Multimodal P3 under different attentional states in mesial temporal lobe epilepsy

Several studies demonstrate that the P3 component of the event-related potentials (ERP) is generated by mesial temporal structures. The P3 is considered as endogenous information processing component independent from modality.

The aim of this investigation was to study whether the P3 latency elicited by auditory and visual stimuli under different attentional states is influenced by the mesial temporal lobe epilepsy (mTLE).

The event related P3 component of 10 right handed patients (7 m/3 f, mean age 31.3 years (SD 7.3), median 31.5, range 20-47) with unilateral mTLE were studied and compared with 10 age matched controls (5 m/5 f, mean age 36.6 years (SD 12.6), median 32.1, range 22-48). Diagnosis of mTLE was based on seizure description, clinical history and examination, prolonged video-EEG monitoring, magnetic resonance imaging (MRI), interictal and ictal SPECT. P3 potentials were elicited with a visual and auditory three stimulus discrimination paradigm.

The latency of the P3 response to the auditory stimulus under automatic and effortful attention was delayed (423.3 ms (SD 60.4) and 436.9 ms (SD 83.4)) compared with a control group (359 ms (SD 42.4) and 354.2 ms (SD 39.7); P = 0.039 and P = 0.012, ANOVA), while the P3 latencies to visual stimuli under both tested attentional states (407.3 ms (SD 52.9) and 390.6 ms (SD 40.2)) did not differ from controls (378.2 ms (SD 48.6) and 378.2 ms (SD 55.4)). P3 latencies to auditory novel paradigm in patients with right sided mTLE, but not left sided mTLE, differed significantly from controls (P = 0.01).

The results suggest a modality dependence of the P3 component in patients with mTLE. The novelty processing of auditory stimuli is disturbed in patients with right sided mTLE.