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1.
Nat Neurosci ; 22(4): 609-617, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30911183

RESUMO

Continuous-attractor network models of grid formation posit that recurrent connectivity between grid cells controls their patterns of co-activation. Grid cells from a common module exhibit stable offsets in their periodic spatial tuning curves across environments, and this may reflect recurrent connectivity or correlated sensory inputs. Here we explore whether cell-cell relationships predicted by attractor models persist during sleep states in which spatially informative sensory inputs are absent. We recorded ensembles of grid cells in superficial layers of medial entorhinal cortex during active exploratory behaviors and overnight sleep. Per grid cell pair and collectively, and across waking, rapid eye movement sleep and non-rapid eye movement sleep, we found preserved patterns of spike-time correlations that reflected the spatial tuning offsets between these grid cells during active exploration. The preservation of cell-cell relationships across waking and sleep states was not explained by theta oscillations or activity in hippocampal subregion CA1. These results indicate that recurrent connectivity within the grid cell network drives grid cell activity across behavioral states.


Assuntos
Córtex Entorrinal/fisiologia , Células de Grade/fisiologia , Sono , Processamento Espacial/fisiologia , Potenciais de Ação , Animais , Região CA1 Hipocampal/fisiologia , Comportamento Exploratório , Masculino , Modelos Neurológicos , Atividade Motora , Ratos Long-Evans
2.
Neuron ; 100(3): 527-529, 2018 11 07.
Artigo em Inglês | MEDLINE | ID: mdl-30408441

RESUMO

Eliav et al., (2018) recently reported hippocampal-entorhinal spiking in bats occurring preferentially at specific phases of nonrhythmic extracellular voltage fluctuations. This disentanglement of phase coding from continuous oscillations raises new questions about the importance of rhythms for neuronal coordination.


Assuntos
Potenciais de Ação/fisiologia , Córtex Entorrinal/fisiologia , Hipocampo/fisiologia , Ritmo Teta/fisiologia , Animais , Humanos , Fatores de Tempo
3.
Neuropsychologia ; 110: 197-207, 2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-28712947

RESUMO

Retrieval of autobiographical memories entails periods of search, access, and elaboration. Women's reports of their memories feature more detail and emotional content relative to men's. A key question is how these gender differences relate to unfolding changes in cortical activity during retrieval. We recorded EEG activity from 32 scalp electrodes as women and men were cued to retrieve positive, negative, and neutral autobiographical memories. Alpha (9-12Hz) oscillations were prominent at all EEG channels. Alpha coherence between channels was calculated as a measure of ms-level cortical synchrony. Across participants and memory types, a frontal cluster showed pronounced decreases in coherence with other channels during the first second of autobiographical retrieval. In the following second, a left parietal-centered cluster showed increased coherence with other channels. This effect strengthened and spread in the third second of retrieval, perhaps reflecting trace elaboration and/or evaluation of the memory. Although women and men gave similar subjective ratings of their memories, the second-by-second pattern of alpha coherence during autobiographical retrieval differed by gender and memory type. Specifically, women sustained the increased pattern of left-parietal coherence throughout the trial, whereas for men, alpha coherence in this cluster returned to baseline by second two for neutral memories and by second three for emotional memories. Examination of the temporal dynamics of cortical oscillations provides novel insight into autobiographical memory retrieval processes and to gendered retrieval in particular, suggesting that women may persist with elaboration and/or evaluation to a greater extent than men.


Assuntos
Ritmo alfa/fisiologia , Encéfalo/fisiologia , Emoções/fisiologia , Memória Episódica , Rememoração Mental/fisiologia , Caracteres Sexuais , Adolescente , Adulto , Sinais (Psicologia) , Humanos , Reconhecimento Visual de Modelos/fisiologia , Leitura , Processamento de Sinais Assistido por Computador , Adulto Jovem
4.
Cell Rep ; 21(9): 2419-2432, 2017 Nov 28.
Artigo em Inglês | MEDLINE | ID: mdl-29186681

RESUMO

Neuronal oscillations in the rat hippocampus relate to both memory and locomotion, raising the question of how these cognitive and behavioral correlates interact to determine the oscillatory network state of this region. Here, rats freely locomoted while performing an object-location task designed to test hippocampus-dependent spatial associative memory. Rhythmic activity in theta, beta, slow gamma, and fast gamma frequency ranges were observed in both action potentials and local field potentials (LFPs) across four main hippocampal subregions. Several patterns of LFP oscillations corresponded to overt behavior (e.g., increased dentate gyrus-CA3 beta coherence during stationary moments and CA1-subiculum theta coherence during locomotion). In comparison, slow gamma (∼40 Hz) oscillations throughout the hippocampus related most specifically to object-location associative memory encoding rather than overt behavior. The results help to untangle how hippocampal oscillations relate to both memory and motion and single out slow gamma oscillations as a distinguishing correlate of spatial associative memory.


