Cognitive Neuroscience Exam 3

What is learning in terms of changes in the brain?

Experiences and neural connectivity

Sensory Memory

• Brief retention of sensory information

• Lasts milliseconds

Echoic

Verbal

Iconic

Vision

Short-Term Memory

• memory for information currently “in mind”;

• ~15 seconds without rehearsal

• Limited capacity (5-9 items)

Long-Term Memory

• Stored information that need not be presently accessed or even consciously accessible

• Virtually unlimited capacity & duration

Memory processes

• Encoding

• Storage

• Consolidation

• Retrieval

Encoding

Processing of incoming information and experiences

Storage

Permanent record resulting from the acquisition and maintenance of information

Consolidation 

The process by which memory representations are stored over time

Retrieval

Utilization of stored info to create a conscious representation or to execute a learned behavior

Types of amnesia

Anterograde amnesia and retrograde amnesia

Anterograde amnesia

Difficulties in acquiring new memories

Retrograde amnesia

Difficulties remembering events from before the brain injury

Baddeley & Warrington (1970) study

2 groups of patients: Korsakoff’s (anterograde) vs control

STM & LTM task: immediate free recall of words

Findings: Controls – primacy & recency effects; Korsakoff’s – just recency effects

No primacy effects

Normal STS cannot transfer to LTS

STM only task: given 3 letters, prevent rehearsal, recall after asking them to count backwards from three

Findings: No difference in performance between the 2 groups

STM Intact

Transfer to LTM impaired

Primacy

LTM/most rehearsal

First words

Recency

STM/least interference

Final word

Double dissociations

STM impaired & LTM intact

K.F. – (Warrington & Shallice, 1969)

damage in L perisylvian cortex

Reduced digit span (STM) and intact LTM when learning word pairs

E.E. (Markowitsch et al., 1999)

tumor in left angular gyrus

Impaired STM ability but preserved LTM after surgery

Working memory

Capacity to hold and manipulate information in conscious attention while carrying out tasks

• “pay” attention

• Inhibiting task-irrelevant information

• Maintenance & Manipulation of information

Baddeley and Hitch’s Model of Working Memory

Phonological loop

Verbal short-term memory

Broca’s & Wernicke’s Areas

Visual spatial sketchpad

STM for visual or special info

Occipital Visual Areas

Episodic buffer

A temporary storage system that integrates information; integrates the other two types

Parietal areas

Central executive

refreshes information for rehearsal and manipulates it

Prefrontal Cortex

How to measure working memory

Complex span task: Encoding of memory items alternates with processing episodes

Declarative Memory

Semantic and Episodic Memory

Semantic Memory

Knowledge of general concepts, not specific to time or place

-Objective knowledge that doesn’t include the context in which it was learned

Episodic Memory

Remembering prior events includes context

-Special kind of awareness

Non-declaritive memory

Priming and Procedural Memory

Procedural Memory

Memory for how to perform different actions and skills

Implicit Memory

retrieval without awareness

tests: memory for past experience without requiring conscious access to the past

Explicit Memory

retrieval with awareness

Tests: require conscious recollection of a previous experience → impaired in amnesia

Fragment completion task

Repetition Priming

produce more completed fragments for words that were on the study list

How do people with amnesia do on implicit vs explicit tasks?

INTACT fragment completion

IMPAIRED on EXPLICIT task

What is the pattern of memory deficits typically like in amnesia (spared vs impaired) for procedural memory?

HM

•Severe epilepsy, treated with surgery to bilaterally remove (parts of) the medial temporal lobes

•Moderate retrograde amnesia with temporal gradient (events 1-2 years before surgery)

Deficits

• Complete loss of episodic learning

  • Events/people since the operation

• Semantic learning deficits

  • Language is essentially frozen in the 50s

• Unimpaired STM

• •Anterograde amnesia - since the lesion

  • Suggests encoding deficit

• Temporally graded retrograde amnesia – before the lesion

Procedural Memory in HM and implicit memory

Intact procedural memory

Can learn new motor tasks

Temporally graded retrograde amnesia

Before the lesion

Role of hippocampus in memory formation

Forms new memories (explicitly episodic)

Evidence from amnesia and the role of the hippocampus in memory formation

H.M. – parts of the hippocampus remained, but there was atrophy

R.B. – anterograde amnesia less severe than H.M.

-Damage restricted to CA1 pyramidal cells of each hippocampus

Evidence from Alzheimer’s Dementia (AD) and the role of the hippocampus in memory formation

Hippocampus deteriorates more rapidly than in typical aging

Amyloid Plaques

sticky buildup of protein fragments (beta-amyloids) outside cells

Neurofibrillary tangles

tangles of protein fibers inside cells

• protein tau

• Forms part of a microtubule, which helps transport nutrients in a nerve cell

What is the role of the hippocampus in AD?

