Probe Layouts

Probe Placement and Brain Regions of Interest

Probes and caps are some of the most important pieces of any NIRS system setup. Both you and your subject will be in intimate contact with these critical components every time the system is used.

NIRx offers complete flexibility for montage definition. The possibilities are nearly limitless. One may place probes on the 'standard' (e.g, 10-20, 10-10, 10-5) layout or in arbitrary positions; one may use short-distance measurements (tomography) or fixed-distance measurements (topography); one may have integrated EEG or other modalities (tDCS, accelerometer, etc.) in addition to NIRS, or simply use NIRS alone on a dedicated NIRScap; and one may use fNIRS concurrently with fMRI, TMS, MEG, EKG, pulse oximetry, EMG, EOG, eye-tracking, motion-tracking, etc.



NIRS Regions of Interest

All NIRx systems allow for flexible placement of probes – data may be collected from any part of the head (actually, the probes can also be set up for peripheral fNIRS data collection as well). Here is just a sample of the areas one can easily measure with a NIRx fNIRS system:

fNIRS Brain Regions of Interest:

  • Pre-frontal cortex
  • Supplementary motor area
  • Premotor cortex
  • Primary Motor cortex
  • Somatosensory cortex
  • Posterior parietal cortex
  • Primary auditory cortex
  • Broca's / Wernicke's area
  • Primary visual cortex



Standard Versus Arbitrary NIRS Layouts

Probes may be placed on the ‘standard’ EEG layout positions or in arbitrary positions. In either case, it is vital that one ensures proper spacing between probes, as probe distance effects light penetration and signal quality. NIRx offers hardware and software solutions that help ensure proper spacing.

NIRS Layout in Standard 10-5 positions

A 16-source/16-detector NIRS layout for motor measurements.

Each source is red, each detector is green, and each 'NIRS channel of interest' is purple.

In this case there are 48 NIRS channels from this 32-probe layout.

This is a 'topographic' layout, with 3cm spacing between each probe.


NIRS Layout in Arbitrary Positions


A 48-source/32-detector NIRS layout for high-density prefrontal measurements

Each source is red, each detector is green. ('NIRS channels of interest' are not shown for simplicity)

In this case there are 182 NIRS channels from this 80-probe layout.

This is a 'tomographic' layout, with multi-distance spacing between probes to yielf short and long distance measurements.



Integrated NIRS EEG Layouts


NIRx NIRS probes may be placed alongside EEG or other integrated cap measurement modality probes (e.g., tDCS, cochlear implants, accelerometer, etc.). It is not necessary for NIRS positions (or EEG, for that matter) to be in the standard layout. Cap montage is flexible.

A 32-position 'standard' EEG layout with an 8-source/8-detector NIRS layout for prefrontal/SMA measurements.

Each electrode is light blue, each source is red, each detector is green, and each 'NIRS channel of interest' is purple.

In this case there are 20 NIRS channels from the 16-probe layout.

NIRSCap Integration with other modalities

In addition to NIRS-EEG integration, NIRx offers cap integration solutions for other modalities that require access to a subject's head: NIRS-tDCS, NIRS-accelerometers, and NIRS-cochlear implants. If you would like to integrate any other sensors with a NIRScap, please get in touch.

Contact our Staff Scientist to discuss your application.



Active and Passive EEG Electrode Integration

NIRx systems, probes, and caps can easily integrate with "active" or "passive" EEG electrodes alike.


Left: integrated NIRScap with active EEG electrodes and active NIRS optodes

Right: integrated NIRScap with passive EEG electrodes and NIRS optodes (active high-powered LEDs and fiber optic detectors)



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