Retrograde amnesia in patients with diencephalic, temporal lobe or frontal lesions.

Patients with focal diencephalic, temporal lobe, or frontal lobe lesions were examined on various measures of remote memory. Korsakoff patients showed a severe impairment with a characteristic 'temporal gradient', whereas two patients with focal diencephalic damage (and anterograde amnesia) were virtually unimpaired on remote memory measures. Patients with frontal lobe pathology were severely impaired in the recall of autobiographical incidents and famous news events. Patients with temporal lobe pathology showed severe impairment but a relatively 'flat' temporal gradient, largely attributable to herpes encephalitis patients. From recognition and cued recall tasks, it is argued that there is an important retrieval component to the remote memory deficit across all the lesion groups. In general, the pattern of performance by the frontal lobe and temporal lobe groups was closely similar, and there was no evidence of any major access/storage difference between them. However, laterality comparisons across these groups indicated that the right temporal and frontal lobe regions may make a greater contribution to the retrieval of past episodic (incident and event) memories, whereas the left temporal region is more closely involved in the lexical-semantic labelling of remote memories.     

Multiple trace theory of human memory: computational, neuroimaging, and neuropsychological results

Hippocampal-neocortical interactions in memory have typically been characterized within the "standard model" of memory consolidation. In this view, memory storage initially requires hippocampal linking of dispersed neocortical storage sites, but over time this need dissipates, and the hippocampal component is rendered unnecessary. This change in function over time is held to account for the retrograde amnesia (RA) gradients often seen in patients with hippocampal damage. Recent evidence, however, calls this standard model into question, and we have recently proposed a new approach, the "multiple memory trace" (MMT) theory. In this view, hippocampal ensembles are always involved in storage and retrieval of episodic information, but semantic (gist) information can be established in neocortex, and will survive damage to the hippocampal system if enough time has elapsed. This approach accounts more readily for the very long RA gradients often observed in amnesia. We report the results of analytic and connectionist simulations that demonstrate the feasibility of MMT. We also report a neuroimaging study showing that retrieval of very remote (25-year-old) memories elicits as much activation in hippocampus as retrieval of quite recent memories. Finally, we report new data from the study of patients with temporal lobe damage, using more sensitive measures than previously the case, showing that deficits in both episodic and spatial detail can be observed even for very remote memories. Overall, these findings indicate that the standard model of memory consolidation, which views the hippocampus as having only a temporary role in memory, is wrong. Instead, the data support the view that for episodic and spatial detail the hippocampal system is always necessary.     

Knowing "what" and knowing "when"

The ability to situate autobiographical memories accurately in the "time-line" of one's own life is a particular aspect of retrograde memory that has received little attention in well-controlled, systematic studies. Here, we addressed this issue by testing the hypothesis that patients with basal forebrain damage would be impaired in their ability to place various autobiographical memories accurately on a 'time-line' of their life. Seven such subjects were contrasted with 11 medial temporal lobe subjects, 8 brain-damaged comparison subjects, and 18 normal comparison subjects, using a procedure in which subjects placed autobiographical events on a time-line of their life. The basal forebrain group was very impaired in this task, relative to the other groups, and on average, misplaced events by more than five years. Although the basal forebrain group was also impaired in retrieving the contents of autobiographical memory, they did not differ statistically from the medial temporal lobe group in this regard (and the medial temporal lobe group did not have impaired time placement of memories). The results indicate an intriguing dissociation between "knowing what" and "knowing when," and suggest that the basal forebrain contains structures that are especially important for "knowing when." Our findings are compatible with the view that the basal forebrain participates critically in retrieval strategies important for memory chronology, which contrasts with the medial temporal lobe's critical role in relational memory per se.     

Differential neural activity during search of specific and general autobiographical memories elicited by musical cues

Previous neuroimaging studies that have examined autobiographical memory specificity have utilized retrieval cues associated with prior searches of the event, potentially changing the retrieval processes being investigated. In the current study, musical cues were used to naturally elicit memories from multiple levels of specificity (i.e., lifetime period, general event, and event-specific). Sixteen young adults participated in a neuroimaging study in which they retrieved autobiographical memories associated with musical cues. These musical cues led to the retrieval of highly emotional memories that had low levels of prior retrieval. Retrieval of all autobiographical memory levels was associated with activity in regions in the autobiographical memory network, specifically the ventromedial prefrontal cortex, posterior cingulate, and right medial temporal lobe. Owing to the use of music, memories from varying levels of specificity were retrieved, allowing for comparison of event memory and abstract personal knowledge, as well as comparison of specific and general event memory. Dorsolateral and dorsomedial prefrontal regions were engaged during event retrieval relative to personal knowledge retrieval, and retrieval of specific event memories was associated with increased activity in the bilateral medial temporal lobe and dorsomedial prefrontal cortex relative to retrieval of general event memories. These results suggest that the initial search processes for memories of different specificity levels preferentially engage different components of the autobiographical memory network. The potential underlying causes of these neural differences are discussed.     

