GGZ2025 Neuropsychological Disorders vvanbeek
TASK 4 – LANGUAGE AND LANGUAGE DISORDERS
PART I - LANGUAGE
WHAT IS LANGUAGE?
Most people think of words as the meaningful units of language. Linguistics consider words
as consisting of fundamental language sounds, called phonemes, that form a word or part of a
word. We combine phonemes to form morphemes, the smallest meaningful units of words,
such as a base (do in undo), and affix (un in undo) or an inflection (ing in doing). Some
morphemes can be a word themselves.
A lexicon comprises a memory store that contains words and their meanings, hypothetically
all words in a given language. Words are strung together in patterns that conform to the rules
of grammar, or 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. Discourse, the
highest level of language processing, involves stringing together sentences to form a
meaningful narrative.
Components of a sound-based language
Phonemes Individual sound units whose concatenation, in particular order, produce
morphemes.
Morphemes Smallest meaningful units of a ward, whose combination forms a word.
Lexicon Collection of all words in a given language; each lexical entry includes
all information with morphological or syntactical ramifications but does
not include conceptual knowledge.
Syntax Grammar – admissible combinations of words in phrases and sentences.
Semantics Meanings that correspond to all lexical items and all possible sentences.
Prosody Vocal intonation, which can modify the literal meaning of words and
sentences.
Discourse Linking sentences to constitute a narrative.
Four core skills underlie human language; 1) categorizing, 2) category labelling, 3)
sequencing behaviors and 4) mimicry.
Categorization
Multiple parallel hierarchical neural channels function to process incoming sensory
stimulation. As the cortex and the number of channels that process parallel sensory
information increases, binding (integrating) information into a single perception becomes
more difficult. The brain must determine which sensory information reaching the cortex
corresponds to a given object in the external world. Thus, it becomes necessary to categorize
information. Assigning tags to information makes it easier to perceive the information and to
retrieve it later when needed.
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Labelling categories
Using words as tags to label categories rests on a pre-existing perception of what categories
are. Development of human language may gave entailed selection for novel means of
categorization that not only allowed for combining and grouping simple sensory stimuli, but
also provided a means of organizing events and relations. This categorizing system can
stimulate the production of word forms about that concept (category); conversely, it can
cause the brain to evoke the concepts in words.
Thus, a man who was once a painter but is now colour-blind can know and use the words
(labels) for colors, even though he can no longer perceive or image 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, but have lost the language with
which to describe it. They experience colors but cannot attach labels to them.
Thus, labelling a category includes not only identifying it (function of temporal lobes), but
also organizing information within the category, as for example within the category label
tools. This is a function of the motor cortices in the frontal lobes within the dorsal visual
stream.
Sequencing behavior
Human language employs transitional larynx movements to form syllables. Left-hemisphere
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 arms to produce non-verbal language. 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. Babies show a preference for listening to speech over
other sounds. They also mimic and subsequently prefer the language sounds made by the
people in their lives. One view related to mimicry is that mirror neurons in the cortical
language regions are responsible for our ability to mimic the sounds, words and actions that
comprise language.
LOCALIZATION OF LANGUAGE
Brain imaging, aphasia analyses and neural modeling show that a large network in the
temporal, parietal, and frontal lobes (on both hemispheres) contribute to language. The
anatomical landmarks researchers use to describe brain regions associated with language vary
considerably. The figure (next page) illustrates various approaches to labelling the cortical
regions most frequently described as core to language.
-Figure A includes the inferior frontal gyrus and superior temporal gyrus, in which
Broca’s area (green) and Wernicke’s area (yellow) are located. Parts of surrounding gyri,
including ventral parts of the precentral and postcentral gyri, supramarginal gyrus, the angular
gyrus and the medial temporal gyrus also lie within the core language regions.
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-Figure B depicts the language areas in accord with Brodmann’s mapping.
-In figure C, the lateral fissure is retracted, showing the language-related areas found within it,
including the insula, a large region of the neocortex lying within the dorsal bank of the lateral
fissure; Heschl’s gyrus (primary auditory cortex) and parts of the superior temporal gyrus
referred to as the anterior (aSTP) and posterior superior temporal planes (pSTP).
Together, Heschl’s gyrus, aSTP and pSTP constitute the planum temporale.
NEURAL CONNECTIONS BETWEEN LANGUAGE ZONES
Wernicke’s early model of language and its revival by
Geschwind, known as the Wernicke-Geschwind model,
were both based entirely on lesion data.
In the model, the classical anterior and posterior speech
zones are connected by the arcuate fasciculus. The
three part model (figure) proposes that;
(1) Comprehension is extracted from sounds in Wernicke’s area,
(2) And passed over the arcuate fasciculus pathway,
(3) To Broca’s area to be articulated as speech.
The Wernicke-Geschwind model has played a formative role in directing language research
and organizing research results. A contemporary language model, based on recent anatomical
and behavioral studies, is illustrated in the figure below.
As proposed, 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. The double headed areas
indicate that information flows both ways between
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.
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