Lecture 2

Question 1

CORTICAL REORGANIZATION

Answer 1

The brain reorganizes its inputs and local circuits through out the course of learning.

Question 2

Vision Puppy Test

Answer 2

Visual system in dogs test-
Covered eyes of young puppies- when sensory input of eyes eliminated, the cortex changed
Spines not as desne, less synaptic connections, - saw that brain was reacting
It was believed that changes could occur only during critical peroids after birth- not true- now we know that local circuits can be altered and remodeleld in the adultu brain

Can be naturally occurins, rxn to injury, and as a result of experiences

Question 3

Plasticity in Individual Neurons Detected Through

Answer 3

Increase in neuronal excitability
Dendritic arborization
Increase in spine density
Increase in synapses

Question 4

How to create long lasting synaptic connections

Answer 4

Repetition of a task
Initial use of lots of cortex
Eventual use of less cortex to execute task

Question 5

Long-term Potentiation

Answer 5

Silent receptors lack glutamate receptors
Stimulation of glutamate-NMDA receptors causes slient glutamate-AMPA receptors to bind with the membrane, making them available for binding
Shape of spines changes
Gene expression increases with increased Ca++

Question 6

Motor Evoked Potentials

Answer 6

• stimulate brain and see what parts of body move

Question 7

Mereznich’s Cortical Map

Answer 7

Electrophysiological mapping-
Put in hundreds of electro into sensory cortex of monkey brain
Stimulate body part- and expect to see evoked potential in a particular area of brain

Question 8

Neural Plasticity

Answer 8

“Brain Plasticity” is the brain’s ability to adaptively revise its processing machinery through out life.

Brain change underlies perceptual, cognitive and motor skill learning - and unlearning.

Question 9

Who developed concept of brain plasticity

Answer 9

Micheal Mereznich

Question 10

Negative Plasticity

Answer 10

Negative plasticity as a contribution to age-related cognitive and motor decline and its impact on the decline of function in ageing
- focal dystonia

Question 11

Mereznich’s Digital Amputation

Answer 11

Amputated 3rd finger of monkey
62 days later mapped monkey and saw reorganization
Cortical area for 2 and 4 expanded bc of no 3rd finger

Question 12

Mereznich’s Digital Syndactly

Answer 12

Sewed 3 and 4 finger together in a monkey
3-4 months of fuse- darkened area
Because they no longer had these clear boundaries
Brain change in response to a lack of input
Brain is changing due to dsorder

Question 13

Mereznich Differential Stimulation Training Task

Answer 13

Rotation disc- monkey had to keep finger on
If he didn’t put enough force the would not get food
Did it for 5 months
Dramatic expansion in cortical area devoted to receiving stimulating
Area increased in side since it has a lot

Question 14

Mereznich Differential Stimulation Training Task Results and Findings

Answer 14

1. There was about a three-fold increase in the cortical representation of the distal parts of these digits.
2. These were adult monkeys
3. The plasticity and reorganization is associated with activity and training

Question 15

Timing and Neuroplasticity

Answer 15

Not only do we make memory traces of the spatial aspects of stimulatory inputs – but we also make traces of the timing of the tactile stimuli.

Inputs that engage cortical neurons nearly simultaneously are integrated in cortical neuronal representations.

Inputs that are active synchronously are represented together

Question 16

Mereznich Finger tap

Answer 16

Stimulate monkey all together on every finger, distally and proximally
For 4-6 weeks 300x a day
Contorlled timing of stimuli

Now represented by two large zones
Red proximal
Orange distal

Structure of representation change
The neurons now had receptive fields that spanned the stimulated surfaces – more than one finger - no longer distinct columns

In other words the spatial properties of the neuronal receptive fields came to reflect the temporal patterning of the stimulation during training.

Question 17

Focal Dystonia

Answer 17

of negative plasticity- focal dystonia- of negative plasticity- focal dystonia- piano players, music – when they have to move fingers repetitively – because of changes in neuronal based on constant stimulation

Question 18

Nudo Monkey Digit Training/ Pronation

Answer 18

Randy Nudo and Jeff Klein- had a device with openings the monkey had to reach through- openings would get smaller and smaller cups so they had to develop skill
Trained three monkeys on a digit training task or task that required pronation and supination
Digit Training- increased cortical area for digigts and decrease in wrist
Pronation Supination- increased wrist, decreased fingers
Outcome:Motor cortex area M1 is alterable by use
There is a use-dependent reorganization of the motor system
Acquired motor skills are reflected in the topography of the neurophysiological maps in the motor cortex.

Question 19

Nudo Digit Study Outcome

Answer 19

Motor cortex area M1 is alterable by use

There is a use-dependent reorganization of the motor system

Acquired motor skills are reflected in the topography of the neurophysiological maps in the motor cortex.

Question 20

Nature Rehab- non skilled?

Answer 20

Non-skilled repetitive tasks do not result in brain map changes

Question 21

fMRI

Answer 21

changes in blood flow and blood oxygenation in the brain are closely linked to neural activity. When neurons become active, local blood flow to those brain regions

Question 22

PET

Answer 22

• A radiotracer is injected into the body, where it travels to cells that use glucose for energy.
  The more energy a group of cells needs, the more the radiotracer will build up in that location
  Active areas are bright on a PET scan, and show up as “hot spots

Question 23

Transcranial Magnetic Stimulation

Answer 23

Mark where youa re stimulated and can see which part of body is moving

Can stimulate specific tract and see if that area responds

Question 24

Ankle Immobilization Study

Answer 24

Liepert used transcutaneous magnetic stimulation to study cortical plasticity in 22 patients

That had unilateral immobilization of the ankle joint without a peripheral nerve lesion.
Cortical area responding to stimulating the Anterior Tibialis of the casted leg was reduced when compared to the non-casted leg.

Reduction correlated with duration of immobilization

Further support for the concept of Use-dependent reorganization of the motor system

Question 25

Implicit and Explicit Knowledge

Answer 25

Pasqual Leone
Test group (shown orderly sequence of numbers) showed progressively
shorter reaction times
and
Significant increases in the maps of
cortical output to the involved muscles
Maps of the cortical outputs enlarged to the
point in which the subject achieved explicit
knowledge of the task

Then the maps went back to their baseline topography

Question 26

Neuroplasticity Findings from studies by Merzenich, Nudo and Kliem

Answer 26

Adult brain can be functionally and architecturally remodeled.
The structure of the cortical maps or brain representations is dynamic.
Dosing is important
This remodeling can have positive or negative consequences.
Plasticity occurs in many areas:
Neuronal level - primary motor and sensory cortices
Axonal level - intracortical pathway
Cellular level - spine density, branching, synapses