Editing Hippocampus (section)

===Theories===
Three main theories of hippocampal function have been in dominance: [[inhibitory control|response inhibition]], [[episodic memory]], and [[spatial cognition]]. The response inhibition theory (caricatured by [[John O'Keefe (neuroscientist)|John O'Keefe]] and [[Lynn Nadel]] as "slam on the brakes!") was very popular up to the 1960s.<ref>{{cite journal | vauthors = Nadel L, O'Keefe J, Black A | title = Slam on the brakes: a critique of Altman, Brunner, and Bayer's response-inhibition model of hippocampal function | journal = Behavioral Biology | volume = 14 | issue = 2 | pages = 151–162 | date = June 1975 | pmid = 1137539 | doi = 10.1016/S0091-6773(75)90148-0 | ref = refNadel1975 }}</ref>  It was based largely on two observations: first, that animals with hippocampal damage tend to be [[hyperactivity|hyperactive]]; second, that animals with hippocampal damage often have difficulty learning to inhibit previously learnt responses, especially if the response requires remaining quiet as in a [[Avoidance learning#Active avoidance, passive avoidance, and escape responses|passive avoidance]] test. British psychologist [[Jeffrey Alan Gray|Jeffrey Gray]] developed this line of thought into a complete theory of the role of the hippocampus in [[anxiety]], called the [[behavioral inhibition system]].<ref>{{cite book | vauthors = Gray JA, McNaughton N | title = The Neuropsychology of Anxiety: An Enquiry into the Functions of the Septo-Hippocampal System | year = 2000 | publisher = Oxford University Press | ref = refGray2000 }}</ref><ref name="Bosecke2025">{{cite journal |vauthors=Bosecke C, Ng M, Dastgheib Z, Lithgow BJ |title=Perspective: Hippocampal theta rhythm as a potential vestibuloacoustic biomarker of anxiety |journal=Eur J Neurosci |volume=61 |issue=1 |pages=e16641 |date=January 2025 |pmid=39662900 |pmc=11664906 |doi=10.1111/ejn.16641 |url=}}</ref>

The second major line of thought relates the hippocampus to memory. Although it had historical precursors, this idea derived its main impetus from a famous report by American neurosurgeon [[William Beecher Scoville]] and British-Canadian neuropsychologist [[Brenda Milner]].<ref name="Scoville">{{cite journal | vauthors = Scoville WB, Milner B | title = Loss of recent memory after bilateral hippocampal lesions | journal = Journal of Neurology, Neurosurgery, and Psychiatry | volume = 20 | issue = 1 | pages = 11–21 | date = February 1957 | pmid = 13406589 | pmc = 497229 | doi = 10.1136/jnnp.20.1.11 | ref = refScoville1957 }}</ref> It described the results of surgical destruction of the hippocampi when trying to relieve [[epileptic seizure]]s in an American man [[Henry Molaison]], known until his death in 2008 as "Patient H.M."<ref name="Squire2009">{{cite journal |vauthors=Squire LR |title=The legacy of patient H.M. for neuroscience |journal=Neuron |volume=61 |issue=1 |pages=6–9 |date=January 2009 |pmid=19146808 |pmc=2649674 |doi=10.1016/j.neuron.2008.12.023 |url=}}</ref><ref name="HMObit">{{cite news | vauthors = Carey B | title=H. M., an Unforgettable Amnesiac, Dies at 82 | work=The New York Times | date=2008-12-04 | url=https://www.nytimes.com/2008/12/05/us/05hm.html | access-date=2009-04-27 | ref=refhMObit | archive-date=2018-06-13 | archive-url=https://web.archive.org/web/20180613184944/https://www.nytimes.com/2008/12/05/us/05hm.html | url-status=live }}</ref> The unexpected outcome of the surgery was severe [[anterograde amnesia|anterograde]], and partial [[retrograde amnesia]]; Molaison was unable to form new [[episodic memories]] after his surgery and could not remember any events that occurred just before his surgery, but he did retain memories of events that occurred many years earlier extending back into his childhood. This case attracted such widespread professional interest that Molaison became the most intensively studied subject in medical history.<ref name ="Squire2009"/> 
[[File:Rats_and_cognitive_maps_and_maze.png|thumb|314x314px|Rats and [[cognitive map]]s]]
The third important theory of hippocampal function relates the hippocampus to space, and [[spatial memory]], with the idea of a [[cognitive map]] first proposed by American psychologist [[Edward C. Tolman|E.C. Tolman]]. This theory was followed further by O'Keefe, and in 1971, he and his student Dostrovsky discovered neurons, in the rat hippocampus that seemed to show activity related to the rat's location within its environment. The neurons were described as [[place cell]]s.<ref>{{cite journal | vauthors = O'Keefe J, Dostrovsky J | 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 | date = November 1971 | pmid = 5124915 | doi = 10.1016/0006-8993(71)90358-1 | ref = refOKeefe1971 }}</ref> A book was later produced in 1978, ''The Hippocampus as a Cognitive Map'' written by O'Keefe and Nadel.<ref name="O'Keefe">{{cite book | vauthors = O'Keefe J, Nadel L | title = The Hippocampus as a Cognitive Map | year = 1978 | publisher = Oxford University Press | url = http://www.cognitivemap.net/HCMpdf/HCMChapters.html | ref = refOKeefe1978 | access-date = 2008-10-23 | archive-date = 2011-03-24 | archive-url = https://web.archive.org/web/20110324042731/http://www.cognitivemap.net/HCMpdf/HCMChapters.html | url-status = live }}</ref> It has been generally agreed that the hippocampus plays a key role in spatial coding but the details are widely debated.<ref name=Moser2008>{{cite journal | vauthors = Moser EI, Kropff E, Moser MB | title = Place cells, grid cells, and the brain's spatial representation system | journal = Annual Review of Neuroscience | volume = 31 | pages = 69–89 | year = 2008 | pmid = 18284371 | doi = 10.1146/annurev.neuro.31.061307.090723 | ref = refMoser2008 | s2cid = 16036900 }}</ref>

