Rhythms of the hippocampal network

Rhythms of the hippocampal network Colgin

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Rhythms of the hippocampal network 2016 Nature reviews. Neuroscience 10.1038/nrn.2016.21 Colgin2016-rhythms-of-the-hippocampal-network Colgin2016-rhythms-of-the-hippocampal-network.txt, the project's staged copy 4664b7370089823d561bd4ff6ed22c99ea50505e not-redistributable neuroscience

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0 spans located by searching the stored text for the quote's exact words, allowing any whitespace between them three rhythms that are DEFINED BY THEIR FREQUENCIES and have been PROPOSED TO PERFORM DISTINCT FUNCTIONS, and the recent findings that have challenged those functions Quotation withheld because this record is not cleared for redistribution. whether the functions traditionally assigned to each rhythm survive the recent evidence Quotation withheld because this record is not cleared for redistribution. an updated, synthesized view of the roles and interactions of the three rhythms, with the evidence for and against each proposed function set out side by side Quotation withheld because this record is not cleared for redistribution. mechanism Quotation withheld because this record is not cleared for redistribution. hippocampal network rhythms Quotation withheld because this record is not cleared for redistribution. review review Quotation withheld because this record is not cleared for redistribution. mechanisms Septal GABAergic pacemaker interneurons rhythmically disinhibit hippocampal pyramidal cells, entraining them to theta Quotation withheld because this record is not cleared for redistribution. mechanisms Ripple-associated shunting inhibition raises spike threshold so that only strongly potentiated cells fire, selecting which memories are sent to long-term storage Quotation withheld because this record is not cleared for redistribution. mechanisms Gamma frequency is set by the balance of excitatory drive onto and GABA conductance within the interneuron network Quotation withheld because this record is not cleared for redistribution. mechanisms Sharp-wave excitation drives place cells outside their place fields, enabling representation of distant locations Quotation withheld because this record is not cleared for redistribution. mechanisms Which gamma subtype is nested in the theta cycle switches the hippocampus between externally driven encoding and internally driven retrieval Quotation withheld because this record is not cleared for redistribution. mechanisms LFP rhythms are visible only because synchronous currents summate while non-synchronous ones cancel Quotation withheld because this record is not cleared for redistribution. gamma-frequency spiking of FAST-SPIKING INTERNEURONS produces the observed gamma rhythms - interneuron spikes CONSISTENTLY PHASE-LOCK to gamma while pyramidal cell spikes DO NOT Quotation withheld because this record is not cleared for redistribution. and the frequency itself is set by the balance of drive - in simulations gamma frequency INCREASED WITH INCREASED EXCITATORY DRIVE onto the interneurons and DECREASED WITH INCREASED GABA CONDUCTANCES Quotation withheld because this record is not cleared for redistribution. with different interneuron classes firing at different theta phases, so DIFFERENT TYPES OF INTERNEURONS SERVE DIFFERENT FUNCTIONS AT DISTINCT PHASES of the theta cycle Quotation withheld because this record is not cleared for redistribution. The review deliberately excludes other brain-state-dependent rhythms that also affect the hippocampus what this limits: the scope of the review: OTHER BRAIN STATE-DEPENDENT RHYTHMS, SUCH AS SLEEP SPINDLES AND SLOW OSCILLATIONS, ALSO INFLUENCE HIPPOCAMPAL OPERATIONS; THESE RHYTHMS WILL NOT BE DISCUSSED IN DEPTH HERE Quotation withheld because this record is not cleared for redistribution. The evidence base is overwhelmingly rodent, because deep human hippocampal rhythm measurement is hard what this limits: the transfer of every finding to humans: MANY OF THE FINDINGS DESCRIBED HERE HAVE BEEN MADE IN STUDIES CARRIED OUT IN LOWER MAMMALS, PARTICULARLY RODENTS Quotation withheld because this record is not cleared for redistribution. The proposed mechanisms for slow versus fast gamma generation are explicitly provisional what this limits: the mechanistic account of slow versus fast gamma: THESE