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Question 23M.3.SL.TZ2.6

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Date May 2023 Marks available [Maximum mark: 5] Reference code 23M.3.SL.TZ2.6
Level SL Paper 3 Time zone TZ2
Command term Comment, Outline, State Question number 6 Adapted from N/A
6.
[Maximum mark: 5]
23M.3.SL.TZ2.6

After the age of 30, the number of synapses in the various parts of the human brain remain relatively constant. An electron microscope was used to measure the number of synapses in the auditory cortex and visual cortex of brains after autopsies. The graph shows the mean synaptic density in the auditory cortex and visual cortex below the age of 30.

[Source: Reprinted from Huttenlocher, P.R. and Dabholkar, A.S., 1997.
Regional Differences in Synaptogenesis In Human Cerebral Cortex.
The Journal of Comparative Neurology
387, pp. 167–178, with permission from Wiley.]

(a)

The capacity to learn certain skills such as reading music and learning foreign languages is greater at an early age. Comment on this statement using the data shown in the graph.

[2]

Markscheme

This statement seems justified as:

  1. data shows there are more synapses at an early age
    OR
    synapses decrease with age;
  2. more synapses allow for greater learning/cognitive activity;
  3. information from the sensory neurons (auditory and visual) used to perform higher order functions (such as learning);
  4. huge variability at very early age in the number of synapses might mean different children might have differences in learning;
  5. insufficient information / no standard deviation;

Do not accept “connection” instead of “synapse”.

Examiners report

Most candidates realised there was more synaptic density in early years but did not say how this could help in learning.

(b)

Outline the process that reduces the number of synapses.

[2]

Markscheme
  1. neural/synaptic pruning;
  2. (neural/synaptic pruning) involves the loss of neurons/dendrites/synapses;
  3. synapses that are not used do not persist;

Do not accept “connection” instead of “synapse”.

(c)

State one method, other than autopsies, to identify the role of different brain parts.

[1]

Markscheme
  1. animal experiments / lesions / fMRI;

“f” must be written in fMRI.

Examiners report

The rest of the question was well answered, though a few candidates responded MRI rather than fMRI in part (c)