Task 4: language
1. What is language and which brain areas are involved?
2. What is aphasia and which subtypes can you define?
3. What are the main causes of aphasia?
4. Which brain areas are linked to fluent and non-fluent aphasia?
5. How can you diagnose and treat aphasia?
Kolb, B. & Whishaw, I.Q. (2015). Fundamentals of Human Neuropsychology (7th Edition). H19
19.1: What is language?
Language structure
Linguists (taalwetenschapers) break language down in different components, as seen in table 19.1.
The traditional criterion linguists use to recognize language is the presence of words and word
components; another characteristic of human language is its use of syllables made up of consonants
(medeklinkers) and vowels (klinkers). Our mouths are capable of producing consonants and
combining them with vowels to produce syllables. However, visual reading also exists: the touch
language of Braille and in movement language of signing.
Words consist of fundamental language sounds, called phonemes, that form a word or part
of a word. Phonological analysis determines how we link phonemes together.
We combine phonemes to form morphemes; the smallest meaningful units of words. Such as
a base (do in undo), an affix (un in undo or er in doer), or an inflection (ing in doing or s in
girls). Some morphemes are themselves complete words; others must be combined to form
words.
A lexicon comprises a memory store that contains words and their meanings, hypothetically,
all of the words in a given language. vocabulary someone has, knowledge of language.
Words are strung together in patterns that conform to the language’s rules of grammar—its
syntax. A key aspect of syntax is appropriate choice of verb tense.
The meaning connected to words and sentences is referred to as semantics. Vocal
intonation, called prosody, can modify the literal meaning of words and sentences by varying
stress, pitch and rhythm.
Discourse, the highest level of language processing, involves stringing together sentences to
form a meaningful narrative.
Core language skills
Four core skills underlie human language: (1) categorizing, (2) category labeling, (3) sequencing
behaviors, and (4) mimicry. One or another of these core skills may be present in other animal
species, including other apes, songbirds, even bees.
1
, Categorization – multiple parallel hierarchical neural channels function to process incoming
sensory information. As the cortex expands and the number of channels that process parallel
sensory information increases, binding (integrating) the information into a single perception
of reality becomes more difficult it becomes necessary to categorize (plants, animals)
Assigning tags to information makes it easier to perceive and to retrieve information.
o The ventral visual stream coursing through the temporal lobes participates in object
categorization, and the dorsal stream may also participate by making relatively
automatic distinctions between objects, such as plant versus animal or human versus
nonhuman.
Labelling categories - Categorization is not only allowed for combining and grouping simple
sensory stimuli but also provided a means of organizing events and relations. Labeling a
category includes not only identifying it, a function of the temporal lobes, but also organizing
information within the category. This is a function of the motor cortices in the frontal lobes
within the dorsal visual stream.
o This categorizing system can stimulate the production of word forms about a concept
(the category); conversely, it can cause the brain to evoke the concepts in words.
A man who was once a painter but is now color-blind can know and use the
words (labels) for colors, even though he can no longer perceive or imagine
what those labels mean. He has, in a sense, lost his concept of color, but his
words can still evoke it.
In contrast, certain brain-lesion patients retain their perception of color, and
thus the concept, but have lost the language with which to describe it. They
experience colors but cannot attach labels to them.
Sequencing behaviour - Left-h structures associated with language form part of a system
that has a fundamental role in ordering vocal movements such as those used in speech. We
can also sequence face, body, and arm movements to produce nonverbal language.
o Sequencing words to represent meaningful actions likely makes use of the same
dorsal-stream frontal cortex circuits that sequence motor action more generally.
Mimicry - Mimicry fosters language development. From birth, babies show a preference for
listening to speech over other sounds. When they begin to babble, they are capable of
making the sounds used in all languages. They also mimic and subsequently prefer the
language sounds made by the people in their lives.
o Mirror neurons in the cortical language regions are responsible for our ability to
mimic the sounds, words, and actions that comprise language.
19.3: localization of language
Brain imaging studies, aphasia analyses, and neural modeling concur in showing that a large network
in the temporal, parietal, and frontal lobes, including both hemispheres, contributes to language.
Anatomical areas associated with language
Figure 19.6 illustrates various approaches to labelling the cortical
regions most frequently described as core to language:
A, fissures and gyri: includes the inferior frontal gyrus and the
superior temporal gyrus, in which Broca’s area (green) and
Wernicke’s area (yellow), respectively, are located. Parts of
surrounding gyri, including the ventral parts of the precentral
and postcentral gyri, the supramarginal gyrus, the angular
gyrus, and the medial temporal gyrus, also lie within the core
language regions.
2
, B, Brodmann’s areas: Broca’s area includes areas 44 & 45.
Wernickes area includes area 11.
C, insula and medial superior temporal gyrus: the lateral fissure is
retracted, showing the language related areas found within it,
including the insula,; Heschl’s gyrus (primary auditory cortex); and
parts of the superior temporal gyrus referred to as the anterior
and posterior superior temporal planes (aSTP and pSTP). Together,
Heschl’s gyrus, aSTP, and pSTP constitute the planum
temporale.
Neural connections between language zones
Wernicke- Gescwind model: three part model that proposes that
comprehension is extracted from sounds in Wernickes’s ares and
passed over the arcute fasciculus pathway to Broca’s area to be
articulated as speech. Other language functions access this
comprehension- speech pathway as well.
A contemporary language model, based on recent anatomical and
behavioral studies, is illustrated in Figure 19.9 (dual language
pathways). As proposed by Fedorenko and Sharon Thompson-
Schill (2014), the temporal and frontal cortices are connected by
pairs of dorsal and ventral language pathways, which are viewed as
extensions of the dorsal and ventral visual streams. Information
flows both ways between the temporal and frontal cortex.
Information from vision enters into the auditory language
pathways via the dorsal and ventral visual streams and contributes
to reading. Information from body-sense regions of the parietal
cortex also contributes to the dorsal and ventral language
pathways and likely contributes to touch language such as Braille.
Dorsal language pathways are proposed to transform
sound information into motor representation to convert
phonological information into articulation. No meaning is
assigned to the sound.
o Information flow in the dorsal pathway is bottom- up, as occurs when we are asked
to repeat non- sense words or phrases. The temporal cortex assembles sounds by
phonetic structure and passed them along to the frontal cortex for articulation.
Bottom- up: zenuwen naar hersenen.
Ventral language pathways are proposed to transform sound information into meaning
to convert phonological information into semantic information.
o Information flow in the ventral pathway is proposed to be more top-down, assigning
meaning to words and phrases.
Top –down: hersenen naar zenuwen.
The dorsal and ventral language pathways are engaged in syntax; with the dorsal pathway
categorizing sounds in terms of frequency of association and the ventral pathway extracting
meaning from the grammatical organization of words. Both sets of language pathways are
also proposed to be involved in short- and long-term memory for the phonetic and semantic
components of speech, respectively. Nonverbal speech, including reading and sign language
from visual cortex and Braille from parietal cortex, also uses these pathways.
We can speculate that some aphasic patients who can read but not understand the meaning of what
they read have damage to the ventral language pathways. Similarly, some patients who cannot
articulate words but can understand them might have damage to the dorsal pathways. Patients with
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