The theory of convergence-divergence zones
[Antonio Damasio, Time-locked multiregional retroactivation: A systems-level proposal for the neural substrates of recall and recognition, Cognition, 33 (1989) 25-62] was proposed by
Antonio Damasio
Antonio Damasio ( pt, António Damásio) is a Portuguese-American neuroscientist. He is currently the David Dornsife Chair in Neuroscience, as well as Professor of Psychology, Philosophy, and Neurology, at the University of Southern California, ...
, in 1989, to explain the neural mechanisms of recollection. It also helps to explain other forms of
consciousness
Consciousness, at its simplest, is sentience and awareness of internal and external existence. However, the lack of definitions has led to millennia of analyses, explanations and debates by philosophers, theologians, linguisticians, and scien ...
: creative
imagination
Imagination is the production or simulation of novel objects, sensations, and ideas in the mind without any immediate input of the senses. Stefan Szczelkun characterises it as the forming of experiences in one's mind, which can be re-creations ...
,
thought
In their most common sense, the terms thought and thinking refer to conscious cognitive processes that can happen independently of sensory stimulation. Their most paradigmatic forms are judging, reasoning, concept formation, problem solving, a ...
, the formation of beliefs and motivations ...
It is based on two key assumptions:
1) Imagination is a simulation of
perception
Perception () is the organization, identification, and interpretation of sensory information in order to represent and understand the presented information or environment. All perception involves signals that go through the nervous system ...
.
2) Brain registrations of memories are self-excitatory neural networks (neurons can activate each other).
Definition
A convergence-divergence zone (CDZ) is a neural network which receives convergent projections from the sites whose activity is to be recorded, and which returns divergent projections to the same sites. When an experiment is recorded, the signals that converge on the CDZ excite their neurons which strengthen their mutual connections (according to the
Hebbian theory
Hebbian theory is a neuroscientific theory claiming that an increase in synaptic efficacy arises from a presynaptic cell's repeated and persistent stimulation of a postsynaptic cell. It is an attempt to explain synaptic plasticity, the adaptatio ...
) and thus form a self-excitatory network. The excitation of this network is then enough to reproduce the combination of initially received signals. In a self-excitatory network the excitation of a part spreads to all the others, just like a memory fragment awakens an entire recorded experience. A CDZ is thus the place of recording and reproduction of memories. It is both a detector and a signal producer (forms of neuronal activation). This is the basic neural mechanism that explains memories and other forms of imagination.{{Citation needed, date=September 2020
Arborescences of CDZ
In addition to convergent-divergent paths, a CDZ may be connected to the rest of the brain in every imaginable way, by input signals that activate or inhibit it, and output signals with which it influences the rest of the system. In particular CDZs may be organized into a system and form an arborescence. A CDZ may recruit converging input channels from many other CDZs. It can thus make a synthesis of detection and production capabilities of all the CDZs thus recruited.
To make a model of the CDZ system, we distinguish in the nervous system a peripheral part and a central one, with a gradual progression from the periphery to the center. The periphery includes all sources of perception: the feeling of the outside and inside, emotions and actions. The periphery, thus understood, includes all cortical sensory, emotional and motor areas, and all intracerebral nuclei that contribute to their functioning.
The CDZ system is organized in a hierarchical fashion, from the periphery to the center. The most peripheral CDZs have convergent paths directly from the periphery. We approach the center going up the arborescence of CDZs. One can think of roots that plunge into the earth, the periphery, and converge to the base of the trunk, the center. But in the brain, there are a large number of centers. The most central CDZs have converging projections from other CDZs, and are not recruited by a more central CDZ. The memory of an episode of our life is preserved in such central CDZs. When we relive the perceptions, emotions and actions of a past experience, the excitation of this central CDZs activates all subordinated CDZs and the peripheral areas. It thereby reconstructs the previously lived experience.
See also
*
Memory
Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembered, ...
Episodic memory
Episodic memory is the memory of everyday events (such as times, location geography, associated emotions, and other contextual information) that can be explicitly stated or conjured. It is the collection of past personal experiences that occurred ...
References
Memory
Psychological theories
Neuroscience