Loss of Recent Memory After Bilateral Hippocampal Lesions

Scoville, William Beecher; Milner, Brenda

doi:10.1176/jnp.12.1.103-a

Cited by 861 publications

(844 citation statements)

References 16 publications

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“…In contrast, our results suggest that neocortical activity propagates through the hippocampus in a dissipating and partly inhibitory fashion (35). The differential response of principal neurons in the hippocampal subfields could contribute to the hypothesized consolidation (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11) or transformation (12) of recently learned information (39, 40) during sleep. …”

Section: Discussionmentioning

confidence: 58%

“…consolidation ͉ hippocampus ͉ neocortex ͉ oscillation ͉ sleep C ortico-hippocampal interaction, especially during quiet wakefulness and sleep, is thought to be important for the formation of long-term memories by a process of consolidation (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12). During these behavioral states and under anesthesia, neocortical neurons are spontaneously active, and their activity is modulated by slow, 0.3-to 1.5-Hz oscillations called up-down states (UDS) characteristic of slow wave sleep (SWS) oscillations.…”

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confidence: 99%

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Differential responses of hippocampal subfields to cortical up–down states

Hahn

Sakmann

Mehta

2007

Proc. Natl. Acad. Sci. U.S.A.

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The connectivity of the hippocampal trisynaptic circuit, formed by the dentate gyrus, the CA3 and the CA1 region, is well characterized anatomically and functionally in vitro. The functional connectivity of this circuit in vivo remains to be understood. Toward this goal, we investigated the influence of the spontaneous, synchronized oscillations in the neocortical local field potential, reflecting up-down states (UDS) of cortical neurons, on the hippocampus. We simultaneously measured the extracellular local field potential in association cortex and the membrane potential of identified hippocampal excitatory neurons in anesthetized mice. Dentate gyrus granule cells showed clear UDS modulation that was phase locked to cortical UDS with a short delay. In contrast, CA3 pyramidal neurons showed mixed UDS modulation, such that some cells were depolarized during the cortical up state and others were hyperpolarized. CA1 pyramidal neurons, located farther downstream, showed consistent UDS modulation, such that when the cortical and dentate gyrus neurons were depolarized, the CA1 pyramidal cells were hyperpolarized. These results demonstrate the differential functional connectivity between neocortex and hippocampal subfields during UDS oscillations.consolidation ͉ hippocampus ͉ neocortex ͉ oscillation ͉ sleep C ortico-hippocampal interaction, especially during quiet wakefulness and sleep, is thought to be important for the formation of long-term memories by a process of consolidation (1-12). During these behavioral states and under anesthesia, neocortical neurons are spontaneously active, and their activity is modulated by slow, 0.3-to 1.5-Hz oscillations called up-down states (UDS) characteristic of slow wave sleep (SWS) oscillations. Both the local field potential (LFP) and the membrane potential (MP) show that UDS are synchronized across large areas of the cortex (13-17). Although neocortex is the major source of input to the hippocampal formation (18), the hippocampal LFP shows large-irregular activity during SWS that seems uncorrelated with the neocortical activity (19,20). This is indicative of minimal cortico-hippocampal interaction during UDS. However, recent studies have shown cortico-hippocampal interaction during various behavioral states including SWS (6,11,(21)(22)(23)(24)(25)(26). The mechanisms underlying this interaction and the contribution of different parts of the hippocampal circuit to this interaction remain to be understood.Each area of the hippocampal trisynaptic circuit sends glutamatergic projections to both excitatory and inhibitory neurons in the next stage (27). Hence, the net output of any hippocampal region would be a complex and, presumably, state-dependent function of the strength and timing of excitatory and inhibitory inputs (28). The functional connectivity of cortico-hippocampal circuits has been extensively investigated by using electrical stimulation [see e.g., special issue of Hippocampus (1995) 5:101-146], whereas its interrelations with spontaneous activity such as UDS have receiv...

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Section: Discussionmentioning

confidence: 58%

mentioning

confidence: 99%

Differential responses of hippocampal subfields to cortical up–down states

Hahn

Sakmann

Mehta

2007

Proc. Natl. Acad. Sci. U.S.A.

