Prospective and retrospective components in the memory for actions to be performed in patients with severe closed-head injury

This study investigated the basic mechanisms of the impairment of memory for actions to be performed in a group of 16 chronic survivors of severe closed-head injury (CHI). The experimental paradigm allowed discrimination between the deficit in spontaneously remembering the intention at the appropriate moment (prospective component of the task) and the deficit in remembering the specific actions to perform (retrospective component). The experimental procedure also contrasted a condition in which the time expiration was marked by the ringing of a timer (event-based condition) and one in which the time expiration was not marked by any event and the patient had to monitor the passing of time and completely self-activate the recall of the intention (time-based condition). Two other experimental manipulations were concerned with the duration of the delay interval from the examiner's instructions to the time expiration (10 vs. 45 min) and the fact that the three actions to be performed could be functionally related or not. With respect to a group of 16 normal controls, the patients with CHI were impaired in both the prospective and retrospective components of the memory for actions. Although an impairment of episodic memory is a plausible explanation for the poor retrieval of specific actions to perform, it is unlikely that this deficit played a major role in the CHI patient's reduced accuracy in spontaneously recalling the intention when the event occurred or the time expired. Instead, reduced frequency and less strategic utilization of time monitoring and/or self-reminding likely played a significant role in this sense.