Welcome to Brain Plasticity!
Hello and welcome to your study guide for the Biological Area: Brain Plasticity for OCR A Level Psychology (H567). Don't worry if brain structures and biological terms seem a bit daunting at first. We will break everything down into clear, manageable steps with helpful analogies and memory aids.
In this chapter, you will learn how the brain can physically change and rewire itself in response to experiences. We will examine two landmark core studies:
• Classic Study: Blakemore & Cooper (1970) – Looking at early visual deprivation in kittens.
• Contemporary Study: Maguire et al. (2000) – Looking at navigation and brain changes in London taxi drivers.
What is Brain Plasticity?
Brain Plasticity (also known as neuroplasticity) is the brain's remarkable ability to alter its physical structure and neural functioning over time as a result of experience, environmental stimulation, learning, development, or damage.
Analogy time: Think of your brain not like a hard plastic toy set in a fixed shape, but like plasticine or play-dough. When you practise a skill or live in a specific environment, your brain physically reshapes its neural pathways to adapt to those demands!
---Classic Study: Blakemore & Cooper (1970)
Title: Development of the brain depends on the visual environment
1. Background and Aim
Psychologists wanted to know whether the visual cortex (the part of the brain that processes what we see) develops based on nature (innate wiring present from birth) or nurture (shaped by the visual environment we experience as we grow).
Aim: To investigate the physiological and behavioural consequences of a restricted early visual environment (vertical vs. horizontal lines) on the development of the primary visual cortex of kittens.
2. Method and Design
• Method: Laboratory experiment.
• Design: Independent measures design.
• Independent Variable (IV): Visual rearing condition — vertically striped environment vs. horizontally striped environment.
• Dependent Variables (DVs):
1. Behavioural visual responses and visuomotor coordination when placed into a normally lit room.
2. Neurophysiological properties of individual neurons in the primary visual cortex (orientation preferences).
3. Sample and Apparatus
• Sample: Kittens studied from birth up to 7.5 months.
• Early Rearing (0–2 weeks): Kittens were kept in complete darkness from birth until 2 weeks of age.
• The Visual Cylinder (2 weeks to 5 months): Kittens spent approximately 5 hours per day inside a specially built visual display cylinder (46 cm diameter). The cylinder was illuminated from above and covered completely in high-contrast black-and-white stripes (either all vertical or all horizontal).
• Key Controls:
1. The floor was a clear Perspex glass sheet placed halfway up the cylinder so kittens saw no corners or edges.
2. Kittens wore a wide black collar restricting their field of view to roughly \(130^\circ\). This prevented them from seeing their own paws or bodies, which would have introduced lines of different orientations!
4. Findings
A. Behavioural Observations (When brought into normal light):
• Kittens showed behavioural blindness: they were functionally blind to lines perpendicular (opposite) to the ones they were raised in.
• Their pupillary reflexes were completely normal (their eyes reacted to light), but they showed no visual startle response and no visual placing reflex (they relied on touch and whiskers to navigate).
• A horizontally reared kitten did not react when a vertical rod was waved in front of it, and a vertically reared kitten completely ignored a horizontally held rod.
• Some deficits recovered after about 10 hours of normal light exposure, but permanent deficits remained in depth perception and visual tracking.
B. Neurophysiological Recordings:
• Microelectrode recordings were taken from 125 single neurons across 2 kittens at 7.5 months (one from each condition).
• In the vertically reared kitten, neurons responded exclusively to vertical or near-vertical lines.
• In the horizontally reared kitten, neurons responded exclusively to horizontal or near-horizontal lines.
• Critical Result: No neurons showed a preferred orientation within \(45^\circ\) of the perpendicular orientation.
5. Conclusion
Orientation selectivity in the visual cortex is not purely innate; the brain physically adapts its neural circuitry to match the visual inputs of its early environment.
Key Takeaway: Blakemore & Cooper showed that early visual deprivation changes the physical wiring of an animal's visual cortex during a critical developmental period.
---Contemporary Study: Maguire et al. (2000)
Title: Navigation-related structural change in the hippocampi of taxi drivers
1. Background and Aim
London taxi drivers must undergo intensive multi-year training known as "The Knowledge" to memorise over 25,000 streets and thousands of landmarks. Maguire et al. wanted to test if this intense spatial navigation training would physically change the adult human brain, specifically the hippocampus (the brain structure responsible for spatial memory and navigation).
Aim: To investigate whether structural changes (plasticity) could be detected in the human brain associated with extensive spatial navigation experience.
2. Method and Design
• Method: Quasi / Natural experiment (comparing existing taxi drivers to non-taxi drivers) combined with a correlational analysis.
• Design: Matched pairs control group.
3. Sample
• Experimental Group: 16 healthy, right-handed, male licensed London taxi drivers (mean age 44 years, age range 32–62; licensed for at least 1.5 years; mean training time 2 years).
• Control Group: 50 healthy, right-handed males who were not taxi drivers (selected from an MRI scan database, matched for age profile). A subset of 16 was used for the matched-pair pixel counting.
4. Brain Imaging and Measurement Techniques
All participants underwent Structural MRI scans (Magnetic Resonance Imaging). The researchers used two distinct, objective techniques to analyse the scans:
• Voxel-Based Morphometry (VBM): An automated, objective 3D computer technique that measures grey matter density across the whole brain.
