User:Neuroit/sandbox

In Fall 2013, I am working on the amorphosynthesis wikipage for the class "Introduction to Neuroscience" at Middlebury College. My partner's sandbox contains all of our collective work, but I have chosen to highlight my individual contributions here so that my professors can easily distinguish our input. The sections "Causes" and "Signs and Symptoms" were written together, so I include them here. The sections on Denny-Brown's research are my own personal input and writing.

Causes

Causes of Amorphosynthesis are:

• Cerebrovascular accidents that have affected cerebral hemispheres.

• Diffused brain lesion and lesions on other parts of the central nervous system (CNS).

Signs and Symptoms

S. Fazlullah, in his article Tactile Perceptual and Tactile-Amorphosynthesis in the Localization of Cerebral Lesions (1956), provides a detailed explanation of the specific signs and symptoms in amorphosynthesis caused by left and right parietal lobe lesions.

Left Parietal Lobe Lesion

Gerstmann syndrome:

• A patient is unable to recognize his/her finger.
• A patient is unable to differentiate right from left.
• A patient makes mistakes while writing.
• A patient is unable to name things.

Parietal apraxia:

• A patient is unable to understand or execute actions.

Constructional apraxia:

• A patient has trouble drawing.

Right Parietal Lobe Lesion

Anosognosia

• A patient cannot perceive a defective function such as hemiplegia, or paralysis of one side of the body.

Hemiasomatognosia

• A patient cannot focus attention on the left side of the body and believes that this side of the body feels “strange.”

Metamorphognosia

• A patient perceives part of the body as too heavy or thick.

Corporeal agnosia

• A patient loses sensation in the left side of the body and mistakenly believes that an extremity has been lost.

Phantom Sensations

• A patient believes that a part of the body has doubled.

Transposition of Parts of the Body

• A patient neglects the left side of the body, always performing actions with her right and searching for her left extremities in places other than the hospital bed, such as a locker.

Constructional apraxia

• When asked to arrange, draw, or copy a simple model of one to three dimensional figures, a patient consistently neglects important details on the model’s left side. For example, when asked to draw a figure of a few matchsticks, the patient would only draw the matchsticks on the figure’s right side.

Disorientation of space:

• A patient is unable recognize depth of space.

Agnosia of left portion of space:

• A patient is unable to perceive sensation on the left of her body.
• A patient is unable to see from the left eye.

Anaesthoagnosia:

• A patient has loss sensation on the left side of his/her body.

Balint optic ataxia:

• A patient is unable to see two things at once.
• A patient is unable to coordinate ocular movement.
• A patient is unable to see objects on the left peripheral field.

Primary Research

Denny-Brown and Banker

According to Denny-Brown’s 1954 article, Amorphosynthesis from Left Parietal Lesion, lesions of the parieto-occipital region cause disturbance of recognition in a patient – left-sided lesions usually cause agnosia, while right-sided lesions usually cause lack of recognition of the person’s left side and extrapersonal space. Denny-Brown defines agnosia as a disorder in formation or use of symbolic concepts, such as recognizing body parts; in naming objects; in understanding numbers; or in understanding geographic and/or spatial location. It applies to both sides of a person, even though a lesion in only one side of the parietal lobe – the dominant one – causes it. He argues that amorphosynthesis, on the other hand, is usually caused by a lesion in the non-dominant parieto-occipital lobe and results in lack of awareness on the opposite side of the body.

Before Denny-Brown, researchers such as Lange , Dide, Lenz, and McFie and associates proposed that the brain's right hemisphere controls a specific function in spatial perception, explaining why damage to the parieto-occipital lobe of the right hemisphere results in the loss of spatial perception. In his article, Denny-Brown alternately proposes that lesions of the parieto-occipital lobe cause errors in spatial summation, not spatial perception. By using a case study, he argues that amorphosynthesis actually may result from lesions of either side of the parietal lobe, depending on the patient’s dominant hemisphere. He further argues that lesions in the dominant lobe cause both amorphosynthesis and agnosia – the agnosia just obscures the amorphosynthesis.

Case Studies

Denny-Brown: Amorphosynthesis From Left Parietal Lesion

A 36 yr. old white married boilermaker named W.F. was admitted to the Boston City Hospital on March 23, 1953 after a week of general weakness and malaise. Three days before his admission, he developed a throbbing bilateral headache, and on the day of admission, he was unable to walk or support himself due to right-sided weakness. On the first day, his symptoms were severe – while he could perform simple movements of his right limbs, he did not feel pain, temperature, or touch on his right side and refused to acknowledge that his right limbs were his. In fact, he repeatedly threw his right arm from the hospital bed, believing that the arm did not belong to him.

On the second day, W.F. was transferred to a neurological division for further examination. Even though he had been right handed his entire life, he ate, wrote, and held a cigarette in his left hand. When asked to extend his arms or grab an object with his right hand, he repeatedly hyperextended the fingers on his right hand without being conscious of doing so. He also shaved with his left hand and only on the left half of his face, not realizing there was anything wrong with his actions.

When stimulated with pain, temperature, touch, and vibration, W.F. reported feeling these sensations on his right side but described them as “not as clear” as on the left. When both sides of his body were simultaneously stimulated, he was unable to distinguish sensation on his right side. Denny-Brown terms this phenomenon extinction, and for the first week, the patient’s left side remained dominant over his right side. In addition, when stimulated by two points simultaneously on his right side, W.F. could not distinguish between them – the right side of his face was dominant over his right arm and leg, and his right leg over his right arm, throughout the first week.

