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Learning & memory

9/11/2001

Where were you on the following day?

Your 10th birthday? What did you do?

Do you remember when you had an accident? How did it happen?

Can you remember a Skill you used to do well that you don't anymore?

Phenomenon:

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Themes of the Learning and Memory

(tensions)(1) Involuntary vs voluntary (unconscious - conscious, procedural - declarative, implicit - explicit , incidental - intentional, automatic- controlled)

(2) functional mapping to neurophysiological processes

(3) representation (i.e., content) in the brain (MEMORY)

(4) relation between acquiring and accessing information (encoding-retrieval) LEARNING

(5) constraints on memory (e.g., duration, capacity/size, physiological)

(6) memory system or systems?

1. Associationism

●Began as a theory about how ideas combine in the mind by John Locke

●John Locke (1632-1704) was an Enlightenment philosopher. An Englishman, Locke's notions of "government with the consent of the governed" and man's natural rights (life, liberty, and estate) lead to the American revolution.

●Locke was one of the British Empiricists, which also included David Hume and George Berkeley. This group of philosophers maintained

● born without innate capabilities—tabula rasa—blank slate.● Representations as result of experiences-- learning● Mind is a mirror of representations of nature● Naturalism--Rousseau● Simple processes (study of animals)

empirical methodology begun by the associationists kept its stronghold, and before the end of the nineteenth century experiments were conducted in areas such as memory (Ebbinghaus) and Animal Learning (Pavlov, Thorndike) (early 20th )

2. Reductionism• More complex concepts result from simpler concepts:

• Red apple == Red + apple

• Simple associations lead to more complex associations

• Laws of more basic sciences can be used to explain less basic

– Physics can explain chemistry– Biology can explain psychology etc..

2. Reductionism• More complex concepts result from simpler concepts:

• Red apple == Red + apple

• Simple associations lead to more complex associations

• Laws of more basic sciences can be used to explain less basic

– Physics can explain chemistry– Biology can explain psychology etc..

3.Mechanistic

• The world as a big “machine”.

• The machine could be grasped by human experience

• Empiricism maintained that different areas of knowledge were independent, hence ethics could not explain physics, physics could not explain politics

• Segregation of knowledge sped progress in each field.

Hume and causality

• Causality is "the cement of the universe"

• All we observe is one billard bill hitting another and the second moving. "This is the whole that appears to the outward senses. The mind feels no sentiment or inward impression from this succession of objects: Consequently, there is not, in any single, particular instance of cause and effect, anything which can suggest the idea of power or necessary connexion."

• Hume maintained that we cannot differientiate between true causal connections and contiguity in space and time. In effect for the observer there is no difference.

Michotte 1970 (causality)

• Dr.Hanson and the “two cups of coffee”

•What has been causing that?

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• Flash Demo:

• http://cogweb.ucla.edu/Discourse/Narrative/michotte-demo.swf

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Learning & memory

“Knowing that”

Vs.

“Knowing how”

Gilbert Ryle, Oxford philosopher of mind, 1949

● Using process to classify memories (e.g., observational, associative,rational)

● Using content to classify memory (e.g., sensory vs motor memory)● Immediate vs permanent retention

(STM / LTM) –W. James reports Ebbinghaus's resultsas reflecting a short-term and long-term memories

Ebbinghaus: The Psychology of Learning (1913) Chapter II

http://www.us.archive.org/GnuBook/?id=psychologyoflear00meumrich#61

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Serial position curve: Primacy and recency effects (Ebbinghaus)

Primacy

Recency

LTM

STM

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Delayed recall with an interference task destroys recency

Primacy effect

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Explanation

• Primacy effect – Due to lack of interference when memorizing the first part of the list.

• Recency effect – The last couple of words are remembered because they are still in working memory

● Elements comprising memory

● Constructive character of remembering

● Consciousness in memory (beyond behaviorism)

Bartlett: Remembering (1932) http://www.ppsis.cam.ac.uk/bartlett/TheoryOfRemembering.htm

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Rapid consolidation: synaptic mechanisms

Three overlapping time courses for consolidation proposed by McGaugh

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MEMORY MODEL – ATKINSON & SHIFFRIN (1968)

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Visuospatial sketchpad

• Closely related to visual imagery

• Used to encode nonverbal visual and spatial information.