• Pixel Counting: A blinded, manual 2D measurement of grey matter slice area across three hippocampal regions: the anterior (front), body (middle), and posterior (rear).
5. Findings
1. Posterior Hippocampus: Taxi drivers had significantly greater grey matter volume in both the left and right posterior hippocampi compared to non-taxi drivers.
2. Anterior Hippocampus: Non-taxi driver controls had significantly greater grey matter volume in the anterior hippocampus compared to taxi drivers.
3. Total Volume: There was no significant difference in total hippocampal volume between the two groups. The grey matter had simply been redistributed!
4. Correlational Analysis: There was a statistically significant positive correlation between time spent working as a taxi driver and grey matter volume in the right posterior hippocampus.
6. Conclusion
The adult human brain exhibits structural plasticity in response to environmental demands and learning. The posterior hippocampus stores a spatial mental map of the environment, expanding with prolonged navigation practice.
Key Takeaway: Maguire et al. demonstrated that human adult brains can physically rewire and expand regional grey matter through occupational practice.
---How Maguire et al. Changes / Extends Our Understanding
In Section A of Component 02, you will often be asked how the contemporary study changes or extends our understanding of the key theme compared to the classic study. Here is the direct comparison:
1. Species & Life Stage:
• Blakemore & Cooper (Classic): Showed plasticity in animals (kittens) during an early critical developmental window.
• Maguire et al. (Contemporary): Extended this to show that plasticity occurs in healthy adult humans as a result of occupational learning.
2. Nature vs. Nurture:
• Blakemore & Cooper: Showed how environmental deprivation restricts brain development.
• Maguire et al.: Showed how environmental enrichment and practice physically expands specific brain regions.
3. Technological Progression:
• Blakemore & Cooper: Relied on invasive single-cell microelectrode recordings under anaesthesia.
• Maguire et al.: Used modern, non-invasive, objective in vivo neuroimaging (structural MRI, VBM, and pixel counting).
Examiner Warnings & Common Misconceptions
Avoid these common traps highlighted by OCR examiners:
• Misconception 1: "Maguire used fMRI and drivers did a task in the scanner."
Correction: Maguire et al. used structural MRI, not functional MRI (fMRI). The drivers were simply lying at rest in the scanner while physical pictures of their brain anatomy were taken. They were not navigating a virtual city during this scan!
• Misconception 2: "Taxi drivers had bigger brains overall."
Correction: Total hippocampal volume did not differ between taxi drivers and controls. The grey matter was regionally shifted (greater in the posterior, smaller in the anterior).
• Misconception 3: "Correlation equals causation."
Correction: Because the taxi driver comparison was a quasi-experiment, you cannot definitively prove navigation caused the hippocampal growth from the group comparison alone (perhaps people with big posterior hippocampi naturally choose to become taxi drivers!). However, the positive correlation between driving experience and posterior volume strongly supports the plasticity explanation.
• Misconception 4: Confusing brain regions.
Correction: Remember that Blakemore & Cooper investigated the primary visual cortex (occipital lobe), whereas Maguire et al. investigated the hippocampus.
Memory Aids & Mnemonics
• Remembering Blakemore & Cooper's kittens: Think "C-C-C" — Collars, Cylinders, visual Cortex.
• Remembering Hippocampal Regions in Maguire:
• Posterior = Past navigation / Practice (Larger in taxi drivers).
• Anterior = Ahead / non-drivers larger.
Methodological Evaluation & Core Debates
1. Nature vs. Nurture
• Blakemore & Cooper: Shows the power of nurture. Although the visual system has an innate basis, visual input is necessary for neurons to tune to specific orientations.
• Maguire et al.: Demonstrates nurture in adulthood. Memorising London's layout physically reshaped the posterior hippocampus over years of experience.
2. Methodological Strengths and Weaknesses
• Reliability: Both studies have high internal reliability due to standardised controls (e.g., identical 46 cm cylinders, fixed darkness periods in Blakemore & Cooper; standardized MRI parameters, automated VBM, and blind pixel counting in Maguire et al.).
• Validity: Blakemore & Cooper used laboratory controls to isolate line orientation, but artificial cylinders lack ecological validity. Maguire et al. investigated real-life occupational experience, providing high ecological validity, though quasi-experiments lack random allocation.
• Ethics: Blakemore & Cooper raises severe animal ethics concerns regarding sensory deprivation and invasive testing, though it provided foundational knowledge of neurodevelopment. Maguire et al. was entirely non-invasive with fully informed adult human volunteers.
Quick Review Summary
• Brain Plasticity: The brain's capacity to change structure and function with experience.
• Blakemore & Cooper (1970): Kittens reared in vertical or horizontal cylinders showed behavioural blindness and matching orientation selectivity in visual cortex neurons (125 neurons sampled).
• Maguire et al. (2000): 16 London taxi drivers showed significantly higher posterior hippocampal grey matter volume compared to 50 controls, positively correlated with years on the job.
• Shift in Understanding: Proved that plasticity is not just an early developmental animal phenomenon, but a lifelong process present in adult humans.