Editing Place cell (section)

==Properties==

===Place fields===
Place cells fire in a specific region of an environment, known as a place field. Place fields are roughly analogous to the [[receptive field]]s of sensory neurons, in that the firing region corresponds to a region of sensory information in the environment. However, unlike receptive fields, place cells show no topography, meaning that two neighboring cells do not necessarily have neighboring place fields.<ref>{{Cite journal|last1=O'Keefe|first1=J|last2=Burgess|first2=N|last3=Donnett|first3=J. G.|last4=Jeffery|first4=K. J.|last5=Maguire|first5=E. A.|year=1998|title=Place cells, navigational accuracy, and the human hippocampus|journal=Philosophical Transactions of the Royal Society B: Biological Sciences|volume=353|issue=1373|pages=1333–40|doi=10.1098/rstb.1998.0287|pmc=1692339|pmid=9770226}}</ref> Place cells fire spikes in [[Bursting|bursts]] at a high frequency inside the place field, but outside of the place field they remain relatively inactive.<ref>{{cite journal|vauthors=Bures J, Fenton AA, Kaminsky Y, Zinyuk L|date=7 January 1997|title=Place cells and place navigation|journal=Proceedings of the National Academy of Sciences|volume=94|issue=1|pages=343–350|doi=10.1073/pnas.94.1.343|pmc=19339|pmid=8990211|bibcode=1997PNAS...94..343B|doi-access=free}}</ref> Place fields are [[Allocentric navigation|allocentric]], meaning that they are defined with respect to the outside world rather than the body. By orienting based on the environment rather than the individual, place fields can work effectively as neural maps of the environment.<ref name="Jeffery 2003 201–218">{{cite journal|last=Jeffery|first=Kathryn|author2=Michael Anderson|author3=Robin Hayman|author4=Subhojit Chakraborty|date=2004|title=A proposed architecture for the neural representation of spatial context|journal=Neuroscience & Biobehavioral Reviews|volume=28|issue=2|pages=201–218|doi=10.1016/j.neubiorev.2003.12.002|pmid=15172764|s2cid=36456584}}</ref> A typical place cell will have only one or a few place fields in a small laboratory environment. However, in larger environments, place cells have been shown to contain multiple place fields which are usually irregular.<ref>{{Cite journal|last1=Geva-Sagiv|first1=Maya|last2=Las|first2=Liora|last3=Yovel|first3=Yossi|last4=Ulanovsky|first4=Nachum|date=2015|title=Spatial cognition in bats and rats: from sensory acquisition to multiscale maps and navigation|journal=Nature Reviews Neuroscience|language=en|volume=16|issue=2|pages=94–108|doi=10.1038/nrn3888|issn=1471-0048|pmid=25601780|s2cid=18397443}}</ref> Place cells may also show directionality, meaning they will only fire in a certain location when travelling in a particular direction.<ref name="O'Keefe-1976" /><ref>{{Cite journal|last=O'Keefe|first=John|date=1979-01-01|title=A review of the hippocampal place cells|journal=Progress in Neurobiology|volume=13|issue=4|pages=419–439|doi=10.1016/0301-0082(79)90005-4|pmid=396576|s2cid=8022838|issn=0301-0082}}</ref><ref>{{Cite journal|last1=McNaughton|first1=B. L.|last2=Barnes|first2=C. A.|last3=O'Keefe|first3=J.|date=1983-09-01|title=The contributions of position, direction, and velocity to single unit activity in the hippocampus of freely-moving rats|journal=Experimental Brain Research|language=en|volume=52|issue=1|pages=41–49|doi=10.1007/BF00237147|pmid=6628596|s2cid=6193356|issn=1432-1106}}</ref>
[[File:Place cel remapping.png|left|thumb|An example of place cell remapping, with the location of the place field of cell 1 changing between environment, and cell 2 losing its place field in environment 2.]]

