Chapter 11 Language
Oliver Selfridge proposed a collection of small components or demons
(a term he used to refer to a discrete stage or substage of information processing) that together would allow machines to recognize patterns
In 1981, James McClelland and David Rumelhart proposed a computational model that has been important for visual letter recognition. This model assumes three levels of representation:
(a) a layer for the features of the letters of words, (b) a layer for letters, and (c) a layer for the representation of words. -An important characteristic of this model is that it permits top-down information (i.e., information from the higher cognitive levels, such as the word layer) to influence earlier processes that happen at lower levels of representation (the letter layer and/or the feature layer). -This model contrasts sharply with Selfridge's model, where the flow of information is strictly bottom-up (from the image demon to the feature demons to the cognitive demons and finally to the decision demon)
Take Homes
- The mental lexicon is the brain's store of words and concepts. ■ A morpheme is the smallest unit of language that has meaning. ■ A phoneme is the smallest unit of sound that makes a difference to meaning. ■ Semantic (meaning) relationships between words are an organizational principle of the mental lexicon. ■ Syntax refers to the way in which words in a particular language are organized into grammatically permitted sentences. ■ Grammar refers to the structural rules that govern the composition of words, phrases, and sentences in a particular natural language. ■ Patients with neurological damage may name an item with an incorrect but semantically-related word (e.g., "animal" for "horse"), which supports the idea that the mental lexicon contains semantic networks of related meanings clustered together.
Key Concepts
-A left-hemisphere network involving the frontal, parietal, and temporal lobes is especially critical for language production and comprehension. -The right hemisphere does have roles in language, especially in processing the prosody of language.
Take Homes
-There are no pauses between phonemes in speech that correspond to words. ■ The prosody of speech is the rhythm and the pitch of the speaker's voice. ■ Sound comprehension involves the superior temporal cortex. People with damage to this area have pure word deafness. ■ Distinguishing speech from nonspeech sounds occurs in the mid-portion of the superior temporal sulcus (STS), but no lexical-semantic information is processed in this area. ■ Spoken-word recognition processing proceeds anteriorly in the superior temporal gyrus (STG): Phoneme processing appears localized to the left mid-STG, integration of phonemes into words appears localized to the left anterior STG, and processing short phrases appears to be carried out in the most anterior locations of STS.
top-down processing
-feedback driven information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations
Elizabeth Warrington Study
-performed groundbreaking studies on the organization of conceptual knowledge in the brain, Warrington and her colleagues found that semantic memory problems fell into semantic categories. They suggested that the patients' problems were reflections of the types of information stored with different words in the semantic network.
deep dyslexia
-they might read the word horse where cow is written
recognizing whether a speech sound is a word or a pseudoword happens in the first:
50-80 ms -This processing tends to be lateralized more to the left hemisphere, where the combinations of the different features of speech sounds are analyzed (pattern recognition).
In an influential model proposed by Collins and Loft us (1975), word meanings are represented in a semantic network in which words, represented by conceptual nodes, are connected with each other.
A major component of this model is the assumption that activation spreads from one conceptual node to others, and nodes that are closer together will benefit more from this spreading activation than will distant nodes
N400 response
A negative-polarity event-related potential that is elicited by words, and that is larger in amplitude for words that do not fit well into the sentence context. -the N400 effect is specific to semantic analysis.
P600 response
A positive polarity event-related potential elicited when words violate syntactic rules in sentences
lexical decision task
A procedure in which a person is asked to decide as quickly as possible whether a particular stimulus is a word or a nonword.
Broca's aphasia
A type of aphasia characterized by partial loss of the ability to produce language (spoken, manual, or written), although comprehension generally remains intact.
Wernicke's aphasia
Also known as posterior aphasia or receptive aphasia, was first described fully by the German physician Carl Wernicke, and is a disorder primarily of language comprehension. -have difficulty understanding spoken or written language and sometimes cannot understand language at all.
pure word deafness
Although they could process other sounds relatively normally, these patients had specific difficulties recognizing speech sounds. Because there was no difficulty in other aspects of language processing, the problem seemed to be restricted primarily to auditory or phonemic deficits—hence the term pure word deafness.
agrammatic aphasia
Difficulty in producing and/or understanding the structure of sentences. Seen in brain-damaged patients who may speak using only content words, leaving out function words such as 'the and 'a'.
progressive semantic dementia
E.g., Alzheimer's disease, Pick's disease -initially show impairments in the conceptual system, but other mental and language abilities are spared. - when viewing a picture of a horse, they will say "animal," and a picture of a robin will produce "bird."
