Charles Bonnet Syndromes, Research Paper Example

Charles Bonnet Syndrome or CBS is a disorder that affects the visual pathways of the people who suffer from this strange disorder. This disorder baffles the minds of doctors and patients because persons suffering from this neurological disorder have vivid hallucinations that allude to a person suffering from mental illnesses. However, these persons do not have any other symptoms that support a diagnosis of mental illness. Many of these victims have no other prior history of mental illness or psychological problems that may cause hallucinations. Nonetheless, doctors have linked CBS to other eyesight ailments such as Glaucoma and Macular Degeneration. People with CBS are well aware that the images they are seeing are unreal. This fact is one way that doctors are able to eliminate mental illness because people suffering from mental illness are unable to understand that what they are seeing is unreal. Charles Bonnet Syndrome is characterized primarily by hallucinations.

Charles Bonnet first observed these symptoms in his grandfather. Charles Lullin, Bonnet’s grandfather began experiencing vivid hallucinations that distorted the surfaces of buildings, people, carriages, and birds. Bonnet’s grandfather was mentally stable and therefore well aware that the images he was seeing was not real. This condition was preceded by Lullin’s development of bilateral cataracts, which alludes to the fact that the disease is linked to vision loss. Later, Charles Bonnet experienced these same symptoms. Hence, the disease was named after Charles Bonnet. The Charles Bonnet Syndrome was first identified in 1936 by Mossier, who name it after a Swiss naturalist who began documenting symptoms from observations of his grandfather and later on observations of himself. The condition is defined by visual hallucinations in the absence of visual acuity, usually from the central field of vision, and in the absence of cognitive impairment. (Caldwell, 2007)

Even today the syndrome is believed to be underestimated or misdiagnosed due to the negative stigma associated with hallucinations. People who may experience these symptoms without any prior mental illness issues may be hesitant to report them to their medical physicians out of fear of being labeled mentally ill. The incidences of these hallucinations with people who have visual impairments are about 16-22 percent. This is a strong indication that people who suffer from Charles Bonnet syndrome may be linked to other visual impairment. (Manford and Anderman, 1991) The development of CBS usually occurs between the ages of 74-86, which is a common age for people to develop vision impairment. It is believed that visual impairment caused by other medical conditions causes a release of hormones in the cortex to compensate for that lack of visual stimulation. In other words , the brain makes up visions to compensate for the loss of vision. This explanation is supported by a study conducted in 200o by (Turrigiano and Nelson, 2000). During this study, subjects were blind folded for five days. While blind folded they recorded their experiences using cameras. The subjects were both male and female and ranged in age from 22-37. None of these subjects were taking any medications daily or had a history of mental illness. Some of the subjects received stimulation in the form of Braille training, games, or just performed everyday tasks. The others did not receive any stimulation. MRI scans indicated that certain areas of the brain lit up during the stimulation. The results of the study indicated that 87 percent of the participants reported having hallucinations. Some experienced flashes of light and images of people they knew. These hallucinations occurred during the stimulation periods. The subjects also reported that the hallucinations had nothing to do with past experiences. The investigators concluded that the study conveys that visual hallucinations are common when a subject suffers from sudden vision impairment of vision loss. (Caldwell, 2007)

The condition is diagnosed when the individuals who lost their vision describe seeing things that are not really there, referred to as visual hallucinations. (RNIB, 2013) CBS mostly occurs in the elderly. In addition, patients suffering from CBS are usually not initially aware of what they are seeing as hallucinations; however, when they becoming aware of the hallucinations many categorized it as a mental issue (Teeble et al., 2009) Consequently, patients are usually vulnerable and lonely, as well as upset from hallucinating in fear of losing their minds.

There are two different categories of hallucinations that occur in CBS cases, simple and complex. Simple hallucinations may consist of constructed lines, flashes, shapes, swirls or patterns and are usually move with the eyes instead of the scene. Complex hallucinations, on the other hand, are more intelligible images, such as distinct objects, people, animals, landscapes, and buildings that integrate with the environment. In most of the CBS patients, the hallucinations do not continue, but stop after some time, most often when blindness occurs or when the eyes are treated and vision is restored. The occurrence of this disease is thought to be underreported due to peoples of being labeled as mentally ill. (Caldwell, 2007)

The visual hallucinations occurring in CBS patients allow researchers to find out how the brain perceives visual perception. In individuals with this syndrome, the hallucinations can be extremely vivid, consisting of all sorts of things from people to animals to buildings. In addition, (Caldwell, 2007) adds that the visual hallucinations are not related to any impairments mental health status. In fact, the primary pathology of the condition is due to loss of vision from eye diseases, not mental related. The key factor in CBS, therefore, has been related to sensory deprivation.

