Carl Wernicke

  Carl Wernicke (born 15 May 1848 in Tarnowitz, Upper Silesia, then Prussia, now Tarnowskie Gory, Poland – died 15 June 1905 in Gräfenroda, Germany) was a German physician, anatomist, psychiatrist and neuropathologist. He earned his medical degree at the University of Breslau (1870). He died in Germany due to injuries suffered during a bicycle accident ^[1].

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Shortly after Paul Broca published his findings on language deficits caused by damage to what is now referred to as Broca's area, Wernicke began pursuing his own research into the effects of brain disease on speech and language. Wernicke noticed that not all language deficits were the result of damage to Broca's area. Rather he found that damage to the left posterior, superior temporal gyrus resulted in deficits in language comprehension. This region is now referred to as Wernicke's area, and the associated syndrome is known as Wernicke's aphasia, for his discovery.

The Wernicke-Geschwind model of language

Wernicke created an early neurological model of language, that later was revived by Norman Geschwind. The model is known as the Wernicke-Geschwind model. 

1. For listening to and understanding spoken words, the sounds of the words are sent through the auditory pathways to area 41, which is the primary auditory cortex (Heschl’s gyrus). From there, they continue to Wernicke’s area, where the meaning of the words is extracted.
2. In order to speak, the meanings of words are sent from Wernicke’s area via the arcuate fasciculus to Broca’s area, where morphemes are assembled. The model proposes that Broca’s area holds a representation for articulating words. Instructions for speech are sent from Broca’s area to the facial area of the motor cortex, and from there instructions are sent to facial motor neurons in the brainstem, which relay movement orders to facial muscles.
3. In order to read, information concerning the written text is sent from visual areas 17, 18, and 19 to the angular gyrus (area 39) and from there to Wernicke’s area, for silent reading or, together with Broca’s area, for reading out loud.

This model is now obsolete. Nevertheless it has been very useful in directing research and organizing research results, because it is based on the idea that language consists of two basic functions: comprehension, which is a sensory/perceptual function, and speaking, which is a motor function.
However, the neural organization of language is more complex than the Wernicke-Geschwind model of language suggests. The localization of speech in Broca’s area is one of the weakest points of this model.^[2]

Neurological syndromes described by Wernicke

• Wernicke aphasia: the eponymous term for receptive or sensory aphasia. It is the inability to understand speech, or to produce meaningful speech, caused by lesions to the posterior superior temporal gyrus.
• Wernicke encephalopathy: an acute neurological syndrome of ophthalmoparesis, ataxia, and encephalopathy brought on by thiamine deficiency. Wernicke's encephalopathy can occur combined with Korsakoff psychosis, which is a subacute dementia syndrome. It is then called the Wernicke-Korsakoff syndrome.

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