Selfridge's (1959) pandemonium model of letter recognition (bottom-up processing)
For written input, the reader must recognize a pattern that starts with the analysis of the sensory input. The sensory input is stored temporarily in iconic memory by the image demon, and a set of 28 feature demons decodes the iconic representations. The cognitive demons are activated by the representations of letters with these features, and the representation that best matches the input is then selected by the decision demon.
semantic paraphasias
Generate words related to meaning of the intended word -Saying "cow" while wanting to say "horse"
H.W.
H.W.'s problems further illustrate that the ability to produce speech is not the same thing as the ability to comprehend language, and indeed the networks involved in language comprehension and language production differ.
Schematic representation of the components involved in spoken and written language comprehension
Inputs can enter via either auditory (spoken word) or visual (written word) modalities. Notice that the information flows from the bottom up in this figure, from perceptual identification to "higher level" word and meaning activation. So-called interactive models of language understanding would predict top-down influences to play a role as well. For example, activation at the word-form level would influence earlier perceptual processes. We could introduce this type of feedback into this schematic representation by making the arrows bidirectional (see "How the Brain Works: Modularity Versus Interactivity")
2) Unification
Integration of lexically retrieved phonological, semantic, and syntactic information into an overall representation of the whole utterance. In language comprehension, the unification processes for phonological, semantic, and syntactic information can operate in parallel (or at the same time); and interaction between these different types of information is possible. Unification makes Hagoort's model a constraint-based interactive model, as discussed earlier
What does this patt ern of facilitated response spee d tell us about the organization of the mental lexicon?
It reveals that words related in meaning must somehow be organized together in the brain, such that activation of the representation of one word also activates words that are related in meaning. Th is makes words easier to recognize when they follow a related word that primes their meaning.
Wernicke's area
Language areas include the left temporal cortex, which includes Wernicke's area
Fragment of a connectionist network for letter recognition. -the model of McClelland and Rumelhart
Nodes at three different layers represent letter features, letters, and words. Nodes in each layer can influence the activational status of the nodes in the other layers by excitatory (arrows) or inhibitory (lines) connections. -The word superiority effect can be explained in terms of the McClelland and Rumelhart model, because the model proposes that top-down information of the words can either activate or inhibit lett er activations, thereby helping the recognition of letters.
One study that has contributed to our new understanding of speech perception is an fMRI study done by Jeffrey Binder and colleagues (2000).
Participants in the study listened to different types of sounds, both speech and nonspeech. The sounds were of several types: white noise without systematic frequency or amplitude modulations; tones that were frequency modulated between 50 and 2,400 Hz; reversed speech, which was real words played backward; pseudowords, which were pronounceable strings of nonreal words that contain the same letters as the real word—for example, sked from desk ; and real words.
3) Control
Relating language to action (e.g., in bilingualism and turn taking)
Syntax
Sentence structure
Sylvian fissure
Separates the temporal from the frontal lobe, and the temporal from the parietal lobe -Split-brain patients as well as patients with lateralized, focal brain lesions have taught us that a great deal of language processing is lateralized to the left -hemisphere regions surrounding the Sylvian fissure
1) memory
Storage and retrieval from the mental lexicon or the long-term memory store for word information, as defined earlier in this chapter.
Results of the Binder study
Superior temporal cortex activations to speech and nonspeech sounds. Four sagittal slices are shown for each hemisphere. The posterior areas of the superior temporal gyrus are more active bilaterally for frequency-modulated tones than for simple noise (in blue). Areas that are more active for speech sounds and tones than for noise are indicated in red. Areas that are more sensitive to speech sounds (i.e., reversed words, pseudo words, and words) are located ventrolaterally to this area (in yellow), in or near the superior temporal sulcus. This latter activation is somewhat lateralized to the left hemisphere (top row).
macroplanning
Th e intention of the communication is represented by goals and subgoals, which are expressed in an order that best serves the communicative plan. Th is aspect of message planning is macroplanning.
Lichtheim's classical model of language processing.
The area that stores permanent information about word sounds is represented by A. The speech planning and programming area is represented by M. Conceptual information is stored in area B. The arrows indicate the direction of information fl ow. This model formed the basis of predictions that lesions in the three main areas, or in the connections between the areas, or the inputs to or outputs from these areas, could account for seven main aphasic syndromes. The locations of possible lesions are indicated by the red line segments. A = Wernicke's area. B = conceptual information stores. M=Broca's area.r
FIGURE 11.22 Cortical language circuit proposed by Angela Friederici, consisting of two ventral and two dorsal pathways.
