Brain Plasticity and Functional Recovery

What is brain plasticity

the brains ability to change and adapt its structure and processes in response to new experiences and learning, including after damage to trauma

how does the human brain grow from birth to 3 years

human brain grows rapidly in the first few years of life reaching 15,000 est. synaptic connections per neuron by age 3 (which is twice the number of an avg. adult)

what is synaptic pruning

when unused or rarely used connections are deleted whilst those frequently used get strengthened, allowing the brain to form neural connections in response to new cognitive demands

what are the limitations of brain plasticity

- plasticity may have negative consequences

what research supports negative plasticity

- Medina et al 2007

- Ramachandran & Hirstein 1998

what did Medina find

adaptation to prolonged drug use results in cognitive decline and increases the risk of dementia

what did Ramachandran & Hirstein find

phantom limb syndrome

what is phantom limb syndrome

amputees may experience pain sensation in their missing limbs due to reogranisation in the somatosensory cortex

what are the strengths of brain plasticity

- it continues throughout the lifespan

- evidence of plasticity in non-human animals

what research supports that plasticity continues throught the lifespan

Bezzola et al 2012

what did Bezzola find

plasticity reduces with age but playing golf caused changes in the neural representations of movement in the motor cortex of 40-60 year olds making them more efficient

who researched plasticity in non-humans

El-Boustani et al 2018

what did El-Boustani find

he stimulated neurons in visual cortices of mice and recorded dendrite growth in stimulated neurons similar to what occurs during learning, at the same time neighbouring neurons shrank to make room for new growth

what is the main study we look at for brain plasticity

Maguire et al 2000 -> London Cabbies

what is the background context for Maguire

- the hippocampus is a major structure in the limbic system involved with motivation, learning, and emotional behaviour (like feeding, fighting, escape, mating)

- there is one hippocampus in each hemisphere of the brain and its role includes spatial memory and navigation

- brain damaged patients show difficulties in remembering location of places and objects

what is the background research for Maguire

- Henry Molaison (Patient HM)

- Lee et al 1998

- Smudlers et al 1995

- in humans: musicians vs non-musicians

who was Henry Molaison

he had brain surgery in 1953 to treat epilepsy as he lost the ability to form new long-term memories, his case revealed the hippocampus is crucial for turning short-term memories into long-term memories transforming understanding of how memory works and shaped brain research

what did Lee conclude

the hippocampus cells in birds retain the ability to retrain cells and grow in times when the hippocampus is used more (for homing, storing food etc.)

what did Smudlers conclude

the black-capped chickadee had increased hippocampal volume when learning food-store locations

what is the aim of Maguire

to investigate whether hippocampal volume differed in navigationally experienced and non-navigationally experienced individuals

what is the method for Maguire 9experiment type, design, analysis, IV, DV, controls)

- quasi experiment (lab setting, taxi drivers vs non taxi drivers)

- IMD (independent measures design) with matched participants

- correlational analysis (how long as a taxi driver in relation to hippocampal volume)

- IV = London taxi driver or not

- DV = 1. the volume of grey matter in the hippocampus (VBM)

2. data from pixel counting procedure

- controls = 1. matched for age (mean and range), sex, and handedness

2. same MRI scanner unit used for both groups

what are the samples for taxi drivers and non-taxi drivers

- Taxi drivers: 16 right-handed males, 32-62 year olds (mean: 44), 1.5-42 years driving experience

- Non-taxi drivers: 50 right-handed males (from MRI databases), 16 used for pixel counting, similar mean age and range as experimental group

what is good about the procedure of Maguire

both procedures are done by the same expert, but the experts are unaware of the p's condition (working blind - limits bias)

what were the two procedures

- Voxel-Based Morphometry (VBM)

- Pixel Counting

what happened in VBM

p's brain aligned with a template (eliminating extraneous variable of overall brain mass), comparisons in density of grey matter across the brain are then recorded

what happened in pixel counting

the number of pixels in cross-sections of anterior, posterior, and the body of hippocampus counted and compared to establish the brain volume, 16 controls compared to taxi drivers

where were the significant differences in Maguire

- in controls

- in both groups

- in taxi drivers

what was the significant differences in controls

greater anterior hippocampal volume than taxi drivers

what was the significant differences in both groups

right hippocampal volume was greater than the left

what was the significant differences in taxi drivers

greater posterior hippocampal volume

what was the results of the correlational analysis in Maguire

- significant positive correlation between time as a taxi driver and right posterior hippocampal volume

- indicates brain plasticity as posterior hippocampal volume increases with experience as a taxi driver

what was the VBM and pixel count of the positive correlation between time as a taxi driver and right posterior hippocampal volume

- VBM = 0.6

- Pixel Counting = 0.5

what were the key conclusions of Maguire

- structural differences in hippocampus are regionally specific in London cabbies (smaller at the front - anterior; bigger at the back - posterior)

- taxi drivers dependence on navigational skills redistributed grey matter in their hippocampi

- changes in hippocampi are due to nurture

- evidence of local plasticity in the average human brain in response to prolonged environmental exposure (stimuli)

what is functional recovery

following trauma such as a stroke, unaffected areas of the brain begin to adapt and compensate for the loss of functions in the damaged areas, an example of brain plasticity

what is spontaneous recovery

when functional recovery happens rapidly only slowing down after several weeks or months at which point rehabilitation is usually needed to continue improving or avoiding regression

what is the process of functional recovery

the brain rewiring and reorganising itself by forming new synaptic connections next to the damaged area that will take over some of the functions of that area where secondary pathways may be unmasked to enable function to continue

what are the secondary pathways

- axonal sprouting

- denervation super-sensitivity

- recruitment of homologous area

what is axonal sprouting

the growth of new nerve endings

what is denervation super-sensitivity

heightened sensitivity in areas where axons responsible for function similar to those lost become aroused to enable compensation which may result in sensations of pain

what is recruitment of homologous areas

when the opposing side of the brain takes on the functions of damaged areas

what is an example of recruitment of homologous areas

Broca's area = damage may activate the right-side equivalent to perform some of its function while recovery is taking place

what are the strengths of functional recovery

- real-world application

- role of cognitive reserve

- meditation and mindfulness

what is the real-world application of functional recovery

research findings have been used in neurorehabilitation constraint-induced movement therapy for stroke patients to support motor recovery in the affected body parts

what is cognitive reserve

where the level of education a person has may influence their recovery rate

who studied cognitive reserve

Schneider et al 2014

what did Schneider find

the more time individuals with brain injury had spent in education, the higher their chances of disability free recovery (DFR) where 40% of those with 16+ years of education and compared to 10% of those with less than 12 years achieved DFR

who studied meditation and mindfulness

Lazar et al 2005

what did Lazar conclude

experienced meditators had a thicker cortex than non-meditators particular in attention and sensory processing centres

what are limitations of functional recovery

- research validity issues

what are the research validity issues in fucntional recovery

small samples and lack of control groups in research