons that are involved in cognitive mapping of the surrounding environment. Speed cells are found in the entorhinal cortex.
With the discovery of grid cells in 2005 by Edvard Moser and May Britt Moser, realized that the grid cells were not alone in deducing the spatial location of the animal. The grid cells used information about direction and speed in order to find the location. The discovery of head direction by James B. Ranck, Jr. located the cells responsible for information on direction of head or heading of animal. The Mosers kept searching for the assumed speed cells and in 2015, were able to prove the presence of such cells in the medial entorhinal cortex.
The speed cells fire in response to variations in speed of the animal. It was also found that unlike place cells, the speed cells are independent of visual cues. Darkness did not influence the firing rate of the animal. Another interesting feature of the cells is that the firing of the cells is better correlated with the future speed of the animal suggesting that the speed of the animal is known in advance by the speed cells.
In the experiment conducted by the Mosers', rats were made to run a constricted 4 meter long track. The module resembled a car from the The Flintstones cartoon with no bottom. The rats were guided by this car to run at speed of 7, 14, 21 and 28 cm/s. The firing of the cells was recorded. The rat was awarded with chocolate at the end of the track. In order to eliminate the response of nearby entorhinal cells on the readings, a second experiment was conducted. In this the rats were allowed to forage freely with speed varying from 0 to 50 cm/s.
The speed cell firing in response to the movement of the animal provides instantaneous running speed to the grid cell. The grid cell in turn uses this information along with the head direction in order to calculate the location of the animal in the cognitive map. [1]
The grid cell along with head direction cells, border cells, speed cells and place cells provide a correlation between different movement aspects of the animal with respect to its environment. [2]
Alzheimer's disease involves damage to the entorhinal cortex. This area contains most of the cells involved in cognitive mapping and this could suggest why patients suffering from Alzheimer's disease tend to forget or become lost. Edvard Moser also suggests that understanding the working of the human GPS can provide cues to understanding other brain functions such as association of smell and memory.
The entorhinal cortex (EC) is an area of the brain's allocortex, located in the medial temporal lobe, whose functions include being a widespread network hub for memory, navigation, and the perception of time. The EC is the main interface between the hippocampus and neocortex. The EC-hippocampus system plays an important role in declarative (autobiographical/episodic/semantic) memories and in particular spatial memories including memory formation, memory consolidation, and memory optimization in sleep. The EC is also responsible for the pre-processing (familiarity) of the input signals in the reflex nictitating membrane response of classical trace conditioning; the association of impulses from the eye and the ear occurs in the entorhinal cortex.
The hippocampus is a major component of the brain of humans and other vertebrates. Humans and other mammals have two hippocampi, one in each side of the brain. The hippocampus is part of the limbic system, and plays important roles in the consolidation of information from short-term memory to long-term memory, and in spatial memory that enables navigation. The hippocampus is located in the allocortex, with neural projections into the neocortex in humans, as well as primates. The hippocampus, as the medial pallium, is a structure found in all vertebrates. In humans, it contains two main interlocking parts: the hippocampus proper and the dentate gyrus.
In cognitive psychology and neuroscience, spatial memory is a form of memory responsible for the recording and recovery of information needed to plan a course to a location and to recall the location of an object or the occurrence of an event. Spatial memory is necessary for orientation in space. Spatial memory can also be divided into egocentric and allocentric spatial memory. A person's spatial memory is required to navigate around a familiar city. A rat's spatial memory is needed to learn the location of food at the end of a maze. In both humans and animals, spatial memories are summarized as a cognitive map.
A place cell is a kind of pyramidal neuron within the hippocampus that becomes active when an animal enters a particular place in its environment, which is known as the place field. Place cells are thought, collectively, to act as a cognitive representation of a specific location in space, known as a cognitive map. Place cells work with other types of neurons in the hippocampus and surrounding regions to perform this kind of spatial processing. They have been found in a variety of animals, including rodents, bats, monkeys and humans.
A cognitive map is a type of mental representation which serves an individual to acquire, code, store, recall, and decode information about the relative locations and attributes of phenomena in their everyday or metaphorical spatial environment. The concept was introduced by Edward Tolman in 1948. The concept was used to explain the behavior of rats that appeared to learn the spatial layout of a maze, and subsequently the concept was applied to other animals, including humans. The term was later generalized by some researchers, especially in the field of operations research, to refer to a kind of semantic network representing an individual's personal knowledge or schemas.
Motion perception is the process of inferring the speed and direction of elements in a scene based on visual, vestibular and proprioceptive inputs. Although this process appears straightforward to most observers, it has proven to be a difficult problem from a computational perspective, and difficult to explain in terms of neural processing.
An apical dendrite is a dendrite that emerges from the apex of a pyramidal cell. Apical dendrites are one of two primary categories of dendrites, and they distinguish the pyramidal cells from spiny stellate cells in the cortices. Pyramidal cells are found in the prefrontal cortex, the hippocampus, the entorhinal cortex, the olfactory cortex, and other areas. Dendrite arbors formed by apical dendrites are the means by which synaptic inputs into a cell are integrated. The apical dendrites in these regions contribute significantly to memory, learning, and sensory associations by modulating the excitatory and inhibitory signals received by the pyramidal cells.