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“…A decade after Allen's study, Brenda Milner and her colleagues (Scoville & Milner, 1957) made a seminal discovery regarding the role of the medial temporal structures, especially the hippocampus, in new learning and memory for declarative information. This finding lead to a great number of paradigms for the assessment of new learning and paved the way for understanding the basis for memory deficits following closed head injury.…”

Section: Progress Since Allen's Article Was Writtenmentioning

confidence: 99%

Commentary and perspectives on R.M. Allen's “The test performance of the brain injured”

Alfano

Satz

2000

J. Clin. Psychol.

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“…A majority of these studies have examined the hippocampus. Although the hippocampus is required for the acquisition and temporary storage of declarative memory, studies with human subjects and animal models suggest that more permanent morphological correlates of long-term memory storage are unlikely to reside in the hippocampus (5)(6)(7). In this context, the amygdala, for which the neural circuit underlying emotional memory formation is well characterized (8), provides a significant advantage.…”

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confidence: 99%

Stress duration modulates the spatiotemporal patterns of spine formation in the basolateral amygdala

Mitra

Jadhav

McEwen

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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500

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It has long been hypothesized that morphological and numerical alterations in dendritic spines underlie long-term structural encoding of experiences. Here we investigate the efficacy of aversive experience in the form of acute immobilization stress (AIS) and chronic immobilization stress (CIS) in modulating spine density in the basolateral amygdala (BLA) of male rats. We find that CIS elicits a robust increase in spine density across primary and secondary branches of BLA spiny neurons. We observed this CIS-induced spinogenesis in the BLA 1 d after the termination of CIS. In contrast, AIS fails to affect spine density or dendritic arborization when measured 1 d later. Strikingly, the same AIS causes a gradual increase in spine density 10 d later but without any effect on dendritic arbors. Thus, by modulating the duration of immobilization stress, it is possible to induce the formation of new spines without remodeling dendrites. However, unlike CIS-induced spine formation, the gradual increase in spine density 10 d after a single exposure to AIS is localized on primary dendrites. Finally, this delayed induction of BLA spinogenesis is paralleled by a gradual development of anxiety-like behavior on the elevated plus-maze 10 d after AIS. These findings demonstrate that stressful experiences can lead to the formation of new dendritic spines in the BLA, which is believed to be a locus of storage for fear memories. Our results also suggest that stress may facilitate symptoms of chronic anxiety disorders like post-traumatic stress disorder by enhancing synaptic connectivity in the BLA.anxiety ͉ dendritic remodeling ͉ immobilization ͉ synapse ͉ rats T he search for cellular substrates underlying experience-related plasticity has focused on dendritic spines ever since Ramón y Cajal (1, 2) proposed that the storage of long-term memory involves strengthening of synaptic connections (or even a building of new connections) among central neurons. More recently, the focus has shifted toward understanding the physiological and molecular basis of synaptic plasticity mechanisms, such as long-term potentiation (LTP), and their relationship to spine plasticity and ultimately behavioral memory (3, 4). A majority of these studies have examined the hippocampus. Although the hippocampus is required for the acquisition and temporary storage of declarative memory, studies with human subjects and animal models suggest that more permanent morphological correlates of long-term memory storage are unlikely to reside in the hippocampus (5-7). In this context, the amygdala, for which the neural circuit underlying emotional memory formation is well characterized (8), provides a significant advantage. The basolateral amygdala (BLA) is believed to be a site of storage for memories of fearful or stressful experiences (9-12). Furthermore, recent studies indicate that the synthesis of new proteins in the BLA is involved in the long-term consolidation of emotional memories (13). Thus, the BLA presents an attractive locus to investigate structural encodi...

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Loss of Recent Memory After Bilateral Hippocampal Lesions

Cited by 861 publications

References 16 publications

Differential responses of hippocampal subfields to cortical up–down states

Differential responses of hippocampal subfields to cortical up–down states

Commentary and perspectives on R.M. Allen's “The test performance of the brain injured”

Stress duration modulates the spatiotemporal patterns of spine formation in the basolateral amygdala

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