Mild-moderate Parkinson's Disease Research Articles

Self-paced saccades and saccades to oddball targets in Parkinson's disease

Patients with Parkinson's disease (PD) manifest difficulty in initiation and execution of movements, particularly when movements are sequential, simultaneous or repetitive. Eye movements are particularly effective in evaluating motor impairments. We utilized a series of saccadic eye movement paradigms to explore the ability of 13 patients with mild-moderate PD and 13 age-matched healthy controls to self-pace saccades between two continuously illuminated targets, before and after an externally cued tracking period, and respond to unexpected changes in task demand. The latter was explored by measuring saccadic responses to unexpected “oddball” targets that appeared during a well-learned reciprocating sequence of saccades, in either the opposite direction to that expected or at twice the anticipated extent. Results indicated that all participants demonstrated a marked increase in saccade amplitudes from the externally cued saccade tracking to the self-paced saccades. Unexpectedly, this difference was magnified in PD patients. Self-paced saccades before externally cueing were also more frequent than requested in the PD group, but timing improved following external cueing. The second key finding was that while patients were able to respond to unexpected changes in target amplitude, performance was more variable (in terms of latency and accuracy) when responding to unexpected changes in target direction. Hence, beneficial effects of external cueing on the timing of self-paced saccades may be mediated through cortical regions, placing less emphasis on striatal regions known to be compromised in PD. Additionally, responding to changes in saccade direction (but not amplitude) may rely on basal ganglia circuitry.

Facial expression decoding in early Parkinson's disease

The ability to derive emotional and non-emotional information from unfamiliar, static faces was evaluated in 21 adults with idiopathic Parkinson's disease (PD) and 21 healthy control subjects. Participants' sensitivity to emotional expressions was comprehensively assessed in tasks of discrimination, identification, and rating of five basic emotions: happiness, (pleasant) surprise, anger, disgust, and sadness. Subjects also discriminated and identified faces according to underlying phonemic (“facial speech”) cues and completed a neuropsychological test battery. Results uncovered limited evidence that the processing of emotional faces differed between the two groups in our various conditions, adding to recent arguments that these skills are frequently intact in non-demented adults with PD [R. Adolphs, R. Schul, D. Tranel, Intact recognition of facial emotion in Parkinson's disease, Neuropsychology 12 (1998) 253–258]. Patients could also accurately interpret facial speech cues and discriminate the identity of unfamiliar faces in a normal manner. There were some indications that basal ganglia pathology in PD contributed to selective difficulties recognizing facial expressions of disgust, consistent with a growing literature on this topic. Collectively, findings argue that abnormalities for face processing are not a consistent or generalized feature of medicated adults with mild-moderate PD, prompting discussion of issues that may be contributing to heterogeneity within this literature. Our results imply a more limited role for the basal ganglia in the processing of emotion from static faces relative to speech prosody, for which the same PD patients exhibited pronounced deficits in a parallel set of tasks [M.D. Pell, C. Leonard, Processing emotional tone from speech in Parkinson's disease: a role for the basal ganglia, Cogn. Affect. Behav. Neurosci. 3 (2003) 275–288]. These diverging patterns allow for the possibility that basal ganglia mechanisms are more engaged by temporally-encoded social information derived from cue sequences over time.

Gastric emptying time and gastric motility in patients with Parkinson's disease.

Gastrointestinal symptoms such as nausea, abdominal pain, and bloating are frequent complaints of patients with Parkinson's disease (PD). It has been postulated that impaired gastrointestinal function may contribute to the development of motor fluctuations such as delay on and no on in patients with PD. Gastrointestinal impaired function and symptoms may be associated with the disease itself or secondary to levodopa treatment. Thus, we assessed gastric emptying (GE) and gastric motility in PD patients to examine the association between clinical status and gastric function. GE and antral contraction (frequency and amplitude) were evaluated by scintigraphy in 29 patients with mild PD (Hoehn and Yahr [H&Y] stage 1.0-2.0); 22 patients with moderate PD (H&Y stage 2.5-3.0); and 22 healthy volunteers, following the ingestion of a labeled standard meal. Gastric emptying (mean +/- SD of T(1/2)) and antral contraction were not significantly different between patients with mild PD (63.4 +/- 28.8 minutes) and moderate PD (54.7 +/- 25.5 minutes). In the control group, GE was 43.4 +/- 10.8 minutes (range 29.0 - 61.0 minutes). The prevalence of delayed emptying (>61 minutes) was not significantly different in patients with mild disease (48.3%) as compared with patients with moderate disease (36.4%). Antral contraction, both frequency and amplitude, were not significantly different between patients with mild and moderate PD throughout the entire 100 minutes of the study. Untreated patients (n = 28) had mean GE T(1/2) of 59 +/- 30.6 minutes. Patients with smooth response to levodopa showed slower GE (n = 10; 73.6 +/- 25.3 minutes), while treated patients with motor response fluctuations when tested at the on state (n = 13), had much faster GE (49.3 +/- 16.2 minutes). This shortened GE in the on state was similar to the GE of normal volunteers. We conclude that gastric emptying time in patients with PD was delayed compared with control volunteers. It was even slower in patients treated with levodopa. This effect of levodopa treatment was reversed to pseudonormalization (normal GE) at the advanced stages of the disease, when patients developed motor response fluctuation. Other clinical features of PD were not associated with delayed gastric emptying.

Studies in Parkinson's Disease: I. Perceptual Speech Analyses

The perceptual speech characteristics of a group of 19 subjects with mild-moderate Parkinson's Disease (PD) were compared with those of a normal non-neurologically impaired control group matched for age and sex. Deficits were found in all aspects of speech production, including respiration, phonation, prosody, articulation and resonance. Observed speech deviations were most often mild. The speech deviation which contributed most to the variance in overall intelligibility of speech was imprecision of consonant articulation. Deficits in the phonatory system, including the presence of hoarseness and a strained strangled phonation with intermittent breathiness, were found to be the frequently occurring speech deviations in PD. Disturbed prosodic features were also noted, including a disturbed general stress pattern and a lack of variation in both pitch and loudness levels. The need for careful instrumentally based assessments of the physiological and acoustic features of hypokinetic dysarthria is emphasized.