Experimental protocol.

(A) Illustrative 42-channel fNIRS Montage. S (red) = source, D (blue) = detector. Placement indicated using the 10-10 standard EEG system. Regions of interest are indicated in yellow = inferior frontal gyrus (IFG), in green = superior temporal gyrus (STG), and in pink = parietal lobes (PL). (B) Familiarization-interference-test paradigm. Each subject was tested in two sequences separated by 9 minutes of silence: in one sequence, newborns heard the same word during familiarization and test (same-word condition; X u X), and in the other sequence, a novel word was presented during the test phase (novel-word condition; Y w Z). The order of the conditions, the words and the voices used in the different phases were counterbalanced across participants.

Standard recognition response with decreased activity for the familiar words and increased activity for the novel words in the test phase.

(A) Mean activity for HbO per block during the familiarization, interference, and test phases. Error bars represent the standard errors. The black continuous line depicts responses averaged across all participants and conditions. The same-word condition (green) and the novel-word condition (purple) are plotted in the test phase. The black asterisks during the familiarization and interference phases indicate that the response differed from zero. The red lines indicate a significant linear trend, as indicated by the red asterisks. Black asterisks during the test phase indicate significant differences between conditions. (B) HRFs for HbO during the second block of the test phase, when relevant differences were observed between conditions. Shaded areas represent the standard error.

Differences in the response across groups during the second test block.

Boxplots represent the mean HbO activity during the second block of the test phase separated by condition (same=green, novel=purple), group (A or B), and sequence (first=full pattern or second=dotted pattern). Whiskers of the boxplot are defined based on 1.5 times the interquartile range, and data points outside these limits are plotted as circles. Asterisks indicated significant differences between conditions or groups. A significant effect of conditions was observed in left IFG and left and right STG. Instead, an interaction effect was present in right IFG with higher activity in the novel-word condition for group A.