Video Link: https://vimeo.com/589924508

Right now, take a moment and look around you.

What do you see?

How do you know the scene is real?

What is 'real' in relation to what you see?

We are not trying to raise philosophical questions. These questions relate to the brain processes creating vision going on in your mind right now.

We need to explain a part of this process to show what visual hallucinations are.

Let us imagine we are all together on the banks of a loch here in Scotland, looking at Linlithgow Palace.

You are the person coloured green in the centre.

What you see is the picture your brain creates, as we have covered in previous lessons.

That picture created in your brain should be an accurate match of what is in front of you.

Brain Image

So vision could be thought of as two matching images:

• the outside image (what is in front of you) and
• the brain image.

The image you are aware of, including the image of what you are looking at right now, is the brain image. Your brain very cleverly makes you think it's the outside image you see, but it isn't.

The brain image can be different to the outside image for many different reasons, covered in multiple previous lessons.

One way it can be different, is if the brain image has things in it, that are not really there.

When this happens it is called a visual hallucination.

There are different types and different causes of visual hallucination.

The reason we want to explain this in detail is because there is a lot of fear around visual hallucinations. What we want to do is show you the processes, and where they do not perform typically to create visual hallucinations, so as to take out some of the mystery and fear.

Age Related Macular Degeneration (AMD) & Visual Hallucinations

With the eye condition age related macular degeneration (AMD) the person can be left with an absence of vision around the centre of their visual field.

In lesson 3i (Visual Recognition) we explained the process of your brain taking the visual information received first through the eyes, to create the picture of what you are looking at and taking that to your visual memory files, to make sense of what you see.

But what if there is a missing part of what you are looking at, because of a problem with the eyes, as with the image above.

Accounts vary, but as the central vision reduces over time, many are only aware that things are less clear towards the centre of their vision.

As their brain goes through the natural process of making sense of the picture it is presented with, by finding matching visual memory files, there is a problem - the brain has an area where it has no incoming visual information to match with visual memory files - what is it to do?

For some people with AMD there is an absence of vision in this area, but for others, their brain tries to fill that gap. What does it fill the gap with? Other images from your visual memory files, including very realistic images or colours, shapes and patterns.

Formed and Unformed Visual Hallucinations

• The very realistic visual hallucinations, for example of people, animals or objects, are called formed visual hallucinations.
• The more abstract visual hallucinations featuring colours, shapes, patterns and flickering are called unformed visual hallucinations.

Sometimes the brain's attempts can be very wrong, including for example filling a space with lifelike images like known people.

The brain image, the image you are aware of, is presented in a way that it represents what is real on the outside.

The visual hallucinations are as real as anything is possible to be real, to the person having them.

Visual hallucinations can be frightening, but also sometimes, for some pleasant.

So in many respects, visual hallucinations represent a very natural visual process that has gone a bit wrong. The brain's response to an absence of information.

The fear of being labelled stops many reporting their visual hallucinations. One study noted:

Other types of vision loss can lead to similar visual hallucinations, and the cause is considered to be broadly due to under-stimulation or lack of information going to the temporal lobes, which are programmed to fill your images with meaning based on the images in their picture files.

These types of visual hallucinations are called Charles Bonnet Syndrome.

Temporal Lobes & Visual Hallucinations

The temporal lobes are typically where most of your picture memories are stored.

Picture memories work in two ways.

• 1.Interpreting your world. The fact that your brain has created a meaningful image in your mind of what you are looking at means you have a good and comprehensive working store of picture memories.
• 2.Thinking in images. Try to think of a picture. Imagine something you are not looking at, like a childhood toy or old friend. Some people do not feel they have very good picture memories because they find it difficult to create pictures in their mind. Thinking in pictures requires picture memories but is a different process to 1, above. We have heard many accounts from people with CVI that they do not think or even dream in pictures.

In our picture (repeated below), you may not recognise the building as Linlithgow Palace, but you would recognise it as a building and different from the grass, trees, water, sky and clouds. To do that requires picture memories, for most stored in their temporal lobes.

But what happens if there is a problem with the temporal lobes?

To explain let us use the example of a large supermarket and the huge stockroom located nearby, that has all the supplies to keep the shelves filled for the shoppers. All day long workers go between the shop floor and the stockroom to get the supplies to fill the shelves as needed.

So when the banana shelf is empty, a worker goes to the stockroom, to the location of the bananas, takes a box from that location and takes it back to the shop floor and the shelf of bananas can be re-filled. That is how the system is meant to work.

• The bananas on the shelf represent what you are looking at, the outside image.
• The worker going to the stockroom to collect a box of bananas represents the white matter pathways of the temporal lobes and their activity.
• The box of bananas in the specific location in the store room represents the visual memory stored in the temporal lobes.