=== Remapping ===
Remapping refers to the change in the place field characteristics that occurs when a subject experiences a new environment, or the same environment in a new context. This phenomenon was first reported in 1987,<ref name="Colgin-2008">{{Cite journal|last1=Colgin|first1=Laura Lee|last2=Moser|first2=Edvard I.|last3=Moser|first3=May-Britt|date=2008-09-01|title=Understanding memory through hippocampal remapping|journal=Trends in Neurosciences|language=en|volume=31|issue=9|pages=469–477|doi=10.1016/j.tins.2008.06.008|issn=0166-2236|pmid=18687478|s2cid=17019065|doi-access=free}}</ref><ref name="Muller-1987">{{Cite journal|last1=Muller|first1=R. U.|last2=Kubie|first2=J. L.|year=1987|title=The effects of changes in the environment on the spatial firing of hippocampal complex-spike cells|journal=The Journal of Neuroscience|volume=7|issue=7|pages=1951–68|doi=10.1523/JNEUROSCI.07-07-01951.1987|pmc=6568940|pmid=3612226}}</ref> and is thought to play a role in the memory function of the hippocampus.<ref name="Colgin-2008" /> There are broadly two types of remapping: ''global'' remapping and ''partial'' remapping.<ref>{{Cite journal|last1=Latuske|first1=Patrick|last2=Kornienko|first2=Olga|last3=Kohler|first3=Laura|last4=Allen|first4=Kevin|date=2018-01-04|title=Hippocampal Remapping and Its Entorhinal Origin|journal=Frontiers in Behavioral Neuroscience|volume=11|pages=253|doi=10.3389/fnbeh.2017.00253|issn=1662-5153|pmc=5758554|pmid=29354038|doi-access=free}}</ref> When global remapping occurs, most or all of the place cells remap, meaning they lose or gain a place field, or their place field changes its location. Partial remapping means that most place fields are unchanged and only a small portion of the place cells remap. Some of the changes to the environment that have been shown to induce remapping include changing the shape or size of the environment,<ref name="Muller-1987" /> the color of the walls,<ref name="Jeffery 2003 201–218" /><ref name="Anderson-2003">{{Cite journal|last1=Anderson|first1=Michael I.|last2=Jeffery|first2=Kathryn J.|date=2003-10-01|title=Heterogeneous Modulation of Place Cell Firing by Changes in Context|journal=Journal of Neuroscience|language=en|volume=23|issue=26|pages=8827–8835|doi=10.1523/JNEUROSCI.23-26-08827.2003|issn=0270-6474|pmid=14523083|pmc=6740394}}</ref> the smell in the environment,<ref name="Jeffery 2003 201–218" /><ref name="Anderson-2003" /> or the relevance of a location to the task at hand.<ref>{{Cite journal|last1=Deadwyler|first1=Sam A.|last2=Breese|first2=Charles R.|last3=Hampson|first3=Robert E.|date=1989-09-01|title=Control of place-cell activity in an open field|journal=Psychobiology|language=en|volume=17|issue=3|pages=221–227|doi=10.1007/BF03337772|issn=0889-6313|doi-access=free}}</ref>

=== Phase precession ===
{{Main|Phase precession}}
The firing of place cells is timed in relation to local [[theta wave]]s, a process termed [[phase precession]].<ref name="OKeefe1993">{{Cite journal|last1=O'Keefe|first1=J|last2=Recce|first2=M. L.|year=1993|title=Phase relationship between hippocampal place units and the EEG theta rhythm|journal=Hippocampus|volume=3|issue=3|pages=317–30|doi=10.1002/hipo.450030307|pmid=8353611|s2cid=6539236}}</ref><ref name="Burgess-2011">{{Cite journal|last1=Burgess|first1=Neil|last2=O’Keefe|first2=John|date=October 2011|title=Models of Place and Grid Cell Firing and Theta Rhythmicity.|journal=Current Opinion in Neurobiology|volume=21|issue=5|pages=734–744|doi=10.1016/j.conb.2011.07.002|issn=0959-4388|pmc=3223517|pmid=21820895}}</ref> Upon entering a place field, place cells will fire in bursts at a particular point in the phase of the underlying theta waves. However, as an animal progresses through the place field, the firing will happen progressively earlier in the phase.<ref name="OKeefe1993" /> It is thought that this phenomenon increases the accuracy of the place coding, and aids in plasticity, which is required for learning.<ref name="OKeefe1993" /><ref name="Burgess-2011" />

