Delayed visual P3 in unilateral thalamic stroke.

The P3 potential is accepted as a neurophysiological correlate of memory and attention. Delayed latencies were reported in different forms of dementias. Although the generator sites are still under debate, the thalamus may play a crucial role. The aim of this study was to investigate the influence of an unilateral thalamic ischaemic infarction on P3 generation. The event-related P3 component of six patients (2 male, four female; mean age 47 years, range 22-63 years) with unilateral thalamic ischaemic infarction was studied and compared to age-matched controls (five male, nine female; mean age 45.8 years; range 22-69 years). All patients underwent full clinical examination, CCT, and MRI scan. P3 potentials were recorded with a visual three stimulus discrimination paradigm. The mean P3 latency of the patient group to the target stimulus was delayed (469.7 ms, SD = 36.8) compared with the controls (378.8 ms, SD = 51.5; P < 0. 05). The mean P3 latency to the unexpected stimulus was delayed in patients with thalamic infarction compared with controls [477 ms (SD = 46.6) vs. 381.2 ms (SD = 48.5); P < 0.001). Delayed P3 components of the event-related potential (ERP) were recorded in six patients with unilateral thalamic infarction, suggesting an important role of the thalamus in the generation of the P3 potential.