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The Study of Hallucinations Related to Neurology and Vision

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The Study of Hallucinations Related to Neurology and Vision

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Neurology and the Parts that Cause Hallucinations

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Neurology and the Parts that Cause Hallucinations

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---The brain causes hallucinations through Schizophrenia, a brain degeneration disorder. This disorder would be characterized by seeing things with anopsia and having visions that don't look like visions.

---Hallucinations can be present in healthy people, as well. They usually see hallucinations after or during grieving for a loved one who passed, commonly because of the change.

--- Having a self-generated stimulus should not be unexpected, but because of schizophrenia, there are a number of ways that one can provide their own stimulation.

---This is also part of the right anterior cingulate cortex, which is the part of the brain that is affected when going through hypnosis. This is affected because people can hallucinate under hypnosis, making it a very weird part of the brain that becomes unusually active during hypnosis.

---Another neurologist proposes that the brain creates hallucinations and that these experiences "arise from synchronization of gamma oscillations in thalamocortical networks."

--- While the above may not be clear, these gamma oscillations are the culprits restraining sensory input, and those with schizophrenia have damaged or physical change regarding these oscillations. Schizophrenia, in short, allows more sensory perception than we are trained to allow, making for surreal hallucinations.

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---To start, light, or our vision, hits our retina and then makes its way to the visual cortex of our brain. The visual cortex is located in the back of the brain, and here is all the information that distinguishes things and pairs it with our background knowledge, like who is who, what is what, etc.

---The visual cortex(s) have more than one pathway. There is the What Pathway, which focuses on recognizing and identifying objects or matter, and the Where Pathway, which involves the location and the movement of matter. These two lead to the processing of our brain.

---The primary visual cortex (V1), is the logical part of the brain, which shows the reaction of neurons to specific formations of light. The V2 cortex is much more detailed and focuses on contours, edges, textures, and the location of something compared to its foreground or background.

---These finished products of light get sent to the Inferior Temporal Cortex, which focuses on complete objects, the product of V1 and V2 in the brain which makes our brain make sense of things.

---Making our brain make sense of things does not mean it will be accurate, however. Looking at the image of the grid, square A isn't actually lighter than Square B. It is darker, but because our brains are not actually trying to seek the truth, they are making sense of it, is a much different way because we do not know what is real.

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---What are visual hallucinations? Visual hallucinations are not just things that we perceive but don't actually exist. The reality is much deeper than that.

---Looking at the previous article, the brain gets all of the information from the eye, then we can make sense of it. Many people, do not have enough information about the lights from the eye that the brain adds things in, like previous information from, background knowledge. While many people affiliate visual hallucinations with schizophrenia and Charles Bonnet syndrome, it can occur in people who have young and healthy vision.

--- Previous information has led to the claim that some parts of the brain use different amounts of energy and take longer to shut off, making hallucinations from the visual cortex when inadequate light is given.

---Charles Bonnet syndrome is when people lose their eyesight or parts of their vision from things like macular degeneration, diabetic retinopathy, and so much more. This would mean that the brain is not receiving enough light, making it create things to therefore fill in the gap of light.

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Vision is the sense we most depend on in our daily lives, and it is complex - despite the huge strides recently made in artificial intelligence and image processing, the way our brains process images is vastly superior. So how do we do it?

From the eye to the brain

The axons of ganglion cells exit the retina to form the optic nerve, which travels to two places: the thalamus (specifically, the lateral geniculate nucleus, or LGN) and the superior colliculus. The LGN is the main relay for visual information from the retina to reach the cortex. Despite this, the retina only makes up about 20% of all inputs to the LGN, with the rest coming from the brainstem and the cortex. So more than simply acting as a basic relay for visual input from retina to cortex, the LGN is actually the first part of our visual pathway that can be modified by mental states.

The superior colliculus helps us to control where our head and eyes move, and so determines where we direct our gaze. Saccades, the jumpy eye movements that you are using as you read this text, are also controlled by the superior colliculus. As with the LGN, the superior colliculus receives strong input from the cortex, which provides the dominant command as to where our gaze moves.