=== Directionality ===
In some cases place cells show directionality, meaning they will only fire in a location when the subject is travelling in a particular direction. However, they may also be omnidirectional, meaning they fire regardless of the direction the subject. The lack of directionality in some place cells might occur particularly in impoverished environments, whereas in more complicated environments directionality is enhanced.<ref name="Muller-1994">{{Cite journal|last1=Muller|first1=R. U.|last2=Bostock|first2=E.|last3=Taube|first3=J. S.|last4=Kubie|first4=J. L.|date=1994|title=On the directional firing properties of hippocampal place cells|journal=Journal of Neuroscience|language=en|volume=14|issue=12|pages=7235–7251|doi=10.1523/JNEUROSCI.14-12-07235.1994|issn=0270-6474|pmid=7996172|pmc=6576887}}</ref> The [[radial arm maze]] is one such environment where directionality does occur. In this environment, cells may even have multiple place fields, of which one is strongly directional, while the others are not.<ref name="Muller-1994" /> In virtual reality corridors, the degree of directionality in the population of place cells is particularly high.<ref>{{Cite journal|last1=Dombeck|first1=Daniel A.|last2=Harvey|first2=Christopher D.|last3=Tian|first3=Lin|last4=Looger|first4=Loren L.|last5=Tank|first5=David W.|date=2010|title=Functional imaging of hippocampal place cells at cellular resolution during virtual navigation|journal=Nature Neuroscience|language=en|volume=13|issue=11|pages=1433–1440|doi=10.1038/nn.2648|pmid=20890294|pmc=2967725|issn=1546-1726}}</ref> The directionality of place cells has been shown to emerge as a result of the animal's behaviour. For example, the receptive fields become skewed when rats travel a linear track in a single direction.<ref>{{Cite journal|last1=Mehta|first1=Mayank R.|last2=Quirk|first2=Michael C.|last3=Wilson|first3=Matthew A.|date=March 2000|title=Experience-Dependent Asymmetric Shape of Hippocampal Receptive Fields|journal=Neuron|language=en|volume=25|issue=3|pages=707–715|doi=10.1016/S0896-6273(00)81072-7|pmid=10774737|doi-access=free}}</ref> Recent theoretical studies suggest that place cells encode a [[successor representation]] which maps the current state to the predicted successor states, and that directionality emerges from this formalism.<ref name="Stachenfeld-2017" /> This computational framework also provides an account for the distortion of place fields around obstacles.<ref>{{Cite journal|last1=Alvernhe|first1=Alice|last2=Save|first2=Etienne|last3=Poucet|first3=Bruno|date=May 2011|title=Local remapping of place cell firing in the Tolman detour task: Place cell firing and detour behavior|url=http://doi.wiley.com/10.1111/j.1460-9568.2011.07653.x|journal=European Journal of Neuroscience|language=en|volume=33|issue=9|pages=1696–1705|doi=10.1111/j.1460-9568.2011.07653.x|pmid=21395871|s2cid=41211033|url-access=subscription}}</ref>

===Sensory input===
Place cells were initially believed to fire in direct relation to simple sensory inputs, but studies have suggested that this may not be the case.<ref name="Jeffery 2003 201–218"/> Place fields are usually unaffected by large sensory changes, like removing a landmark from an environment, but respond to subtle changes, like a change in color or shape of an object.<ref name="Moser-2008" /> This suggests that place cells respond to complex stimuli rather than simple individual sensory cues. According to the functional differentation model, sensory information is processed in various cortical structures upstream of the hippocampus before actually reaching the structure, so that the information received by place cells is a compilation, a functional derivative, of different stimuli.<ref name="Jeffery 2003 201–218"/>
[[File:CajalHippocampus (modified).png|thumb|Anatomy of the [[hippocampal formation]], including the [[entorhinal cortex]] (EC), the [[dentate gyrus]] (DG) and the different hippocampal subfields (CA1 and CA3). Inset shows the wiring between these different areas.]]
Sensory information received by place cells can be categorized as either metric or contextual information, where metric information corresponds to where place cells should fire and contextual input corresponds to whether or not a place field should fire in a certain environment.<ref name="Jeffery 2007 775–785">{{cite journal|last=Jeffery|first=Kathryn|title=Integration of the Sensory Inputs to Place Cells: What, Where, Why, and How?|journal=Hippocampus|date=5 July 2007|volume=17|issue=9|pages=775–785|doi=10.1002/hipo.20322|pmid=17615579|s2cid=3141473}}</ref> Metric sensory information is any kind of spatial input that might indicate a distance between two points. For example, the edges of an environment might signal the size of the overall place field or the distance between two points within a place field. Metric signals can be either linear or directional. Directional inputs provide information about the orientation of a place field, whereas linear inputs essentially form a representational grid. Contextual cues allow established place fields to adapt to minor changes in the environment, such as a change in object color or shape. Metric and contextual inputs are processed together in the [[entorhinal cortex]] before reaching the hippocampal place cells. Visuospatial and [[Olfactory system|olfactory]] inputs are examples of sensory inputs that are utilized by place cells. These types of sensory cues can include both metric and contextual information.<ref name="Jeffery 775–785" />

