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.