Editing Spatial memory (section)

===Hippocampus===
[[File:Hippocampus small.gif|thumb|left|alt=rotating 3D animation of the human hippocampus in skull.|Hippocampus shown in red]]

The [[hippocampus]] provides animals with a spatial map of their environment.<ref>{{cite journal | last1 = O'Keefe | first1 = J. | last2 = Dostrovsky | first2 = J. | year = 1971 | title = The hippocampus as a spatial map. Preliminary evidence from unit activity in the freely-moving rat | journal = Brain Research | volume = 34 | issue = 1| pages = 171–175 | doi = 10.1016/0006-8993(71)90358-1 | pmid = 5124915 }}</ref> It stores information regarding non-egocentric space (egocentric means in reference to one's body position in space) and therefore supports viewpoint independence in spatial memory.<ref name=memory_and_hippo>{{cite journal | last1 = Squire | first1 = L. R. | year = 1992 | title = Memory and the hippocampus: A synthesis from findings with rats, monkeys, and humans | journal = Psychological Review | volume = 99 | issue = 2| pages = 195–231 | doi = 10.1037/0033-295X.99.2.195 | pmid = 1594723 }}</ref> This means that it allows for viewpoint manipulation from memory. It is important for long-term spatial memory of allocentric space (reference to external cues in space).<ref>{{cite journal | last1 = Ramos | first1 = J. M. J. | year = 2000 | title = Long-term spatial memory in rats with hippocampal lesions | journal = European Journal of Neuroscience | volume = 12 | issue = 9| pages = 3375–3384 | doi = 10.1046/j.1460-9568.2000.00206.x | pmid = 10998120 }}</ref> Maintenance and retrieval of memories are thus relational or [[Context-dependent memory|context dependent]].<ref>{{cite journal | last1 = Winocur | first1 = G. | last2 = Moscovitch | first2 = M. | last3 = Caruana | first3 = D. A. | last4 = Binns | first4 = M. A. | year = 2005 | title = Retrograde amnesia in rats with lesions to the hippocampus on a test of spatial memory | journal = Neuropsychologia | volume = 43 | issue = 11| pages = 1580–1590 | doi = 10.1016/j.neuropsychologia.2005.01.013 | pmid = 16009240 }}</ref> The hippocampus makes use of reference and working memory and has the important role of processing information about spatial locations.<ref name="the_effects_of_excitotoxic"/>

Blocking [[Neuroplasticity|plasticity]] in this region results in problems in goal-directed navigation and impairs the ability to remember precise locations.<ref>{{cite journal | last1 = Hebert | first1 = A. E. | last2 = Dash | first2 = P. K. | year = 2004 | title = Nonredundant roles for hippocampal and entorhinal cortical plasticity in spatial memory storage | journal = Pharmacology Biochemistry and Behavior | volume = 79 | issue = 1| pages = 143–153 | doi = 10.1016/j.pbb.2004.06.016 | pmid = 15388294 }}</ref> [[Amnesic]] patients with damage to the hippocampus cannot learn or remember spatial layouts, and patients having undergone hippocampal removal are severely impaired in spatial navigation.<ref name=memory_and_hippo/><ref name=place_navigation>{{cite journal |vauthors = Morris RG, Garrud P, Rawlins JN, O'Keefe J |year=1982 |title=Place navigation impaired in rats with hippocampal lesions |journal=[[Nature (journal)|Nature]] |volume=297 |issue= 5868|pages=681–683 |pmid=7088155 |bibcode=1982Natur.297..681M |doi=10.1038/297681a0 }}</ref>

Monkeys with lesions to this area cannot learn object-place associations and rats also display spatial deficits by not reacting to spatial change.<ref name=memory_and_hippo/><ref name="Save, E. 1992">{{cite journal | last1 = Save | first1 = E. | last2 = Poucet | first2 = B. | last3 = Foreman | first3 = N. | last4 = Buhot | first4 = M. | year = 1992 | title = Object exploration and reactions to spatial and nonspatial changes in hooded rats following damage to parietal cortex or hippocampal formation | journal = Behavioral Neuroscience | volume = 106 | issue = 3| pages = 447–456 | doi = 10.1037/0735-7044.106.3.447 | pmid = 1616611 }}</ref> In addition, rats with hippocampal lesions were shown to have temporally ungraded (time-independent) [[retrograde amnesia]] that is resistant to recognition of a learned platform task only when the entire hippocampus is lesioned, but not when it is partially lesioned.<ref>{{cite journal | last1 = Martin | first1 = S. J. | last2 = de Hozl | first2 = L. | last3 = Morris | first3 = R. G. M. | year = 2005 | title = Retrograde amnesia: neither partial nor complete hippocampal lesions in rats result in preferential sparing of remote spatial memory, even after reminding | journal = Neuropsychologia | volume = 43 | issue = 4| pages = 609–624 | doi = 10.1016/j.neuropsychologia.2004.07.007 | pmid = 15716151 }}</ref> Deficits in spatial memory are also found in spatial discrimination tasks.<ref name= place_navigation/>
[[File:Brainmaps-macaque-hippocampus.jpg|thumb|alt=Brain slice showing areas CA1 and CA3 in hippocampus.|Brain slice showing areas CA1 and CA3 in the hippocampus]]

