Dorsal Stream

One of the two visual “systems” in the brain is called the “dorsal stream.” The dorsal stream tells our body how to get around safely. It helps young people pick objects up avoid bumping into things and falling over.  When the dorsal stream is damaged and dysfunctional it is difficult for us to know where things are in three dimensions.

Many children who are experiencing dorsal stream dysfunction have problems with attention.  This is partly because they can only attend to one or two things at the same time and probably including their own thoughts.  These learners therefore:

• Have a short attention span
• Find it difficult re-attending to the original subject when distracted
• Find it difficult maintaining engagement with others

Learners with attention difficulties regularly walk into things which seem apparently obvious e.g. lamp posts or letter boxes.

Attention problems are more obvious when the learner,

• Feels tired
• Feels ill
• Is thinking his own thoughts
• When there are other distractions such as, 

1. Having a conversation when walking
2. Background noise
3. Peripheral visual stimulation to include particularly movement in the peripheral visual field

Young people with dorsal steam dysfunction who have too much to see, or, who have difficulty estimating where things are in 3 dimensional space, can often feel threatened in certain situations like crowds.   Behaviour may be affected.  Reactions to these situations make cause the learner to,

• Become distressed
• Disruptive
• React by ‘going into her or his shell.’

In a busy supermarket the environment with all its sights, smells and sounds can become over whelming or distressing or, the learner becomes so distracted that it is not possible to pay attention to a task.

Ventral Stream

The brains second visual system is called the ‘ventral stream’. It helps us recognise

• Faces
• Objects
• Places

Some children with damage to the brain affecting the ventral stream have a specific disability in being unable to recognise faces. The difficulty can vary in severity i.e. in some instances no face recognised but in others relatives might be recognised but not friends.

Face recognition training does not seem effective but drawing attention to other identifiers might e.g. voice, shoes or commonly warn clothes help powers of observation. Consequently those interacting regularly with the child can help by wearing individually identifiable items of dress.

Some learners find it easier to recognise someone’s face if the person is facing them but cannot do the same thing if the same person is side ways on. Consequently friends need to be aware of this to let the child know when s/he is there and before running off again.

Recognising Facial Expressions i.e. the language of the face

Being unable to see facial expressions or read facial expressions are therefore both possible in children with low vision. It might be therefore worthwhile finding out the distance a child can read facial expression by gradually increasing the distance and asking the child to read your expression

Those having difficulties recognising the difference between a sad, angry or smiling face need to communicate in a different way. S/he needs to be taught the meaning of words like sad, happy and angry. One way is to show the learner a sad face and then encourage her or him to recognise the intonation of someone who is sad.

Not being able to recognise the nuances of facial expressions can lead to misunderstandings. Consequently everyone working with the learner will need to know that s/he cannot understand facial expressions and as a result may have to communicate information to the leaner in different ways.

Difficulty Looking at another Person’s Face

Some leaners find it difficult to look at the faces of other especially during conversations. We do not know the reasons why. Theories of this include,

• Difficulties seeing any language in facial expressions
• Difficulties handling a lot of information so that looking at a face, listening to what is being said and formulating the answer cannot be done all at once

Naming Colours

A few learners have difficulties naming colours but if given the task of matching colours they have no difficulty. These children can be supported by linking a colour with a noun; e.g. lemon – yellow and grass – green. Eventually it becomes possible to remove the link noun but the child retains the ability to name colours because they remember the link words.

Shape and Object recognition

Those who have great difficulty recognising objects to include shapes often have profound difficulties using vision to interpret what s/he is looking at. However the individual may retain good dorsal stream function (the ability to judge the position of objects moving through space) and good mobility skills. By using language carefully in order to describe what s/he is touching or interested in, and thereby make better sense of the world may help. Try also relating objects to a previous experience or context.

Letter and Word Recognition

There are a number of learners who have difficulties recognising letters or words through damage to the brain – usually left side. They can often recognise words presented as a pictorial image e.g. Coke or Pepsi but have great difficulty naming individual letters and building letters into phonics. However, teaching words by the look and say method can prove effective. For some, longer words can prove easier to learn than short ones as the individual recognises the overall shape of the word rather than individual letters. For those who have good hand function simultaneously reading the word and Braille can help lead to word recognition.

Orientation

To move around we use visual recognition, visual search, a sense of direction and a memory of the number of turns we have to make. There are therefore a number of visual difficulties that can lead to not knowing where we are. However a learner who is unable to follow a route which s/he has been shown a number of times may have a specific problem with orientation. Problem with orientation are most commonly due to damage to the ventral stream on the right and can effect learners who also have difficulties recognising faces.

Learners who have orientation difficulties need a programme designed by a mobility specialist to improve and maximise independence and which offers different ways of finding a route. Some learners may be able to recognise certain landmarks with a route broken down into small stages whilst others will be able to use tactile landmarks. Importantly the learner should be introduced to tactile clues in order to recognise doors or different areas by clues on the wall e.g. a fire extinguisher.

Helping a learner to develop memory skills can help too e.g. encouraging her or him to look back along a route and list land marks and actions in order to remember. Remember also that a return journey is a different route from the outgoing trip and should be address as such.

For certain learners using rhyme or song can help to remember landmarks for others a game like hide and seek or treasure hunt can help the memory process in a fun way. Ideally learners should all be taught to ask appropriately for support where necessary.

Finally, to help some learners with orientation difficulties strictly regimenting the environment may help e.g. a well laid out and consistently laid out classroom or bedroom.    

Finally

An acknowledged expert in this field is Professor Gordon Dutton. (Consultant Ophthalmologist Royal Hospital for Sick children Glasgow.) Reading his work is highly recommended.