A number of different issues can arise when trying to fill the empty banana shelf:

All of these experiences can be caused by issues with the temporal lobes, where most of the images experienced and remembered are stored.

Other Causes of Visual Hallucinations.

Seizures

Some experience visual hallucinations after or during a seizure.

Seizure activity that is local to one or both temporal lobes can cause visual hallucinations with the appearance of patterns, different colours and flickering. This is a type of unformed visual hallucination.

If a child with CVI appears to experience a sudden deterioration in vision, especially in children unable to explain their vision due to limited verbal skills, this may be caused by seizure activity in their temporal lobes. This is something it is important to be mindful of and mention to your doctor. A test called an EEG (electroencephalogram) may be scheduled to check for seizure activity. If found, medications can help and improve the child's vision. In rare cases neurosurgery can help too.

Interpretation of an unformed visual hallucination from a description by a person with CVI who was affected by seizure activity in the temporal lobes.Video Link: https://vimeo.com/640460517

Migraine

The auras experienced by some people with migraine headache and 'floaters' are visual disturbances and do mean you see something that is not there, so technically are a form of visual hallucination, but most do not classify them as such.

Example of migraine aura, created from descriptions of the altered visual experience. Video Link: https://vimeo.com/495465116

Medications & Drugs

Some medications and drugs can cause visual hallucinations.

Palinopsia (lesson 11a)

Palinopsia means that the image of what you were looking at is not disposed of when you look at something new, meaning the previous image can linger. This is a form of visual hallucination in that you are seeing something that is not there, but the underlying cause is due to a different visual processing issue, as explained in lesson 11a.

Visual Synaesthesia & Visual Hallucinations

Synaesthesia is the name given when different senses link together, for example where numbers are understood as colours. A commonly reported form of synaesthesia relates to the experience of listening to music, where the sounds are experienced as visual patterns. This is called visual synaesthesia.

Visual hallucinations can:

• be from birth or acquired
• affect someone mildly or severely
• be temporary, for example the result of taking a medication
• get worse for example with Charles Bonnet Syndrome due to a deteriorating condition
• be very realistic and appear to have three dimensional form
• be extremely abstract, and take the form of colours, patterns and shapes

Visual Behaviours

We know from research that some people experiencing hallucinations are frightened both of them, and to report them, due to the stigma associated with the condition and fear of being labelled. For this reason, rather than reporting seeing things that are not there, the person may suddenly become frightened or disorientated or confused. If the person has a severe degenerative eye condition, it is always worth sensitively considering whether they may be experiencing visual hallucinations - a very natural process of their brain trying to do it's best to help them...but not always getting it right.

The same applies to those with dementia, for whom visual hallucinations need to be sought by carefully asking about what the person is seeing. In more advanced dementia an affected person may appear to be fending off something or someone, but is unable to talk about it.

In complex and non-verbal children with CVI, a sudden deterioration of vision may be an indication of seizure activity in the temporal lobes creating unformed visual hallucinations. This needs to be reported to the child's doctors for further investigations.

Targeted support

• If medications, migraine or seizures are causing visual hallucinations, then alternative medications or treatments, under the supervision of doctors, can help.
• If the visual hallucinations are associated with a degenerative condition so likely to worsen, then trusted support is essential, where a person is encourage to talk about what they see, and another can confirm if it is real, and if a hallucination, reassure that it is not there and they are safe.
• If due to temporal lobe damage, there may be patterns and rhythms you can learn to recognise, for example they may just relate to certain things, like inanimate objects. If this is the case you can plan accordingly.
• Understanding the underlying causes, as we have tried to explain here, can help demystify what visual hallucinations are.

Checklist:

Before moving on, please check you have understood:

• What the word hallucination means
• What a visual hallucination is
• How and why eye disorders can lead to visual hallucinations
• The difference between formed and unformed visual hallucinations
• Different temporal lobe processes that can cause visual hallucinations
• Other causes of visual hallucinations
• Why palinopsia visual hallucinations are different from other visual hallucinations

Next lesson

Level 12a Visual Processing Disorders affecting Reading & Numbers - Dyscalculia

Level 11 Full Checklist

You should understand...

• What palinopsia means.
• The process of discarding and replacing the images of what you are looking at.
• The three broad types of different experiences of palinopsia.
• Why palinopsia can be confused with visual hallucinations.
• The difficulties palinopsia creates.
• Other conditions palinopsia might appear like, but is not.
• Causes of palinopsia.
• Suggestions to help with the effects of palinopsia.
• What the word hallucination means
• What a visual hallucination is
• How and why eye disorders can lead to visual hallucinations
• The difference between formed and unformed visual hallucinations
• Different temporal lobe processes that can cause visual hallucinations
• Other causes of visual hallucinations
• Why palinopsia visual hallucinations are different from other visual hallucinations