S1W12Brain

Question 1

Definition of neuroplasticity

Answer 1

Capacity of the nervous system to reorganize itself by forming new neural connections.

Occurs during:

Brain development
Learning
Brain injury

Question 2

Categorising neuroplasticity

Answer 2

Synaptic (LTP and LTD)

Structural (changes in the wiring)

Developmental (apoptosis, synaptic pruning).

Injury-induced

Question 3

How do we study it?

Answer 3

Need to choose a suitable surrogate marker

Lots of research in animals.

Types of studies:
o Anatomical
o Physiological
o Imaging

Question 4

Anatomical techniques

Answer 4

Looks at cell morphology and connectivity

Question 5

Golgi’s method: silver staining technique

Answer 5

Cell bodies and dendrites visualised

95% of synapses on dendrites

Assumption:
o Increase/decrease in dendritic surface reflects changes in synaptic organisation

Question 6

Physiological and imaging techniques

Answer 6

Transcranial magnetic stimulation (TMS)

Functional magnetic resonance imaging (fMRI)

Magnetoencephalography (MEG)

Question 7

What is neuroplasticity effected by

Answer 7

Experience

Psychoactive drugs

Gonadal hormones (interact with androgen or oestrogen receptors)

Diet

Disease

Stress

Genetics

Question 8

Cohen et al (1997):

Answer 8

Blind (from an early age):

TMS stimulation of visual cortex distorted touch perception

Sighted:

Visual cortex stimulation had no effect on touch perception.

Similar stimulation disrupted their visual performance

Inactivation of occipital cortex interfered with touch perception only in blind people

Question 9

Cohen follow up

Answer 9

Sighted but blindfolded:

Learnt Braille for 5 days
Occipital cortex stimulated by touch

Sighted:
Occipital cortex not stimulated by touch

Inactivation of occipital cortex interfered with touch perception in blindfolded individuals

Suggests neuroplasticity

Question 10

Critical periods

Answer 10

Neuroplasticity maximal in developing brain.

Windows of time where young are most sensitive:

Mice without whiskers within 3 days of birth = impaired facial tactile sensitivity

Kittens without visual input within first 3 months = permanently impaired vision

Critical in humans but length unclear

Absence of normal visual input (lazy eye) = impaired acuity and depth perception

Question 11

Critical period theory 1

Answer 11

Correspond with synaptic excess and pruning in development.

Experiences during this time will determine which synapses are pruned.

Question 12

Critical period theory 2

Answer 12

Learning creates critical periods in developing brain

Longer exposure to experience = less likely able to reverse neuroplasticity

Question 13

Learning/memory neuroplasticity

Answer 13

NP mechanisms underlie learning & memory:

Strengthening of existing synapses

Formation of new synapses

Elimination of old synapses

Modification of dendritic branches

Question 14

Carreiras et al. (2009) reading

Answer 14

Individuals learned to read as adults vs. never learned to read

Increased grey matter and corpus callosum in those learned to read

Suggests brain changed as a result of learning

Question 15

Schneider et al 2002 musicians

Answer 15

Musicians vs non-musicians MRI.

Musicians:

Increased size of Heschl’s gyrus

Increased grey matter in areas for hand control and vision

Musacchia et al. (2007):

Enhanced responses in subcortical areas to music and speech

Question 16

Expert research NP

Answer 16

Maguire et al. (2006)

Posterior hippocampus larger in taxi drivers than bus drivers

Mechelli et al. 2004

Left inferior parietal cortex larger in bilingual brains than monolingual

Question 17

Hyde et al. (2009): piano lessons and NP

Answer 17

6yo = 15 months of piano lessons vs. no lessons

Pre-learning:
o No differences in cognitive tasks/brain scans

Post-learning group:
o Better melody/rhythm discrimination

o Increased size of areas for hearing and hand movements

Question 18

NP and senior moments

Answer 18

Brain training games:

Individuals improve only on that specific task.

Physical activity:

Increased activation in frontoparietal regions and improved semantic memory retrieval.

