Millions of sensory neurons send information to the brain about the external world and the status of the body. The brain sends out information to millions of cells that cause the muscles to contract and the glands to secrete their juices. In order to handle those enormous amounts of information, the brain groups together small pieces of information, and deals with those groups as wholes, without paying too much attention to their details. Information elements that the brain uses as wholes are called here concepts. For example, when someone shakes our hand, millions of sensory cells send signals to the brain. The brain groups all those stimuli into very few concepts such as ‘something is touching the hand’, ‘the pressure on the touched area is light’, ‘the temperature of the touch is mild’, and few more concepts. The brain then uses those few concepts for figuring out our response. The response is also made up of few concepts such as ‘return a hand shake’, ‘smile’, and so on. Each of those concepts, in turn, causes the activation of millions of cells that constitute our response.

Concepts are associated with each other. For example, the concept ‘hand shake’ is associated with concepts such as ‘strength of grip’, ‘duration of grip’, and ‘warmth of grip’. The latter three concepts are parts of the umbrella concept ‘hand shake’.

The brain uses a few basic associations between concepts. It builds elaborate associations from the few basic ones. The basic associations are at the root of all the information handling processes that the brain carries out.

Nodes represent concepts; Active and quiet concepts

Any concept that the brain has may be in one of two states: active or quiet. An active concept is a pattern of firing neurons. At any given time, the active concepts are the realization of our self:  how we perceive the world, what we think, and what is our body doing. Quiet concepts just reside in the memory. Active concepts send signals to some or to all their associated concepts. Those signals may be positive (excitatory) or negative (inhibitory). The receiving concept adds up the signals that it receives. If their sum is greater than a given threshold, the concept becomes active.

Concepts are represented in our brain model by nodes. A node may represent any number of real biological neurons. The associations between concepts are represented in the model by synapses - connections between two nodes. The strength of the association is represented by a synaptic weight. A firing node represents a concept that participates in the ongoing brain's activity, and a quiet node represents a concept stored in the memory. Activation propagates from firing nodes to nodes that are connected to them by synapses. As a result of this propagation, quiet nodes may fire, and firing nodes may be inhibited from firing. Unlike in biological neurons, activation signal between two nodes can propagate in two directions.

A group of neurons that fire together form a spatial concept. A sequence of spatial concepts form a temporal concept. A temporal concept may be represented by a spatial concept. For example, each frame of a video creates a visual spatial concept. The sequence of those frames creates a visual temporal concept. The name of that video is a spatial concept that defines the temporal concept, which is made of spatial concepts.

Reality concepts, mental concepts and labels

The brain has three layers of concepts: Reality concepts, mental concepts, and labels. Reality concepts are activated directly or indirectly by external stimuli, and they activate external units. Reality concepts also activate mental concepts and labels, but they cannot be activated by them.

Many mental concepts are representations of reality concepts. They are the “mind's rendition of reality.” For example, when we hear a song, the sounds activate patterns of neurons. These patterns form the reality representation of the song. Signals that propagate from these representations may create memory records of the song. Later, when we recall that song, those records are activated and create the mental representation of that song. Signals cannot propagate back from the mental representation to the reality representation. Although both represent the same song, the reality concept represent how we really heard it, and the mental concept represent how we hear it in our mind.

The brain may give a name to the entire record of the song and to its reality representation. Such a name serves as a label to the reality concept and to the mental concept that represent the song. By activating the label, we may activate the mental representation of the song; we can play it back in our mind, but this is different from actually hearing it.

Many mental concepts represent combinations of reality concepts; the reality concepts themselves have happened, but not their combination. For example, the mental concept “If I were a Rothschild” is a combination of reality concepts that have happened not together.

Since they are all concepts, reality concepts, mental concepts and labels are represented in the model by nodes, and the associations between them by synapses.