Constructive memory: the ghosts of past and future.
Explore the source record for details and available documents.
Amnesia↗
Biomedical subjects
Donna Rose Addis
Publications and source records attributed to Donna Rose Addis.
Remembering the past and imagining the future: common and distinct neural substrates during event construction and elaboration.
People can consciously re-experience past events and pre-experience possible future events. This fMRI study examined the neural regions mediating the construction and elaboration of past and future events. Participants were cued with a noun for 20s and instructed to construct a past or future event within a specified time period (week, year, 5-20 years). Once participants had the event in mind, they made a button press and for the remainder of the 20s elaborated on the event. Importantly, all events generated were episodic and did not differ on a number of phenomenological qualities (detail, emotionality, personal significance, field/observer perspective). Conjunction analyses indicated the left hippocampus was commonly engaged by past and future event construction, along with posterior visuospatial regions, but considerable neural differentiation was also observed during the construction phase. Future events recruited regions involved in prospective thinking and generation processes, specifically right frontopolar cortex and left ventrolateral prefrontal cortex, respectively. Furthermore, future event construction uniquely engaged the right hippocampus, possibly as a response to the novelty of these events. In contrast to the construction phase, elaboration was characterized by remarkable overlap in regions comprising the autobiographical memory retrieval network, attributable to the common processes engaged during elaboration, including self-referential processing, contextual and episodic imagery. This striking neural overlap is consistent with findings that amnesic patients exhibit deficits in both past and future thinking, and confirms that the episodic system contributes importantly to imagining the future.
Adolescent↗
Prefrontal and hippocampal contributions to the generation and binding of semantic associations during successful encoding.
The ability to form and bind associations between items is an important aspect of successful memory formation. We hypothesize that, during encoding, the left inferior frontal gyrus (IFG) supports generation of associations between items and the hippocampus then binds these associations. This study examined the parametric responses of these regions to varying amounts of generative and relational processing during successful encoding (i.e., for subsequently recognized items). Encoding involved presentation of word triads varying in the number of semantic associations among them (none, one or all); participants judged how many associations were present in each triad. Thus, triads with fewer associations had higher generative load while triads with more associations had higher relational load. Participants later completed a forced-choice recognition test for encoding triads. Successful encoding relative to a control task resulted in activation of bilateral IFG and left hippocampus, and the hippocampus also exhibited a significant subsequent memory effect (hits>misses). Linear parametric analyses revealed that generative load modulated activity in bilateral IFG while relational load correlated with activity in left hippocampus. Although univariate analyses distinguished IFG and hippocampal contributions to the generative and relational stages of encoding, respectively, effective connectivity between these regions did not differ according to condition. Furthermore, this analysis revealed that the left IFG played a pivotal role in coordinating associative encoding processes. Our findings illustrate that modulation of components in a memory network can be independent of patterns of mutual connectivity among those components in mediating successful encoding.
Adult↗
Functional neuroanatomy of remote episodic, semantic and spatial memory: a unified account based on multiple trace theory.
We review lesion and neuroimaging evidence on the role of the hippocampus, and other structures, in retention and retrieval of recent and remote memories. We examine episodic, semantic and spatial memory, and show that important distinctions exist among different types of these memories and the structures that mediate them. We argue that retention and retrieval of detailed, vivid autobiographical memories depend on the hippocampal system no matter how long ago they were acquired. Semantic memories, on the other hand, benefit from hippocampal contribution for some time before they can be retrieved independently of the hippocampus. Even semantic memories, however, can have episodic elements associated with them that continue to depend on the hippocampus. Likewise, we distinguish between experientially detailed spatial memories (akin to episodic memory) and more schematic memories (akin to semantic memory) that are sufficient for navigation but not for re-experiencing the environment in which they were acquired. Like their episodic and semantic counterparts, the former type of spatial memory is dependent on the hippocampus no matter how long ago it was acquired, whereas the latter can survive independently of the hippocampus and is represented in extra-hippocampal structures. In short, the evidence reviewed suggests strongly that the function of the hippocampus (and possibly that of related limbic structures) is to help encode, retain, and retrieve experiences, no matter how long ago the events comprising the experience occurred, and no matter whether the memories are episodic or spatial. We conclude that the evidence favours a multiple trace theory (MTT) of memory over two other models: (1) traditional consolidation models which posit that the hippocampus is a time-limited memory structure for all forms of memory; and (2) versions of cognitive map theory which posit that the hippocampus is needed for representing all forms of allocentric space in memory.
