Prepulse inhibition as an index of attentional processing. A comparison between young and elderly

Abstract

Prepulse inhibition (PPI) is assumed to index attentional processes by inhibition of the startle reflex. By directing attention towards a weak stimulus, i.e., the prepulse, PPI is increased. We investigated controlled and automatic processes related to attention in young and elderly subjects. Both groups (n=41) attended to a task where they were to judge if length of a comparison tone was shorter or longer than prepulse. Degree of PPI was assessed by different stimulus onset asynchronies (SOA) assumed to index automatic and controlled processing. We predicted firstly that the young would show established PPI values. Secondly, that normal elderly would show a increase in PPI compared to young when attending to task compared to no-task. As predicted, we found normal PPI function in the young. In the elderly, the expected hyperbolic and quadric PPI function failed to display. Thus, a straight PPI line suggests a continuously elaborating of the first prepulse and pulse in task and No-task, meaning that task made no difference in attentional processing in the elderly. The hypothesis of a global decline in inhibitory function in elderly is suitable as an explanation for reduction in PPI, and we assume that results is due to inhibitory problems in attention, as a consequence of physiological aging in cortex.