Episodic memory is the memory for specific events from one's own life. Typically, this includes memory for the context in which the event took place, the spacial location where it took place, and many of the details of what or who was present during the event. Episodic memory performance is sensitive to many psychiatric and neurological disorders.
It's often the first mental capacity to be affected in dementia, and is also believed to be diminished in depression and other affective disorders. Measuring episodic memory performance is therefore an important thing to do. Many laboratory and clinical tests of episodic memory require participants to memorize lists of words.
Such lists do not have any context or spacial location in which the words need to be remembered, making them poor models for real episodic memory. Other tests ask participants or patients about real events from their own lives, however, in these tests, the experimenter or clinician does not have objective information against which to test the accuracy of the memories being recalled. We have devised an episodic memory test that includes the spacial and temporal context of the events to be remembered, while at the same time allowing the accuracy of the memories to be measured.
The test is based on previous work with animals, and has been adapted for people. Unlike many new memory tests, we do not use computers, as interaction with computers can be daunting for some older people, or people with cognitive deficits. We call our new test the Real-World What-Where-When Memory Test.
We use a relatively cluttered office room with plenty of possible hiding locations. We place a pile of 20 small, easy to label objects on a desk in the room. Next to the objects, we place a sheet of paper with eight photographs on it.
These are photographs of eight of the objects, which the participants have to take from the pile in the order indicated on the sheet. We do this to make sure the participants will pay attention to the objects they are asked to remember. Thank you for taking part in our study.
When the participant arrives, she is first briefed about the purpose of the experiment and about what to expect. This is done both verbally and using an information sheet that the participant can read. She is also provided with a written consent form.
The participant is then taken to the door of the experiment room. So the purpose of this task is for you to hide some objects in a room and you will be asked to remember them later. You'll be presented with a pile of objects on the desk.
Next to the pile you'll find a sheet with pictures of eight objects that you must hide during the task. At the bottom left of each picture, there is a number indicating the order in which you must hide the objects. You may only pick up and hide one object at a time.
I will point to the location where you should hide each object. Once you enter the room, you should start counting seconds out loud and continue doing that until you leave the room. Later in this study, we will repeat this with different objects in different locations.
After this, you will be asked to remember what objects you hid, where you hid them, and on which occasion. If you have any questions, please ask them now, as you won't be able to once we enter the room. Why do I have to count?
This is called articulatory suppression and we do this for all participants. The reason we do this is to stop you from using language during the task. In order for us to assess your memory for an actual event rather than your memory for a list of words, for objects and locations.
If you're happy, we can start the task now. So thank you for taking part in this part of our study. The participant is thanked and asked to return two hours later.
Alternatively, during this interval, the participant could be tested on other tests of interest to the study. This is the same task as you did before. You will be presented with a pile of objects on the desk.
Please take as much time as you need. Are you ready for the second part of the test? Yes.Thank you for completing part two of our study.
The participant is again thanked and asked to return two hours later. As before, during this interval, the participant could also be tested on other tests of interest to the study. After the participant returns, she is asked to recall the two previous events.
I would like you to try and recall the objects that you hid and the locations you hid them and on which of the occasions, so phase one or phase two. Where possible, try to match the objects with the locations and the phase. If you can only remember one or the other, this is okay, write down whatever you can remember.
Write down everything you can remember on the paper in the order you remember it. You may draw a diagram or a map if you wish. So if you'd like to just start writing there, that would be great.
Thank you. So this is a vividness scale. Please circle the level of vividness with which you feel you are able to visualize the object's location and phases when you were remembering them.
This only applies to the objects that you could actually remember. From the data collected, we could count the number of correctly recalled combinations of which object was hidden in which location, and on which of the two hiding occasions. This is the main output of the test.
It has been shown to be sensitive to aging, and to depression. This number out of 16, can also be correlated with performance in other cognitive tests. However, our test allows for a wider range of measures to be extracted as well.
This way, we can identify whether deficits in episodic memory performance are purely due to object memory, spacial memory, or to the binding of object, spacial, and temporal information. We believe our new task has a number of advantages over existing episodic memory tests. It combines the ecological validity of recalling events from one's own life, with the experimental control of word lists.
It also allows us to test components of episodic memory, such as spacial and object memory within the same task. It is very simple and cheap to run, and does not require any specialized equipment. The task is also easily modified to become a test of incidental encoding, rather than intentional encoding.
All you have to do is change the instructions, such as the participants believe the counting of the seconds is the real task, and the hiding of the objects is a way to distract them from this task. You would then reveal the real nature of the task right before the final retrieval phase. We hope you agree with us, that this task has great potential, both for experimental studies of episodic memory and for clinical assessment of episodic memory problems.
