Freud contributed to the most current debates of his time in the evolving field of neurology.
His most significant pre-psychoanalytic work concerned aphasia (a brain impediment affecting the ability to use, produce, or comprehend language) and infantile cerebral palsy. Freud attributed the development of cerebral palsy to pre-natal conditions, contrary to prevailing medical opinion, which held that it was caused by asphyxiation during birth. He also went against prevailing opinion in suggesting that aphasia did not necessarily result from single or multiple brain lesions, but rather from degeneration of the transmission mechanism between functional zones in the brain. Many years later, medical imaging techniques would validate his groundbreaking insights, which were marginalized in his own time.
The Presentation of Words in Aphasia (1891)
Freud offered an abstract visual language that allowed him to speak on the connectivity of brain areas, rather than identify localized lesions. “Word Presentation” describes the critical connections between the sound-image (Klangbild) and the visual (Visuell) as crucial to the non-pathological presentation of words. In this drawing, we see that Freud no longer makes use of the brain as a graphic template, but instead chose a schematic, and even mechanistic, diagram that could be divorced from human anatomy.
From, On Aphasia (1891). p. 77 [Figure 8]
Introduction to Neuropathology, Kritische Einleitung in die Nervenpathalogie (1885-1887)
Part of an unpublished manuscript on neuroanatomy and neuropathology, this drawing describes different functional connections between the cortex and other parts of the human brain. Unlike many of his contemporaries, Freud opted for a nuanced model, according to which functions (motor, sensory, perceptive, etc.) were encoded in the brain through a system of representation. Aware of the difficulty in representing cognitive functions, let alone dysfunction, Freud would remain attentive to the way representation operates with regards to many of his psychoanalytic concepts.
Sigmund Freud Papers, Library of Congress