====Visuospatial inputs====
Spatial cues such as geometric boundaries or orienting landmarks are important examples of ''metric'' input. An example is the walls of an environment, which provides information about relative distance and location.<ref name="okeefe1999" /> Place cells generally rely on set distal cues rather than cues in the immediate proximal environment,<ref name="Jeffery 775–785" /> though local cues can have a profound impact on local place fields.<ref name="Moser-2008" /><ref>{{Cite journal|last1=Bourboulou|first1=Romain|last2=Marti|first2=Geoffrey|last3=Michon|first3=François-Xavier|last4=El Feghaly|first4=Elissa|last5=Nouguier|first5=Morgane|last6=Robbe|first6=David|last7=Koenig|first7=Julie|last8=Epsztein|first8=Jerome|date=2019-03-01|editor-last=Burgess|editor-first=Neil|editor2-last=Behrens|editor2-first=Timothy E|editor3-last=Burke|editor3-first=Sara N|title=Dynamic control of hippocampal spatial coding resolution by local visual cues|journal=eLife|volume=8|pages=e44487|doi=10.7554/eLife.44487|pmid=30822270|pmc=6397000|issn=2050-084X |doi-access=free }}</ref> Visual sensory inputs can also supply important ''contextual'' information. A change in color of a specific object or the walls of the environment can affect whether or not a place cell fires in a particular field.<ref name="Jeffery 775–785" /><ref name="Anderson-2003" /> Thus, visuospatial sensory information is critical to the formation and recollection of place field.

====Olfactory inputs====
Although place cells primarily rely on visuospatial input, some studies suggest that olfactory input may also affect the formation and stability of place fields.<ref name=Save2000>{{cite journal|last=Save|first=Etienne|author2=Ludek Nerad |author3=Bruno Poucet |title=Contribution of multiple sensory information to place field stability in hippocampal place cells|journal=Hippocampus|date=23 February 2000|volume=10|issue=1|pages=64–76|doi=10.1002/(SICI)1098-1063(2000)10:1<64::AID-HIPO7>3.0.CO;2-Y|pmid=10706218|s2cid=34908637 }}</ref><ref>{{Cite journal|last1=Poucet|first1=Bruno|last2=Save|first2=Etienne|last3=Lenck-Santini|first3=Pierre-Pascal|date=2011|title=Sensory and Memory Properties of Hippocampal Place Cells|journal=Reviews in the Neurosciences|volume=11|issue=2–3|pages=95–112|doi=10.1515/REVNEURO.2000.11.2-3.95|pmid=10718148|s2cid=1952601|issn=2191-0200}}</ref><ref name="Jeffery-2003">{{Cite book|url=https://books.google.com/books?id=ZMLADwAAQBAJ&q=olfaction+%22place+cells%22&pg=PA48|title=The Neurobiology of Spatial Behaviour|last=Jeffery|first=Kathryn J.|date=2003|publisher=Oxford University Press|isbn=978-0-19-851524-1|language=en}}</ref> Olfaction may compensate for a loss of visual information,<ref name="Save2000" /><ref name="Jeffery-2003" /> or even be responsible for the formation of stable place fields in the same way visuospatial cues are.<ref name="Zhang 2013">{{cite journal|last=Zhang|first=Sijie|author2=Denise Manahan-Vaughn|date=5 September 2013|title=Spatial Olfactory Learning Contributes to Place Field Formation in the Hippocampus|journal=Cerebral Cortex|volume=25|issue=2|pages=423–432|doi=10.1093/cercor/bht239|pmc=4380081|pmid=24008582}}</ref> This has been confirmed by a study in a virtual environment that was composed of odor gradients.<ref name="Radvansky 2018">{{cite journal|last=Radvansky|first=Brad|author2=Daniel Dombeck|date=26 February 2018|title=An olfactory virtual reality system for mice|journal=Nature Communications|volume=9|issue=1|page=839|doi=10.1038/s41467-018-03262-4|pmc=5827522|pmid=29483530|bibcode=2018NatCo...9..839R}}</ref> Change in the olfactory stimulus in an environment may also cause the remapping of place cells.<ref name="Anderson-2003" /><ref name="Jeffery 775–785" />

