Age-related decrease in motor cortical inhibition during standing under different sensory conditions

Background: Although recent studies point to the involvement of the primary motor cortex in postural control, it is unknown if age-related deterioration of postural control is associated with changes in motor cortical circuits. We examined the interaction between age and sensory condition in the excitability of intracortical motor pathways as indexed by short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) during standing.Methods: We used magnetic brain stimulation to evoke SICI and ICE in 11 young (range 21 25 years) and 12 healthy old adults (range 60-74 years) while they stood on a rigid platform or foam, with the eyes open or closed.Results: There was an overall age-related 43% reduction in SICI (p = 0.001). SICI lessened when standing on foam in old (31%) but not in young (1%) adults (condition x group interaction, p = 0.049). This reduction was associated with increases in center of pressure velocity (r = 0.648, p = 0.043). Age (p = 0.527) and sensory conditions (p = 0.325) did not affect ICF.Conclusion: Motor cortical circuits controlling leg muscles are modulated differently in healthy old vs. young adults during upright posture. Future experiments will clarify whether this difference mediates impaired postural control or serves as a compensatory mechanism to counteract postural instability.</p

Effects of Age on Brain Activation During Auditory-Cued Thumb-to-Index Opposition

Background and Purpose —Available data indicate a decline in fine finger movements with aging, suggesting changes in central motor processes. Thus far no functional neuroimaging study has assessed the effect of age on activation patterns during finger movement. Methods —We used high-resolution perfusion positron emission tomography to study 2 groups of 7 healthy right-handed subjects each: a young group (mean age, 24 years) and an old group (mean age, 60 years). The task was a thumb-to-index tapping, auditory-cued at 1.26 Hz with a metronome, with either the right or the left hand. The control condition was a resting state with the metronome on. Results —Significant differences between old and young subjects were found, suggesting significant overactivation in older subjects affecting the superior frontal cortex (premotor-prefrontal junction) ipsilateral to the moving fingers, as if the execution of this apparently simple motor task was judged more complex by the aged brain. Similar findings in previous perceptual and cognitive paradigms have been interpreted as a compensation process for the neurobiological changes of aging. Analysis of the control condition data in our sample showed, however, that this prefrontal overactivation in the old group was due at least in part to higher resting perfusion in anterior brain areas in the young subjects. Conclusions —The changes in brain function observed in this study may underlie the subtle decline in fine motor functions known to occur with normal aging. Our findings emphasize the importance of using an age-matched control group in functional imaging studies of motor recovery after stroke

Emerging insights into the genesis of cerebral ischaemia and stroke

Stroke is a global problem with increasing significance because of the ageing population. Except for age, hypertensionisbyfar themostimportantriskfactorfor stroke. Hypertensionpredisposes toanumberof intracerebral and extracerebral vascular lesions which may cause cerebrovascular events by different mechanisms. The high metabolic need and low energy reserve make the braiavery vulnerable to ischaemia. During the last decade a number of experimental studies - supported by PET studies in man - suggest the presence of a therapeutic window, i.e. the time during which the neurons can be saved. The penumbra is the zone surrounding the core of the infarct where the flow is decreased and the neurons are lethargic and may be electrically silent but still viable. The presumed role of calcium, excitatory amino acids, free radicals, platelet-activating factor, acidosis and brain temperature in the process of neuronal death is briefly reviewed.peer-reviewe

Possible Treatment of Parkinson's Disease with Intrathecal Medication in the MPTP Model

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73916/1/j.1749-6632.1988.tb31828.x.pd

Age and features of movement influence motor overflow.

