10 Unsolved Mysteries Of The Brain

From Discover Magazine.

  • How is information coded in neural activity?

    It is likely that mental information is stored not in single cells but in populations of cells and patterns of their activity. Although traveling bursts of voltage can carry signals across the brain quickly, those electrical spikes may not be the only—or even the main—way that information is carried in nervous systems. ­

  • How are memories stored and retrieved?

    Almost all theories of memory propose that memory storage depends on synapses, the tiny connections between brain cells. When two cells are active at the same time, the connection between them strengthens; when they are not active at the same time, the connection weakens. Out of such synaptic changes emerges an association.

    There is no good theory to explain how memory retrieval can happen so quickly. Moreover, the act of retrieval can destabilize the memory. When you recall a past event, the memory becomes temporarily susceptible to erasure.

  • What does the baseline activity in the brain represent?

    Some of the baseline activity may represent the brain restructuring knowledge in the background, simulating future states and events, or manipulating memories. Most things we care about—reminiscences, emotions, drives, plans, and so on—can occur with no external stimulus and no overt output that can be measured.

    The awake state may be essentially the same as the dreaming state, only partially anchored by external stimuli. In this view, your conscious life is an awake dream.

  • How do brains simulate the future?

    Many neuroscientists have suggested over the past few decades that perception arises not simply by building up bits of data through a hierarchy but rather by matching incoming sensory data against internally generated expectations.

    Your memories about your life may come to be understood as a special subtype of emulation, one that is pinned down and thus likely to flow in a certain direction.

  • What are emotions?

    Emotions are measurable physical responses to salient stimuli: the increased heartbeat and perspiration that accompany fear.

    Modern views propose that emotions are brain states that quickly assign value to outcomes and provide a simple plan of action. Thus, emotion can be viewed as a type of computation, a rapid, automatic summary that initiates appropriate actions.

    One goal of emotional neuroscience is to understand the nature of the many disorders of emotion, depression being the most common and costly. Impulsive aggression and violence are also thought to be consequences of faulty emotion regulation.

  • What is intelligence?

    Recent experiments explore the possible relationship of intelligence to the capacity of short-term memory, the ability to quickly resolve cognitive conflict, or the ability to store stronger associations between facts; the results are not yet conclusive. Many other possibilities—better restructuring of stored information, more parallel processing, or superior emulation of possible futures—have not yet been probed by experiments.

  • How is time represented in the brain?

    Your notion of the smooth passage of time is a construction of the brain. Clarifying the picture of how the brain normally solves timing problems should give insight into what happens when temporal calibration goes wrong, as may happen in the brains of people with dyslexia. Sensory inputs that are out of sync also contribute to the risk of falls in elderly patients.

  • Why do brains sleep and dream?

    In humans, continuous wakefulness of the nervous system results in mental derangement; rats deprived of sleep for 10 days die.

    There are at least three popular (and nonexclusive) guesses. The first is that sleep is restorative, saving and replenishing the body’s energy stores. However, the high neural activity during sleep suggests there is more to the story. A second theory proposes that sleep allows the brain to run simulations of fighting, problem solving, and other key actions before testing them out in the real world. A third theory—the one that enjoys the most evidence—is that sleep plays a critical role in learning and consolidating memories and in forgetting inconsequential details. In other words, sleep allows the brain to store away the important stuff and take out the neural trash.

    Dreaming is akin to an off-line practice session.

  • How do the specialized systems of the brain integrate with one another?

    While the brain’s ability to do parallel processing is impressive, its ability to rapidly synthesize those parallel processes into a single, behavior-guiding output is at least as significant.

    There is no special anatomical location in the brain where information from all the different systems converges; rather, the specialized areas all interconnect with one another, forming a network of parallel and recurring links. Somehow, our integrated image of the world emerges from this complex labyrinthine network of brain structures.

  • What is consciousness?

    The mechanisms underlying consciousness could reside at any of a variety of physical levels: molecular, cellular, circuit, pathway, or some organizational level not yet described. The mechanisms might also be a product of interactions between these levels. One compelling but still speculative notion is that the massive feedback circuitry of the brain is essential to the production of consciousness.


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