By Aswin Anilkumar
One of the greatest advantages homo sapiens?have enjoyed over other species is the ability to memorize, and derive conscious inferences from recollections. This ability led to the accumulation of human knowledge over generations.?I enabl learn. We could think, and identify strategies to neutralize the evolutionary advantages of other species. On encountering animals, we learned to override the impulse to kill, and began to domesticate and farm, creating an infinite supply of food for a minimal effort. We learned to do what no other animal ever could ? we learned to shape our environment to suit our needs. In time, we came to dominate our planet and shape a new epoch: The Anthropocene Era, or the Age of Man.
Our ability to form memories is then, unquestionably important. But how exactly are they formed?
Sensory, Short-term, and Long-term Memory
A crucial task performed by the brain each day concerns the filtering of information. The five sense organs together accumulate terabytes of information each minute. If all this information were to be stored in the brain permanently, it would lead to catastrophic overloads of memory. Instead, memories are segregated into sensory, short-term and long-term memories. While sensory memories decay rapidly (~500 milliseconds after capture), they act as the first buffer for sensory information. Sensory information, if important, transfer to the short-term memory, which lasts for as long as 10-15 seconds without conscious effort. The sensation of pressure at an instant isn?t likely to be remembered, and yet a painful pinprick is recalled easily ? which is an example of an important stimulus transferred to short-term memory.
The short-term memory typically stores information for about 15 seconds. This is useful in a number of tasks not limited to: reading a long sentence which requires memory of an earlier section, tracking a long, persuasive argument, and simultaneous translation as performed by interpreters.
The conversion of short-term memory to long-term memory is slightly more difficult, and requires primarily repetition, and the motivation. The difference between reading a textbook and reading a story is grounded in one or both of these factors; reading a novel is relaxing, while reading a textbook requires both concentration and repetition. Motivation is an often ignored, but crucial catalyst of this conversion. The lack of employability in many professions stems from students studying without the desire to apply, leading to inefficient conversion to long-term memory, which is ultimately wasteful. ?
Finally, long-term memory is intended to be stored for extended periods of time. There continues to be much debate whether long-term memory decays at all, or merely becomes increasingly difficult to remember. The use of hypnosis to recollect forgotten details of old memories would lend credence to the latter theory.
The Neuroanatomy of Memory
The Neuroanatomy of memory consists two important classes of structures: Cortical regions, and the Sub-cortical regions. The subcortical zones consist of the Hippocampus, Amygdala, Cerebellum and Basal Ganglia, while the Cortical zones consist of the Frontal, Occipital, Parietal and Temporal lobes. The Prefrontal cortex here plays an important role in both short-term and long-term memory. Apart from acting as a temporary store of transitory information to be used immediately, the prefrontal cortex also ?calls up? information stored elsewhere. ??
The hippocampus is believed to contain ?cognitive maps?. Put simply, the neurons in the hippocampus are physically altered when memories are stored. The number of possible combinations of differences may be close to infinite, allowing for our seemingly endless memory storage. There also exists a division of duties within the hippocampus, but the primary function of the hippocampus is spatial awareness, enabling predators to better judge distances and capture prey. The discovery that removal of the hippocampus impedes new memory formation has been called the ?neural Rosetta stone? ? such has been the hippocampus? importance in the neuroanatomy of memory.
The cerebellum however is related to ?procedural memory?, or the acquiring of motor skills such as learning to ride a bike or drive. The physical dissociation of conscious memory from learned skills explains why amnesiacs retain their ability to perform complex musical pieces or drive. Since two separate regions handle the classes of memory, it?s possible to lose your memory but continue to exercise your motor skills.
Instead of the storage of memory, the frontal lobes differ in that they coordinate information. For example, travelling from your home to a local store would require that you combine various kinds of information about the route and traffic, to arrive at the correct ETA. This coordination and translation of memory is performed in the frontal lobe. The parietal lobe is however extremely diverse, from helping orient your spatial awareness, to integrating sensory information. Finally, the occipital lobe deals with visual perception, damage to which leads to hallucinations, and trouble differentiating colours.
The breadth and diversity of brain function, is the most important take-away here. Rather than a semi-solid store of all information, the brain is a highly organized biological marvel.
The Evolution of Memory
The highly specialized parts of the brain did not evolve simultaneously. Rather, they developed over concurrent evolutionary periods. There are seven ?representational systems? identifiable in our brain native to seven regions ? from the navigation system, to a competition system and a foraging system.
The modern human brain originated from extremely primitive nervous systems in the first flatworms 570-580 million years ago. These animals required the primitive brain to move about, sight predators and forage for food ? needs which only grew complex over time. However, it?s all too easy to regard the tremendous process of forming the modern human brain to ?evolution?, without a true understanding of the complexity involved.
For one, consider the sheer timescales involved. A single generation of human life spans 20 years from the birth of the parent to the birth of the child, and 570 million years would include twenty-seven million generations. Consider for a moment how different a generation is from the parent?s, all the different variations in personality and physique brought about due to changes in diet and genetics. Twenty-seven million iterations of these differences occurred, with several individuals dying in each generation before they could reproduce, because of their unfavourable genetics. This process of amplification and dying-off led to incremental changes, and branching-off as each species found their own ecological niche. And thus, almost all modern animal brains can be traced to a common evolutionary path through the same stages.
Where do we go from here?
Memory implants, may not be too far off. Currently, millions of people around the world struggle with memory-related diseases like Alzheimer?s, causing severe distress to both sufferers, and the family caring for them. However, memory implants such as those being designed by Theodore Berger at the University of South California could solve this, by mimicking the electrical signal relays between neurons, which could potentially restore the ability to form new memories. In a ground-breaking experiment, Berger?s team demonstrated that they could help monkeys retrieve long-term memories from the part of the brain which stores it. This device promises to be as potentially revolutionary as cochlear implants, which bring hearing to the deaf by converting external sounds into electrical signals.
As humans continue to understand the physical formation of memory in the brain, several possibilities emerge, from the implantation of memories to help with treating personality disorders, to the removal of undesirable memories from PTSD survivors. The study of the brain and the formation of memory promises to radically transform our vision of the future.
