Some people are surprised, even disturbed, by the idea that our vision does not give us an accurate picture of what we look at. For example, the colours we experience are not a measure of the wavelength of the light entering our eyes. But accuracy is not the point of vision; the function is to be useful and colour consistency is far more useful then fidelity to wavelength spectra. The same surprise is shown in the reaction to the idea that our memories are reworked continuously so that over time they lose their accuracy. This is not a fault in memory. Again the reason we store memories is to have a useful resource, not necessarily one with detailed accuracy. A great deal of biological energy is used to create memories and to re-consolidate them and therefore we can assume that they have a very important biological role.

In order to have episodic memory, we first have to have the experiences to remember – we create consciousness experiences which become stored as temporary memories. These are soon made more permanent as an event or an episode. Over weeks, months, years, decades they are continually reworked and re-consolidated. They are packaged together and lose their individuality, they are up-dated by newer memories, they are categorized and lose detail not related to their category. Eventually they lose their character as episodic memory and became more a factual or semantic type of memory. What has happened in all this change is that we have learned from experience. This in itself would probably justify the biological cost of consciousness and memory but more has been proposed by Moshe Bar, Donna Rose Addis, Daniel L. Schacter and others. They have put memory at the center not just of the past and learning but of the present and future, of prediction, understanding and cognition.

Bar envisages a ‘proactive brain’ which builds analogues by examining what something is like. If A is like B then they share an analogy which grows as other like things are remembered. Each memory added to a particular analogy brings associations with it, so the associations of each analogy grows. The associations of an analogy are in effect predictions of what else will be found along with the analogy. Thus memory is the material of prediction and foresight. Between memories, predictions and idle imaginings we have the simulations we need to plan our actions. These simulations can even become ‘scripts’ for guiding behaviour and sets of scripts to determine a ‘mindset’ appropriate for a particular type of situation.

Schacter and Addis call their scheme the ‘prospective brain’.

A rapidly growing number of recent studies show the imagining the future depends on much of the same neural machinery that is needed for remembering the past. These findings have led to the concept of the prospective brain; an idea that a critical function of the brain is to use stored information to imagine, simulate and predict possible future events. We suggest that processes such as memory can be productively re-conceptualized in light of this idea.

In fMRI studies of subjects remembering and imagining events, they have identified what they call the ‘core brain system’ which integrates information from past experiences about relationships and associations and uses the information to construct mental simulations. There is a large overlap between the areas of the brain involved in elaborating past and future events. Further there is a large overlap with the default network we use for day-dreaming.

The cognitive machinery outlined by this line of research would convincingly be worth its biological cost by giving us effective and appropriate behaviour. Memory may not be entirely accurate but it is wonderfully useful.

ADDIS, D., WONG, A., & SCHACTER, D. (2007). Remembering the past and imagining the future: Common and distinct neural substrates during event construction and elaboration Neuropsychologia, 45 (7), 1363-1377 DOI: 10.1016/j.neuropsychologia.2006.10.016
Schacter DL, Addis DR, & Buckner RL (2007). Remembering the past to imagine the future: the prospective brain. Nature reviews. Neuroscience, 8 (9), 657-61 PMID: 17700624
Bar, M. (2009). The proactive brain: memory for predictions Philosophical Transactions of the Royal Society B: Biological Sciences, 364 (1521), 1235-1243 DOI: 10.1098/rstb.2008.0310