The cerebrum

This is the largest area of the brain and is the thinking part of the brain and controls your voluntary muscles – the ones that move when you want them to. Your memory also lives in the cerebrum and this part of the brain also helps you reason.

The cerebrum has two halves, one on either side of the head: the left and right cerebral hemispheres.

The two hemispheres are practically symmetrical but vary slightly in their functions. One side is used more for logical thinking. This is known as the dominant hemisphere.

The other side is associated with creativity and is known as the non-dominant hemisphere. In most people, the dominant hemisphere is on the left and the non-dominant on the right. However, in a few people this is reversed.

In most situations, each side of your brain will handle the movement and sensation of the opposite side of your body. So, for instance, if you have difficulty moving your right leg, it is quite probable that your tumour is on the left side of your brain.

The cortex allows you to be aware of things happening around you. It allows you to recognise images, sounds and sensation, then interpret them and consciously decide how to react. It is where all the processing of your thoughts and feelings occurs.

In the few aspects where they differ, the two hemispheres try to complement each other. Your dominant hemisphere handles all aspects of language, calculation and praxis (or ability to perform complex movements). It is focused and logical. Your non-dominant hemisphere has a bigger role in the more creative aspects of life, such as music and art, as well as hand-eye co-ordination. It allows you to ‘see the bigger picture’.

Dominant hemisphere roles

• Reading
• Writing
• Calculation
• Logic and strategy
• The ability to perform complex movements (praxis)

Non-dominant hemisphere roles

• Visio-spatial orientation
• Imagination
• Music
• Shapes and patterns
• Observation

In all right-handed and the majority of left-handed people, the dominant hemisphere will be the left. If you are left-handed, your dominant hemisphere may be on the right. It does not normally matter which way round it is and most people do not ever find out unless one of these functions is affected.

Each of the cerebral hemispheres is further divided into four lobes: the frontal, parietal, temporal, and occipital lobes. The symptoms you may experience depend on the location of the tumour within your brain and the lobe affected.