9.03/9.031
11/10/99 and 11/15/99
Corkin
Noneclarative Memory
Priming, Perceptual Learning, and Emotional Learning
Questions
Why can't amnesic patients make use of priming to assist themselves in recognizing that items are familiar?
Where in the brain does priming occur?
Are visuoperceptual priming and conceptual priming dissociable?
What is perceptual learning?
Where in the brain does perceptual learning occur?
Where are emotional memories stored?
Instructions are Important
Priming
Use this three-letter stem to form the first word that comes to mind.
Recognition
Use this three-letter cue to remember a recently presented word.
Where in the brain does priming occur?
Priming occurs within the same cortical visual pathways that ordinarily participate in perceiving and processing visual information.
Perceptual Learning
An improvement in the ability to discriminate simple perceptual attributes, such as tones or line orientations, simply as the result of performing the discriminations repeatedly.
Evidence for Specificity of Learning
• No transfer to opposite half-field or to untrained quadrant on trained side
• No transfer from horizontal to vertical orientation of background elements
• No transfer to other eye
Where Are Emotional Memories Stored?
Two Possibilities Are:
• The neuronal changes that represent learned fear or some other arousing emotion take place in the neurons of cortical areas (including the perirhinal and insular cortices) that project to the amygdala. The amygdala is the structure through which these changes are integrated and broadcast to other brain areas.
• The amygdala stores information about positive and negative learned emotional responses. If so, it is likely that only the emotional component of the memory is stored there. Other components, such as the memory of what should be done with the emotional situation repeats itself, are probably stored elsewhere.
Memory for Skills, Habits, and Conditioning
Questions
What is habit learning?
Does habit learning describe a class of nondeclarative learning abilities in humans?
Can humans learn associations between stimuli and responses independently of the medial temporal lobe and diencephalic brain regions?
What are the neural substrates for motor learning?
What kind of memory underlies the ability to acquire knowledge about categories?
Where does category learning of visual stimuli take place?
What brain structures are essential for delay conditioning?
What brain structures are essential for trace conditioning?
What aspect of trace conditioning requires the hippocampus?
Is awareness a prerequisite for successful trace conditioning?
What is Habit Learning?
• Habit learning is a process by which stimuli become connected to responses by reinforcement, and information is acquired gradually across many trials.
• Habit learning differs from the type of associative learning that is impaired after lesions of the hippocampal region, which is specialized for rapid acquisition, often in a single trial.
Motor Skills
• Learned skills are embedded in procedures, which can be expressed through performance.
• They are not declarative: One does not need to "declare" anything, and one may not be able, even when pressed, to say very much about what one is doing.
• Indeed, experience shows that trying to express conscious knowledge about a motor skill while performing it is a good way to impair its execution.
Where Is the Memory Trace of a
Motor Skill Ultimately Stored?
Two Hypotheses
• Memory storage occurs within the areas of motor cortex that are engaged during practice.
• The essential synaptic changes occur in the connections from the cortex to the neostriatum.
Which Brain Systems Are Important During Motor Skill Learning? (Petersen/PET)
Early in Learning
Prefrontal cortex: storing information for temporary use
Posterior parietal cortex: visual attention
Cerebellum: coordination and timing
After Practice with the Skill
Motor cortex: storage and execution of skilled movements
Supplementary motor area: storage and execution of skilled movements
Learning the Sugar Production Task
• An individual learns a cognitive skill, which at least in its early stages involves developing a feel for how to do the task.
• The individual does not actually memorize facts about the task but rather develops a general sense or intuition about how to proceed.
• This process in nondeclarative.
• Learning is not accompanied by awareness about how to solve the problem.
• Learning does not require the brain system that supports declarative memory (MTL structures).
What Kind of Memory Underlies the Ability to Acquire
Knowledge about Categories?
• Aspects of category knowledge can develop in the absence of any detectable memory for the training items.
• The brain system supporting the ability to categorize must operate in parallel with, and independently of, the brain system that supports declarative memory.
• Even when the declarative memory system is inoperative, such that specific items do not persist as individual memories, it is still possible to build up a record of what all the items have in common, to discover and hold onto the regularities that exist among a group of items.
How Does the Brain Retain
Knowledge of Categories?
A Hypothesis
• When we encounter visual items like the dot patterns, the circuitry of the visual cortex gradually changes.
• These changes in the cortex are a cumulation of the moment-to-moment synaptic changes laid successively on one another.
• In this way, at any particular moment the pattern of synaptic change provides a running average of cumulative visual experience.
• This running average would correspond to what all the visual items have in common; that is, it would record the category to which the items belonged.
Where Does Category Learning
of Visual Stimuli Take Place?
• Neural activity appears to decrease either when we see a stimulus a second time, as in priming, or when we see a stimulus that is similar to one presented recently, as in category learning.
• Category learning of visual stimuli probably takes place largely in cortical areas that are dedicated to visual information processing.
• Perceptual and cognitive skill learning, as well as category learning, are cases in which the sensory processing stations themselves change, so as to benefit from the specific perceptual experiences that have occurred in the recent past.
Why are Cerebellar Purkinje Cells Important?
• Each Purkinje cell receives input form many different parallel fibers and from only one climbing fiber.
• The Purkinje neurons themselves are important because they are the sole source of output from the cerebellar cortex.
• They exit the cerebellar cortex to synapse on nuclei deep in the cerebellum, including the interpositus nucleus.
Where is the Memory Trace
for Classical Conditioning
Formed and Stored?
Lesions
• Small lesions of the interpositus nucleus (1 mm3) completely and permanently prevent a rabbit from learning the eyeblink CR.
• The same lesion also completely and permanently abolishes retention of a CR that had already been established.
Electrical Stimulation
• Climbing fibers can be stimulated to evoke an eyeblink (substitute for the airpuff).
• Mossy fiber stimulation can serve as a CS (substitute for the tone).
• When climbing fiber and mossy fiber stimulation are paired, mossy fiber stimulation itself comes to evoke an eyeblink. That is, behavior conditioning occurs.
What Aspect of Trace Conditioning Requires the Hippocampus?
Why Does Trace Conditioning Involve Declarative Memory?
Delay Conditioning vs. Trace Conditioning
Delay Conditioning
Depends on the cerebellum
Trace Conditioning
Depends on the cerebellum and the hippocampus
Learning Capacity Critical Brain System
Priming Perceptual circuits of the cortex
Perceptual learning Perceptual circuits of the cortex
Emotional memory Amygdala
Skill learning Neostriatum
Habit learning Neostriatum
Classical conditioning Cerebellum
of motor responses