{'fraction_non_alphanumeric': 0.025, 'fraction_numerical': 0.005597014925373134, 'mean_word_length': 5.33806146572104, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Assessing the cortical processing of spectrally rotated speech using functional near-infrared spectroscopy

Rotated speech (RS) is unintelligible to untrained listeners but contains similar temporal and spectral complexity as ordinary speech. It has been used in many studies to investigate cortical pathways for intelligible speech. Typically, the generation of RS involves the rotation of the spectrum of low-pass filtered speech around a center frequency (e.g., 2 kHz). Due to the inversion, voiced segments of RS contain harmonics that are typically not multiples of the fundamental frequency, and therefore the RS signal is not truly periodic. Here, it was assessed whether cortical responses to such aperiodic RS differ from quasi-periodic RS with preserved harmonic structure. Harmonic RS was constructed by rotating only the spectral envelope while preserving the characteristics of the source, whereas for inharmonic RS both components were rotated. A story listening paradigm was used, in which subjects were presented with 25-s blocks of unprocessed speech, inharmonic RS, and harmonic RS. Functional near-infrared spectroscopy (fNIRS) was used to measure cortical activation based on changes in the concentration of oxygenated and deoxygenated hemoglobin. The results show increased activity in the right posterior superior temporal sulcus (STS) for harmonic RS in comparison with inharmonic RS but not unprocessed speech. This demonstrates that the periodicity of RS should be considered in the interpretation of previous and the planning of future neuroimaging studies. [Wellcome Trust Multi-user Equipment Award and SNSF grant P400PG_180693.]Rotated speech (RS) is unintelligible to untrained listeners but contains similar temporal and spectral complexity as ordinary speech. It has been used in many studies to investigate cortical pathways for intelligible speech. Typically, the generation of RS involves the rotation of the spectrum of low-pass filtered speech around a center frequency (e.g., 2 kHz). Due to the inversion, voiced segments of RS contain harmonics that are typically not multiples of the fundamental frequency, and therefore the RS signal is not truly periodic. Here, it was assessed whether cortical responses to such aperiodic RS differ from quasi-periodic RS with preserved harmonic structure. Harmonic RS was constructed by rotating only the spectral envelope while preserving the characteristics of the source, whereas for inharmonic RS both components were rotated. A story listening paradigm was used, in which subjects were presented with 25-s blocks of unprocessed speech, inharmonic RS, and harmonic RS. Functional near-infrared sp...