My google calendar overflows with tasks that I don't trust myself to remember. Despite the indefinite amount of information we seem to be able to hold in our long-term memory "store", for most of us it is all too easy to forget the epic three or even (dun dun dun) four things we mean to do between when we get in from work and when we go to bed.
This is prospective memory; remembering to do something that you (previously) decided you were going to do.
Of course, in everyday life I rarely have to remember highly important appointment etc. with "just" my mind, as I will use reminders. Interestingly, the Rivermead Behavioural Memory Test allows one to use written notes to help remember to do something. This seems like a nice psychometric acknowledgement of the extended mind (i.e. we do not purely rely on our brains, but use tools and symbols as add-ons for cognition). However, where one is employing this add-ons, it is likely that one is using one's brain in a different manner to when the same brain is running "naked".
It may nonetheless be difficult to identify incidents in everyday life where someone is not using some external cue to jog memory, whether consciously or otherwise. Consider how the time of day, one's location or the content of conversation during a meeting might act as a reminder to do something, even if such cues have not be set up by you in advance to act as reminders. In this vein, Researchers in this area distinguish between time-based prospective memory (remembering to do something at a particular time) and episode-based prospective memory (remembering to do something once some other event occurs).
An interesting research question concerns depression. In addition to the broader evidence base for a negative impact of depression on cognition, depression has been shown by a meta-analysis to be associated with poorer prospective memory (both time-based and episode-based). The authors suggest this may relate to a dysfunction of neural circuits responsible for prospective memory in people with depression, such as connections between the amygdala (associated with emotion) and the anterior cingulate cortex (which is associated with executive function, a suite of cognitive functions that are likely to be integral to prospective memory and its enactment).
A word of warning: methods of cognitive assessment for probing this form of memory have to be appraised carefully.In much of the research in this area one is asked (a) to remember to complete a certain task later on, (b) to do a distracting task for a while, (c) do what you are asked to do in part a. As with much research into cognitive psychology, in order to get more robust data researchers will often have a few test trials. However, a problem with this is that it may only be the first test trial that is really about prospective memory-the subsequent trials may be more related to more short-term memory (because you're now repeating to yourself over and over not to forget again to carry out the instruction mentioned in part a.)
Autobiographical memory and thinking about the future
Where does the mind begin and end?`