The Role of the Hippocampus in Long-Term Memory: Is It Memory Store or Comparator?

Abstract

Several attempts have been made to reconcile a number of rival theories on the role of the hippocampus in long-term memory. Those attempts fail to explain the basic effects of the theories from the same point of view. We are reviewing the four major theories, and shall demonstrate, with the use of mathematical models of attention and memory, that only one theory is capable of reconciling all of them by explaining the basic effects of each theory in a unified fashion, without altogether sacrificing their individual contributions. The key issue here is whether or not a memory trace is ever stored in the hippocampus itself, and there is no reconciliation unless the answer to that question is that there is not. As a result of the reconciliation that we are proposing, there is a simple solution to several outstanding problems concerning the neurobiology of memory such as: consolidation and reconsolidation, persistency of long term memory, novelty detection, habituation, long-term potentiation, and the multifrequency oscillatory self-organization of the brain.

Extracellular Matrix Remodeling Alleviates Memory Deficits in Alzheimer's Disease by Enhancing the Astrocytic Autophagy‐Lysosome Pathway

“…[ 49 ] Specifically, the mPFC is predominantly associated with short‐term memory functions, such as working memory, [ 50,51 ] whereas long‐term memory formation is primarily attributed to the hippocampus. [ 52,53 ] Our results are consistent with previous studies demonstrating that ECM remodeling enhances neuroplasticity and short‐term memory. [ 54,55 ] Furthermore, our study revealed that ChABC treatment did not lead to an improvement in spatial memory among 9‐month‐old AD mice.…”

Extracellular Matrix Remodeling Alleviates Memory Deficits in Alzheimer's Disease by Enhancing the Astrocytic Autophagy‐Lysosome Pathway

“…[ 49 ] Specifically, the mPFC is predominantly associated with short‐term memory functions, such as working memory, [ 50,51 ] whereas long‐term memory formation is primarily attributed to the hippocampus. [ 52,53 ] Our results are consistent with previous studies demonstrating that ECM remodeling enhances neuroplasticity and short‐term memory. [ 54,55 ] Furthermore, our study revealed that ChABC treatment did not lead to an improvement in spatial memory among 9‐month‐old AD mice.…”

Ketamine attenuates habenula activity in response to aversive outcomes during Pavlovian learning

“…We used a Pavlovian aversive conditioning paradigm shown to be a reliable probe of the Hb circuitry in humans 13,14 ; however, this approach lacks behavioural choice during learning, and successful learning must instead be inferred from participants’ subsequent choices in a preference test. This preference test was administered approximately half an hour after the corresponding learning blocks, a delay that likely increases reliance on hippocampal long-term memory systems 39,40 . We observed that participants who had reduced habenula activity, more common in the ketamine group ( Figure 3A ), were more likely to prefer fractals associated with pain ( Figure 3B ).…”

Impaired ILK Function Is Associated with Deficits in Hippocampal Based Memory and Synaptic Plasticity in a FASD Rat Model

“…Prenatal exposure to alcohol can also produce severe to moderate damage to hippocampal neurons [ 46 ]. The hippocampus is considered to be the ‘sorting region’ of the brain, categorizing inputs from other parts of the brain and beginning the process of storage of information into long- and short-term memory [ 47 ]. The Schaffer collateral pathway (CA3 to CA1) of the hippocampus plays an integral role in memory formation; therefore, any change in protein expression or interaction at the CA1 region could lead to memory impairments [ 48 ].…”

Extracellular Matrix Remodeling Alleviates Memory Deficits in Alzheimer's Disease by Enhancing the Astrocytic Autophagy‐Lysosome Pathway

“…[ 49 ] Specifically, the mPFC is predominantly associated with short‐term memory functions, such as working memory, [ 50,51 ] whereas long‐term memory formation is primarily attributed to the hippocampus. [ 52,53 ] Our results are consistent with previous studies demonstrating that ECM remodeling enhances neuroplasticity and short‐term memory. [ 54,55 ] Furthermore, our study revealed that ChABC treatment did not lead to an improvement in spatial memory among 9‐month‐old AD mice.…”

Ketamine attenuates habenula activity in response to aversive outcomes during Pavlovian learning

“…We used a Pavlovian aversive conditioning paradigm shown to be a reliable probe of the Hb circuitry in humans 13,14 ; however, this approach lacks behavioural choice during learning, and successful learning must instead be inferred from participants’ subsequent choices in a preference test. This preference test was administered approximately half an hour after the corresponding learning blocks, a delay that likely increases reliance on hippocampal long-term memory systems 39,40 . We observed that participants who had reduced habenula activity, more common in the ketamine group ( Figure 3A ), were more likely to prefer fractals associated with pain ( Figure 3B ).…”

Impaired ILK Function Is Associated with Deficits in Hippocampal Based Memory and Synaptic Plasticity in a FASD Rat Model

“…Prenatal exposure to alcohol can also produce severe to moderate damage to hippocampal neurons [ 46 ]. The hippocampus is considered to be the ‘sorting region’ of the brain, categorizing inputs from other parts of the brain and beginning the process of storage of information into long- and short-term memory [ 47 ]. The Schaffer collateral pathway (CA3 to CA1) of the hippocampus plays an integral role in memory formation; therefore, any change in protein expression or interaction at the CA1 region could lead to memory impairments [ 48 ].…”

Extracellular Matrix Remodeling Alleviates Memory Deficits in Alzheimer's Disease by Enhancing the Astrocytic Autophagy‐Lysosome Pathway

“…[ 49 ] Specifically, the mPFC is predominantly associated with short‐term memory functions, such as working memory, [ 50,51 ] whereas long‐term memory formation is primarily attributed to the hippocampus. [ 52,53 ] Our results are consistent with previous studies demonstrating that ECM remodeling enhances neuroplasticity and short‐term memory. [ 54,55 ] Furthermore, our study revealed that ChABC treatment did not lead to an improvement in spatial memory among 9‐month‐old AD mice.…”

Ketamine attenuates habenula activity in response to aversive outcomes during Pavlovian learning

“…We used a Pavlovian aversive conditioning paradigm shown to be a reliable probe of the Hb circuitry in humans 13,14 ; however, this approach lacks behavioural choice during learning, and successful learning must instead be inferred from participants’ subsequent choices in a preference test. This preference test was administered approximately half an hour after the corresponding learning blocks, a delay that likely increases reliance on hippocampal long-term memory systems 39,40 . We observed that participants who had reduced habenula activity, more common in the ketamine group ( Figure 3A ), were more likely to prefer fractals associated with pain ( Figure 3B ).…”

Impaired ILK Function Is Associated with Deficits in Hippocampal Based Memory and Synaptic Plasticity in a FASD Rat Model

“…Prenatal exposure to alcohol can also produce severe to moderate damage to hippocampal neurons [ 46 ]. The hippocampus is considered to be the ‘sorting region’ of the brain, categorizing inputs from other parts of the brain and beginning the process of storage of information into long- and short-term memory [ 47 ]. The Schaffer collateral pathway (CA3 to CA1) of the hippocampus plays an integral role in memory formation; therefore, any change in protein expression or interaction at the CA1 region could lead to memory impairments [ 48 ].…”