University of Alberta Dictionary of Cognitive Science: Neuron

These are the specialized, functional cells of the nervous system that conduct neural information.

There were originally 2 basic hypotheses about the structure and function of the nervous system (Kolb & Whishaw, 1996, p.15):

Neuron Hypothesis: the nervous system is composed of discrete, autonomous cells, or units, that can interact but are not physically connected.
Nerve Net Hypothesis: the nervous system is composed of a continuous network of interconnected fibres.

The current understanding of cognition in the brain represents a combination of these hypotheses. Cognition is viewed as occuring by the interaction between neurons through complex excitatory and inhibitory synapses.

As such, cognitive scientists should recognize the need to incorporate basic properties of neurons, and neural organization in the development of models of cognition.

The parallel distributed processing model, is a good example of a model that has attempted to account for the basic neural properties.

References:

Kolb, B., & Whishaw, I. (1996). Fundamentals of human neuropsychology (3rd ed.). New York: W.H. Freeman & Co.
Pinel, J. (1993). Biopsychology (2nd ed.). Toronto: Allyn & Bacon.