2.1 Description of the Database

The CuPiD IMU dataset (Bachlin et al., 2009) contains 3-axis accelerometer and gyroscope data from inertial sensors attached on patient wrists (Mazilu et al., 2013), sampled at 128 Hz. Measurements from 18 patients are included with begin and end timestamps of FoGs, Stops, and Walking-with-Turns.

Subjects in the CuPiD IMU dataset have an age range from 49 to 89 years old (mean: 68.9 years, standard deviation: 10.2 years) and have been diagnosed with PD from 2 to 18 years (mean: 8.8 years, standard deviation: 4.6 years). Each patient performed a walking session with 180° and 360° turns, in wide or narrow trails with obstacles that stimulate FoG events in a controlled environment. During the session, subjects were being asked to perform tasks and walk through crowded hospital rooms. In total, 184 FoG episodes are labeled from clinicians in 11 out of 18 patients, referred as S1–S11. The data of the seven subjects that did not display any episodes during the protocol are not included in the analysis. Time periods in which patients stood and discussed with clinicians or voluntarily stopped are also included in the dataset and are labeled as “Stop.” Labeled FoG events in the dataset can occur from 0.11 s up to 98.8 s (mean: 9.12 s, standard deviation: 15.35 s). Most episodes are short, with 50.8% of them lasting less than 3 s and 64.7% less than 5 s. FoG duration range is an important factor for detecting the events, as it plays an important role in defining the interval of the window and the slide-step.

An excerpt from the accelerometer and gyroscope data acquired from the S2 is depicted in Figure 1. In the latter, the occurrence of a FoG event (denoted with gray area) is evident near the 35s, exhibiting a distinguishable pattern during the walking activity, simultaneously appearing in both types of IMU data at 35s.

Exemplary data streams from triaxial gyroscope (A) and accelerometer (B) IMU recordings. The gray area indicates the FoG events.