Memories Flashcards
(31 cards)
Entorhinal cortex
EC is the main interface between the hippocampus and cortex. EC-hippocampus system plays important role in autobiographical/declarative/episodic memories and in particular spatial memories including memory formation, memory consolidation, and memory optimization in sleep.
Dentate gyrus
Part of the hippocampal formation. Thought to contribute to the formation of new memories, as well as possessing other functional roles.
Perirhinal cortex
Cortical region in the medial temporal lobe that is made up of Brodmann areas 35 and 36. Lesions to this area in monkeys and rats lead to the impairment of visual recognition memory/disruption of object-recognition abilities.
Posterior cingulate cortex
Imaging studies indicate that this area plays a prominent role in episodic memory retrieval.
Medial Temporal Circuitry
Areas belonging to the Hippocampus proper: Dentate Gyrus, CA3, CA1, and Subiculum. Adjacent MTL cortices: Entorhinal, perirhinal, parahippocampal. These interact with one another (see diagram in slides for more info)
Hippocampus
Found in the medial temporal lobe. Plays major role in consolidation of information from short-term to long term memory and spatial navigation.
EC-hippocampus system
Plays an important role in autobiographical/declarative/episodic memories and in particular spatial memories including memory formation, memory consolidation, and memory optimization in sleep.
Retrograde amnesia
Loss of access to memories that occurred, or information that was learned, before and injury. Often graded: very recent memories are more affected than ones from youth. “Ribot” gradient.
Anterograde amnesia
Loss of ability to create new memories after the event that caused the amnesia, while long-term memories from before the event remain intact. Irreversible.
“Ribot” gradient
States that there is a time gradient in retrograde amnesia, so that recent memories are more likely to be lost than more remote ones (look at diagram)
Case of HM
Patient whose hippocampus, parahippocampal gyrus, and amygdala were surgically removed to try to cure his epilepsy had severe anterograde amnesia.
Case of Clive Wearing
Contracted Herpesviral encephalitis - virus attacked hippocampus. Anterograde amnesia where memory only lasts between 7 and 30 seconds. Consciousness restarts every 20 seconds. Yet he still has procedural memory: he can play piano and conduct even though he has no recollection of his musical education.
Alzheimer’s Disease
Atrophy of the brain. Memory loss - difficulty in remembering recently learned facts/inability to acquire new information. Subtle problems with executive functions - attentiveness, planning, flexibility, abstract thinking, impairments in semantic memory - can also be symptoms of AD.
Korsakoff’s syndrome
Characterized by anterograde amnesia; during the late stages there is also retrograde. Caused by lack of thiamine in brain. Onset linked to chronic alcohol abuse and/or severe malnutrition, which causes damage to medial thalamus and hypothalamus; generalized cerebral atrophy.
Areas involved in memory coding
Medial Temporal Lobe - Different features are bound into an episodic representation.
Dorsolateral PFC - Organizes material to be remembered.
Ventrolateral PFC - Elaborative processing of MTL representations to ensure traces are distinct.
Areas involved in memory retrieval
MTL - Comparison of retrieval cue and stored representations using pattern completion.
Anterior PFC - Higher-level mnemonic control operations
Dorsolateral PFC - Monitoring and verification of retrieved information
Ventrolateral PFC - Strategic search of MTL stored representation; maintenance of retrieved information
Two kinds of memory
Long-term and short-term
Long-term has declarative/explicit and nondeclarative/implicit memory: focus on declarative in class.
Declarative memory concerns both events/episodic memory and facts/semantic memory.
Episodic memory
Memory for personally experienced events that occurred in particular place at specific time
Specific events - the first time doing something
General events - the general feeling of doing something, such as stepping into the ocean
Personal facts - biographical, etc
Flashbulb memories - critical autobiographical memories about a major event
Effects of lesions on episodic memory
- Large lesions of bilateral hippocampi, amygdala, rhinal cortex produce severe amnesia.
- Circumscribed lesions of CA1 of hippocampus produce anterograde amnesia.
- Korsakoff’s patients with diffuse damage to medial thalamus, hypothalamus show varied amnesia.
- Alzheimer’s patients show early signs of amnesia, with first lesions in Medial Temporal Lobe
Retrieval of episodic memories - neuroimaging
- Hippocampal activations during episodic encoding.
- Left frontal during encoding, right during retrieval
- Posterior cingulate/precuneus - successful retrieval of remembered episodes.
- Ventral parietal cortex - episodic memory retrieval tasks, such as old/new recognition memory tasks, consistently activate VPC
What different areas are basically responsible for (memory)
Medial Temporal regions - bind different components (temporarily)
Frontal areas control encoding and retrieval of memories
Posterior association areas store components of memories.
Semantic memory
A structured record of facts, concepts, and skills that we have acquired. General knowledge about world, without autobiographical context. Episodic memory can be thought of as a map that ties together items in semantic memory.
Effects of lesions on semantic memory
- Modality-specific visual agnosia after left temporal damage.
- Semantic dementia - failure to name objects, concepts, and people. Graded deterioration of knowledge
Semantic memory - neuroimaging
Activation in left inferior frontal, inferior temporal, temporal pole for semantic judgments to words and pictures
Left inferior temporal activations for animal and tool names, temporal pole for people naming
Activations may reflect the object’s interaction with the world - tool naming activates motor regions, for example.
