Temporal information processing as a basis for auditory comprehension: clinical evidence from aphasic patients.

Background: Temporal information processing (TIP) underlies many aspects of cognitive functions like language, motor control, learning, memory, attention, etc. Millisecond timing may be assessed by sequencing abilities, e.g. the perception of event order. It may be measured with auditory temporal-order-threshold (TOT), i.e. a minimum time gap separating two successive stimuli necessary for a subject to report their temporal order correctly, thus the relation 'before-after'. Neuropsychological evidence has indicated elevated TOT values (corresponding to deteriorated time perception) in different clinical groups, such as aphasic patients, dyslexic subjects or children with specific language impairment.

Aims: To test relationships between elevated TOT and declined cognitive functions in brain-injured patients suffering from post-stroke aphasia.

Methods & Procedures: We tested 30 aphasic patients (13 male, 17 female), aged between 50 and 81 years. TIP comprised assessment of TOT. Auditory comprehension was assessed with the selected language tests, i.e. Token Test, Phoneme Discrimination Test (PDT) and Voice-Onset-Time Test (VOT), while two aspects of attentional resources (i.e. alertness and vigilance) were measured using the Test of Attentional Performance (TAP) battery.

Outcomes & Results: Significant correlations were indicated between elevated values of TOT and deteriorated performance on all applied language tests. Moreover, significant correlations were evidenced between elevated TOT and alertness. Finally, positive correlations were found between particular language tests, i.e. (1) Token Test and PDT; (2) Token Test and VOT Test; and (3) PDT and VOT Test, as well as between PDT and both attentional tasks.

Conclusions & Implications: These results provide further clinical evidence supporting the thesis that TIP constitutes the core process incorporated in both language and attentional resources. The novel value of the present study is the indication for the first time in Slavic language users a clear coexistence of the 'timing-auditory comprehension-attention' relationships.