[1] Prosody refers to the variations in melody, intonation, pauses, stresses, intensity, vocal quality, and accents of speech.
[2] As a result, prosody has a wide array of functions, including expression on linguistic, attitudinal, pragmatic, affective and personal levels of speech.
Speaking in a foreign accent is only one type of dysprosody, as the condition can also manifest itself in other ways, such as changes in pitch, volume, and rhythm of speech.
While the individual's personality, sensory comprehension, motor skills, and intelligence all remain intact, their grammar as well as vocal emotional capacity can be affected.
Prosodic control is essential to speech delivery because it establishes vocal identity, since each individual's voice has unique characteristics.
For example, individuals with linguistic dysprosody may have difficulty distinguishing the production of interrogative and declarative sentences, switching or leaving out the expected rising and falling shift, respectively.
There has been strong evidence that dysprosody does affect the ability to express emotion, however the severity may vary depending on what part of the brain has been damaged.
Studies have shown that the ability to express emotional information is dependent on motor, perceptual, and neurobehavioral functions all working together in a specific way.
[citation needed] When studies of dysprosody first began, diagnosis involved an untrained ear determining impairments in the prosodic elements.
In order to determine linguistic dysprosody, a patient is asked to read sentences that can either be a statement or a question using both declarative and interrogative intonations.
Scientists have attributed major control of the temporal aspects of prosody, including rhythm and timing, to the left hemisphere of the brain.
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.
[3] These conclusions have led scientists to believe that prosodic organization in the brain is extremely complex and cannot be attributed to hemispheric divisions alone.
They have concluded that patients with Parkinson's disease tend to struggle with specific areas of prosody; they are less able to produce the loudness, pitch, and rhythm patterns required for expressing certain emotions, such as anger.
[14] The demonstration of deficits in producing and understanding emotional information in modalities other than speech prosody (e.g. facial and gestural) in individuals with Parkinson's disease, as well as in individuals with other disorders affecting basal ganglia circuitry, are providing increasing evidence for an additional non-motorically based dimension underlying prosodic deficits[16] and a meta-analysis examining almost 1300 individuals with Parkinson's disease reported a "robust link" between Parkinson's disease and deficits in recognizing emotion from voice and facial expression.
[14] The degradation of prosody in Parkinson's disease over time is independent of motor control issues, and is thus separate from those aspects of the condition.
[14] Studies have shown that treatment for Parkinson's disease can help with the dysprosody symptoms, however there is usually an improvement in pitch control only and not in the volume and emotional aspects of the condition.
[3] Several studies found an atypical neural processing of expressive dysprosody in individuals diagnosed with autism spectrum disorder.
The first step in therapy is practice drills which consist of repeating phrases using different prosodic contours, such as pitch, timing, and intonation.
Treatment following the lines of the principles of motor learning (PML) was found to improve the production of lexical stress contrasts.
Scientists believe that studying the connections between dysprosody and these better understood conditions may help them pinpoint specific areas of the brain responsible for prosody.
Pick noticed that not only was the accent altered, but the timing of the speech was slower, and the patient spoke with uncharacteristic grammatical mistakes.
A woman, Astrid L., in Norway was hit with a shell fragment during an air raid in 1941 through her left frontal bone, leaving her brain exposed.
When first starting to speak again, she also spoke with uncharacteristic grammatical errors, but over time they became much less pronounced and eventually she gained back full fluency of speech.
He found that in addition to her altered speech patterns, she had trouble finding the Norwegian words for trivial objects, such as light switch and match box.
She also had to repeat the examiner's questions aloud before answering, had to say words out loud to herself before writing them down, and had difficulty comprehending written instructions.
This is very puzzling for neuroscientists, since dialects and accents are considered to be an acquired behavior of learning pitches, intonations and stress patterns.
Over time, her speech began to improve, eventually recovering full fluency, but she developed a British accent despite having lived in the US for her whole life.