All of our conscious experiences can be deemed emergent from our self whether it be pain in the physical body or a memory that arrives in our awareness. The underpinning neural correlate in the brain has to some extent been identified in pain but the search for the seat of consciousness continues. It is likely to be a widespread group of neurons, similar to the proposed pain matrix or salient network, that are active to create the awareness that we know and only we know as it is completely unique to the individual. Only that individual has his or her genetic blueprint, moulded by experience (epigenetics), evolving moment by moment, learning and adapting.
There are particular memories that remain strong. They are often multisensory, in other words we can relive the moment in full technicolour with sounds, smells and the associated feelings arise as a consequence. The greater the meaning at the time that the memory is being laid down, the stronger will be the subsequent replay. At this time, the brain is processing a range of stimuli from within the body and externally. This is why a piece of music or a smell (e.g./ perfume) can trigger a vivid recollection of a time that can be interoceptively experienced once more. Whether it actually matches the exact original is difficult to confirm as our memories are notoriously unreliable (what did you have for lunch last Tuesday? If you can remember, it must have been important), however, it is reasonable enough to be believable and hence to stimulate an emotional and a physical response.
When a situation has meaning or a high valency, it means that there is a significant emotional aspect that strengthens the connectivity between neurons. This makes sense as to be able to recall an important event is biologically useful. The recently purported salient network (1) helps the conceptualisation of a cortical network that detects multisensory sensory input and triggers a set of responses to protect the self including pain and altered movement.This is different to the processing of a positive event that rewards the individual, driving him or her to desire more. One is about protection and the other craving although both can have emotional valency and be associated with cues that can trigger a memory.
In summary, a memory can be replayed in the mind (consciously), the brain being unable to differentiate wholly between thinking about ‘being there’ and actually being there, triggered by a range of cues that were present at the time of the initial event. This may be a piece of music, a place, a perfume, a word, a sound, a taste; such that the same cue later creates cortical activity that emerges as the memory in its full glory. Of course, we can choose to think about a situation and ‘play the tape’ for full pleasure of the experience or choose a cue that purposely evokes the memory, for example a song. This is an advantage of being human, an ability to metacognate in such a way and then recreate the feeling. The more emotive the original event, the more meaning, the greater the ability to evoke a multisensory experience of memory. We can use this to our advantage and derive absolute pleasure and positive emotion by purposely reliving special moments that usually involve a meaningful connection with another.
RS – Specialist Pain Physio Clinics, London
(1) Prog Neurobiol. 2011 Jan;93(1):111-24. The pain matrix reloaded: a salience detection system for the body; Legrain V, Iannetti GD, Plaghki L, Mouraux A.