PYB102 – Week Nine Revision
Phonemes are the smallest unit of sound that makes a difference to meaning. Morphemes are the
smallest unit of language that has meaning. Semantics are the meaning of words or sentences.
Syntax is the grammatical rules for constructing phrases and sentences. Grammar is all of the rules
for usage of a language. Aphasia is a broad term used clinically to describe impairment or disorders
Broca’s Area (1861)
Paul Broca was a surgeon who performed a post-mortem on a patient’s brain, only to find
severe legions in the left frontal lobe. This area was correctly associated with language and
came to be called ‘Broca’s area’.
This patient had lost ability to speak and could only utter a few small sounds, most
prominently the word ‘tan’.
This patient also exhibited right hemipareses (weakness of the right hemisphere).
Despite this, he exhibited comprehension and could understand language spoken by others.
Wernicke’s Area (1874)
Similarly to Broca, Wernicke’s patients exhibited speech deficits and a post-mortem of their
brains revealed lesions in parts of the brain.
However, these legions were not in Broca’s area. They were located at the back (posterior)
of the temporal lobe. This came to be called Wernicke’s area.
These patients differed from Tan, however, in that they had no problems producing fluent
speech. What was wrong was not their speech production, but rather their speech
comprehension. These patients could not understand language spoken by others, and also
could not understand the language they were producing.
This resulted in fluent but completely incomprehensible ‘word salad’ – that is, sentences
that made no sense whatsoever.
The Wernicke-Geschwind Model of Language
In 1972, Geschwind expanded on the works of both Broca and Wernicke to develop of model of
language which is now referred to as the Wernicke-Geschwind Model. This approach is also
commonly referred to as connectionist or disconnectionist theory because it emphasises the
connection between language impairments and loss of connections within regions of the brain.
Speaking a ‘heard’ word:
1. When a word or a sentence is heard, the auditory cortex transmits information about the
sound to Wernicke’s area where the sound is ‘decoded’ to gain meaning.
2. From Wernicke’s area, the meaning of the sound is then transmitted to Broca’s area via a
bundle of nerve fibres called the arcuate fasciculus.
3. It is in Broca’s area that the word is prepared for reproduction in speech. Broca’s area then
transmits this plan of speech to the adjacent motor cortex which controls the relevant
muscles for actually producing this speech.
Speaking a ‘written’ word: 1. When the written word is first seen, it is processed through the primary visual cortex at the
back of the brain.
2. From the visual cortex, the image is then transferred via the angular gyrus to Wernicke’s
area where it is recognised and its meaning is comprehended.
3. The same pathway as speaking a heard word is then followed, whereby the arcuate
fasciculus transfers the meaning to Broca’s area where it is prepared for speech. The
adjacent motor cortex then passes the message to relevant muscles to actually produce the
The Wernicke-Geschwind models are particularly useful because they can provide a starting point
for helping us determine where legions are in the brain as a result of different language
Different Types of Aphasia
Also called ‘production aphasia’, ‘non-fluent aphasia’, ‘expressive aphasia’ or ‘motor
Generally (but not always) results from damage to Broca’s area (inferior region of the left
Broca’s area is located just in front of the portion of the motor cortex that controls muscles
which create speech such as the tongue, jaw, throat and lips.
Damage to this region is thought to remove memory traces of the movement required to
Symptoms of Broca’s aphasia include a disturbance of language, characterised by slow,
effortful and deliberate speech and telegraphic speech – which includes basic nouns and
verbs e.g. ‘Eat dinner’.
Patients with Broca’s aphasia may also suffer from anomia (inability to com