Research has focused on trying to bridge the disconnect between the two main views of hippocampal function as being split between memory and spatial cognition. In some studies, these areas have been expanded to the point of near convergence. In an attempt to reconcile the two disparate views, it is suggested that a broader view of the hippocampal function is taken and seen to have a role that encompasses both the organization of experience ([[mental mapping]], as per Tolman's original concept in 1948) and the directional behavior seen as being involved in all areas of cognition, so that the function of the hippocampus can be viewed as a broader system that incorporates both the memory and the spatial perspectives in its role that involves the use of a wide scope of cognitive maps.<ref>{{cite journal | vauthors = Schiller D, Eichenbaum H, Buffalo EA, Davachi L, Foster DJ, Leutgeb S, Ranganath C | title = Memory and Space: Towards an Understanding of the Cognitive Map | journal = The Journal of Neuroscience | volume = 35 | issue = 41 | pages = 13904–13911 | date = October 2015 | pmid = 26468191 | pmc = 6608181 | doi = 10.1523/JNEUROSCI.2618-15.2015 }}</ref><ref>{{Cite journal |last1=Tse |first1=Dorothy |last2=Langston |first2=Rosamund F. |last3=Kakeyama |first3=Masaki |last4=Bethus |first4=Ingrid |last5=Spooner |first5=Patrick A. |last6=Wood |first6=Emma R. |last7=Witter |first7=Menno P. |last8=Morris |first8=Richard G. M. |date=2007-04-06 |title=Schemas and Memory Consolidation |url=https://www.science.org/doi/10.1126/science.1135935 |journal=Science |volume=316 |issue=5821 |pages=76–82 |doi=10.1126/science.1135935|pmid=17412951 |bibcode=2007Sci...316...76T }}</ref><ref>{{Cite journal |last1=Tse |first1=Dorothy |last2=Takeuchi |first2=Tomonori |last3=Kakeyama |first3=Masaki |last4=Kajii |first4=Yasushi |last5=Okuno |first5=Hiroyuki |last6=Tohyama |first6=Chiharu |last7=Bito |first7=Haruhiko |last8=Morris |first8=Richard G. M. |date=2011-08-12 |title=Schema-dependent gene activation and memory encoding in neocortex |url=https://pubmed.ncbi.nlm.nih.gov/21737703/ |journal=Science |volume=333 |issue=6044 |pages=891–895 |doi=10.1126/science.1205274 |issn=1095-9203 |pmid=21737703|bibcode=2011Sci...333..891T }}</ref><ref>{{Cite journal |last1=Miller |first1=Adam M. P. |last2=Jacob |first2=Alex D. |last3=Ramsaran |first3=Adam I. |last4=De Snoo |first4=Mitchell L. |last5=Josselyn |first5=Sheena A. |last6=Frankland |first6=Paul W. |date=2023-06-21 |title=Emergence of a predictive model in the hippocampus |journal=Neuron |volume=111 |issue=12 |pages=1952–1965.e5 |doi=10.1016/j.neuron.2023.03.011 |pmid=37015224 |issn=0896-6273|pmc=10293047 }}</ref> This relates to the [[purposive behaviorism]] born of Tolman's original goal of identifying the complex cognitive mechanisms and purposes that guided behavior.<ref>{{cite journal | vauthors = Eichenbaum H | title = The hippocampus and declarative memory: Cognitive mechanisms and neural codes | journal = Behavioural Brain Research | volume = 127 | issue = 1–2 | pages = 199–207 | date = December 2001 | pmid = 11718892 | doi = 10.1016/s0166-4328(01)00365-5 | s2cid = 20843130 }}</ref>

It has also been proposed that the spiking activity of hippocampal neurons is associated spatially, and it was suggested that the mechanisms of memory and planning both evolved from mechanisms of navigation and that their neuronal algorithms were basically the same.<ref>{{cite journal | vauthors = Buzsáki G, Moser EI | title = Memory, navigation and theta rhythm in the hippocampal-entorhinal system | journal = Nature Neuroscience | volume = 16 | issue = 2 | pages = 130–138 | date = February 2013 | pmid = 23354386 | pmc = 4079500 | doi = 10.1038/nn.3304 }}</ref>

Many studies have made use of [[neuroimaging]] techniques such as [[functional magnetic resonance imaging]] (fMRI), and a functional role in [[approach-avoidance conflict]] has been noted. The anterior hippocampus is seen to be involved in decision-making under approach-avoidance conflict processing. It is suggested that the memory, spatial cognition, and conflict processing functions may be seen as working together and not mutually exclusive.<ref name="ReferenceB">{{cite journal | vauthors = Ito R, Lee AC | title = The role of the hippocampus in approach-avoidance conflict decision-making: Evidence from rodent and human studies | journal = Behavioural Brain Research | volume = 313 | pages = 345–357 | date = October 2016 | pmid = 27457133 | doi = 10.1016/j.bbr.2016.07.039 | doi-access = free }}</ref>