HYPOTHESES ARE TENTATIVE, AND MUCH WORK REMAINS TO BE DONE Quotation withheld because this record is not cleared for redistribution. Findings on slow gamma do not all fit the memory-retrieval account the review favours what this limits: the memory-retrieval account of slow gamma: THESE APPARENT INCONGRUITIES ACROSS STUDIES HIGHLIGHT THE NEED FOR FURTHER INVESTIGATION - not all findings fit it Quotation withheld because this record is not cleared for redistribution. MOST OF THE STUDIES DESCRIBED ABOVE DID NOT DIFFERENTIATE BETWEEN DIFFERENT FREQUENCY VARIANTS OF GAMMA, and IT IS POSSIBLE THAT SLOW AND FAST GAMMA ARE GENERATED BY DIFFERENT MECHANISMS what this limits: distinguishing slow from fast gamma, which most of the mechanism literature reviewed here cannot do Quotation withheld because this record is not cleared for redistribution. the observed ~20-40 Hz activity OVERLAPPED WITH BOTH BETA AND SLOW GAMMA FREQUENCY BANDS and thus MAY REFLECT EITHER BETA, SLOW GAMMA, OR A COMBINATION OF BOTH what this limits: the band assignment of that result, and of the band vocabulary generally: the ~20-40 Hz coupling OVERLAPPED WITH BOTH BETA AND SLOW GAMMA FREQUENCY BANDS Quotation withheld because this record is not cleared for redistribution. THE HIGH VARIABILITY OF GAMMA FREQUENCY ALSO COMPLICATES ITS MEASUREMENT IN BEHAVING ANIMALS what this limits: every gamma measurement in behaving animals: THE HIGH VARIABILITY OF GAMMA FREQUENCY ALSO COMPLICATES ITS MEASUREMENT Quotation withheld because this record is not cleared for redistribution. these hypotheses are TENTATIVE, and MUCH WORK REMAINS TO BE DONE to uncover mechanisms underlying slow and fast gamma rhythms what this limits: the same scope as limitations[2] - the generation mechanisms are tentative Quotation withheld because this record is not cleared for redistribution. the precise role of HCN channels REMAINS UNCLEAR because ENHANCED theta rhythms occur in HCN1 knockout mice, where the channel was thought to FACILITATE theta what this limits: the HCN account of theta: HCN1 IS THOUGHT TO FACILITATE THETA RHYTHMIC FIRING, yet ENHANCED theta rhythms occur in HCN1 knockout mice - the review carries both Quotation withheld because this record is not cleared for redistribution. many of the findings are from RODENTS, in part because measuring rhythms in healthy human subjects WITHIN A DEEP-LYING STRUCTURE such as the hippocampus IS DIFFICULT what this limits: the same scope as limitations[1], with the reason: measuring rhythms in healthy humans WITHIN A DE[ep structure] is hard, so the evidence base is rodent Quotation withheld because this record is not cleared for redistribution. Hebb's idea that memories are represented by distributed ensembles activated concurrently, used as the reason synchrony should matter to memory Quotation withheld because this record is not cleared for redistribution. network simulations in which gamma frequency follows excitatory drive and GABA conductance, used to explain why one circuit could produce both subtypes Quotation withheld because this record is not cleared for redistribution. septal inactivation, which removes theta while place fields are being formed eliminates: theta as a requirement for spatial representations - place fields FORMED in novel environments DESPITE theta and theta entrainment being BLOCKED · outcome (stated by the tagger, no quotation): failed Quotation withheld because this record is not cleared for redistribution. an in vitro whole hippocampal preparation with no septal input at all eliminates: the septum as the sole pacemaker - theta OCCURRED IN THE ABSENCE OF MS PACEMAKER INPUTS, which suggests theta can emerge from local circuit interactions · outcome (stated by the tagger, no quotation): partial Quotation withheld because this record is not cleared for redistribution. interneurons checked for phase-locking to both gamma subtypes rather than one eliminates: a clean two-circuit account - A SUBSTANTIAL PROPORTION OF CA1 INTERNEURONS PHASE-LOCK TO BOTH slow and fast gamma · outcome (stated by the tagger, no quotation): failed Quotation withheld because this record is not cleared for redistribution. slow gamma slow gamma Quotation withheld because this record is not cleared for redistribution. CA3 CA3 Quotation withheld because this record is not cleared for redistribution. encoding encoding Quotation withheld because this record is not cleared for