semantic memory

What is semantic memory a subset of?

Declarative memory

What is Semantic Memory?

General knowledge about the world

Abstracted from any one experience

(usually) shared with the community (because they are facts)

What provides evidence for the independence of episodic and semantic memory?

Dementia starting in the anterior frontal and temporal lobes initially presents as a pure semantic deficit, patients have intact episodic memory function and preform similar to controls on recall of episodic details

Interdependence of semantic and episodic memory

Due to the overlapping in our everyday lives older memories go semanticiztion, meaning older memories rely more on semantic information (e.g., as a child you remember lots of details about a vaction, but as you get older you remember year, location, ect)

What is the speed of semantic recall is informed by?

How semantic information is organized and the syntax of a given question. An example would be to name a fruit that starts with the letter P vs name a word that starts with p that is also a fruit

First question: we take all the words we know and filter for all the fruits, and then for which fruits start with p

Second question: look at all the words with p we know, then find the subset of fruit, much more to look through

what does recall for semantic facts vary depending on

Existing expertise, the more you know about a topic the easier it is to sort through the information you know to locate what you need to find

Hierarchical Network Model

Concepts are represented by nodes that are arranged in a hierarchical fashion. Each node is associated with multiple features. Features are shared by all items in sub nodes are stored in the superordinate node

The model predicts that T/F judgements are dependent on the nodal separation of objects and their associated properties

Areas in which the Hierarchical Network Models do not predict recall performance

Familiarity: Semantic judgements are significantly faster for items that are familiar rather than unfamiliar regardless of nodal distance

Typicality: Decisions about category membership depend on how representative the exemplar is of that category (ducks have wings but ostriches don’t)

Semantic Activation Theory

Concepts act as nodes that are linked together based on conceptual relatedness. Distances between nodes represent relatedness, when a concept is activated or “primed”, related concepts are also activated

semantic priming effect

a cognitive phenomenon where exposure to a related word (the "prime") speeds up the recognition or processing of a subsequent word (the "target") In class: showed a list of items that were related to coffee (but not actually the word coffee) (e.g., mug, hot, mug, cream, mocha) then hid the list and asked if the words: stairs, coffee, brown were present, Very quicky said no to stairs but hesitated on coffee and brown because our coffee schema was activated!

Limitations of the Semantic Activation Model

Too simple: everything is represented as a single node

Too rigid: does not account for individual differences in semantic relatedness or temporal differences (things a true for us at different points of our lives)

Tri-Level Categorization Theory

3 levels of categorization exist: Superordinate (least detailed) (e.g., animal), Basic (e.g., dog), and Subordinate (most detailed) (e.g., Australian Sheppard)

Individuals default to the “basic” category level when given freedom to categorize information

Tradeoffs exist between time and accuracy, with the basic categorization scheme being a good “middle ground”

Tri-Level orginization short comings

Studies of semantic categorization often present stimuli without any context. When context is introduced, categorization becomes much more varied and context-dependent

Experts prefer subordinate categorization when assessing stimuli within their domains of expertise

Individuals with semantic dementia rely solely on superordinate information when recreating stimuli

Concepts are Not Likely Stored in Our Brain as they Would be in an Encyclopedia

Conceptual knowledge is context-dependent

Conceptual knowledge is not stable within individuals

Conceptual knowledge is not stable across individuals

Grounded Cognition Theory

Grounded Cognition Theory posits that Concepts are not processed in Isolation. Identification of objects is significantly improved when they are shown in-context. Argues that goals influence conceptual representations

Grounded Cognition Theory challanges what other theory

spreading activation

Grounded Cognition Theory is Supported by the Existence of

Embodied cognition, it posits that conceptual processing uses the same neural resources as those for perception/action

Congruent movement/color pairs are more rapidly processed (doorbell and point, vs doorbell and grasp)

The Hub and Spoke Model

The anterior temporal lobe acts as a hub, connected to various sensory ”spokes”

Damage to the hub should impair semantic memory across modalities

Seen with semantic dementi

What Supports the Existence of Hub and Spoke Model?

Directly Activating Hub and Spoke Areas using Transcranial direct current stimulation (tDCS), tDCS focusing on the Anterior Temporal Lobe boosts semantic processes across all modalities, tDCS focusing on specific spoke areas boosts semantic processing in a modality-specific manner

Schemas Represent A Distinct Form Of Semantic information from

concepts, schemas are broad and abstract and contain semantic memory

Schemas must have

Associative structure (based on multiple experiences of one thing)

Basis in multiple episodes

Lack of unit detail (no specific details because we incorporate a large number of items into a schemas)

Adaptability

What areas of the brain process concept related processing vs schema related processing?

ATL vs pre frontal cortex

Do patients with semantic dementia have worse concept or scripts (schemas)

concepts

Do patients with PFC damage have worse concept or script

scripts

4 Types of Schemas

script, frame, stereotype, spatial

Processing of stereotypes is associated with

activation of unique frontal areas

what brain areas uniquely light up when thinking about unique social categoy judgments vs social stereotypes

Left inferior frontal gyrus and inferotemporal cortex, advanced frontal areas

Low scores on indexes measuring social prejudice are associated with increased recruitment o

frontal brain areas like the anterior cingulate cortex (ACC), and dorsolateral PFC → inhibitory actions towards midbrain to areas such as amygdala

Being aware of social stereotypes activates the frontal areas that "shuts up" our midbrain areas that are related to course emotional processing

Positive and Negative effects of schematic memory performance

Participants recall more schema-consistent stimuli and highly salient, schema-inconsistent information is also more likely to be recalled

BUT participants are also more likely to incorrectly recall the presence of schema-consistent items that were not present in a scene

Social media algorithms and schemas

Social media algorithm reinforces our schemas and therefore we do not attended schema incongruent information