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The muscle changes occurring in Parkinson's disease (PD) may come about as a consequence of the modified pattern of motor unit activation and rigidity, which are characteristic of the disease. A tendency towards hypertrophy of type I fibers and, in some instances, atrophy of type II fibers has been observed. Fourteen patients affected by PD and 10 age-matched controls were studied in order to investigate these muscle changes. We indirectly evaluated muscle modifications by measuring muscle fiber conduction velocity (CV) and median frequency (MDF) of the power spectrum using automatic analysis of surface EMG. The tibialis anterior muscle was selected for the study of contractions electrically induced by 35 Hz pulse trains lasting 30 s; the myoelectric signal was detected using the 4-bar electrode technique described by Broman et al. (Broman, H., Bilotto, G. and De Luca, C.J. Myoelectric signal conduction velocity and spectral parameters: influence of force and time. J. Appl. Physiol., 1985, 58: 1428-1437). Muscle biopsy specimens were obtained in 4 PD patients by surgical excision at the site where the EMG recording electrode had been placed. The main difference observed between PD subjects and controls was the rate of change of MDF and CV during the course of stimulated contraction; patients with PD sustained a smaller fatigue related decrease in both parameters compared to controls. According to our histological data, this result can be explained by a type I fiber percentage which accounts for 79% of the myofiber population on average. As expected, the CV basal values correlated directly with type I fiber diameter. These data suggest that non-invasive surface EMG techniques are useful in assessing the modifications of muscle characteristics that are observed in PD patients and for analyzing some aspects of the peripheral fatigue in this disease.

Olfactory function impairment has been observed in patients with idiopathic Parkinson's disease (PD) using psychophysical procedures. In this study, an electrophysiological technique based on spectral analysis and topographic EEG mapping was used to evaluate EEG arousal response to olfactory stimulation in ten normal subjects and ten PD patients in stage II according to Hoehn and Yahr's scale, all of whom had akinetic-rigid syndrome and were receiving chronic L-Dopa therapy. Olfactory function was stimulated using diluted benzaldehyde by means of an apparatus set up in our laboratory. Spontaneous and post-olfactory stimulus EEGs were recorded from 20 electrodes placed upon the scalp according to the Int. 10-20 System. Total EEG power (from 0.5 to 19.5 Hz) was evaluated over 10 sec. artefact-free epochs. An olfactory arousal reaction was detected in nine of the ten PD patients and was characterised by a significant decrease in total power similar to that observed in all of the 10 normal subjects; these variations in EEG were found in all but the anterior regions of the scalp. The use of this technique does not seem to reveal any clear alteration in the olfactory function of PD patients.

Dream reports of patients with Parkinson's disease (PD) were analyzed to ascertain whether cognitive deficits associated with this nonfocal brain pathology influence dream structure or dream recall. Fifteen outpatients with idiopathic PD were sampled (diagnosed from 1 to 10 years and currently in stage II or III of Hoehn and Yarh's scale); all were without psychiatric symptoms or major medical illnesses and were currently being treated with L-dopa. After an adaptation night in the sleep laboratory, each patient spent a night in which he/she was awakened at least twice in rapid eye movement sleep and asked to report dream experience. Thirteen patients were able to report at least one dream. Overall frequency of dream recall (71.4%) was fully compatible with normative data for the elderly. Multiple regression analyses showed that both the length of the dream report as story and the organization of contents into coherent episodes (analyzed using Mandler and Johnson's story grammar) varied significantly in relation to level of cognitive functioning and, in part, of language comprehension, but not in relation to age, illness duration, and dose of L-dopa.

Cognitive disturbances are frequently encountered in advancing Parkinson's disease (PD). Typically there are visuo-spatial disorders, memory impairment and bradyphrenia, defined as 'subcortical dementia' to distinguish it from the dementia that occurs in Alzheimer's disease, where the most prominent dysfunctions are agnosia, apraxia and aphasia. An electrophysiological test to study cognitive processing is the P300 (or P3) of the Event Related Potentials; in particular the latency of the P3 seems to correlate with cognitive decline. Thirty patients affected with idiopathic PD were investigated using a classic auditory "oddball" paradigm (rare tone--"target"--3000 Hz, frequent tone--"non target"--1000 Hz; the patients were instructed to recognize and keep a mental count of the number of rare tones). Electrophysiological findings were compared with those obtained in twenty normal subjects, age and sex matched with the patient's group. The parameters of P300 were correlated with patient's age, duration of the disease, motor and cognitive impairment levels and L-Dopa therapy. The P300 was loss in 16.6% (5 p.) and delayed in 33.3% (10 p.). Significative correlations were found only with age and cognitive impairment scores, but not with other variables analyzed. These results suggest that P300 could be a useful test to identify demented patients among those with PD, despite different motor disabilities.