Memory consolidation and the hippocampus: further evidence from studies of autobiographical memory in semantic dementia and frontal variant frontotemporal dementia.

Studies of autobiographical memory in semantic dementia have found relative preservation of memories for recent rather than remote events. As semantic dementia is associated with progressive atrophy to temporal neocortex, with early asymmetric sparing of the hippocampus, this neuropsychological pattern suggests that the hippocampal complex plays a role in the acquisition and retrieval of recent memories, but is not necessary for the recall of older episodic events. In an alternative view of memory consolidation, however, the hippocampus plays a role in the retrieval of all autobiographical memories, regardless of the age of the memory [Curr. Opin. Neurobiol. 7(1997)217]. This 'multiple trace theory' predicts that patients with semantic dementia should show no effects of time in their autobiographical recall. In this article, we ask whether it is possible to reconcile the data from semantic dementia with the multiple trace theory by investigating whether the time-dependent pattern of autobiographical retrieval seen in the disease is due to (i) patients showing this effect being exceptional in their presentation; and/or (ii) patients with semantic dementia exhibiting impaired strategic retrieval from concomitant frontal damage. A series of experiments in patients with semantic dementia, the frontal variant of frontotemporal dementia and Alzheimer's disease clearly demonstrates that neither of these two factors can explain the documented effect of time seen in semantic dementia. Nonetheless, we discuss how damage to semantic knowledge could result in an autobiographical memory deficit and suggest that data from semantic dementia may be consistent with both views of hippocampal involvement in long-term memory.     

Retrieval of autobiographical memory in Alzheimer's disease: relation to volumes of medial temporal lobe and other structures

The representation of autobiographical memory is distributed over a network of brain structures, with the medial temporal lobe (MTL) at its epicenter. Some believe that, over time, all memories become independent of their MTL component ("consolidation theories"). Others have suggested that this is true only of semantic memory, while episodic aspects of autobiographical memories are dependent on the MTL for as long as they exist, such as multiple trace theory (MTT). In the present study, the volumes of 28 brain regions, including the MTL, and their relation to autobiographical memory were investigated in a group of patients with Alzheimer's disease with varying degrees of retrograde memory loss as assessed by the Autobiographical Memory Interview (AMI). We used the multivariate analysis method of partial least squares (PLS) to assess patterns of atrophy that can lead to retrograde amnesia. We found that different aspects of autobiographical memory were associated with different patterns of tissue loss. Personal semantics were related to a pattern of bilateral anterior and posterior lateral temporal cortex degeneration, more pronounced on the left, as well as right frontal degeneration. Autobiographical event memory ("episodic") was associated with combined atrophy in bilateral MTL and anterior lateral temporal neocortex, more pronounced on the right. This pattern was invariant for memories from childhood, early adulthood, and recent memories, in line with the predictions of MTT, suggesting that MTL tissue is crucial for retrieval of episodic memories regardless of their age.     

Gender differences in the functional neuroanatomy of emotional episodic autobiographical memory

Autobiographical memory is based on interactions between episodic memory contents, associated emotions, and a sense of self-continuity along the time axis of one's life. The functional neuroanatomy subserving autobiographical memory is known to include prefrontal, medial and lateral temporal, as well as retrosplenial brain areas; however, whether gender differences exist in neural correlates of autobiographical memory remains to be clarified. We reanalyzed data from a previous functional magnetic resonance imaging (fMRI) experiment to investigate gender-related differences in the neural bases of autobiographical memories with differential remoteness and emotional valence. On the behavioral level, there were no significant gender differences in memory performance or emotional intensity of memories. Activations common to males and females during autobiographical memory retrieval were observed in a bilateral network of brain areas comprising medial and lateral temporal regions, including hippocampal and parahippocampal structures, posterior cingulate, as well as prefrontal cortex. In males (relative to females), all types of autobiographical memories investigated were associated with differential activation of the left parahippocampal gyrus. By contrast, right dorsolateral prefrontal cortex was activated differentially by females. In addition, the right insula was activated differentially in females during remote and negative memory retrieval. The data show gender-related differential neural activations within the network subserving autobiographical memory in both genders. We suggest that the differential activations may reflect gender-specific cognitive strategies during access to autobiographical memories that do not necessarily affect the behavioral level of memory performance and emotionality.     