Amnesia↗
Recollective qualities modulate hippocampal activation during autobiographical memory retrieval.
Recent neuroimaging studies report preferential hippocampal engagement during autobiographical memory (AM) retrieval. Although the basis of this preferential activation remains unclear, it may be related to the temporal specificity, recency, or recollective qualities of AMs, such as detail, emotionality, and personal significance. Typically, however, these variables are confounded, and thus we sought to investigate the contributions of each to hippocampal activation during AM retrieval. We conducted an event-related functional magnetic resonance imaging (fMRI) study in which participants retrieved temporally specific AMs and general, repeated AMs, and rated each for level of detail, emotion, or personal significance. These ratings, as well as the recency of AMs, were used in parametric modulation analyses to identify brain regions that correlated positively with ratings, independent of recency, and vice versa. Retrieval of AMs activated a number of regions, including the hippocampus. No differences in hippocampal activation were evident between specific and general AM retrieval, suggesting that temporal specificity, on its own, is not a key modulator of hippocampal activation. Activation of the left hippocampus during specific AM retrieval did vary with the level of detail, personal significance, and at a subthreshold level, emotionality, when the effect of recency was covaried out. Further, during general AM retrieval, all three recollective qualities modulated activity in the right hippocampus. Although the recency of specific AMs modulated hippocampal activation bilaterally, this effect dissipated in the left hippocampus when detail or emotionality was included as a covariate, and was no longer present in either hippocampus when personal significance was taken into account. Our results suggest that recollective qualities are important predictors of hippocampal engagement during AM retrieval independent of factors such as recency. These findings are consistent with theories of hippocampal function that emphasize its role in the recollection of multifaceted autobiographical experiences.
Adult↗
Characterizing spatial and temporal features of autobiographical memory retrieval networks: a partial least squares approach.
Conway (Conway, M.A., 1992. A structural model of autobiographical memory. In: Conway, M.A., Spinnler, H., Wagenaar, W.A. (Eds.), Theoretical Perspectives on Autobiological Memory. Kluwer Academic Publishers, Dordrecht, The Netherlands, pp. 167-194) proposed that two types of autobiographical memories (AMs) exist within a hierarchical AM system: unique, specific events and repeated, general memories. There is little research on whether retrieval of these AMs relies on different neural substrates. To investigate this issue, we used a multivariate image analysis technique, spatiotemporal partial least squares (PLS), to identify distributed patterns of activity most related to AM tasks that we have found to be associated with a medial and left-lateralized network. Using PLS, specific and general memories were more strongly associated with different parts of this retrieval network. Specific AM retrieval was associated more with activation of regions involved in imagery in episodic memory, including the left precuneus, left superior parietal lobule and right cuneus, whereas general AM retrieval was associated with activation of the right inferior temporal gyrus, right medial frontal cortex, and left thalamus. These two patterns emerged at different lags after stimulus onset, with the general AM pattern peaking between 2 and 6 s, and the specific AM pattern between 6 and 8 s. These lag differences are consistent with Conway's theory which posits that general AMs are the preferred level of entry to the AM system. A seed PLS analysis revealed that the regions functionally connected to the hippocampus during retrieval did not differentiate specific from general AM retrieval, which confirms our earlier univariate analysis indicating that some aspects of the memory retrieval network are shared by these memories.
Adult↗
Memory of myself: autobiographical memory and identity in Alzheimer's disease.
A number of theories posit a relationship between autobiographical memory and identity. To test this we assessed the status of autobiographical memory and identity in 20 individuals with Alzheimer's disease (AD) and 20 age-matched controls, and investigated whether degree of autobiographical memory impairment was associated with changes in identity. Two tests of autobiographical memory (Autobiographical Memory Interview, autobiographical fluency) and two measures of identity (Twenty Statements Test, identity items of the Tennessee Self Concept Scale) were administered. AD participants exhibited significant impairments on both memory tests, and changes in the strength, quality, and direction of identity relative to controls. Impairments of some components of autobiographical memory, particularly autobiographical memory for childhood and early adulthood, were related to changes in the strength and quality of identity. These findings support the critical role of early adulthood autobiographical memories (16-25 years) in identity, and suggest autobiographical memory loss affects identity.
Adolescent↗