1.1.2 Neuroplasticity and behavior
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Key Definitions
Cortical remapping: neuroplasticity on the level of the cortex
Neuroplasticity: ability of the brain to change itself in response to environmental demands
Synaptic plasticity: neuroplasticity occurring on the level of a separate neuron, construction of new synaptic connections and elimination of the ones that are not used
Hippocampus: part of the limbic system, known to be implicated in emotional regulation and long-term memory
Essential Understanding
→Neuroplasticity is the ability of the brain to change through the making and breaking of synaptic connections between neurons
↳ occurs on different scales, from synaptic plasticity to cortex remapping
→ can be demonstrated in a study by Merzenich et al (1984), a study that showed cortical remapping of the fingers occur s in adult owl monkeys around two months after amputation
→can also be a biological mechanism of learning shown in Draganski et al (2004), study that showed that there was a structural change in the brain in response to a simple learning routine like practicing juggling
→in Maguire et al (2000), human neuroplasticity was observed in a natural setting in which it demonstrated that London taxi drivers experienced significant changes in relative distribution of gray matter in the hippocampus in response to demands of the job
→Paul Bachy-Rita: one of the first neuroscientists to introduce sense substitution: idea that other senses can take over/ be used to make up for another lost sense (i.e. echolocation)
Researches
Merzenich et al (1984)
↳key: sensory cortex has the ability to remap its functions following an injury
Aim: investigate how sensory cortex responsible for the hand will respond to injury
Participants: eight adult owl monkeys
Method: experiment using repeated measures design
Procedure:
↳sensory inputs from all hand digits (fingers) were mapped using electrodes attached to part of the cortex responsible for hand sensations
↳the different digits were then stimulated and the electrodes that responded were noted
↳one of the digits was then amputated
↳remapping was done 62 days after the amputation to observe the cortex after injury
Results:
→first mapping showed how there was five distinct areas in the cortex responsible for each digit (adjacent fingers=adjacent cortex areas)
→post amputation, the unused area of the sensory cortex was now occupied by adjacent intact fingers
Ex: if digit 3 was amputated, the cortical areas of 2 and 4 would spread and '“consume” the cortical area that was for digit 3
Conclusion:
↳sensory cortex of adult owl monkeys adapts to injury by cortical remapping
Draganski et al (2004)
↳key: since neuroplasticity occurs in response to regular learning practices, this suggests that neuroplasticity is the neural basis of learning
Aim: investigate whether structural changes in the brain would occur in response to practicing a simple juggling routine
Participants: self-selected sample of volunteers with no prior experience of juggling
Method: experiment, mixed design
Procedure:
↳sample randomly divided into two groups: jugglers and non-jugglers
↳jugglers spent 3 months learning a classic juggling routine with three balls
↳after 3 months, they were told to stop
↳for the control group, they would continue juggling
↳three brain scans performed on both groups: one before experiment, one after three months, one after six months
Results:
→no differences in brain structure between jugglers and non-jugglers before the experiment
→after 3 months, jugglers had more grey matter in the mid-temporal area of the cortex in both hemispheres (area known to be responsible for movement coordination)
→after 6 months, differences decreased but jugglers still had more gray matter than first brain scan
Conclusion:
→gray matter grows in response to environmental demands (learning)
→shrinks in absence of stimulation (lack of practice)
→this illustrates the cause and effect relationship between learning and brain structure
Maguire et al (2000)
↳key: neuroplasticity occurs in natural settings where redistribution of grey matter can be observed like when the hippocampus was observed in taxi drivers as a function of their driving experience
Aim: investigate how the brain structure of London taxi drivers is different from the average brain
Participants:
↳16 right-handed male taxi drivers with 14.3 average years of experience
↳Control group: 50 healthy right-handed male subjects who didn’t driver taxis
Method:
→quasi-experiment (comparison of two pre-existing groups)
→correlational study in part where driving experience was correlated with grey matter volume
→measured variables with MRIs
Procedure:
↳MRI scans were compared between drivers and non-drivers
↳researchers also correlated the number of years of taxi driving experience with results of the MRI scans
Results:
↳taxi drivers had increased gray matter volume in the posterior hippocampus compared to control group
↳for the control group, there was increased grey matter volume in the anterior hippocampus
→correlation was observed between number of years of taxi driving experience and grey matter volume in the hippocampus:
↳the longer time driving a taxi, the larger posterior hippocampus
↳the shorter time driving a taxi, the large anterior hippocampus
→redistribution of grey matter occurs from the anterior to posterior
Conclusion:
→redistribution of grey matter in the hippocampus occurs in taxi drivers in response to gaining navigational experience
→posterior hippocampus is known to be involved in using previously learned spatial information
→anterior hippocampus is known to be responsible for learning new spatial information