Remote episodic memory deficits in patients with unilateral temporal lobe epilepsy and excisions.

The nature of remote memory impairment in patients with medial temporal lobe damage is the subject of some debate. While some investigators have found that retrograde amnesia in such patients is temporally graded, with relative sparing of remote memories (Squire and Alvarez, 1995), others contend that impairment is of very long duration and that remote memories are not necessarily spared (Sanders and Warrington, 1971; Nadel and Moscovitch, 1997). In this study, remote memory was assessed in 25 patients with unilateral temporal lobe epilepsy and 22 non-neurologically impaired controls using the Autobiographical Memory Interview (Kopelman et al., 1989). Results indicate that patients have impaired personal episodic memory but intact personal semantic memory. The impairment extends even to the most remote time periods in early childhood, long before seizure onset in many patients. As well, patients awaiting temporal lobectomy for control of seizures perform as poorly as those who have already undergone resective surgery. These results support the hypothesis that temporal lobe damage or dysfunction, caused by recurrent seizures or surgical excision, results in extensive retrograde amnesia for personal episodic memories. Interestingly, patients with radiological evidence of hippocampal sclerosis were not significantly more impaired than those without obvious sclerosis. These results indicate that even minimal damage to medial temporal lobes results in significant impairment to autobiographical episodic memory. These findings are more compatible with a memory loss or retrieval deficit rather than a consolidation account of remote memory impairment.     

Co-activation of the amygdala, hippocampus and inferior frontal gyrus during autobiographical memory retrieval

Functional MRI was used to investigate the role of medial temporal lobe and inferior frontal lobe regions in autobiographical recall. Prior to scanning, participants generated cue words for 50 autobiographical memories and rated their phenomenological properties using our autobiographical memory questionnaire (AMQ). During scanning, the cue words were presented and participants pressed a button when they retrieved the associated memory. The autobiographical retrieval task was interleaved in an event-related design with a semantic retrieval task (category generation). Region-of-interest analyses showed greater activation of the amygdala, hippocampus, and right inferior frontal gyrus during autobiographical retrieval relative to semantic retrieval. In addition, the left inferior frontal gyrus showed a more prolonged duration of activation in the semantic retrieval condition. A targeted correlational analysis revealed pronounced functional connectivity among the amygdala, hippocampus, and right inferior frontal gyrus during autobiographical retrieval but not during semantic retrieval. These results support theories of autobiographical memory that hypothesize co-activation of frontotemporal areas during recollection of episodes from the personal past.     

Psychogenic memory deficits associated with functional cerebral changes: an FMRI study

We studied a case of psychogenic amnesia by means of a functional magnetic resonance imaging (fMRI) experiment involving the retrieval of autobiographical memories. The 38-year-old patient was unable to access most of her autobiographical memories from her childhood up to 16 years of age. Compared with the forgotten period, evocation of the normally retrieved memories elicited increased activity in medial temporal and dorso-lateral frontal regions. Evocation of the preserved scattered recollections was associated with bilaterally distributed temporo-parieto-occipital loci of activations. These functional changes seem to support the idea of common mechanisms involved in both organic and psychogenic amnesias.     

Autobiographical memory in semantic dementia: New insights from two patients using fMRI

