The concept of brain plasticity in relation to the biological area

Brain plasticity, also known as neuroplasticity, refers to the brain's ability to change and adapt as a result of experience, learning, or environmental influences.

How brain plasticity affects behaviour

• Neural adaptation - The brain can reorganise itself by forming new neural connections or altering existing ones in response to stimuli.
• Impact on the visual cortex - Specific cells in the visual cortex can modify their response patterns based on early visual environments, demonstrating adaptability.
• Behavioural outcomes - These neural changes can directly affect how organisms perceive and interact with their surroundings, such as recognising shapes or responding to movement.

Theories underpinning brain plasticity in kittens

Several theories and observations provide the foundation for understanding brain plasticity, particularly in kittens, whose brain structures share similarities with those of humans.

Core ideas behind brain plasticity in kittens

• Structural similarities - Both human and kitten brains have comparable cerebral cortices, with similar lobes, surface folding (gyrencephalic structure), and divisions of grey and white matter.
• Neuroplasticity in kittens - Early control of visual stimuli is linked to changes in RNA structures within the brain, indicating plasticity.
• Visual recognition and flexibility - Kittens possess the ability to encode visual information flexibly and retain visual-recognition memory.
• Adaptability to environment - Their brains can adjust to changing environmental stimuli, allowing for functional adaptation.
• Orientation selectivity - In normal conditions, neurones in the visual cortex are selective for the orientation of lines and edges in the visual field, a trait that can be modified by early experiences.

The classic study by Blakemore and Cooper (1970) on early visual experience

The study by Blakemore and Cooper (1970) is a landmark investigation into how early visual experiences shape brain development and behaviour in kittens. It explores whether orientation selectivity in the primary visual cortex is innate or learned through environmental exposure.

Background to the study

• Previous research by Hirsch and Spinelli (1970) showed that early visual experiences could alter neural organisation in kittens by exposing each eye to different orientations (vertical and horizontal stripes).
• Blakemore and Cooper built on this by allowing kittens normal binocular vision in an environment exclusively featuring either horizontal or vertical stripes, aiming to test the adaptability of the visual cortex.

Method of the study

• Research design - A laboratory experiment using an independent measures design.
• Independent variable (IV) - Whether kittens were reared in a horizontal or vertical stripe environment.
• Dependent variable (DV) - Visuomotor behaviour in a well-lit setting, specifically whether kittens raised with horizontal stripes could detect vertically aligned objects and vice versa.
• Participants - Kittens were randomly assigned to either the horizontal or vertical condition.

Procedure of the experiment

• Kittens were kept in complete darkness from birth.
• Starting at two weeks of age, they were placed in a special apparatus for approximately five hours each day.
• The apparatus consisted of a clear glass platform inside a tall cylinder lined with high-contrast black-and-white stripes (either vertical or horizontal).
• A wide black collar restricted their visual field to roughly 130 degrees.
• This routine persisted until the kittens reached five months of age.
• Afterwards, they were taken weekly to a brightly lit room to assess their visual reactions.
• At around seven months, two kittens (one from each condition) underwent neurophysiological examination under anaesthesia.

Results of the study

• Initial visual impairment - All kittens displayed severe visual deficits at first:
  • Normal pupillary reflexes but no visual placing or startle responses.
  • Relied heavily on touch for guidance.
  • Exhibited 'behavioural blindness', with horizontally raised kittens unable to detect vertical objects and vice versa.
  • Only followed moving objects matching the orientation of their rearing environment.
• Recovery with exposure - Many deficiencies improved within about 10 hours of exposure to normal vision.
• Permanent defects - Some issues remained lifelong:
  • Clumsy, jerky head movements when following moving objects.
  • Frequent attempts to touch objects beyond their reach.
• Neurophysiological findings - Examination revealed:
  • No significant astigmatism.
  • Orientation-specific cells responded only to the orientation of their rearing environment.
  • Approximately 75% of cells were binocular in both tested kittens.
  • Abnormal distribution of preferred orientations, with horizontally raised kittens lacking neurones for vertical orientation and vice versa.

Evaluation of the study

• Strengths - The controlled laboratory setting allowed precise manipulation of visual stimuli, providing clear evidence of brain plasticity.
• Limitations - The artificial environment limits generalisation to natural settings or to humans, as kittens' early development differs from human infants.
• Ethical concerns - Rearing kittens in restricted visual environments and subjecting them to prolonged darkness raises questions about animal welfare.
• Implications - The study underscores the importance of early experiences in shaping neural development, with potential relevance to understanding human visual development.

Key findings and conclusions from the study on visual cortex adaptation

The findings from Blakemore and Cooper's study provide significant insights into how the brain adapts to early visual experiences, with lasting impacts on perception and behaviour.

Major conclusions on brain plasticity

• Early experience matters - Visual experiences during early life can profoundly modify the brain, leading to significant perceptual changes.
• Visual cortex adjustment - The visual cortex in kittens adapts during development to reflect the type of visual input it receives.
• Functional adaptation - The nervous system adjusts to align with the likelihood of certain visual features appearing in the environment, rather than being entirely pre-determined by genetics.
• Environmental influence over genetics - Brain development is largely driven by functional demands and environmental stimuli during critical early periods, rather than solely by pre-programmed genetic factors.