Word recall versus reading speed: evidence of preserved priming in head-injured patients.

This study addressed a number of issues. One purpose was to test whether memory-impaired, head-injured patients show the same pattern of memory task dissociation as reported in amnesics, that is, impaired explicit and intact implicit memory performance. The second purpose of this study was to apply the distinction between the acquisition and retention aspects of memory, which has not, as yet, been investigated adequately in the study of implicit memory. The third purpose was to evaluate the contribution of intra-item and inter-item processes in implicit memory. A group of 18 head-injured (HI) patients and 18 control subjects participated in this study. Subjects read two lists of 15 words seven times: five times consecutively, once after 20 min, and after a 1-hr delay. One list was read in the same order and the other in a different order. Acquisition and retention of the information were measured explicitly (i.e., recall of words) and implicitly (i.e., priming-reading speed). The results indicated that novel information is preserved in HI as in other amnesic patient groups, only when implicit, rather than explicit, measures of memory are used. The effect of contextual manipulation (i.e., order of presentation) was interpreted to suggest similar involvement of intra-as well as inter-memory processes in implicit memory in normal and memory-impaired subjects.