Mnemic Trace/Memory Trace

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The mnemic trace, the notion of unconscious memory that is essential in Freudian theory, results from the inscription upon the psychic apparatus of a perception that is strong enough to cross the barrier of the protective shield. This perception is totally unconscious, whereas the memory of it is conscious. Sigmund Freud envisaged the psychic apparatus as a system of multiple and complex facilitations of mnemic traces. The mnemic trace, usually sensory, can also be the trace of a thought, especially when it is verbal.

Used throughout Freud's works, this notion appeared in his first theories of the neuroses before 1900, mostly in the "Project for a Scientific Psychology" (1950c [1895]); it was then reformulated in The Interpretation of Dreams (1900).

The mnemic trace, a metapsychological construct, originated in neurophysiology. In "Project for a Scientific Psychology," Freud saw in it both the complex reality of "facilitations" in the neurons, which present-day neurobiology would call "neural networks," but also a differential system of inscription of perceptual impressions. The postulate of incompatibility between, on the one hand, consciousness and perception, and, on the other hand, the unconscious and the lasting quality of mnemic traces expressed in 1895 and reiterated in 1900, remained intact throughout the developments of his later work.

In a letter to Wilhelm Fliess dated December 6, 1896, Freud posited that memory consists of multiple strata corresponding to different points in time, and that these are always being rearranged because they are constantly being transformed into different "signs": In the mnemic trace, the sensory perception becomes a sign of perception. The German Erinnerungsspur literally means "trace of a memory." In Freud's text the same linguistic root is used for two notions that are contradictory in other languages: the "mnemic trace," which is unconscious, and a memory (Erinnerung ), which is conscious. The semantic slippage between the two terms in Freud's work reflects the fact that he elaborated the notion of the mnemic trace based on his theory of seduction and trauma in hysteria, in which the trace of the trauma is conceived as being a more or less forgotten and more or less unconscious memory, resulting in the paradox of an "unconscious memory."

Freud discovered the existence of the mnemic trace based on the insistent character of the deformation produced by the traumathat is, the persistent intensity of the symptom, which he envisioned as a state of charge in the neurons that would evacuate a quantity, producing what he described in The Interpretation of Dreams (1900) as "permanent modifications" (p. 538) in the nervous tissues. Mnemic traces tend to "refind" their perceptual and conscious origins in a hallucinatory mode. The mnemic trace is the trace par excellence of the object of desire associated with the scheme of action leading to the satisfaction of the instinct. Essentially a visual tracealthough the mnemic trace can be olfactory, tactile, or verbalit is sometimes called a "mnemic image." In hysteria and in the neuroses more generally, the imprint of mnemic images and obsessive memories is linked to the pregnance of the affects. The mnemic trace corresponds to the impression produced by a perception, not to the perception as such: It is a representation of an absent object, accompanied by affects. In the unconscious, the instinct hallucinatorily cathects the mnemic trace of this absent object, which can be theorized as an "internal object."

In 1895 Freud underscored the question of the coincidence between the unconscious representation and the external object of perception, to the extent that the ability to evaluate their identity or their difference defines the ego as a stable agency situated at the boundary between inside and outside. In "Project for a Scientific Psychology" he explained how the ego inhibits the hallucinatory mode of internal representations and provides the means by which "traces of thought-processes are distinguished from those of reality" (p. 335). His arguments in this essay presume, beyond the difference between mnemic trace and perception, a difference between traces mediated by thought, which exerts a secondary influence on them, and mnemic traces strictly speaking, which come from perception.

It is by means of language that traces originating in thought become mnemic traces, because language is registered at the level of the senses: that is, through hearing speech or reading something written. Verbal mnemic traces are posited as having the power to bring into consciousness all the other mnemic traces that they name. But the secondary processes can never totally inhibit the tendency toward immediate discharge in the coalescence between representation and perception, as Freud concluded in "Project for a Scientific Psychology."

This conception was further elaborated in 1900 in The Interpretation of Dreams, where the dream-work is envisioned as the metabolization of a combination of memories, unconscious mnemic traces, instinctual representatives, and complex thoughts. In chapter 7 Freud proposed a comparison between the mental apparatus and a compound microscope or camera, and wrote: "On that basis, psychical locality will correspond to a point inside the apparatus at which one of the preliminary stages of an image comes into being" (p. 536). He stressed the different types of mnemic traces, based on, but also beyond, the assumptions that there may be several traces corresponding to a single perception, and that memory traces are grouped according to resemblance or simultaneity. Here, the notion of mnemic trace is inseparable from that of the unconscious wish seeking identity between representation and perception. Mnemic traces are "paths which can always be traversed . . . indestructible" (p. 577); when a memory trace "is touched, it springs into life again and shows itself cathected with excitation" (p. 578). The mnemic trace is thus endowed with the capacity to radiate outward that is characteristic of desire.