Large differences in spatial impairment are found among the [[Dorsum (anatomy)|dorsal]] and [[Anatomical terms of location#Dorsal and ventral|ventral]] hippocampus. Lesions to the ventral hippocampus have no effect on spatial memory, while the dorsal hippocampus is required for retrieval, processing short-term memory and transferring memory from the short term to longer delay periods.<ref>{{cite journal | last1 = Bannerman | first1 = D. M. | last2 = Deacon | first2 = R. M. J. | last3 = Offen | first3 = S. | last4 = Friswell | first4 = J. | last5 = Grubb | first5 = M. | last6 = Rawlins | first6 = J. N. P. | year = 2002 | title = Double dissociation of function within the hippocampus: Spatial memory and hyponeophagia | journal = Behavioral Neuroscience | volume = 116 | issue = 5| pages = 884–901 | doi = 10.1037/0735-7044.116.5.884 | pmid = 12369808 }}</ref><ref>{{cite journal | last1 = Moser | first1 = M. | last2 = Moser | first2 = E. I. | year = 1998 | title = Distributed encoding and retrieval of spatial memory in the hippocampus | journal = The Journal of Neuroscience | volume = 18 | issue = 18| pages = 7535–7542 | pmid = 9736671 | pmc = 6793256 | doi = 10.1523/JNEUROSCI.18-18-07535.1998 }}</ref><ref name="Lee, I. 2003">{{cite journal | last1 = Lee | first1 = I. | last2 = Kesner | first2 = R. P. | year = 2003 | title = Time-dependent relationship between the dorsal hippocampus and the prefrontal cortex in spatial memory | journal = The Journal of Neuroscience | volume = 23 | issue = 4| pages = 1517–1523 | pmid = 12598640 | pmc = 6742248 | doi = 10.1523/JNEUROSCI.23-04-01517.2003 }}</ref> Infusion of [[amphetamine]] into the dorsal hippocampus has also been shown to enhance memory for spatial locations learned previously.<ref>{{cite journal | last1 = McGaugh | first1 = J. L. | year = 2000 | title = Memory—a century of consolidation | journal = Science | volume = 287 | issue = 5451| pages = 248–251 | doi = 10.1126/science.287.5451.248 | pmid = 10634773 |bibcode = 2000Sci...287..248M }}</ref> These findings indicate that there is a [[Dissociation (neuropsychology)|functional dissociation]] between the dorsal and ventral hippocampus. {{cn|date=March 2025}}

Hemispheric differences within the hippocampus are also observed. A study on [[London]] taxi drivers, asked drivers to recall complex routes around the city as well as famous [[landmark]]s for which the drivers had no knowledge of their spatial location. This resulted in an activation of the right hippocampus solely during recall of the complex routes which indicates that the right hippocampus is used for navigation in large scale spatial environments.<ref>{{cite journal | last1 = Maguire | first1 = E. A. | last2 = Frackowiak | first2 = R. S. J. | last3 = Frith | first3 = C. D. | year = 1997 | title = Recalling routes around London: Activation of the right hippocampus in taxi drivers | journal = The Journal of Neuroscience | volume = 17 | issue = 18| pages = 7103–7110 | pmid = 9278544 | pmc = 6573257 | doi = 10.1523/JNEUROSCI.17-18-07103.1997 }}</ref>

The hippocampus is known to contain two separate memory circuits. One circuit is used for recollection-based place recognition memory and includes the [[Apical dendrite#Hippocampus|entorhinal-CA1 system]],<ref>{{cite journal | last1 = Brun | first1 = V. H. | last2 = Otnaess | first2 = M. K. | last3 = Molden | first3 = S. | last4 = Steffenach | first4 = H. | last5 = Witter | first5 = M. P. | last6 = Moser | first6 = M. | last7 = Moser | first7 = E. I. | year = 2002 | title = Place cells and place recognition maintained by direct entorhinal-hippocampal circuitry | journal = Science | volume = 296 | issue = 5576| pages = 2243–2246 | doi = 10.1126/science.1071089 | pmid = 12077421 |bibcode = 2002Sci...296.2243B }}</ref> while the other system, consisting of the hippocampus [[trisynaptic loop]] (entohinal-dentate-CA3-CA1) is used for place recall memory<ref name="pmid18298245">{{cite journal |vauthors=Goodrich-Hunsaker NJ, Hunsaker MR, Kesner RP | title = The interactions and dissociations of the dorsal hippocampus subregions: how the dentate gyrus, CA3, and CA1 process spatial information. | journal = Behav. Neurosci. | volume = 122 | issue = 1 | pages = 16–26 | year = 2008 | pmid = 18298245 | doi=10.1037/0735-7044.122.1.16}}</ref> and facilitation of plasticity at the entorhinal-dentate synapse in mice is sufficient to enhance place recall.<ref name="pmid19755107">{{cite journal |vauthors=Saab BJ, Georgiou J, Nath A, Lee FJ, Wang M, Michalon A, Liu F, Mansuy IM, Roder JC | title = NCS-1 in the dentate gyrus promotes exploration, synaptic plasticity, and rapid acquisition of spatial memory | journal = Neuron | volume = 63 | issue = 5 | pages = 643–56 | year = 2009 | pmid = 19755107 | doi = 10.1016/j.neuron.2009.08.014 | doi-access = free }}</ref>

[[Place cell]]s are also found in the hippocampus.