It deteriorates more rapidly than in typical aging

Evidence from nonhuman primates & rodents and the role of the hippocampus in forming new memories

Surgical lesions to different regions of the MTL of monkeys (Zola et al.)

• Lesions to the amygdala didn’t impair learning on task

• Lesions to the hippocampus & parahippocampal & perirhinal cortices produced learning/memory deficits

Similar findings in rodents

What does damage to the TEMPORAL LOBE produce?

Loss of semantic memory, even with intact ability to acquire episodic memories

What is temporally graded retrograde amnesia?

Consolidation

The process by which moment-to-moment changes in brain activity are translated into permanent structural changes in the brain

Role of hippocampus in consolidation

• Rapid, initial storage of episodic & semantic memories in the hippocampus

  • Synaptic consolidation

  • Lasts hours to days

Role of temporal lobes in consolidation

• Can take years

  • Slowly transferred & replaced by permanent memory trace in the neocortex

• Both semantic & episodic memory become independent of the hippocampus

Standard Consolidation Theory

Multiple Trace Theory of Consolidation

Anterograde loss

New information isn’t consolidated

Retrograde amnesia using consolidation

Assume that old memories were not fully consolidated at the time of injury

Years or decades for system consolidation

Temporal gradient amnesia

Newer memories are more vulnerable than older memories

Why would a consolidation deficit affect declarative (or episodic) memory in particular?

What is reconsolidation?

a 2nd consolidation process that involved the re-storage of a memory after retrieval

• Can “update” a memory if new information is available at the time of reconsolidation

• Vulnerable to disruption

Long-term Potentiation

Initial Consolidation: Memory is a result of changes in the strength of synapses (LTP)

•Strengthening of synapses after recent activity

•Produce long-lasting (but not permanent) increases in signal between two neurons

Early LTP

Increased sensitivity of the synapse

Lasts for hours

The same stimulation produces a bigger response

Late LTP

Requires new gene transcription & mRNA translation

Can last for days

Changes in gene expression/receptors

NMDA receptors play a crucial role in many brain pathways

Perineuronal Nets

scaffolds of linked proteins & sugars

specialized extracellular matrix structures responsible for synaptic stabilization in the adult brain

Levels of Analysis

• Computational

• Representational

• Implementational

Computational

Description of language input, output, & processing (cognitive, linguistic)

Representational

Mental representations of the input & how used to produce the output (cognitive)

Implementational

Physical processes (neuroscience)

Purpose of Language

Communication

Characteristics of Language

• Displacement

• Productivity

• Arbitrary

• Discrete

Displacement

can communicate about things not physically present

Productivity

creative – new words & sentences

Arbitrary

no relationship between the signal and the thing it represents

Discrete

language signals are distinct

Basic Components of Language

• Semantics

• Syntax

• Phonology

• Pragmatics

• Morphology

Semantics

the meaning of words and sentences

Syntax

rules for the arrangement of words in a sentence or phrase

Phonology

the sound pattern of language

Pragmatics

how language is used in a social context

Morphology

Four subtasks involved in understanding spoken message

• Phonology

• Morphology/Semantics

• Syntax

• Semantics & pragmatics

Phonemes

distinctive sounds in a given language

ie. /R/ /l/ read _ lead

Allophones

variants of the same phoneme

ie. Pot vs. Spot: [p h ] vs. [P] → both /p/ in English

Free morphemes

can stand alone as words.

ie. Cat, run, pretty

Bound morphemes

must combine with other morphemes to form a word

ie. UN – unzip, RE - do

Inflectional morphology

Constraints on changing a word given its grammatical role in a sentence.

ie. N plural: stem + -s.

Cat + -s = cats.

The mental Lexicon

A mental store of information about words

- Semantics

- Syntactic information

- Word Form

Lexical Access

output of perceptual analysis activates information in LTM about a word (form, meaning, syntax)

Lexical Selection

the stage in which the representation that best matches the input is identified/selected

Lexical Integration

words are integrated into a full sentence, discourse, or larger context to understand the whole message

What area of the brain is associated with phoneme processing

Left inferior frontal gyrus

What area of the brain is associated with semantics

Anterior temportal lobe

How do we recognize spoken words

first, formulate the abstract message and then have to SELECT the lexical semantics

How is Semantics Organized in the Brain

Semantic Memory

Semantic memory

our conceptual knowledge of the world, the meaning of words & objects, and factual knowledge

Amodal

independent of input or output modality

How are similar items grouped according to this theory?

Some categories (e.g. animals) are represented differently in the brain because they possess features (e.g. movement) that are not possessed by other categories (e.g. inanimate objects)

Those with similar features are stored near each other

What determines category membership?

Some categories (e.g. animals) are represented differently by the brain because they are a special category

(e.g. innate endowment of neural resources)

Emergent categories