Internally Generated Reactivation of Single Neurons in Human Hippocampus During Free Recall

By Hagar Gelbard-Sagiv, Roy Mukamel, M. Harel, Rafael Malach, Itzhak Fried. 2008

473 citations recorded by the source corpus.

The emergence of memory, a trace of things past, into human consciousness is one of the greatest mysteries of the human mind. Whereas the neuronal basis of recognition memory can be probed experimentally in human and nonhuman primates, the study of free recall requires that the mind declare the occurrence of a recalled memory (an event intrinsic to the organism and invisible to an observer). Here, we report the activity of single neurons in the human hippocampus and surrounding areas when subjects first view cinematic episodes consisting of audiovisual sequences and again later when they freely recall these episodes. A subset of these neurons exhibited selective firing, which often persisted throughout and following specific episodes for as long as 12 seconds. Verbal reports of memories of these specific episodes at the time of free recall were preceded by selective reactivation of the same hippocampal and entorhinal cortex neurons. We suggest that this reactivation is an internally generated neuronal correlate for the subjective experience of spontaneous emergence of human recollection.

Subfields: Cellular and Molecular Neuroscience, Cognitive Neuroscience, Sensory Systems, Neuroscience

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Citations in the corpus

Continual Lifelong Learning with Neural Networks: A Review (2018, background): “The hippocampus rapidly encodes episodic-like events that can be reactivated during sleep or unconscious and conscious memory recall (Gelbard-Sagiv et al. 2008), thus consolidating information in the neocortex via the reactivation of encoded experiences in terms of multiple internally generated repl”
Continual Learning with Deep Generative Replay (2017, background): “a short period is reactivated during sleep or conscious and unconscious recall [8].”
Lifelong Learning of Spatiotemporal Representations With Dual-Memory Recurrent Self-Organization (2018, background): “Memory replay is argued to occur through the reactivation of neural patterns during both sleep and awake states (e.g., free recall; Gelbard-Sagiv et al., 2008).”
Continual Learning through Retrieval and Imagination (2022, background): “The Complementary Learning Systems (CLS) theory (Gelbard-Sagiv et al. 2008; Kumaran et al. 2016) holds that the hippocampus in human brain stores episodic-like memory that can be reactivated during sleep or in unconscious and conscious recall, thus consolidating knowledge in the neocortex via the re”
Awake replay of remote experiences in the hippocampus (2009, positive): “Our findings complement recent reports of memory-related activity in the huma”
Hippocampal Replay is Not a Simple Function of Experience (2010, background): “This is consistent with recent studies showing reactivation of experiences from previous environments (Jackson et al., 2006; Gelbard-Sagiv et al., 2008), replay of forward sequences from previous environments (Karlsson and Frank, 2009), and backward replay of trajectories that do not begin at the…”
Evaluative and generative modes of thought during the creative process (2012, background): “The spontaneous re-activation of memories in humans has also been associated with neural activity in the MTL (Gelbard-Sagiv et al., 2008), and spontaneous mental processing during rest conditions has been found to consistently recruit the MTL (Binder et al., 1999; Christoff et al., 2004; Stark and…”
Hippocampal “time cells” bridge the gap in memory for discontiguous events (2011, unknown): “In support of these models, experimental studies on both humans (Gelbard-Sagiv et al., 2008; Paz et al., 2010) and animals (Louie and Wilson, 2001; Foster and Wilson, 2006; Karlsson and Frank, 2009; Davidson et al.”
Neural syntax: cell assemblies, synapsembles and readers (2010, unknown): “…can generate numerous trajectories corresponding to different memory episodes and, importantly, that the neurons that fire during free recall are part of the same cell assembly sequences that were activated while watching the cinematic episodes in the learning phase (Gelbard-Sagiv et al., 2008).”
Single neuron responses in humans during execution and observation of actions (2010, background): “We have recently demonstrated that neurons in medial temporal lobe are reactivated during spontaneous recall of episodic memory [34].”
Conscious Processing and the Global Neuronal Workspace Hypothesis (2020, background): “24 become active when these concepts are retrieved from long-term memory (Gelbard-Sagiv et al., 2008).”
Network dynamics underlying the formation of sparse, informative representations in the hippocampus (2008, unknown): “The hippocampus is essential for encoding new memories for space and events (Scoville and Milner, 1957; Squire and ZolaMorgan, 1991; Eichenbaum and Cohen, 2001) and recent work has shown that human hippocampal neurons are active during both memory encoding and retrieval (Gelbard-Sagiv et al., 2008).”
Memory Engram Cells Have Come of Age. (2015, unknown): “In humans, single unit recordings identified cells in the hippocampus and surrounding areas that were reactivated only during the free memory recall of a particular individual, landmark (Quiroga et al., 2005), or episode (Gelbard-Sagiv et al., 2008).”