Cortical processing of visual input

From the thalamus, visual input travels to the visual cortex, located at the rear of our brains. The visual cortex is one of the most-studied parts of the mammalian brain, and it is here that the elementary building blocks of our vision - detection of contrast, colour and movement - are combined to produce our rich and complete visual perception.

Most researchers believe that visual processing in the cortex occurs through two distinct 'streams' of information. One stream, sometimes called the What Pathway (purple in the image below), is involved in recognising and identifying objects. The other stream, sometimes called the Where Pathway (green), concerns object movement and location, and so is important for visually guided behaviour.

Building our visual world step by step

Our visual cortex is not uniform, and can be divided into a number of distinct subregions. These subregions are arranged hierarchically, with simple visual features represented in 'lower' areas and more complex features represented in 'higher' areas.

At the bottom of the hierarchy is the primary visual cortex, or V1. This is the part of visual cortex that receives input the thalamus. Neurons in V1 are sensitive to very basic visual signals, like the orientation of a bar or the direction in which a stimulus is moving. In humans and cats (but not rodents), neurons sensitive to the same orientation are located in columns that span the entire thickness of the cortex.

That is, all neurons within a column would respond to a horizontal (but not vertical or oblique) bar. In a neighbouring column, all neurons would respond to oblique but not horizontal or vertical bars (see image below). As well as this selectivity for orientation, neurons throughout most of V1 respond only to input from one of our two eyes. These neurons are also arranged in columns, although they are distinct from the orientation columns. This orderly arrangement of visual properties in the primary visual cortex was discovered by David Hubel and Torsten Wiesel in the 1960s, for which they were later awarded the Nobel Prize.
Orientation columns in primary visual cortex, as viewed from above. All neurons within a column respond preferentially to bars of a specific orientation, denoted here by colour. Crair et als/Wikimedia
Moving up the visual hierarchy, neurons represent more complex visual features. For example, in V2, the next area up in the hierarchy, neurons respond to contours, textures, and the location of something in either the foreground or background.

Beyond V1 and V2, the pathways carrying What and Where information split into distinct brain regions. At the top of the What hierarchy is inferior temporal (IT) cortex, which represents complete objects - there is even a part of IT, called the fusiform face area, which specifically responds to faces. The top regions in the Where stream are involved in tasks like guiding eye movements (saccades) using working memory, and integrating our vision with our body position (e.g. as you reach for an object).

In summary, the visual cortex shows a clear hierarchical arrangement. In lower areas (those closest to incoming light, like V1), neurons respond to simple visual features. As the visual input works its way up the hierarchy, these simple features are combined to create more complex features, until at the top of the hierarchy, neurons can represent complete visual objects such as a face.

Visual processing isn't all one way

This bottom-to-top processing of our visual world may seem the logical path, but it isn't the whole story. Such a ' bottom-up' approach would be far too slow and laborious, but more importantly, it would render our visual world full of ambiguity and we would struggle to survive. Instead, our perception relies to a very large extent on our previous experience and other ' top-down' mechanisms such as attention. QBI Professors Jason Mattingley and Stephen Williams are both studying how attention can alter visual processing, using cognitive and cellular approaches, respectively.
Wuhazet - Henryk Żychowski
As an example of top-down processing, consider the image below:

Square A looks lighter, but is actually darker than square B. Clearly, our visual system is doing a terrible job at seeing reality. But that isn't its purpose. Instead, our brains are trying to make sense of what they are seeing, rather than seeking the truth.

In the case of the above image, we automatically see - based on past experience - light and dark squares arranged in a checkerboard fashion, with a centrally lit portion and a shadow cast around the edges. With all of this information, we interpret A as a light square in shadow, and B as a brightly lit dark square. It isn't reality, but it is the most likely explanation given all of our previous experience and the data at hand. This is how our visual system works, ultimately to help us understand the world and so promote our survival.

Here are the squares side by side:

And to end, just because it's fun, here's a video with a great demonstration and explanation of how powerful top-down processing can be in visual perception.

