Brain activation during neurocognitive testing using functional near-infrared spectroscopy in patients following concussion compared to healthy controls

Abstract

There is no accepted clinical imaging modality for concussion, and current imaging modalities including fMRI, DTI, and PET are expensive and inaccessible to most clinics/patients. Functional near-infrared spectroscopy (fNIRS) is a non-invasive, portable, and low-cost imaging modality that can measure brain activity. The purpose of this study was to compare brain activity as measured by fNIRS in concussed and age-matched controls during the performance of cognitive tasks from a computerized neurocognitive test battery. Participants included nine currently symptomatic patients aged 18-45 years with a recent (15-45 days) sport-related concussion and five age-matched healthy controls. The participants completed a computerized neurocognitive test battery while wearing the fNIRS unit. Our results demonstrated reduced brain activation in the concussed subject group during word memory, (spatial) design memory, digit-symbol substitution (symbol match), and working memory (X's and O's) tasks. Behavioral performance (percent-correct and reaction time respectively) was lower for concussed participants on the word memory, design memory, and symbol match tasks than controls. The results of this preliminary study suggest that fNIRS could be a useful, portable assessment tool to assess reduced brain activation and augment current approaches to assessment and management of patients following concussion.

Conflict of interest statement

statement A. P. Kontos, T. J. Huppert, N. H. Beluk, R. J. Elbin, L. C. Henry, J. French, S. M. Dakan & M. W. Collins declare that they have no conflict of interest. Dr. Collins is a shareholder in ImPACT Applications, Inc. Dr. Collins involvement in the current manuscript involved interpretation of data. He did not have direct access to the raw data or participate in the analysis of the data

Figures

Fig. 1

FNIRS signals were recorded using a custom-built optical head cap (b) covering the frontal cortex bilaterally as shown in a. The closest points on the International 10–20 system are shown relative to the optical sensor locations. Open and filled circles indicate optical detector and source positions respectively. A 32-channel TechEn Inc fNIRS system (c) was used in this study, which was contained on a portable cart moved into the patient/subject’s neurocognitive testing area

Fig. 2

FNIRS activation maps (oxy-hemoglobin effect size; T-score) were reconstructed for the presentation, recall, and delayed recall parts of the word memory module of the neurocognitive test. The color maps indicate the effect size. Only significant areas (p<0.05; corrected) are shown. Because fNIRS has limited depth penetration and spatial coverage (see Fig. 1), only cortical areas of the frontal cortex are accessible in this study

Fig. 3

FNIRS activation maps (oxy-hemoglobin effect size; T-score) were reconstructed for the presentation, recall, and delayed recall parts of the design memory module of the neurocognitive test. The color maps indicate the effect size. Only significant areas (p<0.05; corrected) are shown

Fig. 4

FNIRS activation maps (oxy-hemoglobin effect size; T-score) were reconstructed for the presentation and recall parts of the symbol match module of the neurocognitive test (panel a). The activation maps for the color match task is shown in panel b. The color maps indicate the effect size. Only significant areas (p<0.05; corrected) are shown. There was no significant activation in the control group for the color match task (panel b bottom)

Fig. 5

FNIRS activation maps (oxy-hemoglobin effect size; T-score) were reconstructed for the presentation and recall parts of the Three-Letters Memory module of the neurocognitive test (panel a). The activation maps for the X’s and O’s task is shown in panel b. The color maps indicate the effect size. Only significant areas (p<0.05; corrected) are shown