Abstract: There is described a probe device for optically investigating a tissue of a subject, comprising: a first probe element, a second probe element, and a third probe element each to be positioned at a respective vertex of a triangle for sensing the tissue, the first probe element each comprising a first light source for emitting light having a first wavelength, the second probe element each comprising a second light source for emitting light having a second wavelength and a first photodetector for detecting light having the first wavelength and scattered by the tissue, and the third probe element comprising a second photodetector for detecting light having the first and second wavelengths and scattered by the tissue.

Abstract: A method for assessing a subject perception of a stimulus property, comprising: applying to a subject at least a first sensory stimulus having a first value for the stimulus property and a second sensory stimulus having a second value for the stimulus property different from the first value; requesting the subject to identify a characteristic of the first and second sensory stimuli during the application thereof, the characteristic being unrelated to the stimulus property to be assessed, thereby focusing an attention of the subject on a decision making task; measuring an activity of at least one brain region of the subject during the application of the first and second sensorial stimuli and the identification of the characteristic thereof, thereby obtaining a brain activity measurement; and determining a difference of stimulus property perceived by the subject between the first and second sensory stimuli from the brain activity measurement.