The perception experiences are constructed in the brain and what we perceive is usually restrained through the physical environment and therefore, hallucinations are the images in our brain that are not constrained. A good description of a hallucination and perception was provided by Shultz and Malzak, (1991). It was indicated that if we see an object, we can ask a hypothesis in regard to whether it is there or not. The hypothesis may or may not be supported. Theories support the fact that the development of CBS has been attributed to earlier experiences or neuronal activity in the brain. (Reichert et al.) Synesthesia and Charles Bonnet Syndrome are closely related in that they both affect the relationship between the victims’ neurons. Both synesthesia and Charles Bonnet Syndrome occurs when a specific sense or experience is activated by a known stimulus.

The physiological mechanisms resulting in hallucinations from Charles Bonnet syndrome (CBS) have not been identified; however, there are multiple theories and studies that have described the syndrome. One theory Shultz and Malzak, (1991) describes the hallucinations created in CBS as perceptual traces that are released that would normally be prevented from sensory input. Basically, the theory is suggesting that the hallucination experience is prompted from sensory neurons that would have normally been offset. In addition, the neurons are described as a network or matrix. (Shultz and Malzak, 1991) Furthermore, it is further implicated that visual learning is driven by experience and predication of visual or sensory input and could explain how the brain would produce these hallucinations. In fact it explains how sensory system of normal vision generates images and causes hallucinations in people with vision loss (Reichart et al.)

One group, Turrigiano and Nelson (2000) of researchers has implied the use of a modeling framework to illustrate the generative learning in neural pathways. The modeling framework is known as the Deep Boltzmann Machine (DBM). The DBM is technical machine; however, the researchers suggest that the model could help gain insight into the context of cortical learning and perception. Another study by Reichart et al., investigated the mechanisms of cortical perception through reference to the DBM. The scientists used the DBM model to find the exact mechanisms causing hallucinations and hypothesized “homeostasis” as the pinpoint. These findings support previous research that this disorder greatly affects the proper firing of neurons. Previous research has shown experimental data illustrating homeostatic systems as a necessity in the stabilization of neuronal pathways though both cellular and cell synapse mechanisms. (Turrigiano and Nelson, 2000) In addition, it is thought that the cortex in the brain becomes over excited as a result from homeostasis. In the case of CBS, the lack of any visual sensory input could lead to an increase in excitability of the cortex as a result of homeostasis and the neurons try to compensate to return to normal levels, resulting in hallucinations.

In the study conducted by Sagiv, N. & Ward, J. (2006), the model was presented with increased corrupted training images. For instance, the pixels were turned off and set to show pre-cortical damage to vision. Homeostasis mechanisms were applied using a preferred activation level through inputs. After the model was trained with the inputs, the unit’s activation levels were computed for all training images. The visual input was then blanked out to stimulate Charles Bonnet syndrome. The results of the study indicated that homeostasis in DBM restored activity levels and in some instances through increasing neuron activity. In addition, in order to model CBS, which is mostly started though vision loss; homeostasis was repeated with blank images using the DBM. Therefore, any type of representations formed would be referred to as a hallucination. The question that there were trying to answer further from this, was whether or not the representations correlated to the images that the DBM learned or if they were just random. (Reichart et al, 2007) The results of the experiment showed that visual impairment has an impact on how and when hallucinations are formed. For instance, CBS patients start to develop hallucinations as vision starts too degraded; however, eventually the hallucinating is lost completely. This was also found to be true in the DBM model. It was found that as long as there was some input, even noise, the hallucinations were formed, but losing the input stopped the hallucinations. (Richart at al, 2007)

Other research suggests that hallucinations are usually prompted from a state of drowsiness, suggesting that there is an implication of cholinergic and serotonergic possibilities. A person who has loss vision sends false signals to the brain that he/she is in sleep modes which cause the firing of the neurons just like in synesthesia. As a result, the CBS person experiences hallucinations. (Manford and Anderman, 1991) Reichart et al. also used this theory and tested it using the DBM. Research supports that with decreased levels of Ach, there is a decrease in homeostasis neuronal excitability that would normally create the hallucinations.