• Disrupted by performing additional visuospatial tasks, eye movement, or irrelevant visual material (Baddley 1992)

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The sketchpad has separate visual and spatial-sequential components

• Dellasala 1999 – Visual and spatial components

Corsi block tapping Visual patterns test

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Parts of the phonological loop

• Inner ear

• Inner voice

• Limited by recording length

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Evidence for Phonological Loop

• Phonological similarity effect:– BBGTCD is harder to memorize than FKYWMR

• Wordlength effect: easier to remember short wordsthen long words..

– Pay,wit,bar,hop,sum vs. helicopter, university, television, alligator,opportunity

• Subvocal articulation, auditory noise, interferes with verbal memory

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Central executive

• Attentional control

– Making changes to practiced routine. (Example: Altering driving to work routine when there is a traffic accident)

• Dividing attention

– Multitasking• Switching attention from one task to another

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Current model

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Current model

Networks: AssociationismJames, 1890

Actual Neural Networks

Activation Models: Mclelland & Rummelhart (1980)Grossberg, 1978Jack Cowan, 1971

DEMO

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Prefrontal cortex, consciousness and working memory

Different types of working memory

In his seminal work on working memory, Baddeley proposed that there were differing types of working memory: a visuospatial sketchpad for visual inputs and a phonological loop for sound-based inputs.

Neuroimaging studies have shown differing brain areas for visual and verbal working memory processes, with the DL-PFC (D) interacting with Broca’s area (B), a phonological loop (P) and with the frontal eye fields (F).

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Prefrontal cortex, consciousness and working memory

Combining prefrontal and MTL regions for working memory

One view of visual working memory suggests that the hippocampus may encode working memory items that are novel, the wider MTL may combine them with other modalities, and the inferior temporal (IT) area is involved with high-level visual object representation.

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Memory and Learning

Memory can be defined as a lasting representation that is reflected in thought, experience, or behavior.

Learning is the acquisition of such representations -- involving a wide range of brain areas and activities.

Memory storage is believed to involve widespread synaptic alterations in cortex.

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Memory and Learning

Memory can be defined as a lasting representation that is reflected in thought, experience, or behavior.

Learning is the acquisition of such representations -- involving a wide range of brain areas and activities.

Memory storage is believed to involve widespread synaptic alterations in cortex.

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The MTL encodes information across sensory domains such as smell, vision, and touch.

The MTL is a highly interactive crossroads, well-placed for integrating multiple brain inputs, and for coordinating learning and retrieval in many parts of the cortex. It is a ‘hub of hubs’.

H. M. B.Milner1960s, M.N.I.

Important brain structures in the study of memory are the cortex and the medial temporal lobes (MTL), which contain the two hippocampi and their surrounding tissue.

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High-resolution MPRAGE

32 channel coil, 3T Trio 0.38x0.38x1mm MPRAGE (ipat x 2, 10 min acq time, 112 slices), Seven acquisitions were motion-corrected and averaged. Beautiful contrast & anatomic

detail is present, including thalamic nuclei, claustrum, tiny perforating vessels

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Medial temporal lobe memory systemMedial temporal lobe memory system

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The limbic system:Memory & emotion

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Medial temporal lobe memory systemMedial temporal lobe memory system

Courtesy of S. Heckers (J N Trans, 2002)

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High-resolution MR imagingHigh-resolution MR imaging7 Tesla ex vivo7 Tesla ex vivo

Courtesy of Jean Augustinack & Bruce Fischl

100-150um resolution

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Penfield and Olds 1940s

Electrically evoked autobiographical memories

For more than 50 years, neurosurgeons have reported that awake patients report vivid, specific conscious recollections during temporal lobe stimulation.

Electrode grids are typically placed on the surface of the temporal lobe and areas are systematically stimulated and the patient’s reported memories are noted.