The black lines indicate direct pathways and direction of information flow between language-related regions. The broken line suggests an indirect connection between the pSTG/STS and the MTG via the inferior parietal cortex. The ventral pathways are important for the comprehension of the meanings of words. The dorsal pathway that connects to the premotor cortex is involved in speech preparation. The other dorsal pathway connects Broca's area (specifically BA44) with the superior temporal gyrus and superior temporal sulcus and is involved in syntactic processing
Outline of the theory of speech production developed by Willem Levelt
The processing components in language production are displayed schematically. Word production proceeds through stages of conceptual preparation, lexical selection, morphological and phonological encoding, phonetic encoding, and articulation. Speakers monitor their own speech by making use of their comprehension system.
Ned Sahin and his colleagues (2009) had the rare opportunity to shed some light on this question of how different forms of linguistic information are combined during speech production:
The results are also consistent with the idea that Broca's area has distinct circuits that process lexical, grammatical, and phonological information.
Lorraine Tyler and her colleagues: Findings
This model suggests that the dissociation between naming of nonliving and living things in patients with category-specific deficits may also be due to the complexity of the features that help distinguish one thing from another. -Tyler and colleagues observed that patients with lesions to the anterior temporal lobes cannot reliably name living things at the specific level, indicating that the retrieval and integration of more detailed semantic information is impaired. -Functional MRI studies in unimpaired participants showed greater activation in the anterior temporal lobe with specific-level naming of living things than with domain-level naming
How damage to the brain leads to Wernicke's aphasia.
Thus, although Wernicke's area remains in the center of a posterior region of the brain whose functioning is required for normal comprehension, lesions confined to Wernicke's area produce only temporary Wernicke's aphasia. It appears that damage to this area does not actually cause the syndrome. Instead, secondary damage due to tissue swelling in surrounding regions contributes to the most severe problems. When swelling around the lesioned cortex goes away, comprehension improves.
global aphasia
When both production and understanding of language is damaged -Typically, this type of aphasia is associated with extensive left -hemisphere damage, including Broca's area, Wernicke's area, and regions between them.
transcortical motor aphasia
a condition in which language is not fluent, but the ability to repeat is retained
speech apraxia
a developmental or acquired problem with speech production not associated with muscle weakness. Its symptoms include difficulty putting sounds and syllables together in the correct order to form words
conduction aphasia
a speech disorder characterized by the inability to repeat words with intact spontaneous speech production and comprehension; usually due to injury to the arcuate fasciculus
Transcortical Sensory Aphasia
a speech disorder in which a person has difficulty comprehending speech and producing meaningful spontaneous speech but can repeat speech; caused by damage to the region of the brain posterior to Wernicke's area
Words can be symbolized in writing in three different ways:
alphabetic, syllabic, and logographic
The middle temporal gyrus (MTG) and the superior temporal gyrus (STG) :
are important for the translation of speech sounds to word meanings
syntactic parsing
building the syntactic structure of a sentence -Syntactic parsing is, therefore, a building process that does not, and cannot, rely on the retrieval of representations of sentences.
arcuate fasciculus
connects Wernicke's area and Broca's area
aphasia
impairment of language, usually caused by left hemisphere damage either to Broca's area (impairing speaking) or to Wernicke's area (impairing understanding). -very common after stroke
phoneme
in a language, the smallest distinctive sound unit.
Morpheme
in language, the smallest unit that carries meaning -As an example consider the words frost , defrost , and defroster .
alexia
inability to read words
Levelt maintains that there are two crucial aspects to message preparation:
macroplanning and microplanning
Peter Hagoort (2005) model that divides language processing into three functional components:
memory, integration, and control—and identifies their possible representation in the brain -The three components of the model are shown in colors overlaid onto a drawing of the left hemisphere: the memory component (yellow) in the left temporal lobe, the unification component (blue) in the left inferior frontal gyrus, and the control component (purple) in the lateral frontal cortex.
right superior temporal sulcus
plays a role in processing the rhythm of language (prosody), and the right prefrontal cortex, middle temporal gyrus, and posterior cingulate activate when sentences have metaphorical meaning.