redistribution. novelty novelty Quotation withheld because this record is not cleared for redistribution. fast gamma → memory encoding THE RELATION FAILS: the review reports that results do not support a memory-encoding function for fast gamma, and that a study found it linked to working memory BUT NOT memory encoding. No schema 0.3 type can express a relation that does not hold, so recording it at all means recording it here. Replaces the retracted concept_edges[9], which quoted this same sentence as evidence FOR the relation. Quotation withheld because this record is not cleared for redistribution. theta frequency → functional significance DECLARED OPEN BY THE REVIEW: 'some important questions remain ... Quotation withheld Specifically, is there any functional significance to the lower frequency of theta that occurs during novel experiences compared to familiar ones?' A relation the field has not established, stated as a question. Every edge type asserts that a relation HOLDS. Quotation withheld because this record is not cleared for redistribution. THE OBJECT IS DEFINED BY FREQUENCY AND JUDGED BY FUNCTION: these rhythms ARE DEFINED BY THEIR FREQUENCIES, have behavioral correlates, and HAVE BEEN PROPOSED TO PERFORM DISTINCT FUNCTIONS - HOWEVER, RECENT FINDINGS HAVE CHALLENGED TRADITIONAL VIEWS ON THESE BEHAVIORAL FUNCTIONS Quotation withheld because this record is not cleared for redistribution. and the assignment is stated as an expectation rather than a result: each rhythm is observed during particular behaviors and generated by specific mechanisms, so IT IS THEREFORE NOT SURPRISING THAT THESE DIFFERENT RHYTHMS ARE THOUGHT TO PERFORM DISTINCT FUNCTIONS - with THERE IS LESS AGREEMENT IN THE FIELD ABOUT THE FUNCTIONAL SIGNIFICANCE OF GAMMA Quotation withheld because this record is not cleared for redistribution. A LIVE NAMING CONFLICT SETTLED IN A PARENTHESIS: the same activity HAS BEEN TERMED FAST GAMMA IN SOME STUDIES AND MIDFREQUENCY GAMMA IN OTHERS - (THE FORMER TERMINOLOGY WILL BE USED HERE). One review, one clause, and the field's vocabulary is decided for the reader Quotation withheld because this record is not cleared for redistribution. AND THE EARLIER LITERATURE COULD NOT HAVE TOLD THEM APART: MOST OF THE STUDIES DESCRIBED ABOVE DID NOT DIFFERENTIATE BETWEEN DIFFERENT FREQUENCY VARIANTS OF GAMMA, and IT IS POSSIBLE THAT SLOW AND FAST GAMMA ARE GENERATED BY DIFFERENT MECHANISMS - a whole mechanism literature written with one word for two things Quotation withheld because this record is not cleared for redistribution. A RESULT THAT CANNOT BE ASSIGNED TO A CATEGORY BECAUSE THE CATEGORIES OVERLAP: the observed ~20-40 Hz activity OVERLAPPED WITH BOTH BETA AND SLOW GAMMA FREQUENCY BANDS AND THUS MAY REFLECT EITHER BETA, SLOW GAMMA, OR A COMBINATION OF BOTH Quotation withheld because this record is not cleared for redistribution. with the same term carrying two ranges inside one review - slow gamma introduced as ~25-55 Hz here, and reported as ~30-80 Hz three paragraphs later, against ~60-100 Hz for the fast one Quotation withheld because this record is not cleared for redistribution. and the second range printed where a layer difference is being claimed: SLOW GAMMA (~30-80 Hz) ACTIVITY DOMINATED IN STRATUM RADIATUM, WHEREAS ~60-100 Hz GAMMA DOMINATED IN STRATUM LACUNOSUM-MOLECULARE - the two definitions overlap by 20 Hz Quotation withheld because this record is not cleared for redistribution. with the measurement problem named as a property of the object: THE HIGH VARIABILITY OF GAMMA FREQUENCY ALSO COMPLICATES ITS MEASUREMENT IN BEHAVING ANIMALS Quotation withheld because this record is not cleared for redistribution. A FOUNDING THEORY CALLED INTO QUESTION BY ONE STUDY: in the 1970s the extent to which theta was present PREDICTED HOW QUICKLY ANIMALS LEARNED, which LED TO THE THEORY that theta plays an essential role in learning and memory - HOWEVER, THE THEORY HAS BEEN CALLED INTO QUESTION Quotation withheld because this record is not cleared for redistribution. and the evidence is two facts that no amount of theta-learning correlation can absorb: place fields WERE FORMED in novel environments DESPITE THETA BEING BLOCKED by septal inactivation, and FLYING BATS HAVE PLACE CELLS EVEN THOUGH these cells exhibit LITTLE TO NO THETA RHYTHMICITY - so THETA RHYTHMICITY IS NOT REQUIRED FOR THE FORMATION OF PLACE FIELDS Quotation withheld because