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Vision is the sense we most depend on in our daily lives, and it is complex - despite the huge strides recently made in artificial intelligence and image processing, the way our brains process images is vastly superior. So how do we do it?

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Charles Bonnet Syndrome (CBS) is a condition that some people get when they lose some or all their vision. It causes them to have visual hallucinations (seeing things that aren't really there).

What Causes Charles Bonnet Syndrome?

With healthy vision, light enters the eye and is received by the retina (the light-sensitive tissue in the back of the eye). The retina converts these light rays into visual messages, which are sent to the brain, so we can see.

When people lose vision from diseases like age-related macular degeneration, glaucoma, or diabetic retinopathy, their visual system doesn't process new images. Without visual data coming in through the eyes, the brain fills the void and makes up images or recalls stored images for you to see. This is what causes the visual hallucinations of CBS.

What Are Symptoms of Charles Bonnet Syndrome?

The main symptom of CBS is having visual hallucinations. Most people have them when they wake up. What people see varies, but can include:

repeating patterns of lines, dots, or other geometric shapes

landscapes, such as mountains or waterfalls

people, animals, or insects

people dressed in costume from an earlier time

imaginary creatures, like dragons

The hallucinations may move or remain still, and they can appear in black and white or color. The length of the hallucinations can last seconds, minutes, or hours.

How Is Charles Bonnet Syndrome Diagnosed?

There is no special test to find out if you have CBS. Your doctor will want to talk to you about your medical history. They will try to rule out other sources of visual hallucinations, including:

mental health problems, like schizophrenia

other neurological (brain) conditions, like dementia or Parkinson's

whether you take certain medications

If you have vision loss and visual hallucinations without these other conditions, you likely have CBS.

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Charles Bonnet Syndrome (CBS) is a condition that some people get when they lose some or all their vision. It causes them to have visual hallucinations (seeing things that aren't really there). With healthy vision, light enters the eye and is received by the retina (the light-sensitive tissue in the back of the eye).

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Notes on the Brain and How it Causes Hallucinations

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Notes on the Brain and How it Causes Hallucinations

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The brain causes hallucinations through Schizophrenia, but they can also be active in healthy-minded, healthy-visioned people. These people have lessened restrictions on what they can take in from sensory input.

This is part of the right anterior cingulate cortex which is the part of the brain that controls hypnosis. They also arise from the occurrence of gamma oscillations at the same time through thalamocortical waves.

These oscillations, occurring at the same time, lessen the brain's range for sensory input, making it hallucinate more than it needs to. People with this Schizophrenia disease actually have abnormalities in the gamma oscillations.

Having these diseases is not the only way that people can hallucinate, they can also have a self-generated stimulus due to having more sensory input than needed.

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Notes on How the Eye Connects to the Brain

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Notes on How the Eye Connects to the Brain

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The light that comes into our eyes, how we have input through our vision senses goes through a complex thought before turning the information given into something that the brain can make sense of. To start, the visual input comes through the retina, a soft tissue, which then processes the information back into the visual cortex, which can go on one or two pathways depending on it, such as the where or the what. They both have different purposes but provide the brain with information to process.

There is also a flaw in our brain, as it does not seek the truth, but tries to make sense of it in any way possible, which leads to hallucinations or illusions.

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How the Eye is the Main Culprit in Hallucinations

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How the Eye is the Main Culprit in Hallucinations

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Visual hallucinations are something we perceive as reality with one of our five senses, but they also are not reality.

The brain gets most of its information from the eye, and when the eye cannot deliver visual input, the brain has to resort to its own methods of ideas. We all affiliate visual defects with Charles Bonnet syndrome and schizophrenia, and while this may be true, this is not the only time our brains deceive us because of eye input. This can happen when we are tired, experiencing sensory things our brains cannot handle, and some things our visual cortex cannot handle. Charles Bonnet syndrome is the main cause though. It causes people to lose some of their vision which makes the brain create its own information, which causes hallucinations from past knowledge.