The Memory Side Of The Brain

The capacity to bring elements of an experience from one moment in time to another is the unique property of life forms. This remarkable property - the carrying of information across time - is the foundation of every biological process from reproduction to gene expression to cell division – from receptor-mediated communication to the development of more complex physiological systems (including neurodevelopment). To some degree, all of the organ systems in the human body have “memory.” This ability to carry elements of previous experience forward in time is the basis of the immune, the neuromuscular, and neuroendocrine systems. Through complex physiological processes, elements of experience can even be carried across generations. Elements of the collective experience of the species are reflected in the genome, while the experience of the individual is reflected in the expression of that genome. No other biological system has developed more sophisticated capacity to make and store internal representations of the external world – and the internal world – than the human central nervous system, the human brain. All nerve cells ‘store’ information in a fashion that is contingent upon previous patterns of activity (see Singer, 1995; Thoenen, 1995). Neurons are specifically designed to modify in response to external cues (e.g., neurohormones, neurotransmitters, neurotrophic factors; Lauder, 1988). These neurophysiological and molecular neurobiological properties underlie all of the complex functions mediated by the brain (thinking, feeling and acting). During development, the cognitive, motor, emotional and ‘state’-regulating areas of the brain organize in response to experiences . And in each of the diverse brain systems which mediate specific functions, some element of previous experience is stored. This storage involves complex neuromolecular processes – use-dependent changes in synaptic microarchitecture and intracellular alterations in various important chemicals involved in cellular communication and gene expression. The details – those that are known – are outside the scope of this chapter. Yet to understand that the physical properties of neurons change with experience is crucial to understanding the concept of memory. Simply stated – the brain changes with experience – all experience, good and bad. The focus of this chapter is how the brain changes by storing elements of a traumatic experience. The brain allows the individual to sense the external and internal environment, process this information, perceive and store elements of these sensations, and act to promote survival, and optimize our chances for successful mating – the key to survival of the species. In order to do this, the brain creates internal representations of the external world -- taking information that was once external to the organism, transforming this into patterned neuronal activity and, in a ‘use-dependent’ fashion, creating and storing these representations (e.g., Kandel and Schwartz, 1982; Maunsell, 1995). A further remarkable characteristic of this internal representation is that the brain makes and stores associations between the sensory information (e.g., sights, sounds, smells, positions, and emotions) from that specific event (e.g., the pairing of the growl of the sabertooth tiger and danger) allowing the individual to generalize to sensory information present in current or future events.