Episodic autobiographical memory (EAM) consists of personal events embedded within a specific spatiotemporal context. Patients with semantic dementia (SD) generally show preserved recent EAMs, but a controversy remains concerning their ability to retrieve remote ones. Only one fMRI study examined remote autobiographical memory in SD through a longitudinal case study (Maguire, Kumaran, Hassabis, & Kopelman, 2010). Here, we propose a cross-sectional study to test the hippocampo-neocortical up-regulation hypothesis, through a multimodal approach (gray matter volume, activation, connectivity analyses), directly comparing recent and remote autobiographical memory retrieval and collecting data to asses phenomelogical re-experiencing. EAM retrieval recruits a distributed network of brain regions, notably the hippocampus which is shown to be atrophied in SD, although some studies report no hippocampal atrophy in SD. Using fMRI, we examined recent and remote EAM retrieval in two SD patients with different profiles of hippocampal atrophy, compared to 12 healthy elders (HE). JPL presented severe bilateral hippocampal atrophy, while EP showed sparing of both hippocampi. Behaviourally, JPL was impaired at retrieving EAMs from both life periods and showed poorer use of visual mental imagery than HE, while EP retrieved memories which were as episodic as those of HE for both periods and relied on greater use of visual mental imagery than HE. Neuroimaging results showed that, for JPL, hyperactivations of the residual hippocampal tissue and of frontal, lateral temporal, occipital and parietal cortices did not efficiently compensate his autobiographical memory deficit. EP however presented hyperactivations in similar neocortical regions which appeared to be more efficient in compensating for atrophy elsewhere, since EP's EAM retrieval was preserved. Functional connectivity analyses focusing on the hippocampus showed how the residual hippocampal activity was connected to other brain areas. For JPL, recent autobiographical retrieval was associated with connectivity between the posterior hippocampus and middle occipital gyrus, while for EP, connectivity was detected between the anterior hippocampus and numerous regions (medial temporal, occipital, temporal, frontal, parietal) for both recent and remote periods. These findings suggest that intensification of hippocampal atrophy in SD strongly affects both recent and remote autobiographical recollection. Up-regulation of neocortical regions and functional hippocampal–neocortical connectivity within the autobiographical network may be insufficient to compensate the lifelong episodic memory deficit for patients with extensive hippocampal atrophy.     

Patterns of hippocampal–neocortical interactions in the retrieval of episodic autobiographical memories across the entire life‐span of aged adults

We previously demonstrated that episodic autobiographical memories (EAMs) rely on a network of brain regions comprising the medial temporal lobe (MTL) and distributed neocortical regions regardless of their remoteness. The findings supported the model of memory consolidation, which proposes a permanent role of MTL during EAM retrieval (multiple‐trace theory or MTT) rather than a temporary role (standard model). Our present aim was to expand the results by examining the interactions between the MTL and neocortical regions (or MTL–neocortical links) during EAM retrieval with varying retention intervals. We used an experimental paradigm specially designed to engage aged participants in the recollection of EAMs, extracted from five different time‐periods, covering their whole life‐span, in order to examine correlations between activation in the MTL and neocortical regions. The nature of the memories was checked at debriefing by means of behavioral measures to control the degree of episodicity and properties of memories. Targeted correlational analyses carried out on the MTL, frontal, lateral temporal, and posterior regions revealed strong links between the MTL and neocortex during the retrieval of both recent and remote EAMs, challenging the standard model of memory consolidation and supporting MTT instead. Further confirmation was given by results showing that activation in the left and right hippocampi significantly correlated during the retrieval of both recent and remote memories. Correlations among extra‐MTL neocortical regions also emerged for all time‐periods, confirming the critical role of the prefrontal, temporal (lateral temporal cortex and temporal pole), precuneus, and posterior cingulate regions in EAM retrieval. Overall, this paper emphasizes the role of a bilateral network of MTL and neocortical areas whose activation correlate during the recollection of rich phenomenological recent and remote EAMs. © 2009 Wiley‐Liss, Inc.     

Psychogenic Memory Deficits Associated with Functional Cerebral Changes: An fMRI Study

We studied a case of psychogenic amnesia by means of a functional magnetic resonance imaging (fMRI) experiment involving the retrieval of autobiographical memories. The 38-year-old patient was unable to access most of her autobiographical memories from her childhood up to 16 years of age. Compared with the forgotten period, evocation of the normally retrieved memories elicited increased activity in medial temporal and dorso–lateral frontal regions. Evocation of the preserved scattered recollections was associated with bilaterally distributed temporo-parieto-occipital loci of activations. These functional changes seem to support the idea of common mechanisms involved in both organic and psychogenic amnesias.     

New views on old memories: re-evaluating the role of the hippocampal complex.

