CA1 neurons in the human hippocampus are critical for autobiographical memory, mental time travel, and autonoetic consciousness

Abstract

Autobiographical memories in our lives are critically dependent on temporal lobe structures. However, the contribution of CA1 neurons in the human hippocampus to the retrieval of episodic autobiographical memory remains elusive. In patients with a rare acute transient global amnesia, highly focal lesions confined to the CA1 field of the hippocampus can be detected on MRI. We studied the effect of these lesions on autobiographical memory using a detailed autobiographical interview including the remember/know procedure. In 14 of 16 patients, focal lesions in the CA1 sector of the hippocampal cornu ammonis were detected. Autobiographical memory was significantly affected over all time periods, including memory for remote periods. Impairment of episodic memory and autonoetic consciousness exhibited a strong temporal gradient extending 30 to 40 y into the past. These results highlight the distinct and critical role of human hippocampal CA1 neurons in autobiographical memory retrieval and for re-experiencing detailed episodic memories.A utobiographical memory is one of the multifaceted forms of human memory that constitutes a major source for selfidentity, self-continuity, and self-awareness of an individual's life. Episodic autobiographical recollection includes conscious awareness for specific episodic situations embedded in time and space, and the ability of mental reliving of episodes of a person's history along the subjective and mental time axis (1). Considering the phenomenological experience of remembering, episodic recollection involving re-experiencing requires autonoetic consciousness in contrast to semantic knowledge of memory, which is associated with noetic consciousness (2).It is generally accepted that the hippocampus plays a critical role in episodic memory, including autobiographical memory, as neuroimaging data show hippocampal activation in autobiographical memory retrieval tasks, supporting that the hippocampus is an integral structure of the autobiographical network (3, 4). The involvement of the hippocampus culminates in the question of the temporal contribution of the hippocampal-neocortical interaction in the consolidation and recollection of remote episodic memory (5). One view, according to the standard model of consolidation, considers the hippocampus as a temporary relay structure that facilitates the transition of newly encoded hippocampus-dependant memory traces to its permanent storage and consolidation in neocortical structures, resulting in hippocampus-independent remote memories (6). This transitory role of the hippocampus is thought to be reflected in the temporal gradient of retrograde amnesia seen in patients with lesions to the medial temporal lobe (MTL). Evidence for this time-limited role of the hippocampus has come from lesion studies of amnestic patients and neuroimaging studies (7,8). In contrast, the multiple trace theory (MTT) postulates a permanent contribution of the hippocampus in retrieving and recollection in terms of a binding module for episodic memories (9). This v...

Prospective and retrospective duration memory in the hippocampus: is time in the foreground or background?

“…For example, humans with selective bilateral hippocampal damage sustained relatively early in life have a robust impairment in episodic memory, but show spared semantic memory [2]. Moreover, patients that develop acute, transient lesions of the HPC (specifically, area CA1) are amnesic for personal experiences with a flat retrograde gradient that extends decades into the past [5]. Accordingly, fMRI studies show that the HPC is involved in remembering personal experiences and the order in which they occurred on an autobiographical timeline [6,7].…”

A longitudinal study on intrinsic connectivity of hippocampus associated with positive symptom in first-episode schizophrenia

“…The hippocampus plays a key role in both the consolidation and the retrieval of memories, particularly episodic memory [34]. The hallucinations, which refer to retrieval function of memories, may be caused by inappropriate recollections from memory [35]. Several studies have demonstrated that several parietal regions are coherently spontaneously activated without task, stimuli, or explicit mnemonic demands, which suggest that these regions associated with the hippocampus can constitute a memory network [36].…”

Effects of Prenatal Stress on Fetal Neurodevelopment and Responses to Maternal Neurosteroid Treatment in Guinea Pigs

“…Previous studies have also found site-specific (CA1 region) disturbances in hippocampal development following exposure to prenatal stressors [50,51,52]. The CA1 region of the hippocampus contains a high concentration of important efferent projections and pyramidal cells involved in processes such as memory and learning, which are known to be affected by exposure to prenatal stress [53,54,55]. Furthermore, this region of the hippocampus has also been shown to be selectively vulnerable to the deleterious effects of glucocorticoid exposure [56,57].…”