The subiculum is the most inferior component of the hippocampal formation. It lies between the entorhinal cortex and the CA1 subfield of the hippocampus proper.
Head direction (HD) cells are neurons found in a number of brain regions that increase their firing rates above baseline levels only when the animal's head points in a specific direction. They have been reported in rats, monkeys, mice, chinchillas and bats, but are thought to be common to all mammals, perhaps all vertebrates and perhaps even some invertebrates, and to underlie the "sense of direction". When the animal's head is facing in the cell's "preferred firing direction" these neurons fire at a steady rate, but firing decreases back to baseline rates as the animal's head turns away from the preferred direction.
Path integration is the method thought to be used by animals for dead reckoning.
The hippocampal formation is a compound structure in the medial temporal lobe of the brain. There is no consensus concerning which brain regions are encompassed by the term, with some authors defining it as the dentate gyrus, the hippocampus proper and the subiculum; and others including also the presubiculum, parasubiculum, and entorhinal cortex. The hippocampal formation is thought to play a role in memory, spatial navigation and control of attention. The neural layout and pathways within the hippocampal formation are very similar in all mammals.
A grid cell is a type of neuron within the entorhinal cortex that fires at regular intervals as an animal navigates an open area, allowing it to understand its position in space by storing and integrating information about location, distance, and direction. Grid cells have been found in many animals, including rats, mice, bats, monkeys, and humans.
Spatial view cells are neurons in primates' hippocampus; they respond when a certain part of the environment is in the animal's field of view.
The retrosplenial cortex (RSC) is a cortical area in the brain comprising Brodmann areas 29 and 30. It is secondary association cortex, making connections with numerous other brain regions. The region's name refers to its anatomical location immediately behind the splenium of the corpus callosum in primates, although in rodents it is located more towards the brain surface and is relatively larger. Its function is currently not well understood, but its location close to visual areas and also to the hippocampal spatial/memory system suggest it may have a role in mediating between perceptual and memory functions, particularly in the spatial domain. However, its exact contribution to either space or memory processing has been hard to pin down.
Boundary cells are neurons found in the hippocampal formation that respond to the presence of an environmental boundary at a particular distance and direction from an animal. The existence of cells with these firing characteristics were first predicted on the basis of properties of place cells. Boundary cells were subsequently discovered in several regions of the hippocampal formation: the subiculum, presubiculum and entorhinal cortex.
Edvard Ingjald Moser is a Norwegian professor of psychology and neuroscience at the Kavli Institute for Systems Neuroscience, at the Norwegian University of Science and Technology (NTNU) in Trondheim. In 2005, he and May-Britt Moser discovered grid cells in the brain's medial entorhinal cortex. Grid cells are specialized neurons that provide the brain with a coordinate system and a metric for space. In 2018 he discovered a neural network that expresses your sense of time in experiences and memories located in the brain's lateral entorhinal cortex. He shared the Nobel Prize in Physiology or Medicine in 2014 with long-term collaborator and then-wife May-Britt Moser, and previous mentor John O'Keefe for their work identifying the brain's positioning system. The two main components of the brain's GPS are; grid cells and place cells, a specialized type of neuron that respond to specific locations in space. Together with May-Britt Moser he established the Moser research environment, which they lead.
May-Britt Moser is a Norwegian psychologist and neuroscientist, who is a Professor of Psychology and Neuroscience at the Norwegian University of Science and Technology (NTNU). She and her then-husband, Edvard Moser, shared half of the 2014 Nobel Prize in Physiology or Medicine, awarded for work concerning the grid cells in the entorhinal cortex, as well as several additional space-representing cell types in the same circuit that make up the positioning system in the brain. Together with Edvard Moser she established the Moser research environment at NTNU, which they lead. Since 2012 she heads the Centre for Neural Computation.
John O'Keefe, is an American-British neuroscientist, psychologist and a professor at the Sainsbury Wellcome Centre for Neural Circuits and Behaviour and the Research Department of Cell and Developmental Biology at University College London. He discovered place cells in the hippocampus, and that they show a specific kind of temporal coding in the form of theta phase precession. He shared the Nobel Prize in Physiology or Medicine in 2014, together with May-Britt Moser and Edvard Moser; he has received several other awards. He has worked at the University College London for his entire career, but also held a part-time chair at the Norwegian University of Science and Technology at the behest of his Norwegian collaborators, the Mosers.
Phase precession is a neurophysiological process in which the time of firing of action potentials by individual neurons occurs progressively earlier in relation to the phase of the local field potential oscillation with each successive cycle. In place cells, a type of neuron found in the hippocampal region of the brain, phase precession is believed to play a major role in the neural coding of information. John O'Keefe, who later shared the 2014 Nobel Prize in Physiology or Medicine for his discovery that place cells help form a "map" of the body's position in space, co-discovered phase precession with Michael Recce in 1993.
Lisa Giocomo is an American neuroscientist who is Associate Professor in the Department of Neurobiology at Stanford University School of Medicine. Giocomo probes the molecular and cellular mechanisms underlying cortical neural circuits involved in spatial navigation and memory.