Assuntos
Região CA1 Hipocampal/metabolismo , Região CA1 Hipocampal/fisiologia , Região CA3 Hipocampal/metabolismo , Região CA3 Hipocampal/fisiologia , Giro Denteado/metabolismo , Giro Denteado/fisiologia , Memória/fisiologia , Potenciais de Ação/fisiologia , Animais , Eletrofisiologia , Hipocampo/metabolismo , Hipocampo/fisiologia , Masculino , Ratos , Ritmo Teta/fisiologia
5.
Front Syst Neurosci ; 11: 57, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28824388

RESUMO

At rest, hippocampal "place cells," neurons with receptive fields corresponding to specific spatial locations, reactivate in a manner that reflects recently traveled trajectories. These "replay" events have been proposed as a mechanism underlying memory consolidation, or the transfer of a memory representation from the hippocampus to neocortical regions associated with the original sensory experience. Accordingly, it has been hypothesized that hippocampal replay of a particular experience should be accompanied by simultaneous reactivation of corresponding representations in the neocortex and in the entorhinal cortex, the primary interface between the hippocampus and the neocortex. Recent studies have reported that coordinated replay may occur between hippocampal place cells and medial entorhinal cortex grid cells, cells with multiple spatial receptive fields. Assessing replay in grid cells is problematic, however, as the cells exhibit regularly spaced spatial receptive fields in all environments and, therefore, coordinated replay between place cells and grid cells may be detected by chance. In the present report, we adapted analytical approaches utilized in recent studies of grid cell and place cell replay to determine the extent to which coordinated replay is spuriously detected between grid cells and place cells recorded from separate rats. For a subset of the employed analytical methods, coordinated replay was detected spuriously in a significant proportion of cases in which place cell replay events were randomly matched with grid cell firing epochs of equal duration. More rigorous replay evaluation procedures and minimum spike count requirements greatly reduced the amount of spurious findings. These results provide insights into aspects of place cell and grid cell activity during rest that contribute to false detection of coordinated replay. The results further emphasize the need for careful controls and rigorous methods when testing the hypothesis that place cells and grid cells exhibit coordinated replay.

6.
ACS Chem Neurosci ; 7(10): 1393-1405, 2016 10 19.
Artigo em Inglês | MEDLINE | ID: mdl-27479319

RESUMO

The muscarinic M1 acetylcholine receptor is a key target for drugs aimed at treating cognitive dysfunction, including the memory impairment in Alzheimer's disease. The overall question of the current study was to ask how systemic administration of the bitopic M1 agonist VU0364572, the M1 positive allosteric modulator BQCA, and the acetylcholinesterase inhibitor donepezil (current standard of care for Alzheimer's disease), would impact spatial memory-related hippocampal function in rats. Hippocampal pyramidal neuron spiking and local field potentials were recorded from regions CA1 and CA3 as rats freely foraged in a recording enclosure. To assess the relative stability versus flexibility of the rats' spatial representations, the walls of the recording enclosure were reshaped in 15-m intervals. As compared to the control condition, systemic administration of VU0364572 increased spatial correlations of CA1 and CA3 pyramidal neuron spiking across all enclosure shape comparisons, whereas BQCA and donepezil appeared to decrease these spatial correlations. Further, both VU0364572 and BQCA increased intrahippocampal synchrony as measured by CA3-CA1 field-field coherence in frequency ranges that tended to align with the prominence of those oscillations for the behavioral state (i.e., theta during locomotion and slow gamma during stationary moments). The results indicated that VU0364572 and BQCA influenced hippocampal function differently but in ways that might both be beneficial for treating memory dysfunction.


Assuntos
Região CA1 Hipocampal/efeitos dos fármacos , Região CA3 Hipocampal/efeitos dos fármacos , Colinérgicos/farmacologia , Células Piramidais/efeitos dos fármacos , Receptor Muscarínico M1/metabolismo , Percepção Espacial/efeitos dos fármacos , Potenciais de Ação/efeitos dos fármacos , Potenciais de Ação/fisiologia , Animais , Benzamidas/farmacologia , Compostos de Bifenilo/farmacologia , Região CA1 Hipocampal/metabolismo , Região CA3 Hipocampal/metabolismo , Inibidores da Colinesterase/farmacologia , Donepezila , Eletrodos Implantados , Comportamento Exploratório/efeitos dos fármacos , Comportamento Exploratório/fisiologia , Indanos/farmacologia , Masculino , Atividade Motora/efeitos dos fármacos , Atividade Motora/fisiologia , Periodicidade , Piperidinas/farmacologia , Células Piramidais/metabolismo , Quinolinas/farmacologia , Ratos Endogâmicos F344 , Receptor Muscarínico M1/agonistas , Percepção Espacial/fisiologia , Memória Espacial/efeitos dos fármacos , Memória Espacial/fisiologia , Ritmo Teta/efeitos dos fármacos , Ritmo Teta/fisiologia
8.
Hippocampus ; 24(3): 341-53, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24227610

RESUMO

Neuronal oscillations and cross-frequency interactions in the rat hippocampus relate in important ways to memory processes and serve as a model for studying oscillatory activity in cognition more broadly. We report here that hippocampal synchrony (CA3-CA1 coherence) increased markedly in the low gamma range as rats were exploring novel objects, particularly those for which the rat subsequently showed good memory. The gamma synchrony varied across phases of the theta rhythm such that coherence was highest at the falling slope and trough of the theta wave. Further, the shape of the theta wave was more asymmetric and elongated at the falling slope during exploration of objects for which the rat subsequently showed good memory as compared with objects for which the rat subsequently showed poor memory. The results showed a strong association between event-related gamma synchrony in rat hippocampus and memory encoding for novel objects. In addition, a novel potential mechanism of cross-frequency interactions was observed whereby dynamic alterations in the shape of theta wave related to memory in correspondence with the strength of gamma synchrony. These findings add to our understanding of how theta and gamma oscillations interact in the hippocampus in the service of memory.


Assuntos
Ondas Encefálicas/fisiologia , Região CA1 Hipocampal/fisiologia , Região CA3 Hipocampal/fisiologia , Sincronização de Fases em Eletroencefalografia , Comportamento Exploratório/fisiologia , Memória Episódica , Reconhecimento Psicológico/fisiologia , Animais , Eletrodos Implantados , Masculino , Ratos , Ratos Long-Evans , Ritmo Teta/fisiologia
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