Freud coined the medical term agnosia

Person: Sigmund Freud
Lived: 1856–1939
Field: Psychology
From: Austrian

The story

Aphasia, the loss of the ability to understand or express language after brain damage, was one of the great puzzles of nineteenth-century neurology. Leading researchers of the classical German school, including Theodor Meynert, Carl Wernicke and Ludwig Lichtheim, tried to explain each form of aphasia by damage to a precise centre in the brain. Wernicke, for example, linked an inability to understand speech to lesions in a specific part of the left temporal lobe.

Sigmund Freud had trained in Brücke's physiology laboratory and worked in Meynert's clinic at Vienna General Hospital, and by the late 1880s he was a lecturer in neuropathology in private practice. In 1891 he published his first book, On Aphasia: A Critical Study (Zur Auffassung der Aphasien). In it he challenged the main authorities of the time, arguing that their way of understanding aphasias was no longer tenable because it confused psychological and physiological concepts.

Freud counselled against too strict a localist view of neurological deficits. Like his contemporary Eugen Bleuler, he emphasised how the brain functions rather than simply mapping its structures. In the book he also introduced a new term. For disturbances in the recognition of objects, which the physician Finkelnburg had classed as asymbolia, Freud proposed the word agnosia, from the Greek for absence of knowledge.

Agnosia remains a standard term in neurology and neuropsychology today. It describes an inability to recognise objects, people, sounds, shapes or smells even though the senses themselves work and memory is largely intact. Doctors now distinguish many forms, such as visual agnosia and prosopagnosia, the inability to recognise faces, which can follow strokes, dementia or other brain injuries.

On Aphasia also contains Freud's earliest thinking about psychology and language, including speculation about how children acquire speech. He returned to the subject in his 1915 paper The Unconscious. His interest in how the mind links words and meanings carried over into psychoanalysis, which treats a patient's speech as a window into mental life.