this record is not cleared for redistribution. THE REVIEW'S STRUCTURE IS THE ARGUMENT: several studies have begun to address whether slow and fast gamma perform different functions, A FEW MAIN HYPOTHESES HAVE EMERGED, and EVIDENCE FOR AND AGAINST EACH OF THESE HYPOTHESES IS DISCUSSED BELOW Quotation withheld because this record is not cleared for redistribution. and both hypotheses survive with their counter-evidence attached: HOWEVER, Quotation withheld - one study links it to WORKING MEMORY, BUT NOT MEMORY ENCODING Quotation withheld because this record is not cleared for redistribution. and for the other: NOT ALL FINDINGS FROM STUDIES OF SLOW GAMMA FIT WITH THIS MEMORY RETRIEVAL HYPOTHESIS - THESE APPARENT INCONGRUITIES ACROSS STUDIES HIGHLIGHT THE NEED FOR FURTHER INVESTIGATION Quotation withheld because this record is not cleared for redistribution. A MECHANISM THAT CONTRADICTS ITSELF IN TWO CITATIONS: HCN1 IS THOUGHT TO FACILITATE theta rhythmic firing and its blockade REDUCED theta entrainment - HOWEVER, THE PRECISE ROLE OF HCN CHANNELS REMAINS UNCLEAR BECAUSE IT HAS ALSO BEEN REPORTED THAT ENHANCED THETA RHYTHMS OCCUR IN HCN1 KNOCKOUT MICE Quotation withheld because this record is not cleared for redistribution. and a pacemaker that turns out not to be necessary in vitro but necessary in vivo: THETA RHYTHMS CAN OCCUR IN THE ABSENCE OF MS PACEMAKER INPUTS in a whole hippocampal preparation, suggesting theta CAN ALSO EMERGE FROM LOCAL CIRCUIT INTERACTIONS - NONETHELESS, IT IS CLEAR THAT MS INPUTS ARE IMPORTANT for driving theta in behaving animals Quotation withheld because this record is not cleared for redistribution. with the clean two-circuit story qualified by the cells themselves: A SUBSTANTIAL PROPORTION OF CA1 INTERNEURONS PHASE-LOCK TO BOTH SLOW AND FAST GAMMA, and MAY BE PART OF A NETWORK THAT CAN GENERATE EITHER, DEPENDING ON THE STATE OF THE NETWORK Quotation withheld because this record is not cleared for redistribution. and the frequency is a consequence of drive rather than an identity: gamma frequency INCREASED WITH INCREASED EXCITATORY DRIVE onto the interneurons and DECREASED WITH INCREASED GABA CONDUCTANCES - which means the label follows the input, not the circuit Quotation withheld because this record is not cleared for redistribution. with the mechanism section closing on its own status: HOWEVER, THESE HYPOTHESES ARE TENTATIVE, AND MUCH WORK REMAINS TO BE DONE Quotation withheld because this record is not cleared for redistribution. THE OBJECT IS VISIBLE ONLY WHERE IT IS SYNCHRONOUS: rhythms reflect synchronized activity BECAUSE SYNCHRONOUS CURRENTS SUM TOGETHER to generate large-amplitude fluctuations, WHEREAS NON-SYNCHRONIZED CURRENTS DO NOT SUM AND THUS REMAIN TOO SMALL TO BE DETECTED - the measurement selects what it can see Quotation withheld because this record is not cleared for redistribution. and the region was chosen for the same reason: the hippocampus contains DENSELY PACKED NEURONS THAT GENERATE LARGE LFPs, especially CA1 because THE PYRAMIDAL CELL DENDRITES ARE ALIGNED IN PARALLEL - ACCORDINGLY, MANY STUDIES of the role of brain rhythms in memory HAVE BEEN CONDUCTED IN THE HIPPOCAMPUS Quotation withheld because this record is not cleared for redistribution. and the species too: many findings are from LOWER MAMMALS, PARTICULARLY RODENTS, IN PART BECAUSE THE MEASUREMENT of brain rhythms in healthy human subjects WITHIN A DEEP-LYING STRUCTURE such as the hippocampus IS DIFFICULT Quotation withheld because this record is not cleared for redistribution. THE OPEN QUESTIONS ARE LISTED AS OPEN: what exactly IS the functional significance of variations in theta frequency, and WHY WOULD MEMORIES BE STORED OR CONSOLIDATED IN REVERSE ORDER? DO FORWARD AND REVERSE REPLAY SERVE DIFFERENT FUNCTIONS? Quotation withheld because this record is not cleared for redistribution. with a gap at the center of the leading hypothesis: according to the consolidation hypothesis replay TRANSFERS MEMORIES FROM THE HIPPOCAMPUS TO THE NEOCORTEX, HOWEVER IT REMAINS UNKNOWN WHETHER COORDINATED SEQUENCE REPLAY OCCURS between the hippocampus and its major downstream target Quotation withheld because this record is not cleared for redistribution. and the question this whole review turns on, asked last: DO DIFFERENT FREQUENCIES OF GAMMA REPRESENT DIFFERENT FUNCTIONAL STATES, AND IF SO, ARE DIFFERENT CIRCUITS INVOLVED IN THEIR GENERATION OR IS