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Learning & memory

What task would you use to show differential hippocampal activation?(When is the hippocampus “off”? And when is it “on”?)

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Functional MRI ParadigmFunctional MRI ParadigmScene encoding (block design)

+ +

+ ++Novel NovelRepeated Repeated

Adapted from C.E. Stern et al., PNAS, 1996

5s 40s 25s

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Learning & memory: Novelty

Stern CE, PNAS 1996

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Learning & memory: Single Events

Brewer J, Science 1998; Wagner A, Science 1998

During scanning of medial temporal lobe and frontal lobe regions, subjects viewed complex, color photographs. Subjects later received a test of memory for the photos. The magnitudes of focal activations in right prefrontal cortex and in bilateral parahippocampal cortex predicted

which photographs were later remembered well, remembered less

well, or forgotten.

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Learning & memory: Frontal lobe & episodic memory

Brewer J, Science 1998; Wagner A, Science 1998

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Varieties of memory

Memory is not unitary: the Schacter-Tulving classification of memory types

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StriatumThe grouping formed by thecaudate nucleus (orange) and the putamen (green)is called the striatum. It constitutes the major target for the cortical afferents of the basal ganglia. The efferents from the basal ganglia to the thalamus arise in the globus pallidus. The part of the ventrolateral nucleus of the thalamus that then projects to Area 6 is called "pars oralis" and usually designated by the symbol VLo.

The other structures of the basal ganglia form various internal loops that modulate the activity of the main loop, in which information passes through the following brain structures in succession: cortex – striatum – globus pallidus – VLo – cortex (supplementary motor area, or SMA).

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Striatum:Basal Ganglia

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The Striatum and Implicit Memory

• Two elements of basal ganglia Striatum– Caudate nucleus – Putamen

• Rodent Recordings and Lesions in the Striatum– Lesions to striatum: Disrupts procedural memory (classical

conditioning/implicit) – Damaged hippocampal system: Degraded performance on

standard maze task-spatial memory.. (Operant conditioning/explicit)

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EBAY and Overbidding.

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Multiple memory systems

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Systems for LearningMost of what has been presented has been cortical processes for memory, but there are other kinds of memory and brain areas that have not been discussed:

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CATEGORY AND CONCEPTS

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Complexity— and the threshold for implicit learning..

Categorization and Learning

Depending on how complex the rulesAre to learn.. the more the memory system tends towards implicit encoding/learning.

Bruner Goodnow & Austin (1956) RULE Learning

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Concepts & Categories: Bruner Goodnow & Austin, (1956)

If striped must be square;if square must be striped

If striped must be square;if ~striped then any

Concepts & Categories: Bruner Goodnow & Austin, (1956)

Polymorphy: Pigeons & Humans

Human Subjects take 10 time longer to learn then simple disjunctionand never seem to be able to articulate a RULE—instead discussfamily resemblance, similarity etc.. Concept appears Implict.

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Spared functions in amnesia: implicit / procedural learning and memory

A way to investigate implicit and explicit learning was developed by Knowlton and colleagues. The patterns on the cards ‘predict’ either rainy or sunny weather with an 80% probability. Healthy individuals implicitly extract the rules in this weather task before they are aware of them explicitly.

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Spared functions in amnesia: implicit / procedural learning and memorySpared functions in PD: Explicit Learning

Amnesia patients perform as well as the controls in the early trials that involve implicit rule extraction, but perform worse in the later trials when explicit rule learning is involved.

PD patients perform poorly implicit—early trials, but eventually learn “rule”.

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The Striatum and Procedural Memory

• Amnesic-- poor in Explicit memory

• PD-- poor in Implicit memory

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How does (explicit) memory work?

• MTL-- both episodic and semantic (declarative) information—whats the relationship?

