User:Tothje/Dysprosody Rough Draft

Introduction

Prosody refers to the variations in melody, intonation, pauses, stresses, intensity, vocal quality and accents of speech. In effect, prosody has a wide array of functions including expression on linguistic, attitudinal, pragmatic, affective and personal levels. Dysprosody, also known as psuedo-foreign dialect syndrome, refers to a disorder in which one or more of these prosody functions are compromised or wholly eliminated. People diagnosed with dysprosody most commonly experience difficulties in pitch or timing control, or sometimes both. Essentially, a person diagnosed with dysprosody can comprehend language and vocalize what they intend to say, however, they speak in an accent which is not their own. Dysprosody is the rarest neurological speech disorder discovered, therefore not much is conclusively known or understood about the disorder. It is interesting to note that those who suffer from dysprosody have sometimes never been to the countries from which their accents are derived. This fact is very puzzling for neuroscientists, since dialects and accents are considered to be an acquired behavior of learning pitches, intonations, stress patterns, and such. It is still very unclear as to how damage to the brain can cause a person to speak in an accent that they have never been exposed to previously.

Causes

Dysprosody is usually attributed to neurological damage, such as brain tumors, brain trauma, brain vascular damage, stroke and severe head injury. In a study done in order to better understand the causes of dysprosody, 25 cases of dysprosody diagnosed between 1907-1978, were examined more closely. It was found that the majority developed dysprosody after a cerebrovascular accident while another 6 cases developed after a head trauma. In that same study, 16 of the patients were female while 9 were male. However, there has been no conclusive evidence that gender affects the onset of dysprosody. There has been no evidence that ethnicity, age, or genetics has any impact on the development of dysprosody.

Symptoms

Dysprosody is a disorder which is "characterized by alterations in intensity, in the timing of utterance segments, and in rhythm, cadency, and intonation of words." These differences cause a person to lose the characteristics of their particular individual speech. Dysprosody is classified as a speech disorder, and there has been almost no evidence of other effects. A person's personality, emotional capacity, motor skills, and intelligence all remain intact. However, there have been some case studies in which seizures began to develop in patients who were also suffering from dysprosody. No decisive conclusions could be made regarding this observation. Dysprosody can last for differing durations, from a few months to years, although the reason seems to be unclear.

Dysprosody in the Brain

Since the discovery of dysprosody, scientists have been attempting to declare a particular area of the brain responsible for prosody control. It was long believed that the right hemisphere of the brain was responsible for prosodic organization, ultimately leading to a grossly oversimplified hemispheric model. This model argued that the organization of language, centered in the left hemisphere, parallels the organization of prosody in the right hemisphere. Since its release, however, very few studies have given the model any substantial support.

Scientists have attributed major control of the temporal aspects of prosody, including rhythm and timing, to the left hemisphere of the brain. On the other hand, pitch perception, such as singing and linguistics related to emotion, are believed to be organized in the right hemisphere. This belief led to the development of the “Functional Lateralization” hypothesis, stating that dysprosody can be caused by lesions in either the right or left hemispheres. It further states that the left is responsible for acoustic and temporal aspects of prosody while the right is responsible for pitch and emotion . This hypothesis, however, has also been a cause for concern as studies have shown that people with left hemispheric damage exhibit prosodic deficiencies associated with the right hemisphere as defined by the Functional Lateralization hypothesis and vice versa In addition, it has also been found that medulla, cerebellum, and basal ganglia damage may cause dysprosody. These conclusions have led scientists to believe that prosodic organization in the brain is extremely complex and cannot be attributed to hemispheric divisions alone. Although not well understood as of yet, studies to identify prosodic organization in the brain continue.

Occurrences

The first documented occurrence of dysprosody was described by Pierre Marie, a French neurologist, in 1907. Marie described the case of a Frenchman who started speaking in an Alsatian accent after suffering from a cerebrovascular accident causes right hemiplagia. The next documented report of dysprosody occurred in 1919 by Arnold Pick, a German neurologist. He noticed a 29 year old Czechoslovakian speaking in a Polish accent following a cerebrovascular accident. Pick's patient also suffered from right hemiparesis, a lesser version of hemiplagia. In 1941, a woman in Norway was hit with a shell fragment during an air raid though her left frontal bone, leaving her brain exposed. When she regained consciousness at the hospital, she was hemiplegic on her right side, was suffering from seizures, and was aphasic. Initially she could only speak in monosyllables, but eventually gained full fluency of speech back. However, she sounded as though she was speaking her native Norwegian with a German accent. There have been another 21 cases documented up until 1978. 13 of those cases were documented at the Mayo Clinic while the others were documented elsewhere. There have been more recent occurrences of people who have developed accents after brain injuries, specifically strokes. In 1999, Judi Roberts suffered a stoke which paralyzed the right side of her body, leaving her unable to speak. Over time, her speech began to improve, eventually recovering full fluency, however, she developed a British accent despite living in the US all her life. In 2006, another report was documented of Linda Walker, a native of England, who developed a foreign accent after suffering from a stroke.

Parkinson's Disease and Dysprosody

Parkinson's disease, or sometimes referred to as PD, is a chronic neurodegenerative disorder that involves the loss of dopaminergic neurons in the brain. While common symptoms of PD are tremors, rigidity, bradykinesia, and postural instability, dysprosody is also a common issue in individuals diagnosed with PD. A proven characteristic feature of dysprosody in Parkinsons is monopitch, or an inability to vary pitch when speaking.

Several studies have been performed investigating the link between Parkinson's and dysprosody. It has been found that there are specific areas of prosody in which PD patients have more difficulty with. Parkinson's patients are less able to produce the loudness, pitch, and rhythm patterns required for expressing certain emotions, such as anger. The voice modulations needed to express strong emotions such as anger are difficult for PD patients. It is dysprosody that is causing this inability to express emotion and not a more general disorder regarding the processing of emotions, because PD patients generally have normal abilities to appreciate vocal or visual emotion that is presented to them. Abnormal pauses in speech is also a characteristic of Parkinsonian dysprosody. Parkinson's patients tend to have more pauses in their speech. This includes both pauses in general speech and intra-word pauses. A decrease in speech rate can also be observed in Parkinson's.

Studies have also shown a progression in dysprosody in patients with Parkinson's Disease over time. Abnormalities in speech rate, pauses, and variation range in speech become worst over time as the disease progresses. It is important to note the degradation of prosody in PD over time is independent of motor control issues, and is thus separate from those aspects of the disease.

Treatments

The most effective course of treatment for dysprosody has been speech therapy. Over time, there have also been cases of people suffering from dysporosdy gaining their native accent back with no course of treatment.