Suzana Herculano-Houzel

Signals that form patterns become information, which once applied becomes knowledge

The contagious excitation of a neuron is a signal: it represents an event by virtue of being correlated with it through cause and effect. The event represented, or signaled, may be en external event in the world, or simply the activation of the previous neuron that caused it, whether or not that activation can be traced to any single…...

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More cortical neurons, more self-control

Nervous systems, and brains in particular, add flexibility to behavior, making it much more than simple responses to events. Sure, responding (or not) is a behavior in itself. But when a nervous system is involved in organizing, shaping and eventually controlling the behavior, the intrinsic properties of nervous systems allow them to spontaneously generate actions; impart context to behavior, including a past history; anticipate future…...

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Behavioral flexibility increases together with number of cortical neurons

If we consider neurons as the information-processing building blocks of nervous systems, then it follows that the more the neurons in a system, the more capable of processing information it should be. Of course, the comparison only applies across systems that are connected the same way, as similar circuits. Given a certain pattern of circuitry, the…...

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Animal behavior is patterned neuronal activity

In animals that have a nervous system, all motor, mental and visceral actions (and therefore behavior) are the product of neuronal activity. When neuronal activity in the relevant structures or pathways is disrupted or impeded – for example, with anesthetics -, that behavior stops. But this does not yet explain what is it about neuronal activity that…...

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Behavior with a nervous system becomes fast, flexible and complex

Two distribution systems allow large organisms to act as integrated wholes. One is the immunoendocrine system, which through the release of wide-acting substances in the circulatory system allows slow and lasting (stable) integration of bodily functions. The resulting integrated behaviors take seconds to minutes to occur, and last for hours to several days, as long as the substances released are still active. The other is…...

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Behaviour without a nervous system depends on diffusion

All actions, and therefore behaviors, require energy transfer. Behaviors happen as potential energy is dissipated, channeled through natural or man-made circuits, networks, or natural paths of least resistance. Ultimately, the source of energy is external to the system, and transferred to it in an original explosion (case of the solar system), through a power line or induction (appliances), or fuel (vehicles and…...

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Behavior is any observable action

We usually equate nervous systems with behaviors, but as it turns out, a nervous system – that is, an ensemble of organs and tissues made of excitable cells that carry signals rapidly across the body – is actually not necessary for behavior. If behavior is defined simply as sets of observable actions in a given context, then plants have behaviors, like orienting to sunlight; so do single-cell…...

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First Principles: Neuronal circuits are branched and depend on signal integration

Any drawing of a neuron connected to another neuron to represent a nervous system is a gross oversimplification that may serve a didactic purpose, but comes with a problematic danger: the risk of implying that neuronal networks are simple one-to-one circuits in structure (anatomy) and function (physiology). That only happens in exceptional cases, like the neuromuscular junction…...

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First Principles: Neuronal activity is contagious excitation, an electrochemical signal

“Activity” is a term that, in a neuron, usually describes the undoing of the voltage of their cell membrane. If such changes occurred in other cells, they would most likely soon be dead, intoxicated by high levels of calcium released from intracellular stores. In neurons, in contrast, either the undoing of the membrane potential is quickly reversed, or else it…...

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First Principles: Neuronal circuits are directional

Electric fields spread wherever a current can be physically carried, for instance along paths that are called circuits. In theory, because electric fields spread omnidirectionally, electrical circuits are non-directional, and changes in charges are propagated along all available wires – unless a gating mechanism is in place. In the nervous system, in contrast, the circuits formed by neurons are directional by way…...

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