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The sight of a coffee cup activates visual cortex up to the level of object perception

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Memory storage: MTL coordinates widespread memory traces throughout cortex

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When the episodic memory -- the sight of the coffee cup -- is cued the following day, MTL is once again involved in retrieving and organizing widespread memory traces

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Varieties of memory

Episodic and semantic memory: ‘Remembering’ versus ‘knowing’

Remembering autobiographical episodes involves an active reconstruction of the original (conscious) episode

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Varieties of memory

Episodic and semantic memory: ‘Remembering’ versus ‘knowing’

Knowing semantic memories does not require active reconstruction of the original episode, it is assessed by a ‘feeling of knowing’.

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Varieties of memory

Episodic memories may turn into semantic memories over time

A model for how semantic and episodic memories may be related: semantic memories may be the cortical residue of many episodic memories.

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Consolidation: interaction between the medial temporal lobes and cortex

Two kinds of consolidation are thought to exist: cellular and systems consolidation. Both are evoked by activation of the MTL and cortex.

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Sleep promotes memory consolidation.

More later.

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LTM modulating factors

• Long term memory modulating factors improves all performance except for recency (eg Sumby 1963)

– Slower list presentation– More familiar words

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Atkinson and Shiffrin (1968)

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Atkinson and Shiffrin (1968)

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Problems with Atkinson and Shiffrin

• Model says STS required for entry into LTS– A neurological patient with defective short term memory

(as measured by digit span) showed normal long term learning. (Shallice and Warrington 1970)

• Model says length of time in STS determines likelihood of LTM storage– Length of time in STM does not necessarily result in

transfer to LTM. Depth of processing is more important (Craik and Tulving 1975)

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The Temporal Lobes and Deficits

• The Diencephalon and Memory Processing

– Korsakoff’s Syndrome• Symptoms: Confusion, confabulations, severe memory

impairment, and apathy

– Alcoholics: Develop thiamin deficiency • Leads to symptoms: Abnormal eye movements, loss of

coordination, tremors

– Treatment: Supplemental thiamin • Thiamin deficiency: Structural brain damage

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Prefrontal InteractionsShort Term/Working Memory

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Prefrontal cortex, consciousness and working memory

The delayed-match-to-sample task is widely used in studies investigating the role of the PFC in working memory.

In the classic experiment, a monkey is trained to delay responding to a stimulus (‘sample’, typically a red, blue, or white light). The monkey shows recognition of the stimulus after the delay by correctly pressing the light that matched the sample.

Neurons active during the delay period are shown in red at the bottom of the panel.

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Prefrontal cortex, consciousness and working memory

Working with memory: the frontal lobe works purposefully with memory

The prefrontal cortex (PFC) plays a critical role in working memory. The macaque monkey has been the primary experimental animal if many studies of working memory.

PFC in monkeys (top) and humans (bottom). The most common division is between upper and lower halves of the PFC, called the dorsolateral prefrontal cortex (DL-PFC, purple shading) and the ventrolateral prefrontal cortex (VL-PFC, green shading).

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Retrieval and metacognition

Metacognition is the ability to know our own cognitive functions, and to be able to use that knowledge. Many neurological patients who are severely impaired have no metacognitive insight that anything is wrong.

Healthy individuals use metacognition in memory retrieval. For example, semantic memories may be retrieved by using episodic cues and vice versa

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Retrieval and metacognition

Theta rhythms may coordinate memory retrieval: theta oscillations may coordinate MTL and the prefrontal lobe during retrieval

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Retrieval and metacognition

Hemispheric lateralization in retrieval

Do the two hemispheres play differing roles in memory encoding and retrieval?

Tulving and colleagues found that the left hemisphere showed greater activity in episodic learning (encoding), while the right hemisphere showed more activity in episodic retrieval.

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Learning & memory:Working memory & sleep deprivation

Drummond SP, Nature 2004

After full night sleep After sleep deprivation

N-back task

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Memories are made of this

Long-term potentiation and long-term depression: excitatory and inhibitory memory traces

These two processes are thought to occur in long-term potentiation (LTP) for excitatory cells and long-term depression (LTD) for inhibitory cells.

Recording from a cell in the hippocampus showing long lasting (90 minutes) activity in an excitatory cell (center).

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Coordination of the Brain FunctionsCoordination of the Brain Functions

Figure 9-19: The diffuse modulatory systems modulate brain function