Description and Prediction of Freezing of Gait in Parkinson's Disease from Wearable Inertial Measurements Units

Parkinson's disease (PD) is a neuro-degenerative disorder, the second most common after Alzheimer's disease. After diagnosis, treatments can help to relieve the symptoms, but there is no known cure for PD. PD is characterized by a combination of motor and no-motor dysfunctions. Among the motor symptoms there is the so called Freezing of Gait (FoG). The FoG is a phenomenon in PD patients in which the feet stock to the floor and is difficult for the patient to initiate movement. FoG is a severe problem, since it is associated with falls, anxiety, loss of mobility, accidents, mortality and it has substantial clinical and social consequences decreasing the quality of life in PD patients. Medicine can be very successful in controlling movements disorders and dealing with some of the PD symptoms. However, the relationship between medication and the development of FoG remains unclear. Several studies have demonstrated that visual or auditory rhythmical cuing allows PD patients to improve their motor abilities. Rhythmic auditory stimulation (RAS) was shown to be particularly effective at improving gait, specially with patients that manifest FoG. While RAS allows to reduce the time and the effects of FoGs occurrence in PD patients after the FoG is detected, it can not avoid the episode due to the latency of detection. An improvement of the system would be the prediction of the FoG. This thesis was developed following two main objectives: (1) the finding of specifics properties during pre FoG periods different from normal walking context and other walking events like turns and stops using the information provided by the inertial measurements units (IMUs) and (2) the formulation of a model for automatically detect the pre FoG patterns in order to completely avoid the upcoming freezing event in PD patients. The first part focuses on the analysis of different methods for feature extraction which might lead in the FoG occurrence.

(Table1) Sedimentation rates and age-control points form ODP Hole 152-919A

Planktic d18O and d13C records and point count records of biogenic, volcanic, and nonvolcanic terrigenous [ice-rafted debris (IRD)] sediment components from Hole 919A in the Irminger basin, northern North Atlantic provide a comprehensive dataset from which a paleoceanographic reconstruction for the last 630 kyr has been developed. The paleoceanographic evolution of the Irminger basin during this time contains both long-term patterns and significant developmental steps. One long-term pattern observed is the persistent deposition of hematite-stained ice-rafted debris. This record suggests that the modern and late Pleistocene discharges of icebergs from northern redbed regions to the Irminger Sea lie in the low end of the range observed over the last 630 kyr. In addition, Arctic front fluctuations appear to have been the main controlling factor on the long-term accumulation patterns of IRD and planktic biogenic groups. The Hole 919A sediment record also contains a long-term association between felsic volcanic ash abundances and light d18O excursions in both interglacial and glacial stages, which suggests a causal link between deglaciations and explosive Icelandic eruptions. A significant developmental step in the paleoceanographic reconstruction based on benthic evidence was for diminished supply of Denmark Strait Overflow Water (DSOW) beginning at ~380 ka, possibly initiated by the influx of meltwater from broad-scale iceberg discharges along the east Greenland coast. There is also planktic evidence of a two-step cooling of sea surface conditions in the Irminger basin, first at ~338-309 ka and later at ~211-190 ka, after which both glacials and interglacials were colder as the Arctic front migrated southeast of Site 919. In addition to offering these findings, this reconstruction provides a longer-term geologic context for the interpretation of more recent paleoceanographic events and patterns of deposition from this region.

(Table 1) Age control points of ODP Site 160-968

The astronomical timescale of the Eastern Mediterranean Plio-Pleistocene builds on tuning of sapropel layers to Northern Hemisphere summer insolation maxima. A 3000-year precession lag has become instrumental in the tuning procedure as radiocarbon dating revealed that the midpoint of the youngest sapropel, S1, in the early Holocene occurred approximately 3000 years after the insolation maximum. The origin of the time lag remains elusive, however, because sapropels are generally linked to maximum African monsoon intensities and transient climate modeling results indicate an in-phase behavior of the African monsoon relative to precession forcing. Here we present new high-resolution records of bulk sediment geochemistry and benthic foraminiferal oxygen isotopes from ODP Site 968 in the Eastern Mediterranean. We show that the 3000-year precession time lag of the sapropel midpoints is consistent with (1) the global marine isotope chronology, (2) maximum (monsoonal) precipitation conditions in the Mediterranean region and China derived from radiometrically dated speleothem records, and (3) maximum atmospheric methane concentrations in Antarctica ice cores. We show that the time lag relates to the occurrence of precession-paced North Atlantic cold events, which systematically delayed the onset of strong boreal summer monsoon intensity. Our findings may also explain a non-stationary behavior of the African monsoon over the past 3 million years due to more frequent and intensive cold events in the Late Pleistocene.