==== Vestibular inputs ====
Stimuli from the [[vestibular system]], such as rotations, can cause changes in place cells firing.<ref name="Smith-Darlington2009">{{cite journal|last=Smith|first=Paul F.|author2=Darlington, Cynthia L.|author3=Zheng, Yiwen|date=29 April 2009|title=Move it or lose it—Is stimulation of the vestibular system necessary for normal spatial memory?|journal=Hippocampus|volume=20|issue=1|pages=36–43|doi=10.1002/hipo.20588|pmid=19405142|s2cid=10344864}}</ref><ref name="Jacob-2014">{{Cite journal|last1=Jacob|first1=Pierre-Yves|last2=Poucet|first2=Bruno|last3=Liberge|first3=Martine|last4=Save|first4=Etienne|last5=Sargolini|first5=Francesca|date=2014|title=Vestibular control of entorhinal cortex activity in spatial navigation|journal=Frontiers in Integrative Neuroscience|language=en|volume=8|pages=38|doi=10.3389/fnint.2014.00038|pmid=24926239|pmc=4046575|issn=1662-5145|doi-access=free}}</ref> After receiving vestibular input some place cells may remap to align with this input, though not all cells will remap and are more reliant on visual cues.<ref name="Jacob-2014" /><ref>{{Cite journal|last1=Wiener|first1=S. I.|last2=Korshunov|first2=V. A.|last3=Garcia|first3=R.|last4=Berthoz|first4=A.|date=1995-11-01|title=Inertial, substratal and landmark cue control of hippocampal CA1 place cell activity|journal=The European Journal of Neuroscience|volume=7|issue=11|pages=2206–2219|doi=10.1111/j.1460-9568.1995.tb00642.x|issn=0953-816X|pmid=8563970|s2cid=10675209}}</ref> [[Bilateral symmetry|Bilateral]] lesions of the vestibular system in patients may cause abnormal firing of hippocampal place cells as evidenced, in part, by difficulties with spatial tasks such as the [[radial arm maze]] and the [[Morris water navigation task]].<ref name="Smith-Darlington2009" />

==== Movement inputs ====
[[File:Path integration diagram.svg|thumb|upright=1.25|Grid and place cells contribute to [[path integration]], a process which sums the [[Euclidean vector|vector]]s of distance and direction travelled from a start point to estimate current position.]]

Movement can also be an important spatial cue. Mice use their self-motion information to determine how far and in which direction they have travelled, a process called [[path integration]].<ref name="Moser-2008" /> This is especially the case in the absence of continuous sensory inputs. For example, in an environment with a lack of visuospatial inputs, an animal might search for the environment edge using touch, and discern location based on the distance of its movement from that edge.<ref name="okeefe1999" /> Path integration is largely aided by [[grid cell]]s, which are a type of neuron in the entorhinal cortex that relay information to place cells in the hippocampus. Grid cells establish a grid representation of a location, so that during movement place cells can fire according to their new location while orienting according to the reference grid of their external environment.<ref name="Jeffery 775–785" />