Kap. 7 - Memory Systems

What is the distinction between explicit memory and implicit memory?

Explicit memory

• Declarative memory

• “Ability to consciously remember and report facts, events, and associations”

  • Either:

    • Episodic

    • Semantic

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Implicit memory

• Non-declaraitve memory

• “Skills and habits that are learned but that are usually not consciously accessible”

• Revealed though performance (rather than recollection)

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Give some examples of episodic memory versus semantic memory.

Both are types of explicit memory!
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Episodic memory

• Allows people to recall past experiences, single events in specific places at specific times

  • What, where, when

  • Recognition:

    • Recollection vs familiarity

      • Tested with “Remember/know procedure”

      • Recollection

        • Conscious experience of remembering details

      • Familiarity

        • (Weak or strong) sense of having seen something or someone before

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Semantic memory

• Facts and knowledge that can be stated or recounted - learned though accumulation of information over time across repeated occasions

  • Either:

    • Procedural

    • Priming

    • Statistical

    • Contextual

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Amnesia

• Amnesic patients show greater impairments in episodic memory than in semantic memory - also in learning new information after lesion

What is procedural learning?

• Give an example.

• “The aquisition of skills and habits”

• Motor sequence learning

  • A task for studying procedural learning in the lab

  • Asking participants to quickly respond to a target that can appear in one of four different locations

• Amnesia

  • Capable of normal motor sequence learning - activate motor areas of the brain

  • E.g. - can improve in mirror tracing tasks

    • Proves separation between explicit and implicit memory!

What is priming?

Distinguish between different types of priming.

Priming

• “How a perception, response, or thought is enhanced by prior exposure to an identical or related stimulus, action, or idea”

• A form of implicit/non-declarative memory

• Amnesia:

  • Show normal priming - even if don’t recognize the repeated pictures as familiar/don’t remember having been tested before

…………………………………………………………………..

Repetition priming

• Priming that occurs because of direct repetition

  • Faster at recognizing and responding to repeated items than to new items

• Studied in naming task

  • Participants name a stimulus as quickly and accurately as possible

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Associative priming

• Priming that occur from related items (usually related in everyday life)

  • E.g. if presented with “nurse” before being asked to name a word starting with “d” - people are more likely to say “doctor”

• Studied naming task or lexical decision task

  • Latter: quickly judge whether a string of letters forms a word or not

    • e.g. “candy” or “curfy”

      • Make lexical decision more quickly if “candy” is preceded by “sweet” rather than “prickly”

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Perceptual priming

• Priming where “perception is improved by repeated exposure to perceptual features”

  • Perceptual features are shared, but no semantic ones:

    • E.g. seeing “cat” improves subsequent recognition of the word “cot”

  • fMRI shows: relies on perceptual brain areas

    • When same stimuli is repeated, fMRI shows less activity - indicating:

      • Processing now requires less effort (and therefore time)! - aka “Repetition suppression”

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Conceptual priming

• Priming where recognition is improved by semantic relations (shared meaning/categorization)

• Reveals how the meanings of stimuli are processed

  • E.g. seeing word “cat” improves subsequent recognition of the word “dog”

Describe an example of statistical learning and contextual cueing.

Statistical learning

• The brain calculates probabilities based on statistical regularities - temporal focus

• “Encodes statistical regularities, which help us function in the world by making it more predictable”

  • Statistical regularities

    • Meaningful patterns in the sights and sounds we experience daily

    • Stable and predictable features of an environment, object, or task

    • E.g. structure in language - a statistical regularity

      • Help us in learning languages!

      • E.g. sequential probabilities: “pri-tee-bay-bee”

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Contextual cueing

• An effect of statistical learning - specifically for visual/spatial features

• “Learning where to attend and what to expect based on statistical regularities“

• “Enables faster search of targets whose location or identity is predictable from surrounding context”

  • Brain “extracts” repeating spatial regularities in visual scenes to speed up and guide visual search

  • E.g. - faster search time for targets in repeated displays versus targets in novel displays

    • An implicit mechanism!

      • Observers aren’t aware that contexts were repeated and predictive of target locations

How do you test for the serial position curve, and what explains the primacy effect and the recency effect?

Serial position curve

• A U-shaped curve for memory performance according to serial position

• Evidence for distinction between STM and LTM

  • Primacy effect - LTM

    • Rehearsal time

  • Recency effect - STM

    • Close to the time of recall with minimal distraction

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Primacy effect

• Higher memory performance for the items at the beginning of the list

• Testing primacy and STM:

  • Interference added to end of the list (counting backwards)

    • Result: Poorly performance on the latter items in the list

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Recency effect

• Higher memory for the items toward the end of the list

What is reactivation in memory?

The act of remembering is to reactivate distributed records within the modality-specific or category-specific brain regions that were engaged during initial encoding

• LTM - Stored in neocortex

  • Neocortex: Outer layers of neurons forming the bulk of the human brain - same place where initial perception and processing of an experience happens

    • Entire cortex as a storage device for memories!

  • Processing of experiences leave a distributed code:

    • Experiences are multisensory and are initially processed in multiple cortical regions - where the code (record) will then be distributed

  • Episodic details in memories - also encoded i modality-specific areas

    • The brain mechanisms from the initial perception and cognitive experience are reactivated - they show patterns of activity similar to what occured during the initial encoding

Describe the roles of the hippocampal system and the neocortex in forming a complementary memory system?

Hippocampal system and neocortex work together to form new memories and make them accessible for later retrieval

• Hippocampal system - active during initial encoding

  • Damage to hippocampal structures —> Anterograde amnesia

  • First: Associates items and their contexts across different brain areas

    • e.g. contexts: time, space, characters etc.

  • Second: Binds all the features together so that they are all associated and can activate each other when any of the pieces are activated

    • i.e. so that activation of one feature is a cue for activation for the other pieces

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• Hippocampal system + medial temporal lobe - active during retrieval

  • Reactivating the pieces of information from around the cortex!

  • Hippocampal system - mainly active during memory retrieval of relatively new memories

    • Over time the connections in cortical regions are gradually strengthened to a point where cortical memory can be accessed without hippocampal involvement

      • H.M - hippocampal lesion —> anterograde amnesia:

        • Able to retrieve older memories - formed prior to the removal of hippocampus

          • i.e. - over time memories become encoded strongly in neocortical regions such that the hippocampus is no longer necessary to retrieve information

      • Lesions in some non-hippocampal, cortical regions —> Retrograd amnesia

        • Consistent with idea that memories are stored outside the hippocampus and medial temporal lobe regions

How does the subsequent memory paradigm work, and what does it tell us about how the brain encodes and retrieves memories?

What is the function of spatial memory?

Describe cognitive map theory.

Explain what place cells and grid cells are, and what role they play in spatial navigation and memory.

Give examples distinguishing an egocentric spatial framework from an allocentric spatial framework.