THE SAME CIRCUITRY SIMPLY ENTRAINED BY DIFFERENT INPUTS? Quotation withheld because this record is not cleared for redistribution. claim_type: critique a second reading DIFFERING from the recorded value. Recorded: mechanism — note: a second reading, verbatim-verified, disagreeing with the value on the record. Not applied - a person decides. Quotation withheld because this record is not cleared for redistribution. method: review of the generation mechanisms and the functional evidence for each rhythm, with the incongruities left standing rather than resolved a second reading DIFFERING from the recorded value. Recorded: review — note: a second reading, verbatim-verified, disagreeing with the value on the record. Not applied - a person decides. Quotation withheld because this record is not cleared for redistribution. phenomenon: periodically fluctuating waves of neuronal activity in the local field potential, visible only because synchronous currents sum and non-synchronous ones do not a second reading DIFFERING from the recorded value. Recorded: hippocampal network rhythms — note: a second reading, verbatim-verified, disagreeing with the value on the record. Not applied - a person decides. Quotation withheld because this record is not cleared for redistribution. critiques → the traditional assignment of one memory function to each rhythm, which recent findings have challenged differs in: whether the frequency variants within gamma were distinguished at all, since most studies did not Quotation withheld because this record is not cleared for redistribution. contradicts → the theory that theta is required for forming spatial memory representations, since place fields form without it and bats have place cells with little theta differs in: THE AXIS IS WHETHER PLACE-FIELD DEVELOPMENT TRACKS LEARNING. 'Place fields emerge as animals gain experience with new environments, and Quotation withheld. It was therefore SURPRISING that this study showed...' The contradiction is aimed at the ASSUMED CORRESPONDENCE, which the span states before contradicting it. Quotation withheld because this record is not cleared for redistribution. qualifies → the memory-encoding hypothesis for fast gamma, which one study links instead to working memory differs in: THE AXIS IS WHICH MEMORY PROCESS. 'a recent study has found that Quotation withheld, in mice performing a delayed nonmatching-to-place task.' The encoding hypothesis is not denied its association with fast gamma; it is denied THIS process. Quotation withheld because this record is not cleared for redistribution. qualifies → the memory-retrieval hypothesis for slow gamma, which novelty-related increases do not fit differs in: THE AXIS IS NOVELTY. 'However, not all findings from studies of slow gamma fit with this memory retrieval hypothesis. Specifically, Quotation withheld.' The hypothesis is qualified by a condition it does not cover, not replaced. Quotation withheld because this record is not cleared for redistribution. critiques → the medial septum as sole pacemaker, since theta occurs in a preparation with no septal input Quotation withheld because this record is not cleared for redistribution. predicts → that whether different gamma frequencies mean different circuits or the same circuit differently driven is the question to settle next Quotation withheld because this record is not cleared for redistribution. theta —is-a→ rhythm theta rhythm strength of the relation: 1 · note: IT IS THEREFORE NOT SURPRISING THAT THESE DIFFERENT RHYTHMS ARE THOUGHT TO PERFORM DISTINCT FUNCTIONS - and THERE IS LESS AGREEMENT IN THE FIELD ABOUT THE FUNCTIONAL SIGNIFICANCE OF GAMMA Quotation withheld because this record is not cleared for redistribution. RETRACTED (REVERSED) · CA3 —causes→ slow gamma CA3 slow gamma RETRACTED: REVERSED. The span says slow gamma IS DRIVEN BY CA3, so the arrow runs CA3 -> slow gamma. The edge asserts the opposite causal direction. — strength of the relation: 1 · note: introduced as ~25-55 Hz and DRIVEN BY CA3 - and reported as ~30-80 Hz three paragraphs later — direction corrected 2026-08-20 by the project: the quote puts 'CA3' on the causing side. The edge previously read slow gamma --causes--> CA3, which is the reverse of its own sentence. Nothing else on the row changed; the quote, weight and anchor are untouched. Quotation withheld because this record is not cleared for redistribution. slow gamma —part-of→ gamma slow gamma gamma strength of the relation: 1 · note: SLOW GAMMA (~30-80 Hz) DOMINATED IN STRATUM RADIATUM, WHEREAS ~60-100 Hz GAMMA DOMINATED IN STRATUM LACUNOSUM-MOLECULARE - the two definitions overlap by 20 Hz Quotation withheld because this record is not cleared for redistribution. beta —contrasted-with→ slow gamma beta slow gamma strength of the relation: 1 · note: A RESULT THAT CANNOT BE ASSIGNED BECAUSE THE CATEGORIES OVERLAP - the ~20-40 Hz activity OVERLAPPED WITH BOTH BANDS and MAY REFLECT EITHER BETA, SLOW GAMMA, OR A COMBINATION OF BOTH Audit 2026-09-28: DOUBTFUL - read against its span and kept, but the span describes 20-40 Hz coupling; the contrast with slow gamma is not stated. Quotation withheld because this record is not cleared for redistribution. theta —causes→ memory theta memory strength of the relation: 1 · note: A FOUNDING THEORY CALLED INTO QUESTION - the 1970s correlation LED TO THE THEORY that theta plays an essential role, and THE THEORY HAS BEEN CALLED INTO QUESTION BY A RECENT STUDY Audit 2026-09-28: DOUBTFUL - read against its span and kept, but the span says theta predicted learning speed; causes overstates a prediction. Quotation withheld because this record is not cleared for redistribution. slow gamma —causes→ retrieval slow gamma retrieval strength of the relation: 1 · note: NOT ALL FINDINGS FIT WITH THIS MEMORY RETRIEVAL HYPOTHESIS - THESE APPARENT INCONGRUITIES ACROSS STUDIES HIGHLIGHT THE NEED FOR FURTHER INVESTIGATION Audit 2026-09-28: DOUBTFUL - read against its span and kept, but the span refers to a retrieval hypothesis that some findings do not fit; causes states a hypothesis as a finding. Quotation withheld because this record is not cleared for redistribution. novelty —causes→ slow gamma novelty slow gamma status: CITED, AND CITED AS A COMPLICATION: the review reports these studies as findings that do NOT fit the memory-retrieval hypothesis it has just set out · direction on the measure: increases · strength of the relation: 1 Quotation withheld because this record is not cleared for redistribution. interneuron —causes→ gamma interneuron gamma strength of the relation: 1 · note: INTERNEURON SPIKES CONSISTENTLY PHASE-LOCK TO GAMMA OSCILLATIONS, WHEREAS PYRAMIDAL CELL SPIKES DO NOT Quotation withheld because this record is not cleared for redistribution. interneuron —causes→ frequency interneuron frequency strength of the relation: 1 · note: gamma frequency INCREASED WITH INCREASED EXCITATORY DRIVE onto the interneurons and DECREASED WITH INCREASED GABA CONDUCTANCES - the label follows the input, not the circuit Audit 2026-09-28: DOUBTFUL - read against its span and kept, but the span says the frequency of interneuron-generated gamma varies with input strength; the endpoint 'frequency' drops 'gamma'. Quotation withheld because this record is not cleared for redistribution. HCN —causes→ theta HCN theta status: ATTRIBUTED, WITH ONE CITED EXPERIMENT BEHIND IT AND A QUALIFICATION AFTER IT: 'Quotation withheld 41, 42, and HCN1 BLOCKADE REDUCED theta entrainment of pyramidal cell spikes 38. HOWEVER, THE PRECISE ROLE OF HCN CHANNELS IN THETA PRODUCTI[ON]...' Enriched rather than retracted because the middle clause is a cited experimental result, not only a belief - but neither the belief nor the experiment is this review's, and the sentence after it reopens the question. · strength of the relation: 1 · note: A MECHANISM THAT CONTRADICTS ITSELF IN TWO CITATIONS - HCN1 IS THOUGHT TO FACILITATE theta, and ENHANCED THETA RHYTHMS OCCUR IN HCN1 KNOCKOUT MICE Audit 2026-09-28: DOUBTFUL - read against its full span and kept, but HCN1 is 'THOUGHT TO facilitate' theta and its role 'remains unclear'; causes is hedged. Quotation withheld because this record is not cleared for redistribution. LFP —operationalised-as→ rhythm LFP rhythm strength of the relation: 1 · note: THE OBJECT IS VISIBLE ONLY WHERE IT IS SYNCHRONOUS - synchronous currents SUM TOGETHER, WHEREAS NON-SYNCHRONIZED CURRENTS DO NOT SUM AND THUS REMAIN TOO SMALL TO BE DETECTED Audit 2026-09-28: DOUBTFUL - read against its span and kept, but rhythms appear as LFP fluctuations; operationalised-as is loose. Quotation withheld because this record is not cleared for redistribution. hippocampus —causes→ LFP hippocampus LFP strength of the relation: 1 · note: DENSELY PACKED NEURONS THAT GENERATE LARGE LFPs, especially CA1 because THE PYRAMIDAL CELL DENDRITES