Periodic Reporting for period 2 - MemUnited (Hippocampus unites Memory Systems by preserving Sequential Order)
Período documentado: 2024-06-01 hasta 2025-05-31
Memory is the fundamental human capacity that underlies our personality, mental life as well as our knowledge and motor skills that we use on a daily basis. Work with patient HM, beginning in the 1950s, established key principles on the organization of memory function in the human brain. This research revealed that a surgical procedure involving the removal of both hippocampi (performed to relieve HM from severe epilepsy) significantly impaired his ability to form new episodic memories, while his capacity to learn and remember new motor tasks remained intact. This seminal work introduced the idea of specialized memory systems that are functionally and anatomically independent. Declarative memory (including episodic and semantic memory) was identified as being dependent on the hippocampus, while non-declarative memory (such as procedural motor and perceptual memory) was considered independent of it. This dichotomy caused memory research to become fragmented, with studies on the neural mechanisms supporting declarative and procedural memories developing along separate lines. Nevertheless, recent evidence has led to a reassessment of this division by demonstrating that the hippocampus has roles extending beyond episodic memory. Accordingly, the current project proposes and tests an integrative framework that specifies the shared neural processes that support learning and memory across multiple memory systems.
At the conceptual level, the findings will offer the opportunity to reconsider the historical models of memory classification and develop more integrative views of memory organization in general and hippocampal functioning in particular. Over the last decades our understanding about the hippocampal contribution to learning and memory has greatly increased. The proposed research will reveal to what extent hippocampal coding principles also apply to the domain of procedural learning and therefore greatly advance the field of fundamental research in learning and memory. At the applicative level, my findings will contribute to the development of integrative treatments of both procedural and declarative memory deficits.
At the conceptual level, the findings will offer the opportunity to reconsider the historical models of memory classification and develop more integrative views of memory organization in general and hippocampal functioning in particular. Over the last decades our understanding about the hippocampal contribution to learning and memory has greatly increased. The proposed research will reveal to what extent hippocampal coding principles also apply to the domain of procedural learning and therefore greatly advance the field of fundamental research in learning and memory. At the applicative level, my findings will contribute to the development of integrative treatments of both procedural and declarative memory deficits.
During the fellowship, significant progress was made in understanding the shared neural processes supporting learning and memory across multiple memory systems. Functional MRI (fMRI) and behavioral data were collected from 25 young adults to investigate the role of the hippocampus in the encoding and consolidation of temporal order information in declarative and procedural memory systems. To investigate the role of the hippocampus during encoding, fMRI data were acquired while participants learned sequences of finger movements (procedural learning) as well as sequences of objects (declarative learning). Multivariate pattern analyses (MVPA) performed on the encoding data demonstrated the hippocampus’s role in representing sequential information across memory domains. Results were presented at the Society for Cognitive Neuroscience and Society for Neuroscience conferences, with a manuscripts currently in preparation. The neural mechanisms underlying sequence memory consolidation were examined during rest periods after sequence learning. By applying multivariate decoding techniques on the resting-state fMRI data, we detected fast replay events as ordered activation of sequential fMRI patterns. The analyses revealed evidence of hippocampal replay of task-related sequences after learning, with a faster reactivation rate compared to domain-specific regions. These findings were also presented at major conferences, with a publication in progress. In summary, the project achieved substantial advancements in the understanding of hippocampal involvement in memory processes.
Decades ago, research in rodents has shown that hippocampal representations of spatial locations are reactivated sequentially during rest periods after learning. This sequential reactivation is related to better memory consolidation. By applying multivariate decoding techniques on fMRI data acquired in humans, we were able in this project to detect fast replay events as ordered activation of sequential fMRI pattern. Such sequential replay was detected both after procedural and declarative learning. The current results show that hippocampal reactivation mechanisms extend beyond the declarative memory domain and also apply to the domain of procedural learning. The publication of the results in international peer-reviewed journal (two manuscripts in preparation) will therefore greatly advance the field of fundamental research in learning and memory.