Data Quality

Signal quality & data samples

Products designed by our engineers meet stringent quality and safety criteria. Below we present selected signal samples from our products based on standard signal quality measurement methods.

Finger Tapping 

Finger Tapping Task is commonly used in validation studies of fNIRS temporal resolution (Drenckhahn et al., 2015)

This example shows a simple single-subject finger tapping experiment, where the participant was asked to perform finger-to-thumb movements with the right hand as fast as possible. The subject was asked to perform the following sequence:

2 — 3 — 4 — 5 — 5 — 4 — 3 — 2, where

2 — index finger,
3 — middle finger,
4 — ring finger,
5 — little finger.

There were 8 repetitions of the task with 20 seconds of the task itself and 43 seconds of rest periods between them. This is a measurement for a single channel localized between C3 (source) and CP3 (detector) optode positions. 

Single-trial hemodynamic response over the left motor cortex area

Fig 1. The time traces of oxy- (red line) and deoxyhemoglobin (blue line) across eight repetitions of the right-hand finger tapping task (yellow boxes) and rest period (white boxes) at C3-CP3 channel position.

8-trial average HRF

Fig. 2. The hemodynamic average response during right-hand finger tapping task (yellow box) and rest condition (white box). The signal over the left motor area (Source: C3; Detector: CP3) shows increased oxy-Hb (red line) and decreased deoxy-Hb (blue line), interpreted as the activation of this area.

Sample data – Finger Tapping Test

Motor Imagery

Motor imagery is defined as the mental simulation of a movement without any real action. Mental representation of a right hand movement evokes higher activation of motor cortex areas located on the opposite side of the head (contralateral) and lower activation of areas located on the same side (ipsilateral) (Fig. 3.). In the case of the BOLD response measured by fNIRS, greater activation corresponds to increased oxyhemoglobin levels and a decrease in deoxyhemoglobin levels. Our study results present a difference in the motor cortex activations registered in both hemispheres during imagined and real right-hand movement (Fig. 4.).

Fig 3. Localization of the fNIRS sources (red) and detectors (blue).
Fig. 4. The hemodynamic average (n=4) response during movement imagery and execution of right-hand movement over contralateral (left) and ipsilateral (right) motor cortices. Channel over the left-hemisphere (S7-D3) show increased oxy-Hb and decreased deoxy-Hb, interpreted as the activation of this area. A similar but smaller response has been observed on the opposite side of the head (S8-D4).


Source-detector separation distances for up to 60 mm





Fig 5. The figure shows raw signal for source-detector separation distances of 40 mm (fig.5A), 50mm (fig.5B) and 60 mm (fig.5C). Fig. 5D shows a filtered signal (15-sample median filter) for source-detector separation of 60 mm.

Sample Raw Data

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