Optical imaging of human brain function: application of near-infrared spectroscopy in a language study
I. Jaquet 1, M. van der Hoeven1, P. Hagoort2, B. Oeseburg1 and W.N.J.M. Colier1
1Department
of Physiology, University Medical Center St. Radboud, Nijmegen, The Netherlands
2Max Planck Institute for Psycholinguistics, Nijmegen, The Netherlands
Introduction
In the past decade, Near Infrared Spectroscopy (NIRS), a non-invasive optical
technique, has proven itself useful for investigating oxygenation changes in
the human brain. It has already been successfully applied in cognitive, visual,
auditory, and motor studies. In this study, we applied functional NIRS to assess
the human language area. We used a picture naming protocol to investigate the
area for phonological encoding (Broca's area) in the left inferior frontal gyrus.
Methods and materials
Eight right-handed healthy volunteers participated in the study. The optodes
of a NIRS instrument (Oxymon® [1]) were placed over the posterior part of the
left inferior frontal gyrus. The language task consisted of the aloud naming
of 12 different pictures that were presented on a computer screen (1 per 2 seconds),
followed by a rest period of 34-46 s. Twenty cycles of picture naming were performed
by each volunteer. A series of 12 pictures represented either high frequency
(HF) words or low frequency (LF) words. Optodes of a second NIRS device were
fixed over the right parietal region of the head. Data obtained here were used
as a control. Data were averaged over 20 cycles. The stimulus period was compared
to baseline values 10 s before the start of the stimulus, and to the rest period
afterwards.
Results
A significant increase in [O2Hb] and decrease in [HHb] compared to baseline
values was found during the picture-naming task (p<0.01). No significant differences
were found between cycles of naming pictures with HF words and those with LF
words. In the control area, no change in oxygenation corresponding to the stimulus
was found.
Conclusion
This study shows that it is possible to monitor oxygenation changes in Broca's
area in response to a picture-naming task. The results furthermore suggest the
utility of NIRS to study speech production and recognition.
This research has been supported in part by the European Commission-DG XII
Poster presented at Measuring Behavior 2000, 3rd International Conference on Methods and Techniques in Behavioral Research, 15-18 August 2000, Nijmegen, The Netherlands