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Flashcards in Episodic & semantic memoryGluck Deck (17)
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1

Agnosia

Disruption in the ability to process a particular information
o Associative visual agnosia: Damage to inferior temporal lobe (loss of ability to recognize & name objects)
o Auditory agnosia: Damage to Superior temporal lobe (do not understand the meaning of a word)
o Tactile agnosia: Damage in the parietal lobe- Recognize objects by description, not by touch

2

patient HM

removed hippocampus

result: Anterograde amnesia= Inability to form new episodic and semantic memories
o Personality remains unchanged
o Awareness of his problems
o As long as attention is paid to a task, performance is good- Turning attention to something else deletes information

3

hippocampal region 6 memory in animals

Animals with lesions of the hippocampal region have difficulty learning new information

4

Hippocampal function in the healthy brain

 Encoding of information, retaining information, Retrieving information

o Differing activity during learning for words that will be remembered and the ones that will be forgotten (stronger activity for words that will be remembered)
o Left medial temporal lobe more active during learning of words
o Bilateral medial temporal lobe activity for learning of pictures

 Hippocampus is important in encoding the ‘What- happened-Where’ Aspect of episodic memory

5

Hippocampus is important in encoding the ‘What- happened-Where’ Aspect of episodic memory

o More activity in hippocampus when source & word/ item are recalled together instead of only the word
o Binding together memory of objects with unique spatial & temporal context
o Difference in hippocampal activity for real memory and false memory
 Medial temporal lobe as the only place in the brain that can distinguish between true
episodic memories and false ones

6

Retrograde amnesia=

Loss of memories for events that occurred before the injury

7

Ribot gradient

Having lost memory that formed just before an injury while maintaining memory of
months or years earlier

8

Standard consolidation theory

= hippocampus & related medial temporal lobe structures initially required for episodic memory storage &
retrieval but contribution diminishes over time until cortex can retrieve memory without hippocampal help
o Episodic memory consists of components stored in different areas of the cortex
o Initially, all components are linked together via the hippocampus into a single memory
o Over time (consolidation), components form direct connections with each other and therefore don’t need hippocampal mediation
+Can account for graded retrograde amnesia

Problem:
It does not explain well how some patients have retrograde memory loss that extends as far back as childhood

9

Multiple memory trace theory

=Episodic memories are encoded and ensemble of hippocampal and cortical neurons and the cortical neurons never become fully independent of hippocampal neurons
o Over time, more connections accumulate, memories are partially spared if hippocampal damage occurs  Semantic memory spared even when episodic memory is lost
o Some people have retrograde amnesia extending into childhood
 Degree of retrograde amnesia in patients could also reflect the amount of damage done to the hippocampus and surrounding areas

10

The Role of the Frontal Cortex in Memory Storage and Retrieval

- Left frontal lobe activity is also increases during exposure to verbal information that is later remembered than during exposure to information that is later forgotten
- The frontal cortex determines what we store, and therefore remember (attention, judgment, cognitive control)

Prefrontal cortex suppresses hippocampal activity, inhibiting storage and retrieval of unwanted memories
- Study by Anderson: Directed forgetting

The PFC may also help to bind contextual information with event memory (Encode What, Where, When)
o Frontal lobe damage leads to greater source amnesia

11

Subcortical Structures involved in Episodic and Semantic Memory

 Parts of the diencephalon and basal forebrain connect to the hippocampus via the fornix: Damage to one of the three can lead to anterograde amnesia

12

Diencephalon:

Helps guiding consolidation- Diencephalic structures may be responsible for the interaction between frontal cortex and the hippocampus during memory storage and consolidation

13

Korsakoff’s disease

deficiency in thiamine
o Damage to mammillary bodies & mediodorsal nucleus of the thalamus
o These people develop the same kind of anterograde amnesia and time- graded retrograde amnesia as H.M.
o Confabulation: They report untrue memories, but believe they are true  without frontal help, one might confuse what memory is recent and what is old and therefore not applicable

14

Basal forebrain

Helps determining what the hippocampus stores

- Basal forebrain nuclei send Ach and GABA to the hippocampus affecting the plasticity of hippocampal neurons, which helps to determine how likely the hippocampus is to store information
- Basal forebrain may signal the hippocampus to turn attention to processing and encoding incoming information

o If there is damage, the hippocampus might fail to encode the relevant information as there are no instructions from the basal forebrain

15

Confabulation during conjoint damage of basal forebrain & frontal cortex

o Basal forebrain damage: unable to store new memories, so they cannot remember but retrieve a plausible answer
o Frontal cortex: Inability to determine whether the retrieved information is old or new

16

Proactive interference

previously aquired information intereferes with new learning

old disrupts new

17

Retroactive Interference

recently aquired infor interferes with old memory
new disrupts old