A factor analytic model of prospective memory, retrospective memory and executive functions, with age-dependent effects

Prospective memory (PM), the carrying out of delayed intentions, is a fairly new field of investigation. This thesis presents a theoretical framework and research designed to elucidate the cognitive processes and brain areas involved in PM. Prospective memory is described as a system involving retrospective association of cue and response information, and prospective encoding of the intention. A representation of the intention is then maintained across the delay interval requiring inhibition of interference. Successful maintenance of the representation of the intention allows cue recognition that activates retrieval of the response information. It is proposed that the integrative circuit required for PM includes areas of the prefrontal cortex (PFC), the hippocampal formation and the medial frontal (anterior cingulate) cortex.; This dissertation was designed to test the hypotheses that: (1) both event-based and time-based PM tasks are differentially related to tests of retrospective memory and executive functions, (2) prospective memory is compromised in 65 to 90 year old subjects, and (3) prospective memory performance is affected by interference from the cognitive demands of ongoing tasks. To accomplish this, a neuropsychological battery was given to both younger and older subjects and included tests of retrospective memory, executive functions and prospective memory tasks.; Factor analysis revealed that tests of executive functions made up one factor, and retrospective memory tests made up a second factor. Performance on the time-based PM task had more in common with the first factor and performance on the event-based PM tasks had more in common with the second factor. The results also showed that the older subjects displayed significant deficits in both types of prospective memory, retrospective memory and executive functioning. Supporting previous findings, the results showed that the cognitive load of the underlying task had a detrimental effect, particularly on older subjects' performance and on the time-based PM task. The results indicated that although they are related, the two different types of PM tasks require different types of processing. Time-based PM tasks may rely more on executive functioning and thus the prefrontal lobes, and event-based PM tasks may rely more on retrospective memory, and thus the hippocampal formation.