Blakemore & Cooper

• Background

  • Kittens' brains have neuroplasticity.
  • This means their brains change with experience.
• Background

  • Studies have shown that changes in the visual stimuli that cats receive is correlated with changes in RNA structures.
• Background

  • Kittens' brains develop and adapt according to what they see.
• Background

  • Studies have shown that cats possess a visual-recognition memory (they can recognise things they have seen before).
  • They also have the flexibility of cerebral encoding (the brain processes information it sees in different ways).
• Background

  • In a normal cat, neurones of the visual cortex correspond to the orientation of lines and edges in the visual field.
  • Essentially, when a kitten sees something upright, laid down or on a slant, its brain creates a neural pathway to represent that angle of orientation.
  • The kittten will therefore respond appropriately to the stimulus if it sees it again.
• Background

  • Hirsch and Spinelli conducted a study where they only allowed kittens monocular vision (vision in which each eye is used separately).
  • Blakemore and Cooper allowed the kittens in their study to have binocular vision (vision in which both eyes are used together).
• Aim

  • To investigate the effect of kittens' visual development of a restricted visual environment, consisting of either vertical stripes only or horizontal stripes only, in which the animal could move freely.
• Research Method

  • This was a laboratory experiment.
• Research Method

  • It used an independent measures design.
• Research Method

  The independent variables were:

  • Whether the kittens were reared in a horizontal environment
  • Whether the kittens were reared in a vertical environment
• Research Method

  The dependent variables were:

  • The kittens' visuomotor behaviour once they were placed in an illuminated environment (ie whether the horizontally reared kittens could detect vertically aligned objects and/or if the vertically raised kittens could detect horizontally aligned objects).
  • Neuronal activity in the brain was looked at to investigate brain plasticity.
• The key theme is brain plasticity.
• Sample

  • Kittens (studied from birth until this study was complied) were randomly allocated to one of the two conditions (horizontal or vertical).
• Sample

  • 2 of the kittens (one reared in the horizontal and one reared in the vertical environment) were used to study neurophysical effects.
  • They were anesthetized. Then their brains were used.
• Procedure

  • The kittens were housed from birth in a completely dark room.
• Procedure

  • After 2 weeks, the kittens were placed into a special apparatus for an average of 5 hours a day.
• Procedure

  Control variables:

  • The kitten stood on a clear glass platform
  • The apparatus was a tall cylinder
  • The entire inner surface was covered with high contrast black and white stripes (either horizontal or vertical).
  • There were no corners or edges, and the upper and lower limits to the apparatus were a long way away.
  • The kitten couldn't see its body- it was wearing a wide black collar restricting its visual field to a width of about 130 degrees.
• Procedure

  Control variables:

  • The kitten couldn't see its body- it was wearing a wide black collar restricting its visual field to a width of about 130 degrees.
• Procedure

  Control variables:

  • There were no corners or edges, and the upper and lower limits to the apparatus were a long way away.
• Procedure

  Control variables:

  • The entire inner surface was covered with high contrast black and white stripes (either horizontal or vertical).
• Procedure

  Control variables:

  • The apparatus was a tall cylinder
• Procedure

  Control variables:

  • The kitten stood on a clear glass platform
• Procedure

  • The routine was stopped when the kittens were 5 months old.
  • This was considered way beyond the 'critical period' in which total visual deprivation causes psychological deficits.
• Procedure

  • After 5 months, the kittens were taken for several hours each week from their dark cage to a small, well-lit room, furnished with tables and chairs.
  • Their visual reactions were observed and recorded/ noted.
• Procedure

  • At 7.5 months, two of the kittens (one vertical, one horizontal) were anaesthetised so their neurophysiology could be examined.
• Behavioural observations

  • Their pupil responses were normal but they showed no visual placing when brought up to a table top (they did not put their paws out ready to stand on it).
  • They also showed no startle response when an object was thrust towards them.
• Behavioural observations

  • They guided themselves mainly by touch rather than vision.
• Behavioural observations

  • They showed "behavioural blindness" in that the kittens raised in a horizontal environment could not detect vertically aligned objects and vise versa.
  • For example, only the eyes of a kitten raised in a vertically striped environment followed a rod held vertically and remained blind to the contours opposite to the stripes they had lived with.
• Behavioural observations

  The kittens recovered quickly from many of the deficiencies:

  • Within a total of about 10 hours of normal vision, they showed 'startle responses' and 'visual placing' and would jump with ease from a chair to the floor.
• Behavioural observations

  Whilst the kittens recovered quickly from many of the deficiencies, some of their defects remained permanent:

  • They always followed moving objects with very clumsy, jerky head movements.
  • They often tried to touch things moving on the other side of the room, well beyond their reach.
• Neurophysiological Examination Results

  • No evidence of severe astigmatism was found (a condition in which the eyeball is not perfectly round).
• Neurophysiological Examination Results

  • Horizontal plane recognition cells did not 'fire-off' in the kitten from the vertical environment and vise versa.
  • This means there was distinct orientation selectivity- the kittens suffered from 'physical blindness'.
• Neurophysiological Examination Results

  • The vertically raised cats could not see horizontal lines and surfaces.
  • The horizontally raised cats could not see vertical lines and surfaces.
• Neurophysiological Examination Results

  • About 75% of cells in both cats were clearly binocular.
  • In almost every way, responses were like that of a normal kitten.
  • This shows little neurophysical response to the rearing environments.
• Neurophysiological Examination Results

  • In a normal cat, the visual neurones demonstrate a 'preferred orientation'.
  • A normal cat's pattern of neurons would have a balance of vertical and horizontal neurons.
  • However, a kitten raised in a vertical environment had no neurones within 20 degrees of a horizontal orientation (and vise versa). These distributions of orientation are not normal.
• Result- kittens showed 'Behavioural Blindness' in that the kittens raised in the horizontal environment could not detect vertically aligned objects and vise versa.


  Conclusion- Visual experiences in the early life of kittens can modify their brains and have profound perpetual consequences.
• Result- Horizontal plane recognition cells did not "fire-off" in the kitten raised in the vertical environment and vertical plane recognition cells did not "fire-off" in the kitten raised in the horizontal environment.


  Conclusion- A kitten's visual cortex may adjust itself during maturation to the nature of its visual experience.