PSI (ψ) SYSTEM

In his unfinished 1895 "A Project for a Scientific Psychology" Freud defines the psi (ψ) system as a subdivision of the nervous system concerned with psychic processes (1950a[1895]). Later, in The Interpretation of Dreams (1900a) he used the term to refer to components of the "psychical apparatus."

In the "Project," Freud hypothesized two neuronal systems, φ (phi) and ψ (psi), and employed the principle of inertia and the concept of permeability. Elements of what he called the system were permeable but retained nothing; while the impermeable neurons, equipped with resistance and retentive of quantity, are the vehicles of memory and psychic processes in general, and receive endogenous excitations. Subject to the principle of constancy, neurons that make up the system mitigate its impermeability by "facilitation" (Bahnung ), creating a permanent alteration in "contact barriers." Freud here adumbrated the concept of the synapse and the idea of synaptic change.

In later work, Freud abandoned the nomenclature of the "Project." He only employed the term "ψ system" in The Interpretation of Dreams, where it was used in the plural to describe the components of the psychic apparatus. (1900a, Chap. 7). The systems possess spatial and temporal qualities in terms of arousal, which begins with internal or external stimulation and ends in "innervation" or discharge.

After 1900, Freud employed the term "ψ systems" without as much spatial precision, and made use of new subdivisions: the systems Pcpt. (perceptual), Cs (conscious), Ucs (unconscious), among others.

Bertrand Vichyn

See also: Ego; Principle of (neuronal) inertia; "Project for a Scientific Psychology, A".

Bibliography

Freud, Sigmund. (1900a). The interpretation of dreams. Part I, SE, 4: 1-338; Part II, SE, 5: 339-625.

——. (1950c [1895]). Project for a scientific psychology. SE, 1: 281-387.