Declarative and Non-Declarative Memory Quiz

Declarative and Non-Declarative Memory

• Declarative memory involves conscious recollection and can be expressed through language. It includes episodic and semantic memory.
• Non-declarative memory, on the other hand, does not involve conscious recollection and is often nonverbal. It includes procedural memory.

Lesion Evidence and Human Studies

• Patient H.M.: Bilateral removal of medial temporal lobes for epilepsy led to severe anterograde amnesia, impacting declarative memories. Retrograde memory was relatively intact.
• Patient K.C.: Damage to parahippocampal regions resulted in impaired anterograde and retrograde episodic memory, but semantic memory remained intact.
• General observation: Hippocampal damage selectively affects declarative memories, leaving procedural memory largely unaffected.

fMRI Studies and Human Spatial Memory

• Navigation studies: Accuracy in virtual navigation tasks correlates with hippocampal activation, particularly in the right hippocampus.
• Taxi drivers: Taxi drivers, requiring extensive spatial navigation, demonstrate larger hippocampal volumes, particularly in the posterior hippocampus. This volume difference correlates with the duration of their driving experience.

Hippocampal Role in Disease and Dementia

• Alzheimer's Disease (AD): AD is associated with damage to the temporal lobe, where the hippocampus is located. The presence of amyloid plaques begin in the hippocampus.

Rodent Studies on Spatial Learning and Memory

• Spatial tasks: Rodents are often used in tasks like finding a submerged platform to assess their ability to use external cues for spatial learning.
• Hippocampal lesions: Lesions in the rodent hippocampus impair spatial memory performance.
• In vivo recordings: Studies recording neuron activity in the hippocampus (place cells, grid cells, head-direction cells, border cells, etc.) during spatial tasks allow investigation of neural processes involved.
• Place Cells (CA1): Spatially modulated neurons firing at specific locations.
• Grid cells (entorhinal): Located in the cortex, they have neurons firing at the corners of a spatial grid.
• Nobel Prize (2014): Recognition for discoveries on hippocampal place cells and cortical grid cells, clarifying neural mechanisms of spatial memory.

Lashley's Experiments and Memory Encoding

• Engram research: Lashley's experiments on the effects of cortical lesions on spatial tasks suggested that the amount of damage, rather than location, correlated with poorer performance, implying a distributed nature of memory storage.

Memory Consolidation & Storage

• Short-term memory: Hippocampus plays a crucial role in short-term declarative memory.
• Long-term memory: Long term memories are stored in various cortical areas (visual, parietal, Wernicke's, temporal cortices). There is a strong connectivity between the hippocampus and the cortex essential to the process of memory consolidation.
• Non-declarative memory: Consolidation of non-declarative memories occurs in other brain regions such as the cerebellum, basal ganglia, premotor cortex, and other motor areas. The exact location of storage for non-declarative memory during short-term storage is unclear.