PS2111_Memory_L2_MemoryConsolidation.pptx

Memory Consolidation Dr. Kathleen Kang [email protected] Structure of Memory Lectures Lecture 1: Introduction Lecture 2: Memory Consolidation Lecture 3: Forgetting Memories Lecture 4: Emotional Memory PS2111- Information Processing and Cognition 2 Previously on Brain & Behaviour.... Memories are...

Memory Consolidation Dr. Kathleen Kang [email protected] Structure of Memory Lectures Lecture 1: Introduction Lecture 2: Memory Consolidation Lecture 3: Forgetting Memories Lecture 4: Emotional Memory PS2111- Information Processing and Cognition 2 Previously on Brain & Behaviour.... Memories are encoded as engrams, explained in terms of connections between neurons.. With repeated experience/practice, strength of connections increases  memory consolidation (less likely to be forgotten) For connections to be established, a period of consolidation following learning is critical Guskjolen & Cembrowski (2023) Learning Objectives By the end of this lecture, you will: 1. Define memory consolidation 2. Critically evaluate the different models of memory consolidation 3. Evaluate the evidence supporting the concept of reconsolidation 4. Describe the roles of the hippocampus What is memory consolidation? Nadel et al. (2012) Transformation of a temporary, labile memory into longer-lasting, stable form (Kandel et al., 2015) Determines what will be preserved and duration Preservation-consolidation hypothesis (Müller & Pilzecker, 1900) Memory traces are initially fragile but become more resistant to forgetting with time Interference at the initial stages should cause more forgetting than in the later stages Evidence for memory consolidation and interference Both groups showed better performance in the ‘unfilled’ condition (i.e., no interference) vs. ‘early’ and ‘mid’ interference condition Amnesic patients (MCI) retained more word list material during ‘late’ interference Severe forgetting in amnesia could Dewar et al. (2010 Memory consolidation and the Hippocampus Gazzaniga et al. (2019) Hippocampus is critical for early memory consolidation Synaptic consolidation - Long-term potentiation (LTP) Systems/Systemic consolidation – Standard consolidation theory, Multiple trace theory, Scene construction theory Key roles of the hippocampus Declarative memory Amnesia Represent relations among elements of memories spatially and temporally Spatial navigation “place cells” Support spatial navigation by path integration Eichenbaum & Cohen Key roles of the hippocampus According to the declarative memory view, the hippocampus: 1. Represents events based on the relationship between items 2. Represent episodes as flow of events across time 3. Interleave events and episodes Eichenbaum & Cohen Key roles of hippocampus In spatial memory, the hippocampus: 1. Encodes events as mapping of actions and objects within spatial contexts 2. Represents routes as sequences of places traversed 3. Connects spatial episodes to pre-existing semantic maps  Enable navigation through construction of novel routes based on stored spatial knowledge Both views can be reconciled if we extend hippocampal function to the organization of events in spatial and nonspatial contexts Eichenbaum & Cohen Synaptic consolidation Memory = result of strength of synaptic interactions among neurons Synaptic connections change depending on their activity Simultaneous activation of cells leads to pronounced increase in synaptic strength (Hebb, 1949) “Cells that fire together wire together” [Hebbian learning] Long-term potentiation (LTP) Activity-dependent increase in synaptic transmission Long-term depression (LTD) Activity-dependent decrease in synaptic transmission Trisynaptic circuit of hippocampal formation Schlichting & Preston (2017 Trisynaptic circuit of hippocampal formation 3 major cell groups: 1) Granule cells in dentate gyrus 2) Pyramidal cells in CA3 3) Pyramidal cells in CA1 Stimulating the axons of the perforant pathway Long-term increase in excitatory postsynaptic potentials (Bliss & Lømo, 1973) When axons stimulated again later, larger postsynaptic responses in the Hippocampal memory engrams and memory consolidation Transformation from short-term, labile memory to permanent memory requires synaptic consolidation Synaptic consolidation occurs at the molecular, structural and functional level preferentially in neurons engaged during learning Repeated internal representations of learning event (e.g., hippocampal replay) during "offline" periods drives consolidation Synaptic consolidation --> systems-level consolidation Guskjolen & Cembrowski (2023 Systems-Level Consolidation I: Standard consolidation theory (Squire & Alvarez, 1995) 1. Declarative memory initially encoded in hippocampalneocortical trace 2. Becomes stabilized through connectivity between neocortical modules Barry & Maguire (2019) 3. Original hippocampal trace no longer essential for memory reactivation Systems-Level Consolidation I: Evidence for Standard consolidation theory The hippocampal group performed worse when recalling news since the onset of amnesia and 1-5 years before amnesia Hippocampal group performed identical for events 11-30 years before amnesia  Hippocampus has a time-limited role  Connections among cortical regions are strengthened until it becomes independent of hippocampus Bayley et al. Systems-Level Consolidation I: Evidence against Standard consolidation theory Public events test Famous faces test Patient VC = decrease in