Question 19

Rosana et al. (2010): physical activity

Answer 19

Exercise group compared to control:

Increased bilateral activity superior/medial frontal gyrus

Faster response times on attentional control task

Question 20

Causes of brain damage:

Answer 20

• Trauma
• CVA
• Tumours
• Infections
• Radiation
• Toxicity
• Neurodegeneration

Question 21

Animal brain injury

Answer 21

Brain cells surrounding damaged area alter to enable them to take on functions of damaged cells.

Question 22

Boatman, 1999: brain injury

Answer 22

6Six 7-14yo with Rasmussen’s syndrome

Left hemispherectomy

Language capabilities of remaining right hemisphere

16 days post surgery:
• Improved phoneme discrimination
• Remaining language functions severely impaired

1 year post surgery:
• Naming impaired and speech limited to single words
• Improved single word comprehension
• Word repetition intact

NP in right hemisphere enabled recovery despite being beyond critical period.

Question 23

Injury-Induced NP In Stroke/CVA

Answer 23

Damages brain cells and impairs Na+/K+ pump so increased sodium inside neurons

Excess glutamate release

Overstimulation of neurons

Excess positive ions enter neuron

Block mitochondria metabolism

Neuron dies

Cell won’t regenerate

Damaged glia cells release chemicals inhibiting axon growth

Question 24

Haemorrhagic (bleeds) injury

Answer 24

Ruptured blood vessel

Neurons flooded with too much blood, oxygen & chemicals

Question 25

Ischaemic injury

Answer 25

Blood clot

Neurons loose oxygen & glucose supply as no blood

Question 26

Diaschisis

Answer 26

Sudden loss/change of function in portion of brain connected to a distant, but damaged area.

Question 27

Treatment of Stroke/CVA

Answer 27

tPA - breaks up clots

Microcatheter – device that reaches target

Block glutamate.

Cool to 34-35°C.

Early intervention better.

Question 28

Denervation Supersensitivity after damage

Answer 28

Remaining synapses more responsive and easily stimulated

Compensates for decreased input - can lead to normal behaviour returning

But can also result in hypersensitivity e.g. chronic pain

Question 29

Increased synapse formation after damage

Answer 29

Area near damage = high rate of new synapse formation

Induced by neurotrophin release from cell body

Question 30

Surviving regions increase/reorganise activity after damage

Answer 30

May take over function or may compensate

Question 31

Therapy to promote NP

Answer 31

Practice impaired skills

Learning to enhance spared abilities

Typedepends on impairment eg. physiotherapy

Question 32

Brain-derived neurotrophic factor (BDNF)

Answer 32

A protein that is encoded by the BDNF gene and encourages nerve growth.

Key facilitator of NP.

Less common compared to therapy but potentially quicker.

Aerobic exercise increases BDNF production

Question 33

Fetal alcohol spectrum disorder

Answer 33

Mother abused alcohol during pregnancy.

In animals:

Alterations in brain anatomy

Neuronal plasticity persistently impaired

In humans:

Varying degrees of CNS dysfunction

Facial anomalies

Growth impairment

Question 34

Drug addiction (Robinson, 2004)

Answer 34

Amphetamine treated rats

Persistent changes in motor behaviour

More dendrites in prefrontal cortex and nucleus accumbens

Question 35

Musician’s dystonia definition

Answer 35

Pathological NP.

Affects digits of most active hand.

Muscular spasm/abnormal posture

Differs depending on instrument used

Question 36

Musician dystonia in somatosensory cortex

Answer 36

Non-expert player:

Normal representation of fingers in primary motor cortex and primary somatosensory cortex

Expert player:

Representation of middle finger expands

Overlaps and displaces representation of neighbouring fingers

Question 37

Sensory re-education in dystonia

Answer 37

Reverses NP changes in somatosensory representation of affected finger.

Requires practice and commitment.

Numerous tasks involved.

E.g. discrimination & matching of objects by affected hand.

Question 38

Proprioceptive training in dystonia

Answer 38

Reverses excessive reorganization in musician’s dystonia

Random bursts of differing vibration frequencies to hand

15 min treatment improves motor control for 24 hours.

Question 39

Phantom limb sensation/pain

Answer 39

A continuing sensation of amputated limb.

From tingling to intense pain.

Lasts days to a lifetime.

Involves NP changes.