Blakemore & Cooper

Question 1

The study:

Answer 1

-B&C worked in uni of Cambridge and conducted study into effects of environment on development of brain in cats.

Question 2

Background

Answer 2

-work by Hirsch and Spinelli at Stanford University in California-researchers reared kittens-one eye viewing vertical stripes, other eye viewing horizontal stripes and found most neurons of visual cortex were monocularly driven (one eye) and preferred orientation (vertical/horizontal) of the neurons reflected the pattern experienced in that eye.
-This suggested that the neurons of visual cortex showed PLASTICITY in that they developed according to environment experienced.

Question 3

Visual cortex

Answer 3

Eye receives info about the world in which they then process by an area of brain (visual cortex).
Located at back of brain, above where head meets neck.
Produces ‘detailed map’ of visual image we see. It has regions devoted to diff aspects of stimulus, such as its source (from left or right eye), its colour and individual features of its shape.
The arrangement of neurons is highly organised, with columns of adjacent cells responding to similar but slightly different features.

Question 4

Monocular (one eye)

Answer 4

Can be used to refer to vision itself, you are engaging in monocular vision if you can close one eye, or to properties, such as cells that are monocular. i.e respond to input from one of the two eyes.

Question 5

Binocular (both eyes)

Answer 5

If both eyes are open, you are using binocular vision.

Question 6

Visual tracking

Answer 6

Ability to follow the path of a moving object. This is normally smooth and accurate progression with the eyes or head.

Question 7

Depth perception

Answer 7

Ability to judge the position of an object in space. e.g to decide how far away it is.

Question 8

Single cell recording

Answer 8

Technique to measure the activity of a single neuron using a micropipette (very fine tube filled with a solution of ions = molecules carrying a + or - charge.
These micropipettes respond to electrical activity inside a neuron when an impulse is generated and this is displayed on a screen.

Question 9

Aim

Answer 9

To investigate the effect on 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.

Question 10

further aim

Answer 10

To consider whether brain development/plasticity occurs due to nurture (experience) rather than nature.

Question 11

Method

Answer 11

-lab experiment
-independent measures design. (2 groups of ps)

Question 12

IV

Answer 12

whether kittens’ early experience was of a totally horizontal or vertical environment.

Question 13

DV 1

Answer 13

Behavioural differences, making comparisons between the 2 cats (one raised in horizontal environment, one raised in vertical) and also between the cats and ‘normal’ cats behaviours.

Question 14

DV 2

Answer 14

Neurophysiological differences were also studies.
i.e cells in the visual cortex were tested to see how they responded to lines of different orientations.

Question 15

Sample

Answer 15

Lab raised kittens, housed in complete darkness until 2 weeks of age.
Only one cat was studied in depth for each level of the IV- i.e one reared in horizontal environment and one vertical.
They were newborn kittens at start of study and, as such, their visual cortex was unaffected by experience. Thus their visual cortex at beginning of study was only influenced by innate factors(nature).
In testing phase, when DV’s were assessed the cats were 5 months old during behavioural tests & had been exposed to environmental influences(nurture).
They were 7.5 months old at time of neurological tests.

Question 16

Materials/apparatus

Answer 16

Special cylinder was constructed-kitten stood on clear glass platform.
Entire surface of cylinder was covered with contrasting black and white stripes (vertical or horizontal). Stripes were of varying widths. There were no corners or edges anywhere in this environment. Top & bottom of cylinder were long way away.
Kitten wore a black and white collar to prevent seeing its own body and beyond the world of its stripes. (can only see stimulus)

Question 17

Procedure: Early experience

Answer 17

1. For first 2 weeks kittens were in completely dark room, were allowed normal binocular vision (both eyes)
   (input received from both left and right visual fields).
2. At 2 weeks they were placed in cylinder (either horizontal or vertical environment) for average of 5 hours daily. Rest of time was spent in dark room.

Question 18

Procedure: Exposure to normal environment

Answer 18

3. At 5 months the visual deprivation was STOPPED. Kittens were now cats and their visual systems were fully developed. They were past the critical period during which changes can take place to biological system.
4. For several hours weekly the cats were taken from their dark room to another, small, well-lit, furnished room with tables and chairs.
5. Cats were given artificial lenses to ensure any visual difficulties were not due to astigmatism (causes blurred vision) as this may have acted as an extraneous variable.

Question 19

Testing: Behavioural assessment

Answer 19

-Cats initial responses to new visual world were observed, before any learning could take place.
-Further observations were made over following weeks as they learned to ‘see’ the new visual environment.
i.e whether kittens raised in horizontal environment could detect vertically aligned objects and vice versa.

Question 20

Testing: Neurological assessment

Answer 20

-At 7.5 months old, cats were anaesthetised and temporarily paralysed so the responses of individual ‘units’ (columns of neurons in their visual cortex could be tested using an electrode inserted into the unit(a micropipette). This measures the electrical firing of each individual neuron.
-Cats’ eyes were shown lines of all possible orientations ‘around the clock’ to test what neurological responses there were.

Question 21

Results from the behavioural assessment

Answer 21

1. some cats’ reflexes were normal, such as pupils contracting in brighter light.
2. Temporary deficit- the visual placing reflex was NOT shown immediately(where cats reach out with their legs when surface is near by( usually innate).)
   Cats also didn’t initially show the ‘startle response’= defensive reaction to sudden noise or movement.
   Within 10 hrs of visual experience however, they recovered the ‘startle response’ and also their visual placing reflex had recovered, cats could jump from floor to table easily.

Question 22

Results from the behavioural assessment: Permanent deficit

Answer 22

when following a moving object with their eyes, ctas head movements were jerky.
Cats often reached out to touch something actually far away, suggesting depth perception was abnormal.
Cats bumped into table legs as they rushed around- suggests they may be blind to certain orientations.

Question 23

Results from the behavioural assessment: Difference between ‘horizontal’ and ‘vertical’ cats.

Answer 23

when shown long black rod held VERTICALLY and shaken, cats raised with VERTICAL stripes would watch it, run to it and play with it.
If the rod was then held HORIZONTALLY, the other cat (HORIZONTAL) would do the same, but the first one (VERTICAL) ignored it completely.

Question 24

Results from neurological assessment

Answer 24

In both cats 75% of the cells were clearly binocular- received information from both right and left visual fields. And in almost every way, responded as a normal animal would do.
However, the responses to lines of certain orientations were completely ABNORMAL:
-HORIZONTAL cats’ cells in visual cortex did NOT respond to lines within 20 degrees of the vertical orientation, and only 12 of the 52 neurons (columns) responded within 45 degrees of the vertical orientation (vertical lines were NOT seen!)
-VERTICAL cats’ cells showed similar responses but this time to horizontal/near horizontal lines.

Question 25

Conclusions

Answer 25

-the visual cortex may adjust itself as it matures in response to visual experience.
-NATURE (the brain) is modified by NURTURE (experience). This is called PLASTICITY; ability of being able to be changed/moulded. Brains innate structure turns out to be quite plastic.
-In this study cells appeared to change from their preferred innate orientation towards the orientation that was common in the experience, suggesting that the unused parts of innate nervous system did NOT simply degenerate but they ADAPTED to match the actual visual input experienced.

Question 26

Practical applications

Answer 26

-visual impairments cortical area damage if not corrected early.
-squint-eyes not seeing same direction-lack of depth perception decline binocular cells.
-astigmatism- eyeball is not round, so, lines in orientation cannot be seen accurately if not detected neurons associated orientation will decline through lack of stimulation.