Neurophysiological characterization of normal hearing and unilateral hearing loss children: a comparison among EEG-based indices for information processing and decision-making levels.

The identification of measurable indices of cerebral functions to be applied in clinical settings is ever more felt as necessary for a more thorough and objective evaluation of patients cognitive performance. In the present paper, the electroencephalographic-based indices of mental workload (WL = frontal θ/parietal α) and of mental engagement (ME = β/(α+θ)), calculated along the brain midline, have been employed to characterize the eventual specific patterns of cerebral activations during a speech in noise perception task in normal hearing (NH) and unilateral hearing loss (UHL) children. Results showed no differences between the groups for the frontal bilateral noise condition (in which both signal and noise were emitted by two loudspeakers placed +45° and -45° in relation to the participant), while in lateralized noise conditions the UHL group showed higher parietal ME values for the Noise to the Deaf Ear condition). Finally, the NH group showed a different distribution of ME values among frontal, central and parietal electrodes, with higher ME values in the central and parietal ones in correspondence of the Noise to the Left Ear condition. The WL index analysis did not provide any significant differences. Results suggest the relevance of including the analysis of the beta rhythm in the neurophysiological assessment of the neural processing of speech in noise stimuli in normal hearing and hearing impaired participants.