Review of EHCA(eye-head coordination analyzer)

EHCA is a MATLAB software which was developed to analyze eye-head shift. It can be used to investigate motion behaviour, which can lead to further insights into attentional and motor symptoms of certain neurological or psychiatric diseases, e.g. schizophrenia. To use this software MATLAB is required. In order to do that,after the software package is downloaded and extracted to a directory, it should be added to the MATLAB Path so that the functions are available from the MATLAB command line.

Bellow I describe a study published in the publishing paper of EHCA, named: "Analysis of eye and head coordination in a visual peripheral recognition task" by Simon Schwab, Othmar Wurmle,Andreas Altorfer; University of Bern

For saccade detection EHCA has a class ehcaEmov that provides a popular eye movement analysis algorithm (I-VT) based on Salvucci and Goldberg.

For exploring the eye-head coordination, a study was done on 11 healthy subjects, all of which had no history of neurological or psychiatric diseases and had normal vision. Eye movements were recorded of the dominant eye, with a video-based infrared eye tracker (iView X HEDMHT, SMI, Germany) at a sampling rate of 200 Hz and a spatial resolution of 0.5–1◦. Head movements were recorded using magnetic coils (Fastrack, Polhemus, USA) with a sample rate of 40 Hz and a spatial resolution of 0.15◦

For recording they used the manufacturer’s software (iView X 2.5, SMI), which provided them with online gaze vectors upon head and eye tracking.

Pic.1 The settings of theequipment and the subjects under which the experiment was done

Pic.2 Statisticts gained from the experiment, after pre-processing of the data

(a) Number of head shifts (HS) towards the targets for each subject with group statistic (right). Saccade latency

(b) the saccadic response time toward the peripheral stimulus onset - Head offsets

(c) the time between saccade onset and head-shift onset.

(d) POR indicated how closely subjects approached the targets, which in eye-head shifts means head amplitudes

(e) head-eye amplitude

(f) Amplitude ratios

Pic.3 The results of the Saccades (red), head shifts (blue), and CEM (green) plotted using EHCA of the 11 subjects