Evidence of temporally graded retrograde amnesia (RA) following hippocampal damage has fuelled the long-standing belief that memory undergoes a consolidation process, whereby memories are progressively modified in neocortical regions until they are independent of the hippocampal (HPC) complex. Support for this position derives from both the animal and human RA literature, although the results are not consistent. Specifically, consolidation theory does not account for loss of episodic (detail) information in humans and context-dependent information in animals, which often extend back for much of the life span. We discuss an alternative approach, the Multiple Trace Theory, which suggests that the HPC complex contributes to the retrieval of recent and remote episodic and context-dependent memories. According to this view, such memory traces are represented as spatially distributed interactions between the HPC and neocortex that persist for as long as those memories exist. On the other hand, semantic, or context-free, memories can become independent of the HPC as consolidation theory predicts. In support of this view, we report recent accounts of relatively flat RA gradients in autobiographical and spatial detail loss in patients and animal models with extensive bilateral HPC lesions. By comparison, temporally graded RA was observed in tests of semantic and context-free memory. We also report neuroimaging studies in which hippocampal activity, elicited during recollection of autobiographical memories, did not distinguish recent from remote episodes. Our discussion suggests ways to reconcile discrepancies in the literature and guide predictions of the occurrence of flat versus temporally limited gradients of remote episodic and semantic memory loss following lesions to HPC.     

The medial temporal lobes distinguish between within‐item and item‐context relations during autobiographical memory retrieval

During autobiographical memory retrieval, the medial temporal lobes (MTL) relate together multiple event elements, including object (within‐item relations) and context (item‐context relations) information, to create a cohesive memory. There is consistent support for a functional specialization within the MTL according to these relational processes, much of which comes from recognition memory experiments. In this study, we compared brain activation patterns associated with retrieving within‐item relations (i.e., associating conceptual and sensory‐perceptual object features) and item‐context relations (i.e., spatial relations among objects) with respect to naturalistic autobiographical retrieval. We developed a novel paradigm that cued participants to retrieve information about past autobiographical events, non‐episodic within‐item relations, and non‐episodic item‐context relations with the perceptuomotor aspects of retrieval equated across these conditions. We used multivariate analysis techniques to extract common and distinct patterns of activity among these conditions within the MTL and across the whole brain, both in terms of spatial and temporal patterns of activity. The anterior MTL (perirhinal cortex and anterior hippocampus) was preferentially recruited for generating within‐item relations later in retrieval whereas the posterior MTL (posterior parahippocampal cortex and posterior hippocampus) was preferentially recruited for generating item‐context relations across the retrieval phase. These findings provide novel evidence for functional specialization within the MTL with respect to naturalistic memory retrieval. © 2015 Wiley Periodicals, Inc.     

Common and unique neural activations in autobiographical, episodic, and semantic retrieval

This study sought to explore the neural correlates that underlie autobiographical, episodic, and semantic memory. Autobiographical memory was defined as the conscious recollection of personally relevant events, episodic memory as the recall of stimuli presented in the laboratory, and semantic memory as the retrieval of factual information and general knowledge about the world. Our objective was to delineate common neural activations, reflecting a functional overlap, and unique neural activations, reflecting functional dissociation of these memory processes. We conducted an event-related functional magnetic resonance imaging study in which we utilized the same pictorial stimuli but manipulated retrieval demands to extract autobiographical, episodic, or semantic memories. The results show a functional overlap of the three types of memory retrieval in the inferior frontal gyrus, the middle frontal gyrus, the caudate nucleus, the thalamus, and the lingual gyrus. All memory conditions yielded activation of the left medial-temporal lobe; however, we found a functional dissociation within this region. The anterior and superior areas were active in episodic and semantic retrieval, whereas more posterior and inferior areas were active in autobiographical retrieval. Unique activations for each memory type were also delineated, including medial frontal increases for autobiographical, right middle frontal increases for episodic, and right inferior temporal increases for semantic retrieval. These findings suggest a common neural network underlying all declarative memory retrieval, as well as unique neural contributions reflecting the specific properties of retrieved memories.     