Other hypotheses have been formulated to explain the origin of hallucinations. Teeple et al. (2009) has suggested that there are three processes that account for the origin of hallucinations in vision conditions. All three processes are path physiological. The first process causes seizure activity. The irritation is occurs in the primary visual cortex of the brain. Irritations from seizures cause more complex hallucinations. The second process refers to lesions in the sensory system. As mentioned in Charles Bonnet syndrome that researchers have suggested that the hallucinations are caused by the excitability of neurons, these researchers also suggest that the hallucinations are due to the excitability of the neurons much like in the phantom limb syndrome when a lesion is present. In the phantom limb syndrome, patients that lose a limb often feel the sensations of the limb still being there. Again, this is in the realm of hallucinations and sensory conditions that is initiated by neuron activity. As a result, the third process is linked to drowsiness or individuals with sleep disorders. This suggestion coincides with the previous author’s research on ACh release. Burke (2002)

Other current research in regard to Charles Bonnet Syndrome (CBS) is also focused on neural pathways. It seems that researchers are in agreement that understanding neural pathways can help lead to diagnoses in this condition, as well as treatment of the condition. Burke (2002) suggests the concept of deafferentation in which hallucinations result from the deafferentation of the visual cortex, or the silencing of the afferents in the cortex. Basically, the researcher indicates that the deafferentiation leads to an increase in neuronal excitability due to biochemical and molecular changes resulting in spontaneous changes and activity, or hallucinations. Burke further explains how the nervous systems react when a region within the nervous system becomes deafferented. Burke indicates that the cells become more excitable leading to a multitude of different outcomes, such as atrophy or death or it may survive from input from other sources. The difference in this research to the previous research mentioned above is that the author describes the synapse of the neurons as the source. The author indicates that there are changes in the size of the synapse, the vesicle of the synapse, the release zone and in the release probability. In addition, research supports the fact that biochemical changes in the deafferented synapses, such as an increase in glutatergic NMDA (n-methyl-d-aspartate) response and a decrease in GABA (g-amino butyric acid). Consequently, the hallucinations become more vivid over time due to the increase of the enabling hormones.

Research has shown this increase in neural activity after deafferentation. For instance, in cases where the region of the cerebral cortex was isolated from neurons, the activity resulted in periods of inactivity to waves or bursts of activity. The crucial finding is that the activity was not so much the level of the activity, but the high frequency in the amount of bursts of activity. The bursts of activity show strong discharges from the cortical cells in the cortex. In addition, other research has applied resonance imaging (fMRI) to illustrate that different types of hallucinations are found in different regions of the visual cortex. For instance, individuals experiencing hallucinations from CBC responded indicating that faces were found to be located in the superior temporal sulcus of the cortex. (Burke, 2002) Objects and scenery were found to be localized in the ventral occipital-temporal cortex and the eye referenced frames. (Burke, 2002) As a result, victims suffering from CBS tend to have similar hallucinations.

The findings of all research regarding Charles Bonnet Syndrome is extremely difficult to decode since the occurrence is reported from the individual themselves. Therefore, researchers have developed models that compute the reports from victims suffering from CBS. Consequently, these models have been able to link CBS to the activity of neurons. The models address visual hallucinations as a whole. With these models and with the sound input from patients diagnosed with Charles Bonnet syndrome, researchers are able to try and determine the mechanism in which perception and the resulting hallucinations occur.

Investigations have led to two types of predictions in helping patients with Charles Bonnet Syndrome. One, the interference of cortical homeostasis mechanism in an individual that has perceived loss of vision could delay or in fact prevent hallucinations from occurring. Two, since it was found that the lack of acetylcholine, in CBS patient particular, results in the occurrence of hallucinations, that the implementation of acetylcholine could help neural response and balance the firing of neural pathways to decrease hallucinations from occurring. Overall, there have been advancements done in research in regard to the mechanisms causing hallucinations in CBS patients; however, more research needs to be conducted with these models in regard to the concepts of normal perception in the visual cortex and the changes that occur with vision loss or damage. The models serve as great tools in generating spontaneous images to help further the understanding of CBS. Hubbard, E., PhD. (2007)

References

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