Comparative effects of age on limbic and scalp P3.

Abstract

We studied the effects of age on the limbic and scalp P3 in 45 patients with intracranial electrodes implanted for pre-surgical investigation of focal seizures. Scalp P3 data from a reference group of 24 healthy control subjects were also analyzed for comparison. An auditory oddball paradigm with infrequent stimuli being presented with a probability of 0.20 was used. In normals P3 latency increased by 1.34 msec/year (r = 0.60, P less than 0.01). In the patients limbic and scalp P3 latency increased linearly as a function of increasing age at a rates of 3.85 msec/year (r = 0.58, P less than 0.001) and 2.71 msec/year (r = 0.56, P less than 0.01), respectively. The rate of increase of P3 latency with age was significantly lower in the normal controls, as compared to both the patient scalp (t = 1.79, P less than 0.05) and depth (t = 2.25, P less than 0.005) ERP data. There was no significant difference between the slopes of the patient P3 latency versus age scalp and depth data (t = 1.09, P greater than 0.1). Unlike for normal controls, there was no relationship between age and limbic P3 amplitude (r = 0.02, P greater than 0.1) or age and scalp P3 amplitude (r = 0.17, P greater than 0.1). The differences between controls and patients could be due to: (i) effects of chronic seizures; (ii) long-term effects of anticonvulsant use; (iii) the use of a relatively long inter-stimulus interval which may have selectively affected the patients.(ABSTRACT TRUNCATED AT 250 WORDS)