Prospective Memory

Prospective memory is a form of memory that involves remembering to perform a planned action or intention at the appropriate time. Prospective memory tasks are highly prevalent in daily life and range from relatively simple tasks to extreme life-or-death situations. Examples of simple tasks include remembering to put the toothpaste cap back on, remembering to reply to an email or remembering to return a rented movie. Examples of highly important situations include a patient remembering to take medication or a pilot remembering to perform specific safety procedures during a flight.

In contrast to prospective memory, retrospective memory involves memory of people, events and words that have been encountered in the past. Prospective memory and retrospective memory differ in the fact that retrospective memory emphasizes memory for events that have previously occurred, while prospective memory focuses on intended future events and is thus considered a form of memory for the future. Retrospective memory involves the memory of what we know, containing informational content; prospective memory focuses on when to act, without focusing on informational content. There is some evidence demonstrating the role of retrospective memory in the proper performance of prospective memory, but this role seems to be relatively small.

There are two types of prospective memory: event-based and time-based prospective memory. Event-based prospective memory involves remembering to do a certain action when the specific circumstances are present. For example, driving past the local library cues you to remember that you need to return an overdue book. Time-based prospective memory involves remembering to do an action at a particular point in time. For example, seeing that it is 10:00 PM acts as a cue for you to know that is it time to watch your favorite television show.

Research performed by Sellen et al. (1997) compared event-based and time-based cues on prospective memory tasks. The experimenters gave participants a place (event-based cue) and a time (time-based cue) and were told to press a button each time those cues appeared during the study. It was found that performance on event-based tasks was better than performance on time-based tasks, even when participants took more time to think about their responses. The difference in task performance between the two types of prospective memory suggests that the intended action was better triggered by external cues of the event-based task than internal cues of the time-based task. External cues, as opposed to internal cues, act as a prompt for better performance, making it easier to complete event-based tasks.

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Remembering to remember supported by two distinct brain processes   PhysOrg - August 19, 2013
You plan on shopping for groceries later and you tell yourself that you have to remember to take the grocery bags with you when you leave the house. Lo and behold, you reach the check-out counter and you realize you've forgotten the bags. Remembering to remember - whether it's grocery bags, appointments, or taking medications - is essential to our everyday lives. New research sheds light on two distinct brain processes that underlie this type of memory, known as prospective memory.

To investigate how prospective memory is processed in the brain, psychological scientist Mark McDaniel of Washington University in St. Louis and colleagues had participants lie in an fMRI scanner and asked them to press one of two buttons to indicate whether a word that popped up on a screen was a member of a designated category. In addition to this ongoing activity, participants were asked to try to remember to press a third button whenever a special target popped up. The task was designed to tap into participants' prospective memory, or their ability to remember to take certain actions in response to specific future events.

When McDaniel and colleagues analyzed the fMRI data, they observed that two distinct brain activation patterns emerged when participants made the correct button press for a special target.

When the special target was not relevant to the ongoing activity - such as a syllable like "tor" - participants seemed to rely on top-down brain processes supported by the prefrontal cortex. In order to answer correctly when the special syllable flashed up on the screen, the participants had to sustain their attention and monitor for the special syllable throughout the entire task. In the grocery bag scenario, this would be like remembering to bring the grocery bags by constantly reminding yourself that you can't forget them.

When the special target was integral to the ongoing activity - such as a whole word, like "table" - participants recruited a different set of brain regions, and they didn't show sustained activation in these regions. The findings suggest that remembering what to do when the special target was a whole word didn't require the same type of top-down monitoring. Instead, the target word seemed to act as an environmental cue that prompted participants to make the appropriate response - like reminding yourself to bring the grocery bags by leaving them near the front door. These findings suggest that people could make use of several different strategies to accomplish prospective memory tasks. McDaniel and colleagues are continuing their research on prospective memory, examining how this phenomenon might change with age.