Dual task performance in amnesic and normal people: does resource depletion cause amnesia?

Normal peoples' memory can be seriously disrupted if their cognitive resources are depleted by means of an experimental manipulation (such as distraction at encoding or at retrieval). By analogy, it has also been suggested that amnesia might result directly from pathological loss of cognitive capacity. This hypothesis was examined in 12 mixed amnesics and 12 normal people by means of a 'dual task' study. It was argued that if amnesics have reduced cognitive resources they should be disproportionately impaired in dual task performance relative to single task performance and in comparison to controls. This result was unambiguously demonstrated using a visual (letter detection) task combined with an auditory (semantic decision) task. However, correlations with measures of frontal function and with indicants of severity of amnesia proved insignificant and so the role of resource depletion in amnesia remains, as yet, unproven.