Summary

Language Processing and the Human Brain

Have you ask to yourself, how our brain works? As you know the human brain not only acquires and stores the metal lexicon and grammar, but also accesses that linguistics storehouse to speak and understand language in real time, so when we speak we access our lexicon to find the words and we use the rules of grammar to construct novel sentences and to produce the sounds that express them. However we do not have difficulty understanding or producing sentences in our language, we do it without effort or conscious
awareness of the processes involved.

The speech signal

Understanding a sentence involves analysis at many levels; to begin with, we must comprehend the individual speech sounds we hear. We are not conscious of the complicated processes we use to understand speech any more than we are conscious of the complicated processes of digesting food and utilizing nutrients.
We must study these processes deliberately and scientifically. To understand this process, some knowledge of the signal can be helpful.

Speech perception

Speech is a continuous signal. In natural speech, sounds overlap and influence each other, and yet listeners have the impression that they are hearing discrete units such as words, morphemes, syllables, and phonemes.
How does a listener know that two physically distinct instances of a sound are the same? This is called “the lack of invariance problem.” despite these problems; listeners are usually able to understand what they hear because our speech perception mechanisms are designed to overcome the variability and lack of discreteness in the speech signal.

Bottom - up and top – down models

Language comprehension is very fast and automatic. We understand an utterance as fast as we hear it or read it, ordinarily, we can process spoken language at a rate of around twenty phonemes per second.

Bottom – up processing moves step by step from the incoming acoustic or visual
signal, to phonemes, morphemes, words and phrases , and ultimately to semantic
interpretation.
In top – down processing the listener relies on higher level semantic, syntactic, and contextual information to analyze the acoustic signal.

Lexical access and word recognition

Psycholinguistics have conducted a great deal of research on lexical access or word recognition, the process by which listeners obtain information about the meaning and syntactic properties of a word from their mental lexicon; several experimental techniques have been used in studies of lexical access.

Speech production

The listener's job is to decode the intended meaning of a message from the speech
signal produced by a speaker.
Application and misapplication of rules
Spontaneous errors show that the rules of morphology and syntax are also applied or misapplied when we speak. It is difficult to see this process in normal error – free speech, but when someone says groupment instead of grouping, ambigual instead of ambiguous, or bloodent instead of bloody, it shows that regular rules are applied to combine morphemes and from possible but nonexistent words.

Planning units

We might suppose that speakers' thoughts are simply translated into words one after the other via a semantic mapping process. Grammatical morpheme would be added as demanded by the syntactic rules of the language.
The comprehension and production of language is an enormously complex process that depends on many aspects of our linguistic knowledge, as well as dedicated processing principles and other cognitive capacities such as memory.

Brain and language

The brain is the most complex organ of the body. The surface of the brain is the cortex, often called “gray matter”, consisting of billions of neurons. The cortex is the decisions – making organ of the body. It receives massages from all of the sensory organs, initiates all voluntary and involuntary actions, and it is the storehouse of our memories and the seat of our consciousness; it is the organ that most distinguishes human from other animals, somewhere in this gray matter resides the grammar that represents our knowledge of language.
The brain is composed of a right and a left cerebral hemisphere, joined by the corpus callosum.
The corpus callosum allows the two hemisphere of the brain to communicate with
each other, without this system of connections, the hemispheres would operate independently. In general, the left hemisphere controls the right side of the body, and the right hemisphere controls the left side.

The localization of language in the brain

An issue of central concern has been to determine which parts of the brain are
responsible for human linguistic abilities.

Aphasia

The study of the aphasia has been an important area of research in understanding
the relationship between the brain and language. Aphasia is the neurological term
for any language disorders that results from acquired brain damage caused by disease or trauma.

Language and the brain development

Numerous neurolinguistics studies have found that the way that the brain is organized for language and grammar in the adult is already reflected in the brains of newborns and young infants, even before they have entered the period during which language actively develops.

The critical period

Under ordinary circumstances a child is introduced to language virtually at the
moment of birth. Adults talk to him and to each other in his presence. Children do not require language instruction, but they do need exposure to language to develop normally. Children who do not receive linguistic input during their formative years do not achieve native like grammatical competence.
The critical age hypothesis asserts that language is biologically based and that the
ability to learn a native language develops within a fixed period from birth to middle
childhood.