ARE ALIGNED IN PARALLEL - ACCORDINGLY, MANY STUDIES HAVE BEEN CONDUCTED IN THE HIPPOCAMPUS Audit 2026-09-28: DOUBTFUL - read against its span and kept, but the span says hippocampal neurons generate large LFPs; 'hippocampus causes LFP' is loose. Quotation withheld because this record is not cleared for redistribution. RETRACTED (A HYPOTHESIS EXPLICITLY FRAMED AS A GAP IN KNOWLEDGE) · replay —causes→ consolidation replay consolidation RETRACTED: A HYPOTHESIS EXPLICITLY FRAMED AS A GAP IN KNOWLEDGE. The span: 'ANOTHER CRITICAL…' The sentence naming the relation is bracketed by 'critical gap in knowledge' before and 'remains unknown' after. A reader joining on 'X --causes--> Y' takes it as a causal relation this paper reports. — strength of the relation: 1 · note: a gap at the center of the leading hypothesis - IT REMAINS UNKNOWN WHETHER COORDINATED SEQUENCE REPLAY OCCURS between the hippocampus and its major downstream cortical target Audit 2026-09-28: DOUBTFUL - read against its span and kept, but the span states the consolidation hypothesis of replay; causes states a hypothesis as a finding. Quotation withheld because this record is not cleared for redistribution. Theta rhythmicity is not necessary for single place cells to form place fields, undercutting the assumption that theta is required for building spatial memory representations at the single-cell level. Quotation withheld because this record is not cleared for redistribution. Blocking theta by MS inactivation impaired a delayed spatial alternation task and disrupted ordered place-cell ensembles. Quotation withheld because this record is not cleared for redistribution. RIPPLES ARE GENERATED LOCALLY IN CA1 by ripple-frequency spiking of PERISOMATICALLY TARGETING BASKET CELL INTERNEURONS Quotation withheld because this record is not cleared for redistribution. Sharp waves are excitatory events transmitted from CA3 to CA1. Quotation withheld because this record is not cleared for redistribution. Recent evidence suggests sharp wave-ripples also play a key role in aspects of active spatial navigation. Quotation withheld because this record is not cleared for redistribution. Slow (~25-55 Hz) and fast (~60-100 Hz) gamma appear to have different origins and may serve different functions. Quotation withheld because this record is not cleared for redistribution. these findings suggest that SLOW GAMMA IS IMPORTANT IN MEMORY RETRIEVAL, since replay is thought to reflect REACTIVATION OF MEMORIES OF EARLIER EXPERIENCES Quotation withheld because this record is not cleared for redistribution. these rhythms ARE DEFINED BY THEIR FREQUENCIES and HAVE BEEN PROPOSED TO PERFORM DISTINCT FUNCTIONS - HOWEVER, RECENT FINDINGS HAVE CHALLENGED TRADITIONAL VIEWS ON THESE BEHAVIORAL FUNCTIONS Quotation withheld because this record is not cleared for redistribution. THERE IS LESS AGREEMENT IN THE FIELD ABOUT THE FUNCTIONAL SIGNIFICANCE OF GAMMA RHYTHMS Quotation withheld because this record is not cleared for redistribution. this type of activity HAS BEEN TERMED FAST GAMMA IN SOME STUDIES AND MIDFREQUENCY GAMMA IN OTHERS - THE FORMER TERMINOLOGY WILL BE USED HERE Quotation withheld because this record is not cleared for redistribution. MOST OF THE STUDIES DESCRIBED ABOVE DID NOT DIFFERENTIATE BETWEEN DIFFERENT FREQUENCY VARIANTS OF GAMMA, AND IT IS POSSIBLE THAT SLOW AND FAST GAMMA ARE GENERATED BY DIFFERENT MECHANISMS Quotation withheld because this record is not cleared for redistribution. the observed ~20-40 Hz activity OVERLAPPED WITH BOTH BETA AND SLOW GAMMA FREQUENCY BANDS AND THUS MAY REFLECT EITHER BETA, SLOW GAMMA, OR A COMBINATION OF BOTH Quotation withheld because this record is not cleared for redistribution. SLOW GAMMA (~30-80 Hz) ACTIVITY DOMINATED IN STRATUM RADIATUM, WHEREAS ~60-100 Hz GAMMA DOMINATED IN STRATUM LACUNOSUM-MOLECULARE Quotation withheld because this record is not cleared for redistribution. THE HIGH VARIABILITY OF GAMMA FREQUENCY ALSO COMPLICATES ITS MEASUREMENT IN BEHAVING ANIMALS Quotation withheld because this record is not cleared for redistribution. THE THEORY HAS BEEN CALLED INTO QUESTION BY A RECENT STUDY involving recordings from place cells Quotation withheld because this record is not cleared for redistribution. THETA RHYTHMICITY IS NOT REQUIRED FOR THE FORMATION OF PLACE FIELDS, and thus theta is NOT REQUIRED FOR THE FORMATION OF SPATIAL MEMORY REPRESENTATIONS AT THE SINGLE