2.2 Engrams
From Greek philosophers to modern-day neuroscientists, questions regarding the nature of human memory and experience have been at the forefront of great minds. While much remains a mystery, theoretical deductions and experimental setups over the last two centuries have elucidated [or shed light on] many aspects of the problem.
What is experience?
Human experience has a qualitative property that colours everyday life. If you were asked to imagine what it is like to be a baseball bat, you might not be able to imagine anything. We intuitively believe that a bat does not have that first-person, egocentric, qualitative characteristic to experience as a human does. Unlike the bat, there is such a thing as to be a human; we do not only interact with our environment, but we “feel” our environment. This is not just because humans are more complex than baseball bats; even other complex systems, which process inputs to produce behavioural or non-behavioural outputs, are intuitively thought to lack the privilege of “experiencing” events like a human. For example, a spectrometer can tell me what colour a beam of light is based on its wavelength, and so can a human. However, the human not only classifies the colour but “experiences” what red looks like. There is an ineffable quality that defines seeing the colour red. Trying to explain the experience of seeing red to a person who was born blind. It is impossible. Similarly, we do not simply “sense” that something is salty and then eat more of it for sodium homeostasis. We instead “taste” the saltiness, “enjoy” the flavour, and “want” more of it. Whether it is seeing colour, having an itch, or being in love, there is a subjective property to the human condition that can only be discovered through conscious experience.
Why is there such a feeling as to “be” in an experience? This mystery, dubbed the hard problem of consciousness, remains a much more mysterious phenomenon than memory is today. Throughout history, philosophers and theologians have pondered this question, putting forward numerous spiritual and materialistic models as solutions. Unfortunately, the heart of the issue is out of reach of the scientific method. It is impossible to test and measure subjectivity in an objective manner. The only way to proxy what someone is experiencing is to ask them and trust their answer. While not the best compromise, such methodologies have provided valuable empirical observations which intricately correlate the activities of the brain with conscious experience. These observations form theoretical constraints around the mystery of consciousness, pointing towards the fact that we do not experience the real world. Instead, we experience the internal representations of the world as simplified by the brain.
Humans report that they experience life as a series of multi-modal sensory episodes. “Multi-modal” is a commonly used phrase in neuroscience to differentiate sensory modalities of an experience. For instanc