Aspartame use and Parkinson's disease: review of associated effects on neurotransmitters, oxidative stress, and cognition.

Objective: The purpose of this review was to assess the current evidence regarding the associated physiological and cognitive effects of aspartame (APM) consumption and Parkinson's Disease (PD). METHODS: A total of 32 studies demonstrating effects of APM on monoamine deficiencies, oxidative stress, and cognitive changes were reviewed. RESULTS: Multiple studies demonstrated decreased brain dopamine, decreased brain norepinephrine, increased oxidative stress, increased lipid peroxidation, and decreased memory function in rodents after APM use. In addition, PD animal models have been found to be more sensitive to the effects of APM. DISCUSSION: Overall, studies of APM use over time yielded more consistent results; however, no study has examined long-term effects on APM in human PD patients. Based on the current evidence, long-term human based observational research is needed to further investigate the potential effect of APM on PD.

Dynamic networks of cortico-muscular interactions in sleep and neurodegenerative disorders.

The brain plays central role in regulating physiological systems, including the skeleto-muscular and locomotor system. Studies of cortico-muscular coordination have primarily focused on associations between movement tasks and dynamics of specific brain waves. However, the brain-muscle functional networks of synchronous coordination among brain waves and muscle activity rhythms that underlie locomotor control remain unknown. Here we address the following fundamental questions: what are the structure and dynamics of cortico-muscular networks; whether specific brain waves are main network mediators in locomotor control; how the hierarchical network organization relates to distinct physiological states under autonomic regulation such as wake, sleep, sleep stages; and how network dynamics are altered with neurodegenerative disorders. We study the interactions between all physiologically relevant brain waves across cortical locations with distinct rhythms in leg and chin muscle activity in healthy and Parkinson's disease (PD) subjects. Utilizing Network Physiology framework and time delay stability approach, we find that 1) each physiological state is characterized by a unique network of cortico-muscular interactions with specific hierarchical organization and profile of links strength; 2) particular brain waves play role as main mediators in cortico-muscular interactions during each state; 3) PD leads to muscle-specific breakdown of cortico-muscular networks, altering the sleep-stage stratification pattern in network connectivity and links strength. In healthy subjects cortico-muscular networks exhibit a pronounced stratification with stronger links during wake and light sleep, and weaker links during REM and deep sleep. In contrast, network interactions reorganize in PD with decline in connectivity and links strength during wake and non-REM sleep, and increase during REM, leading to markedly different stratification with gradual decline in network links strength from wake to REM, light and deep sleep. Further, we find that wake and sleep stages are characterized by specific links strength profiles, which are altered with PD, indicating disruption in the synchronous activity and network communication among brain waves and muscle rhythms. Our findings demonstrate the presence of previously unrecognized functional networks and basic principles of brain control of locomotion, with potential clinical implications for novel network-based biomarkers for early detection of Parkinson's and neurodegenerative disorders, movement, and sleep disorders.

Dry Eye Syndrome and Sicca Complex are Commonly Found in Patients with Postural Orthostatic Tachycardia Syndrome.

PURPOSE: Patients with postural orthostatic tachycardia syndrome (POTS) present to outpatient dysautonomia clinics endorsing a wide range of symptoms. Dry eyes and mouth, or sicca complex are frequently reported. This retrospective study investigates the incidence and quantifies the severity of dry eye syndrome (DES) in patients with POTS. PATIENTS AND METHODS: This retrospective study compiles survey results, and dry eye clinical data from twenty-three POTS patients (22 females, average age 34.9 and st dev 14.0 years) surveyed during their initial or follow-up appointments. Patient's medication lists were documented to account for anticholinergics, antihistamines, and anticholinesterase use. Patients endorsing dry eye symptoms were tested with Schirmer's test strips to identify clinically dry eyes and stratified for severity. RESULTS: Sixty-five percent of patients endorsed dry eye symptoms (15/23). Seventy-four percent of patients endorsed dry mouth symptoms (17/23). Among patients endorsing dry eyes, 81% of eyes had decreased tear production with Schirmer's strip wetting less than 10 mm/5 min (13/16). CONCLUSION: DES is an additional and significant disease burden for the POTS patient population. Dry eye and exocrine gland function should be evaluated as part of the dysautonomia work up with referral to ophthalmology as appropriate. Patients with clinically dry eyes who report additional autonomic dysfunction should be further evaluated for widespread autonomic dysfunction.