Immature precursors of neurons formed during the first phase of proliferation. It is estimated that they are formed at an average rate of 250,000 per minute throughout the nine months of human gestation, with a peak being reached of 500,000 per minute early in development (i.e., around 2 to 4 months of gestation in the …
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Neuroconstructivist networks
Neuroconstructivismis a theoretical framework for cognitive development that emphasizes the closeinteractions between experience and structural development of the brain. Whereas all connectionist models involve some sort of adaptation to theenvironment, in most models this is limited to changing the strength of apre-determined set of connections between a fixed pool of units. Neurocontructivist models allow for …
Neurite
A process growing out of a neurone. Due to difficulty in distinguishing a dendrite from an axon in culture, the term neurite is used for both. The growth of neurites is promoted,for example, by cell adhesion molecules and nerve growth factor (NGF). See Axon, Cell adhesion molecules (CAMs), Dendrite, Filopodia, Growth cone, Muscle spindle, Nerve growth …
Neural plate
The embryonic precursor of the neural tube, it is a region of embryonic ectodermal cells called neuroectoderm that lie directly about the notochord. It is the first embryonic rudiment of the nervous system top be formed. See Blastopore, Ectoderm, Embryogenesis, Gastrulation, Neural tube, Neurula, Neurulation, Notochord
Neural tube
The embryonic precursor or the neural tube containing neural cells in early stages of differentiation, it is one of the rudiments of the central nervous system, which forms from a thickened plate of ectoderm that rolls up around its long axis to form a hollow tubular structure (i.e., the neural tube) extending from the rostral …
Neural net
Computer simulation of biological inter-activation of neurons. A common simple structure involves an input layer of nodes, a middle or ‘hidden’ layer, and an output layer. Cognitive tasks are solved by progressive change in the pattern of activation over the network of interconnections. The methodology and related theory is referred to as connectionism. It differs …
Neural crest
The (two) lines of ectodermal cells, adjacent to the strip of ectoderm (folding into the neural tube during neurulation), from which the dorsal ganglia and various cell types (e.g.,Schwann cells) arise. In fact, itdevelops into most of the peripheral nervous system (neurons and glial cells). Neural crest cells, which tend to undergo longmigrations, give rise …
Neural determinism
The doctrine that development arises from genetically determined changes in neural structures. Some, however, consider geneticdeterminism and neural determinism to have quite different connotations. See Determinism, Genetic determinism, Neurological ‘soft’ signs, Neuromaturation, Neuromaturational theories
Network theory
Manyof the structures that are studied in the social sciences, and in fact in allthe sciences that deal with processes of communication and interaction, takethe form of networks. Formally speaking, a network is a graph (see graphtheory), but the term network is often applied to graphs consisting of many,concrete components connected by many interactions (e.g., …
Neural cell adhesion molecule (N-CAM)
A cell adhesion molecule expressed on the surfaces of most neurons. See Adhesion molecules, Cell recognition molecules (CAMs), Lamillipodia