OBJECTIVES:To measure the magnitude and prevalence of motor overflow to the arm at rest during attempted unilateral arm movements. DESIGN:Cross-sectional assessment. SETTING:Motor physiology laboratory. PARTICIPANTS:Healthy young (n=20) and elderly (n=20) adult subjects. MEASUREMENTS:Surface electromyography (EMG) was obtained from bilateral forearm muscles during performance of 12 different unilateral finger-tapping tasks. RESULTS:For all subjects, faster movement rate (F=2.56-3.30, P&lt;.05), cognitive distraction (F=4.09, P&lt;.05), and fatigue (F=15.15, P&lt;.001) were each associated with a significant increase in the magnitude of EMG in the arm intended to be at rest. In elderly subjects, tapping at maximum rate and fatigue were each associated with a further increase in motor overflow across the midline. In addition, better left hand dexterity correlated with greater motor overflow to the right hand during rapid left hand tapping (r=0.63, P&lt;.005). Prevalence of motor overflow was also higher in older subjects for some tasks, for example during 1 Hz tapping by the right index finger (motor overflow present in 45%, vs 15% young subjects, P&lt;.05). CONCLUSION:Several behavioral variables increase motor overflow across the midline in young and elderly adults. Motor overflow was even greater in elderly subjects with the most demanding tasks and was greater in those with better motor status, suggesting that this form of motor system change is a compensatory event of normal aging rather than age-related dysfunction. The results support the hypotheses that healthy aging is associated with an increase in the degree to which brain function is bilaterally organized

Bedeutung des Neurotoxins MPTP für Ätiologie und Therapie der idiopathischen Parkinsonkrankheit [Significance of the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine for the etiology and therapy of idiopathic Parkinson disease]

Exposure of drug addicts to MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) has caused a Parkinsonian syndrome accompanied by a selective destruction of dopamine containing neurones in the pars compacta of the substantia nigra. MPTP in the human causes a severe irreversible state that very closely resembles idiopathic Parkinson's disease both in its clinical features and response to pharmacological treatment. Interest in potential environmental agents that might play a role in the aetiology of idiopathic Parkinson's disease is likely to increase as the result of the discovery of the relatively simple molecule MPTP which is highly toxic to the substantia nigra. Until the discovery of the neurotoxicity of MPTP there was no effective animal model of Parkinson's disease. Administration of PTP to monkeys induces persistent parkinsonism which responds to classical antiparkinsonian therapy. The morphological and biochemical changes in the brains of the animals are more limited and selective than those seen in idiopathic Parkinson's disease. The model of MPTP-treated monkeys appears to provide a useful testbed for the evaluation of future treatments for the disease. The precise mechanism of MPTP toxicity has yet to be determined and may provide the clue to the mechanism of neuronal death in Parkinson's disease. After entering the brain MPTP is oxidized to MPP+ (1-methyl-4-phenylpyridine) at an extraneuronal site.(ABSTRACT TRUNCATED AT 250 WORDS

A smartphone-based architecture to detect and quantify freezing of gait in Parkinson’s disease

Introduction The freezing of gait (FOG) is a common and highly distressing motor symptom in patients with Parkinson’s Disease (PD). Effective management of FOG is difficult given its episodic nature, heterogeneous manifestation and limited responsiveness to drug treatment. Methods In order to verify the acceptance of a smartphone-based architecture and its reliability at detecting FOG in real-time, we studied 20 patients suffering from PD-related FOG. They were asked to perform video-recorded Timed Up and Go (TUG) test with and without dual-tasks while wearing the smartphone. Video and accelerometer recordings were synchronized in order to assess the reliability of the FOG detection system as compared to the judgement of the clinicians assessing the videos. The architecture uses two different algorithms, one applying the Freezing and Energy Index (Moore-Bächlin Algorithm), and the other adding information about step cadence, to algorithm 1. Results A total 98 FOG events were recognized by clinicians based on video recordings, while only 7 FOG events were missed by the application. Sensitivity and specificity were 70.1% and 84.1%, respectively, for the Moore-Bächlin Algorithm, rising to 87.57% and 94.97%, respectively, for algorithm 2 (McNemar value = 28.42; p = 0.0073). Conclusion Results confirm previous data on the reliability of Moore-Bächlin Algorithm, while indicating that the evolution of this architecture can identify FOG episodes with higher sensitivity and specificity. An acceptable, reliable and easy-to-implement FOG detection system can support a better quantification of the phenomenon and hence provide data useful to ascertain the efficacy of therapeutic approaches

Dynamics of motor network overactivation after striatocapsular stroke: a longitudinal PET study using a fixed-performance paradigm.

