Extended high-frequency hearing predicts neural encoding and perception of speech in the standard frequency range

The role of extended high frequencies (EHF; > 8 kHz) in human auditory processing remains poorly understood. Recent behavioral studies have shown associations between EHF hearing sensitivity and speech perception in noise, discrimination of talker head orientation, and spatial hearing. The neurophysiologic mechanisms linking EHF hearing to these abilities remain unclear. This study investigated how the brainstem encodes (EHF) speech components and explored connections between EHF hearing and both neural and perceptual speech processing. We measured frequency-following responses (FFRs) to different speech stimuli (broadband and high-pass filtered at > 4 kHz and > 8 kHz) in 47 normal-hearing adults. Additionally, we assessed digits-in-noise speech recognition thresholds using various low-pass noise maskers (broadband, < 2 kHz, < 4 kHz, < 8 kHz). Results suggest the brainstem encodes fast (f0) and slow (f0 modulation) temporal speech features within the EHF range. Individuals with poorer EHF sensitivity exhibited weaker FFR f0 amplitudes for both broadband and >4 kHz speech, and they showed generally poorer speech recognition thresholds. Crucially, EHF thresholds predicted both neural encoding strength and performance in speech-in-noise tasks. These results suggest that EHF speech information is encoded in the brainstem, and that EHF sensitivity is linked to degraded broadband neural speech encoding and poorer behavioral performance.