The Role of the Midbrain in the Perception of Tone Sequences and Speech: An Analysis of Individual Studies
Human speech is a complex combination of sounds and auditory events. To date, there is no consensus on how speech perception occurs. Does the brain react to each sound in the flow of speech separately, or are discrete units distinguished in the sound series and analyzed by the brain as one sound event. The pilot study analyzed the responses of the human midbrain to simple tones, combinations of simple tones (“complex” sounds), and lexical stimuli. The study is a description of individual cases obtained in the frame of intraoperative monitoring during surgical treatment of deep midline tumors of the brain or brain stem. The study included local-field potentials from the midbrain in six patients (two women, four men). The S- and E-com-plexes that emerge at the beginning and end of the sound, as well as the S-complexes that emerge when the structure of the sound changes, were identified. The obtained data suggest that the selected complexes are markers of the primary coding of audio information and are generated by the structures of the neural network that provides speech perception and analysis.