Importantly, W.F. gave no evidence of agnosia. He expressed himself clearly, named objects well, had no trouble finding his way about the hospital, and could even draw maps of Boston, Massachusetts, and the USA fairly well. He was able to identify all the parts of his body and distinguish right from left on his own body, and his initial belief that his right arm belonged to somebody else ceased after the second day of hospitalization. But he still had difficulty perceiving the right side of his body – even on the 12th day, he would properly put his left hand into the sleeve of his shirt when dressing but simply drape the shirt around his right side, not realizing he had done so.

Even though left-sided lesions of the parieto-occipital lobe usually cause agnosia, W.F. appeared to have a left-sided lesion causing amorphosynthesis. Electroencephalograms, obtained on admission and a week later, showed focal slow waves in the left parietal and occipital leads, and the clinical diagnosis was a left anterior parietal lesion, most likely caused by a small hemorrhage in the brain.

In analyzing W.F., Denny-Brown raises the question of why the patient’s left-sided lesion caused amorphosynthesis rather than agnosia. In general, as Denny-Brown explains in his introduction, left-sided lesions cause agnosia while right-sided lesions cause amorphosynthesis. He gives two possible explanations – first, that the right hemisphere might be dominant in the patient, not the left. This would suggest that just as right-handed and left-handedness differ among the population, so too does the dominance of the parieto-occipital lobe. While Denny-Brown notes that he cannot refute this explanation, he sees it as more likely that the patient’s lesion simply did not extend posteriorly to produce agnosia. Therefore, he argues that the difference between causes of amorphosynthesis and agnosia is directly related to the size and extension of the parieto-occipital lesion. As a whole, he concludes that amorphosynthesis of the opposite side of the body from a parieto-occipital lesion can occur on as a result of either left or right-sided lesion, even though amorphosynthesis from right parietal lesion is more commonly observed.

Project Proposal

This is a start on our Amorphosynthesis research project. We welcome any comments or advice concerning our research. In addition, we would like to note that in our search of PubMed's archive of journal articles, we found no journal articles about amorphosynthesis published after Cherington's 1975 article. Therefore, our page will provide the history of this term's use and its major research, and it will also explain that current research is not being done on the topic.

Amorphosynthesis, caused by a lesion of the parietal lobes, leads to loss of somatic sensation on the opposite side of the body affected. Our primary research sources are the journal articles by Fazlullah, Denny-Brown, Cherington, and Mountcastle. We will summarize these researchers’ main findings in this proposal, and explain their research in depth on our Wikipedia page.

One of the chief difficulties of studying amorphosynthesis is that some sources, such as Denny-Brown, define the term as only occurring in the left parietal lobe and affecting the right side of the body, while other sources, such as Fazlullah, claim that the right parietal lobe can also be affected. In our Wikipedia article we will give equal attention to each article and try to resolve this inconsistency between sources.

In Tactile perceptual Rivalry and Tactile-Amorphosynthesis in the Localization of Cerebral Lesions, Fazlullah concludes that lesions in the parietal lobes cause the entire brain to malfunction due to combining impulses of sensory stimuli, conceptual, and perceptual defects. These “combining impulses” are Fazlullah’s definition of amorphosynthesis (Fazlullah 346).

We do not currently have access to the Denny-Brown and Cherington articles; however, we have requested the items through Interlibrary Loan. As soon as we receive the articles, we will read them thoroughly and begin to compile their information for our Wikipage. Interestingly, Mountcastle’s article attributes Denny-Brown with coining the term “amorphosynthesis” (Mountcastle et al. 872). Though Mountcastle himself only references the term briefly, this tells us that once we receive Denny-Brown’s article we will have access to the very first research ever done on this topic.

Primary Research:

Tactile perceptual Rivalry and Tactile-Amorphosynthesis in the Localization of Cerebral Lesions by FAZLULLAH, S Postgraduate medical journal, ISSN 0032-5473, 07/1956, Volume 32, Issue 369, pp. 338 – 352

Posterior parietal association cortex of the monkey: command functions for operations within extrapersonal space by V. B. Mountcastle, J. C. Lynch, A. Georgopoulos, H. Sakata and C. Acuna, J Neurophysiol 38:871-908, 1975.

Amorphosynthesis from Left Parietal Lesion by D. Denny-Brown, M.D.; Betty Q. Banker, M.D.

AMA Arch NeurPsych. 1954;71(3):302-313. doi:10.1001/archneurpsyc.1954.02320390032003

Amorphosynthesis, Encyclopedia of Neuroscience, 2009, ISBN 3540237356, Volume 1, p. 98

Amorphosynthesis on the chess board by Cherington, M., & Yarnell, P. (1975), Scand J Rehabil Med. 1975;7(4):176-8, Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/1220001

Table of Contents/Points to Consider:

History of Research

1.) Denny-Brown

2.) Fazlullah

3.) Cherington and Yarnell

4.) Mountcastle et al.

Cause/brain regions affected

1.) Left vs. Right Parietal Lobe Lesions

2.) Main Causes

a.) Cerebrovascular Accidents

b.) Diffused Brain Lesions

c.) Lesions on Other Parts of the Central Nervous System

Case studies

1.) Cherington and Yarnell’s Amorphosynthesis on the Chess Board

Research 1.) Summary of Procedures in Primary Sources

2.) Summary of Main Conclusions and Results

3.) Discussion of Conflicts Between Sources

Further Reading

Works Cited

We will split up the work evenly, each reading two of the primary research articles we have found and coming together to provide each other with the information we have learned. We will combine this information and present it on our Wikipedia page, as outlined above, by writing summaries of the articles we have read and working together to create a unified article that comments intelligently on amorphosynthesis as a whole.