hippocampal volume Performance on more remote events and famous faces (i.e., > 30 years) were also impaired Not consistent with the view that hippocampus is only critical for the retention of Cipolotti et al. (2001 recent events Systems-Level Consolidation II: Multiple trace/trace transformation theory Semantic (Nadel & Moscovitch, 1997) information Episodic information 1. Hippocampalneocortical trace is always needed 2. Repeated retrieval increases the number of permanent hippocampal traces (but traces are not Barry & Maguire (2019) 3. Intrinsic neocortical connectivity supports semantic memories Systems-Level Consolidation III: Scene construction theory 1. During recall, hippocampus constructs coherent scenes from this event via hippocampalneocortical 2. These scenes rapidly fade from the hippocampus as representations are consolidated in neocortex Barry & Maguire (2019) 3. With each recall, the neocortically consolidated elements are reconstructed into a new hippocampal trace Reconsolidation Reactivated fixed memory can become labile once again Can be changed in several ways Weakening/disruption Strengthening Alteration Memories must restabilize after reactivation = reconsolidation Nadel et al. Evidence for Reconsolidation Experiment 1 No-reminder group was more accurate for Set 2 objects than reminder group Memory reactivation of Set 1 objects makes it malleable Hupbach et al. Evidence for Reconsolidation Rats were presented with a single pairing of tone (CS) and foot-shock (US) Freezing = index of fear learning Influsion of anisomycin into lateral & basal nuclei of amygdala (LBA) or artificial CSF (ACSF) Anisomycin (after CS)  decrease in freezing (i.e., disruption of reconsolidation)  Consolidated fear memories can return to a labile state (destabilization) Nader et al. (200 Can reconsolidation/destabilization be targeted as a means of therapy? Kida (2019) Can reconsolidation/destabilization be targeted as a means of therapy? Fear-conditioning paradigm: CS1 trials: Spider (CS1) -> loud noise -> shock (US) CS2 trials: Spider (CS2) -> loud noise NA trials: Loud noise alone Propanolol = beta-blocker that acts on receptors in amygdala Nadolol = water-soluble drug Propanolol reduced startle amplitude of CS1 memory at memory reactivation and extinction, as compared to nadolol ​ locking reconsolidation via beta-adrenergic receptors in amygdala B neutralizes fear memory Kindt & Soeter Can reconsolidation/destabilization be targeted as a means of therapy? Decay process which degrades memory stored in hippocampus (Frankland & Josselyn, 2016) Ishikawa et al. (2016); Figure taken from Kida (2019) Core Reading Barry, D. N., & Maguire, E. A. (2019). Remote memory and the hippocampus: A constructive critique. Trends in Cognitive Sciences, 23(2), 128–142. https://doi.org/10.1016/j.tics.2018.11.005 Eichenbaum, H., & Cohen, N. J. (2014). Can we reconcile the declarative memory and spatial navigation views on hippocampal function? Neuron, 83(4), 764–770. https://doi.org/10.1016/j.neuron.2014.07.032 Hupbach, A., Gomez, R., & Nadel, L. (2009). Episodic memory reconsolidation: Updating or source confusion? Memory, 17(5), 502–510. https://doi.org/10.1080/09658210902882399 Nadel, L., Hupbach, A., Gomez, R., & Newman-Smith, K. (2012). Memory formation, consolidation and transformation. Neuroscience & Biobehavioral Reviews, 36(7), 1640–1645. https://doi.org/10.1016/j.neubiorev.2012.03.001 Nader, K., Schafe, G. E., & Le Doux, J. E. (2000). Fear memories require protein synthesis in the amygdala for reconsolidation after retrieval. Nature, 406(6797), 722–726. https://doi.org/10.1038/35021052 Other sources Bayley, P. J., Hopkins, R. O., & Squire, L. R. (2006). The fate of old memories after medial temporal lobe damage. The Journal of Neuroscience, 26(51), 13311–13317. https://doi.org/10.1523/JNEUROSCI.4262-06.2006 Cipolotti, L., Shallice, T., Chan, D., Fox, N., Scahill, R., Harrison, G., Stevens, J., & Rudge, P. (2001). Long-term retrograde amnesia… the crucial role of the hippocampus. Neuropsychologia, 39(2), 151–172. https://doi.org/10.1016/S0028-3932(00)00103-2 Dewar, M., Garcia, Y. F., Cowan, N., & Sala, S. D. (2009). Delaying interference enhances memory consolidation in amnesic patients. Neuropsychology, 23(5), 627–634. https://doi.org/10.1037/a0015568 Ishikawa, R., Hotaka, F., Frankland, P. W., & Satoshi, K. (2016). Hippocampal neurogenesis enhancers promote forgetting of remote fear memory after hippocampal reactivation by retrieval. https://doi.org/10.7554/eLife.17464 Kida, S. (2019). Reconsolidation/destabilization, extinction and forgetting of fear memory as therapeutic targets for PTSD. Psychopharmacology, 236(1), 49–57. https://doi.org/10.1007/s00213-018-5086-2 Kindt, M., & Soeter, M. (2018). Pharmacologically induced amnesia for learned fear is time and sleep dependent. Nature Communications, 9(1), 1316. https://doi.org/10.1038/s41467-018-03659-1 Nader, K., & Hardt, O. (2009). A single standard for memory: The case for reconsolidation. Nature Reviews Neuroscience, 10(3), 224–234. https://doi.org/10.1038/nrn2590 Schlichting, M. L., & Preston, A. R. (2017). The hippocampus and memory integration: Building knowledge to navigate future decisions. In D. E. Hannula & M. C. Duff (Eds.), The Hippocampus from Cells to Systems: Structure, Connectivity, and Functional Contributions to Memory and Flexible Cognition (pp. 405–437). Springer International Publishing. https://doi.org/10.1007/978-3-319-50406-3_13