BACKGROUND AND PURPOSE: Although excessive brain activation during affected hand motion after stroke is well documented, its time course has been rarely studied, and when studied, this has either been with passive movement or with active but cognitively complex task and uncontrolled performance over time, complicating interpretation. METHODS: According to a prospective and longitudinal design, we studied 5 right-handed patients with right-sided hemiparesis due to first-ever left striatocapsular infarction. Three-dimensional PET H(2)O(15) studies were performed twice ( approximately 7 and approximately 31 weeks after stroke [PET1 and PET2, respectively]) during right thumb-to-index tapping executed at the same rate in both studies (1.26 Hz, auditory cued). With SPM96 software, significant group and individual overactivations (P<0.05, corrected for multiple comparisons) were computed by comparison with a group of 7 healthy age-matched right-handed control subjects performing the same task. RESULTS: Motor recovery was significant from PET1 to PET2. Both the group and individual analyses revealed striking overactivations at PET1, affecting notably the cortical hand area and the whole motor network bilaterally. These overactivations were less prominent at PET2 over both hemispheres, not only in terms of Z score but also in terms of spatial extent (almost reaching statistical significance in the affected hemisphere for the latter, P=0.09). However, new overactivations were found at PET2 in the left prefrontal areas, the putamen, and the premotor cortex. CONCLUSIONS: This study is the first to document that to perform the same simple movement of the paretic fingers, the brain with subcortical infarction shows less overactivations at the late than at the early timepoint, especially on the affected side, suggesting reduced recruitment of affected-hemisphere motor networks. However, unaffected-hemisphere prefrontal, premotor, and putaminal overactivations, observed at PET2 only, may suggest late-appearing compensatory reorganization

Detecting Incident Delirium within Routinely Collected Inpatient Rehabilitation Data: Validation of a Chart-Based Method

Delirium is a brain condition associated with poor outcomes in rehabilitation. It is therefore important to assess delirium incidence in rehabilitation.; To develop and validate a chart-based method to identify incident delirium episodes within the electronic database of a Swiss rehabilitation clinic, and to identify a study population of validated incident delirium episodes for further research purposes.; Retrospective validation study.; Routinely collected inpatient clinical data from ZURZACH Care.; All patients undergoing rehabilitation at ZURZACH Care, Rehaklinik Bad Zurzach between 2015 and 2018 were included.; Within the study population, we identified all rehabilitation stays for which ≥2 delirium-predictive key words (common terms used to describe delirious patients) were recorded in the medical charts. We excluded all prevalent delirium episodes and defined the remaining episodes to be potentially incident. At least two physicians independently confirmed or refuted each potential incident delirium episode by reviewing the patient charts. We calculated the positive predictive value (PPV) with 95% confidence interval (95% CI) for all potential incident delirium episodes and for specific subgroups.; Within 10,515 rehabilitation stays we identified 554 potential incident delirium episodes. Overall, 125 potential incident delirium episodes were confirmed by expert review. The PPV of the chart-based method varied from 0.23 (95% CI 0.19-0.26) overall to 0.69 (95% CI 0.56-0.79) in specific subgroups.; Our chart-based method was able to capture incident delirium episodes with low to moderate accuracy. By conducting an additional expert review of the medical charts, we identified a study population of validated incident delirium episodes. Our chart-based method contributes towards an automated detection of potential incident delirium episodes that, supplemented with expert review, efficiently yields a validated population of incident delirium episodes for research purposes