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Sensation and perception

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What is sensation and perception?

Sensation and perception take place when we interact with the world around us.

Sensation is about detecting things that exist in the world through: sight, sound, smell, touch and taste. To do this the body uses the sensory organs: eyes, ears, nose, skin and tongue which send messages to a specialised area in the brain called the ‘sensory cortex’.

Perception is about turning the sensory messages and signals into a thought, or a piece of useful information that the brain can act on e.g. I can see a cat; I feel pain in my left leg; I am losing my balance.

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How is ‘sensation and perception’ involved in behaviour?

We need the combined input from our senses to tell us about what is happening in the world around us. The brain perceives and uses lots of information to work out if and when to do something in response: to act or behave.

For example:

  • Our sense of smell might tell us that milk has turned sour so we do not drink it.
  • Our sense of sight detects the difference between the edge of a cliff and the edge of a step (which might feel similar under foot). The additional information helps us to decide whether to step off or not.

Getting from seeing or hearing something to acting on it involves many of the brain’s processes. Closely linked to sensation and perception is attention. You can read about attention separately but this is where the brain’s ‘command centre’ or Executive Functions also become involved. As soon as something is sensed and perceived, the brain’s Executive Functions ‘tell’ (or direct) the senses to pay attention to particular things. By looking at or listening out for the ‘right’ things we get a more complete picture of the situation: we can perceive the situation as a whole to understand it better.

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What happens to sensation and perception when someone has hydrocephalus?

Because the sensory cortex is on the surface of the brain, it can be pressed against the inside of the skull when the brain swells (see About Hydrocephalus for a more detailed description of why this happens). This pressure can cause damage to the cells on the surface of the brain which could make it difficult for sensory signals to be received and understood.

Hydrocephalus also stretches the many connections in the brain. This could mean that processes that usually work together don’t ‘communicate’ as well as they should. So, a child or young person’s apparent failure to see or hear something (for example) may be due to affects that hydrocephalus can have on other, related, processes such as attention or executive functioning.

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Closely related processes

None of the brain’s processes work alone. Problems with attention, for example, may make it difficult to focus on the ‘right’ things. This might be particularly difficult in busy situations where there are lots of different things to think about. Read more about how attention works here.

Busy or complex situations also mean the brain has to work harder to make sense of what is going on. For example, being asked to use the single pencil lying on the desk is an easier task than being asked to use a red pencil from a drawer full of many pencils.

Being able to perceive and attend to the ‘right’ things in a situation also depends on understanding or ‘comprehension’ of the situation. You can read more about comprehension here. If a question, instruction or situation is not properly understood, it will be difficult to work out how to respond or behave.

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Getting the right information in

As mentioned already, none of the brain’s processes work alone. So, it may be useful to think about how these key processes relate to each other.

getting right information diagram

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Possible problems

Altered sensation and perception may contribute to difficulties with:
  • Navigation (orientating self in relation to surrounding landmarks)
  • Finding things in bag/drawer/cupboard (finding a single object among many)
  • Geometry (how we perceive shapes, angles)
  • Perceiving social cues (eg body language, changing facial expression)
  • Distance/spatial awareness (eg depth of field)

Sensation and perception are at the start of a complex line of processes that allow us to interact with the world. Problems with sensation and perception could have an impact on almost any area of life. If a child or young person has difficulty in only some situations this might indicate that other processes in the brain have been affected.

It can be very difficult to tell which of the brain’s processes have been affected by hydrocephalus. Suggestions for dealing with everyday problems and difficulties are given throughout the Living with Hydrocephalus pages.

Some of the pages that may be of particular interest are:

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Added complications

Hydrocephalus is often associated with other conditions such as spina bifida, cerebral palsy and cerebral haemorrhage. Each condition may or may not change sensation and perception. Spina bifida for example can cause changes to sensation and perception that are related to damage to the spinal cord, not necessarily to the brain itself. A cerebral haemorrhage may damage areas of the brain’s cortex and could change many of the brain’s processes and functions with or without hydrocephalus.

People are unique anyway but every individual will be slightly different in the way their thoughts and actions are affected by hydrocephalus (and associated conditions). While this site aims to give something to suit everyone, it is important to think about each individual’s pattern of strengths and difficulties. Patience, determination and trial and error are likely to be needed to find solutions that suit your child’s unique needs.

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