CELL LEVEL Quotation withheld because this record is not cleared for redistribution. HOWEVER, Quotation withheld Quotation withheld because this record is not cleared for redistribution. NOT ALL FINDINGS FROM STUDIES OF SLOW GAMMA FIT WITH THIS MEMORY RETRIEVAL HYPOTHESIS - THESE APPARENT INCONGRUITIES ACROSS STUDIES HIGHLIGHT THE NEED FOR FURTHER INVESTIGATION Quotation withheld because this record is not cleared for redistribution. THE PRECISE ROLE OF HCN CHANNELS IN THETA PRODUCTION REMAINS UNCLEAR BECAUSE IT HAS ALSO BEEN REPORTED THAT ENHANCED THETA RHYTHMS OCCUR IN HCN1 KNOCKOUT MICE Quotation withheld because this record is not cleared for redistribution. THETA RHYTHMS CAN OCCUR IN THE ABSENCE OF MS PACEMAKER INPUTS, in a whole hippocampal in vitro preparation Quotation withheld because this record is not cleared for redistribution. A SUBSTANTIAL PROPORTION OF CA1 INTERNEURONS PHASE-LOCK TO BOTH SLOW AND FAST GAMMA Quotation withheld because this record is not cleared for redistribution. gamma frequency was found to INCREASE WITH INCREASED EXCITATORY DRIVE onto the interneurons, and to DECREASE WITH INCREASED GABA CONDUCTANCES Quotation withheld because this record is not cleared for redistribution. HOWEVER, THESE HYPOTHESES ARE TENTATIVE, AND MUCH WORK REMAINS TO BE DONE to uncover mechanisms underlying slow and fast gamma rhythms Quotation withheld because this record is not cleared for redistribution. synchronous currents SUM TOGETHER to generate large-amplitude fluctuations in LFP, WHEREAS NON-SYNCHRONIZED CURRENTS DO NOT SUM TOGETHER AND THUS REMAIN TOO SMALL TO BE DETECTED Quotation withheld because this record is not cleared for redistribution. IT REMAINS UNKNOWN WHETHER COORDINATED SEQUENCE REPLAY OCCURS BETWEEN THE HIPPOCAMPUS AND ITS MAJOR DOWNSTREAM CORTICAL TARGET Quotation withheld because this record is not cleared for redistribution. DO DIFFERENT FREQUENCIES OF GAMMA REPRESENT DIFFERENT FUNCTIONAL STATES OF THE HIPPOCAMPAL NETWORK, and if so ARE DIFFERENT CIRCUITS INVOLVED IN THEIR GENERATION OR IS THE SAME CIRCUITRY SIMPLY ENTRAINED BY DIFFERENT INPUTS? Quotation withheld because this record is not cleared for redistribution. brain rhythms brain rhythms Quotation withheld because this record is not cleared for redistribution. place cells place cells Quotation withheld because this record is not cleared for redistribution. replay replay Quotation withheld because this record is not cleared for redistribution. theta phase precession theta phase precession Quotation withheld because this record is not cleared for redistribution. neuronal ensembles neuronal ensembles Quotation withheld because this record is not cleared for redistribution. rhythm rhythm Quotation withheld because this record is not cleared for redistribution. slow gamma slow gamma Quotation withheld because this record is not cleared for redistribution. fast gamma fast gamma Quotation withheld because this record is not cleared for redistribution. ~4-12 Hz — frequency band the review assigns to hippocampal theta Quotation withheld because this record is not cleared for redistribution. ~25-55 Hz and ~60-100 Hz — frequency bands separating slow gamma from fast gamma Quotation withheld because this record is not cleared for redistribution. ~30-80 Hz — gamma band dominating in stratum radiatum, versus ~60-100 Hz in stratum lacunosum-moleculare Quotation withheld because this record is not cleared for redistribution. ~25-55 Hz — slow gamma as this review first defines it - the same term is given as ~30-80 Hz three paragraphs later Quotation withheld because this record is not cleared for redistribution. ~30-80 Hz — slow gamma as reported in the layer comparison, overlapping the ~60-100 Hz fast range by 20 Hz Quotation withheld because this record is not cleared for redistribution. ~20-40 Hz — the coupling that cannot be assigned to a band, since it overlaps both beta and slow gamma Quotation withheld because this record is not cleared for redistribution. frequency frequency Quotation withheld because this record is not cleared for redistribution. theta theta Quotation withheld because this record is not cleared for redistribution.

The full text of this article is not redistributable, so it is not included here. The evidence sentences are withheld with it; the tag layer and its grounding status remain. The article itself is at https://doi.org/10.1038/nrn.2016.21.