Microplanning
proposes how the information is expressed, which means adopting a perspective.
image demon
receives sensory input -the sensory input (R) is temporarily stored as an iconic memory by the so-called image demon
semantic
relating to meaning in language or logic
Heschl's gyri of both hemispheres are activated by
speech and nonspeech sounds (e.g., tones) alike, but that the activation in the STS of both hemispheres is modulated by whether the incoming auditory signal is a speech sound or not
Wernicke found that patients with lesions in the left temporoparietal region that included the STG (Wernicke's area) had difficulty understanding:
spoken and written language -This observation led to the now-century-old notion that this area is crucial to word comprehension -We can now conclude that the STG alone is probably not the seat of word comprehension.
bottom-up processing
stimulus-driven analysis that begins with the sense receptors and works up to the brain's integration of sensory information
What part of the brain is important for sound perception?
superior temporal cortex (A1)
the evidence suggests that the left inferior frontal cortex (in and around classical Broca's area) has some involvement in
syntactic processing.
anomia
the inability to find the words to label things in the world
dysarthria
the inability to use speech that is distinct and connected because of a loss of muscle control after damage to the peripheral or central nervous system slurred speech
Broca's area
the left inferior frontal cortex, which includes Broca's area
segmentation problem
the listener's problem of dividing the almost continuous sounds of speech into separate phonemes and words -Speech waveform for the question, "What do you mean?"
mental lexicon
the mental dictionary of words and their meanings -a mental store of information about words that includes semantic information (the words' meanings), syntactic information (how the words are combined to form sentences), and the details of word forms (their spellings and sound patterns)
lexical integration
the process of linking the selected word form to the overall semantics and syntax of the utterance
Lexical access
the process of matching a perceptual description of a word on to a stored memory description of that word
Lexical selection
the process of selecting from a collection of representations the activated word that best matches the sensory input
They also showed that the frontal cortex regions were important in
the selection process and that greater involvement of dorsal IFG occurred when selection required choosing the actual word from among many lexical candidates (lexical competition).
phonology
the system of contrastive relationships among the speech sounds that constitute the fundamental components of a language
tip of the tongue phenomenon
the temporary inability to remember something you know, accompanied by a feeling that it's just out of reach
hemiparesis
weakness on one side of the body in which strength and control are greatly reduced
Activation of the perceptual features occurs in primary cortices:
within the first 100 ms aft er a picture is presented; activation of more detailed semantic representations occurs in the posterior and anterior ventral-lateral cortex between 150 and 250 ms; and starting around 300 ms, participants are able to name the specific object that is depicted in the picture, which requires the retrieval and integration of detailed semantic information that is unique to the specific object.
Take Homes
■ Animal calls can carry meaning and show evidence of rudimentary syntax. In general, however, animal calls tend to be infl exible, associated with a specifi c emotional state, and linked to a specifi c stimulus. ■ Many researchers suggest that language evolved from hand gestures, or a combination of hand gestures and facial movement. ■ Areas that control hand movement and vocalizations are closely located in homologous structures in monkeys and humans.
Take Homes
■ Models of language production must account for the selection of the information to be contained in the message; retrieving words from the lexicon; sentence planning and grammatical encoding using semantic and syntactic properties of the word; using morphological and phonological properties for syllabification and prosody; and preparing articulatory gestures for each syllable. ■ Each stage in Levelt's model for language production occurs serially, and its output representation is used for input to the next stage. It avoids feedback, loops, parallel processing, and cascades, and it fits well with the findings of ERPs recorded intracranially.
Take Homes
■ Three classes of models attempt to explain word comprehension: Modular models, interactive models and hybrid models. ■ Lexical selection can be influenced by sentence context. ■ Lexical access and selection involve a network that includes the middle temporal gyrus (MTG), superior temporal gyrus (STG), and the ventral inferior and bilateral dorsal inferior frontal gyri (IFG) of the left hemisphere. ■ Left MTG and STG are important for the translation of speech sounds to word meanings. ■ Syntactic parsing is the process in which the brain assigns a syntactic structure to words in sentences. ■ In the ERP method, the N400 is a negative-polarity brain wave related to semantic processes in language, and the P600/SPS is a large positive component elicited after a syntactic and some semantic violations. ■ Syntactic processing takes place in a network of left inferior frontal and superior temporal brain regions that are activated during language processing.
Take Homes
■ Written-word processing takes place in occipitotemporal regions of the left hemisphere. Damage to this area can cause pure alexia, a condition in which patients cannot read words, even though other aspects of language are normal. ■ Occipitotemporal regions of the left hemisphere may be specialized for the identification of ortho graphic units.
Take Homes
■Models of language involve unifying information from linguistic inputs or from retrieved linguistic representations with stored knowledge. ■ White matter tracks in the left hemisphere connect frontal and temporal lobes to create specific circuits for speech, semantic analysis, and syntactic processing.
