Language reorganization patterns in global aphasia-evidence from fNIRS

Abstract

Background: Exploring the brain reorganization patterns associated with language recovery would promote the treatment of global aphasia. While functional near-infrared spectroscopy (fNIRS) has been widely used in the study of speech and language impairment, its application in the field of global aphasia is still limited.

Aims: We aimed to identify cortical activation patterns of patients with global aphasia during naming and repetition tasks.

Methods and procedures: We recruited patients with post-stroke aphasia from the Department of Rehabilitation Medicine at Huashan Hospital. These individuals were diagnosed with global aphasia without cognitive impairments, as assessed by speech-language pathology evaluations. Age- and sex-matched healthy controls were recruited from the greater Shanghai area. During fNIRS measurement, patients and healthy controls completed the picture-naming and phrase repetition task. Cortical activation patterns on each of these language tasks were then compared between groups.

Outcomes and results: A total of nine patients with global aphasia and 14 healthy controls were included in this study. Compared with the healthy subjects, patients with global aphasia showed increased activation in the left Broca's area, middle temporal gyrus (MTG), superior temporal gyrus (STG), and pre-motor and supplementary motor cortex (SMA) (p < 0.05) in the picture-naming task. Furthermore, the latency of the oxyhemoglobin (HbO) concentration in the left supramarginal gyrus (SMG) region had a strong negative correlation with their score of the naming task (p < 0.01). In the phrase repetition task, decreased activation was detected in the left SMA and SMG (p < 0.05) of patients relative to controls.

Conclusion: The left SMG plays a critical role in the language function of patients with global aphasia, especially in their abilities to name and repeat. fNIRS is a promising approach to revealing the changes in brain activities in patients with aphasia, and we believe it will contribute to a deeper understanding of the neurological mechanisms and the establishment of a novel treatment approach for global aphasia.

Keywords: fNIRS; global aphasia; left SMG; picture naming; repetition phrase.

Figure 1

fNIRS behavioral tasks. (A) Picture-naming task. (B) Phrase repetition task.

Figure 2

(A) fNIRS probe design; sources are represented by S, while detectors are represented by D and channels with lines between S and D. The arrangement of the optodes with an interoptode distance of 30 mm. (B) Sensitivity profile; sources are displayed with red dots, while detectors are displayed with blue dots and channels with yellow lines. Results of the Monte Carlo simulation based on 1 × 10⁻⁸ photons over the frontal, parietal, temporal, and occipital lobes: colors represent the spatial sensitivity of the fNIRS measurements. Warmer colors suggest higher sensitivity to the cortex, while cooler colors suggest lower sensitivity to the cortex.

Figure 3

Cortical activation associated with the picture-naming task. HbO activation maps between patients with global aphasia and healthy individuals. The color bar represents the t-statistic. Warmer colors with positive values represent increases in HbO in patients with global aphasia compared with healthy individuals, while cooler colors with negative values represent opposite results (p < 0.05).

Figure 4

Significant correlation between the naming score and latency of HbO concentration in the left SMG (r = −0.8532, p = 0.0093). (A) The average HRF of the left SMG in patients with global aphasia and healthy individuals. (B) The accuracy of HbO concentration in the left SMG was negatively correlated with the naming score (p < 0.01) (The latency of HbO concentration and the naming score in some patients are very similar (refer to Supplementary Table 5 for more detail).

Figure 5

Cortical activation associated with phrase repetition task. HbO activation maps between patients with global aphasia and healthy individuals, and the color bar represents the t-statistic. Cooler colors with negative values represent decreases in HbO in patients with global aphasia compared with healthy individuals (p < 0.05).