Topographical, autobiographical and semantic memory in a patient with bilateral mesial temporal and retrosplenial infarction

According to Consolidation Theory (Squire, 1992, Psychological Review, 99, 195; Squire & Alvarez, 1995, Current Opinion in Neurobiology, 5, 169), the mesial temporal lobes have a time-limited role in the maintenance, storage and retrieval of retrograde declarative memories, such that they are not necessary for recalling remote memories. In contrast, proponents of the Multiple Trace Theory (Fuji, Moscovitch, & Nadel, 2000, Handbook of neuropsychology, 2nd ed., p 223, Amsterdam, New York: Elsevier; Nadel & Moscovitch, 1999, Current Opinion in Neurobiology, 7, 217) posit that the mesial temporal lobe (MTL) is necessary for remembering detailed autobiographical and topographical material from all time periods. A third theory of hippocampal function, the Cognitive Map Theory (O'Keefe & Nadel, 1978, The hippocampus as a cognitive map. Oxford: Clarendon), states that the hippocampus is involved in the processing of allocentric spatial representations. The precise role of the MTL in remote memory has been difficult to elucidate, as the majority of studies present cases with widespread brain damage that often occurred many years prior to testing. We investigated retrograde autobiographical, semantic and topographical memories in a subject (SG) who had recently sustained infarctions confined to the MTL and retrosplenial region bilaterally. Inconsistent with the predictions of Cognitive Map Theory, memory for spatial maps that were learned in the past was preserved. Additional testing indicated that SG suffered from a landmark agnosia, which affected remotely and recently acquired information equally. SG was also poor at imagining which direction he would have to turn his body to move from one landmark to another. In accordance with Consolidation Theory, SG performed similarly to control subjects for remote time periods on various measures of retrograde autobiographical memory and demonstrated intact knowledge regarding famous faces and vocabulary terms that were acquired in the past. In contrast, memory for remote public events was impaired. The current findings indicate that the mesial temporal and/or retrosplenial regions have little role to play in memory for remotely acquired spatial maps, autobiographical memories, famous faces or vocabulary terms. However, the findings for landmark naming, directional calculations between landmarks and knowledge of public events suggest that the MTL and/or retrosplenial cortices remain important for accessing these types of memories indefinitely.     

Reliving lifelong episodic autobiographical memories via the hippocampus: a correlative resting PET study in healthy middle-aged subjects

We aimed at identifying the cerebral structures whose synaptic function subserves the recollection of lifetime's episodic autobiographical memory (AM) via autonoetic consciousness. Twelve healthy middle-aged subjects (mean age: 59 years +/- 2.5) underwent a specially designed cognitive test to assess the ability to relive richly detailed episodic autobiographical memories from five time periods using the Remember/Know procedure. We computed an index of episodicity (number of Remember responses justified by the recall of specific events and details) and an index of retrieval spontaneity, and additionally an index of semanticized memories (number of Know responses). The regional cerebral blood flow (rCBF) was measured in the resting state, with H(2)O(15) as part of an activation PET study. The indexes were correlated with blood flow using volumes of interest in frontotemporal regions, including hippocampus and voxel-wise analyses in SPM. With both analyses, significant correlations were mainly found between the index of episodicity and rCBF in the medial temporal lobe, including hippocampus, across the five time periods (unlike the index of semanticized memories) and between the spontaneity index and rCBF in the prefrontal areas. These results highlight, in healthy subjects, the distinct role of these two structures in AM retrieval and support the view that the hippocampus is needed for reexperiencing detailed episodic memories no matter how old they are.     

The medial temporal lobe functional connectivity patterns associated with forming different mental representations

The medial temporal lobes (MTL), and more specifically the hippocampus, are critical for forming mental representations of past experiences—autobiographical memories—and for forming other “nonexperienced” types of mental representations, such as imagined scenarios. How the MTL coordinate with other brain areas to create these different types of representations is not well understood. To address this issue, we performed a task‐based functional connectivity analysis on a previously published dataset in which fMRI data were collected as participants created different types of mental representations under three conditions. One condition required forming and relating together details from a past event (autobiographical task), another required forming and relating together details of a spatial context (spatial task) and another condition required relating together conceptual/perceptual features of an object (conceptual task). We contrasted the connectivity patterns associated with a functionally defined region in the parahippocampal cortex (PHC) and anatomically defined anterior and posterior hippocampal segments across these tasks. Examining PHC connectivity patterns revealed that the PHC seed was distinctly connected to other MTL structures during the autobiographical task, to posterior parietal regions during the spatial task and to a distributed network of regions for the conceptual task. Examining hippocampal connectivity patterns revealed that the anterior hippocampus was preferentially connected to regions of default mode network during the autobiographical task and to areas implicated in semantic processing for the conceptual task whereas the posterior hippocampus was preferentially connected to medial‐posterior regions of the brain during the spatial task. We interpret our findings as evidence that there are MTL‐guided networks for forming distinct types of mental representations that align with functional distinctions within the hippocampus.