In "A Note upon theu 'Mystic Writing Pad"' (1925a), the dominance of the mnemic trace over consciousnessof which it is ostensibly the necessary prior stageis attributed to consciousness being switched on and off in alternation within perception, openings and closings of the psychic apparatus at the interface between the Pcs.-Cs. and Ucs. The sense of the passage of time is posited as being the effect of these openings and closings; the screen between inside and outside, a veil that covers unconscious memory, the protective shield, is above all a receptive surface for impressions destined to become mnemic traces.

Alongside this metapsychological conception, Freud's work also reflects a historian's approach, with the mnemic trace attesting to the historical reality of a psyche that develops based on the past. In the case of Emma (reported in "Project for a Scientific Psychology"), the phobic young woman believed that her symptom had originated in an episode during her adolescence in which she had felt seduced by a young man; Freud interpreted this as a screen and displacement of a childhood episode in which she had been sexually molested by an adult. According to Freud, it had to be the case, even if Emma believed she had felt nothing during the childhood incident, and even if the disturbance and the affect of a seduction were only apparent in deferred form during the episode in her adolescence, that at the time of the childhood incident a tension had been established and inscribed as a mnemic trace that could later be reactivated at the time of her sexual maturation at puberty. The mnemic trace of the childhood trauma repeated a deformation, a lasting modification, in Emma. Here the trace took a different form, an associative linking as much as a quantitative libidinal charge. It sought in external reality forms that were equivalent to what the early impression aroused, both to expunge its unpleasurable character and to replicate the exciting aspect of seduction.

As early as 1895 in Freud's work, the notion of what will come to be called repetition compulsion is based on the idea that the unconscious mnemic trace is far more evident in repetitionand therefore in what would later be theorized as the transferencethan in memories of past events. In a memory there is always a discrepancy between the perception as it was at the time and the current representation of it, whereas in repetition, through "refindings" of situations and substitute objects, the mnemic trace remains extremely close to the mode of hallucinatory wish fulfillment. In Studies on Hysteria (1895d) and "The Aetiology of Hysteria" (1896c), Freud brought out the notion of the mnemic trace based on the phenomenon of the "excessively intense idea" in the hystericthat is, as close as possible to the state of hallucinatory wish fulfillment without actually falling into it.

The postulate of an incompatibility between perception and consciousness, on the one hand, and the mnemic trace, on the other, in some respects comes out of an ontological dualism. Freud held that mnemic traces are indestructible, but what happens in the case of severe traumas or in certain psychotic states? Are we to take literally Freud's hypothesis, advanced in Moses and Monotheism: Three Essays (1939a), of a hereditary phylogenetic transmission of transgenerational mnemic traces? The notion of the mnemic trace raises epistemological questions. The paradox of deferred action in the case of Emma's seduction defines the mnemic trace as both the mirror of an elementary reality and a hypercomplex construction, midway between a materialist ontology and a formalism within a perspective of constant transformation. In the "Project for a Scientific Psychology" Freud compared the charge of the mnemic trace to the notion of the "moving quantity" from quantum physics, bringing together traditional materialism and a more modern point of view on self-organization and complexity.

Similarities (correspondences) exist between the Freudian notion of the mnemic trace and some contemporary research in neurobiology and the cognitive sciences, even though the psychoanalytic approach distinguishes itself radically from the latter with its specification of the psychic dimension of a subject governed by the pleasure/unpleasure principle in object relations. The mnemic trace is not a cognitive representation of the external world; it results from a singular historical construction in which representations are stabilized into thoughts, but also into fantasies and affects. However, the question of the degree of coincidence between mnemic trace and object of perception, which Freud emphasized, in some respects falls within the purview of the "mentalism" characteristic of cognitive psychologyagainst a background of Darwinism, because for Freud the search for identity between mnemic trace and object of perception is what makes possible efficacious action adapted to the environment.

The fiction of the "Mystic Writing Pad" is as much a neurobiological model of memory as it is a metaphor of the mind. There are mnemic traces that come out of internal psychical productions, rather than from perceptions: The question of the coincidence between mnemic trace and object of perception must be included in a conception in which it is the subject who constructs his or her "psychology" in a unitary way. As if to protect himself from any form of spiritualism, Freud wrote in chapter 7 of The Interpretation of Dreams that consciousness is "only . . . a sense organ for the perception of psychical quantities" (p. 615)in other words, that it is constituted only of mnemic traces of a particular kind. He linked psychology and metapsychology when he used Erinnerung for "memory" and Erinnerungsspur for "mnemic trace," in a conception where it is the conscious ego that remembers the impression (Eindruck ) of lived experience (Erlebnis ), but it is unconscious mnemic traces, independently of consciousness, that contain memory. Alongside Erinnerungsspur, the notion of Gedächtnis-spur, or "trace memory," is found in Freud's work.

FranÇois Richard

See also: Amnesia; Forgetting; Memory; Remembering; Reminiscence.


Freud, Sigmund. (1896c). The aetiology of hysteria. SE, 3: 186-221.

. (1900a). The interpretation of dreams. SE, 4-5: 1-625.

. (1925a [1924]). A note upon the "Mystic writing pad." SE, 19: 225-32.

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

Freud, Sigmund, and Breuer, Josef. (1895d). Studies on hysteria. SE, 2: 48-106.