Speech and language

significance Social interaction and private intellectual life Any disturbance due to brain disease- functional loss more grave than blindness, deafness and paralysis

language Symbolic representation of objects, actions and events Mirror of higher mental activity Means of communication between patient and physician- medium of delicate interpersonal transaction

Abilities in which humans surpass other animals Developing and using verbal symbols for our ideas Transmitting those ideas by written or spoken word Facility to use our hands Both language and manual dexterity are functions of dominant hemisphere

Emotional language Seen in other animals – by vocalization or gestures It is a feeling or reaction of that moment Earliest modes of emotional expression appear in infancy Emotional expression is well developed in human infants even when cerebrum is immature

Utterances used to express joy, anger, fear are retained even after destruction of all language areas in the dominant hemisphere

Symbolic language Essence of language Means of transferring ideas from one person to another Learned – subject to social and cultural influences of the environment Learnt only after nervous system has attained a certain level of maturity

Mature language involves comprehension, formulation and transmission of ideas and feelings using verbal symbols, sounds, gestures their sequential ordering according to accepted rules of grammar

Needs Thinking Analysis Synthesis Creativity

Speech and language are closely interwoven but not synonymous Derangement of language reflects an abnormality of brain – specifically the dominant hemisphere Speech disorder may have a similar origin, but not necessarily; it may be a result of abnormalities in different parts or extracerebral mechanisms

Speech refers to articulation and phonetic aspects of verbal expression

types of speech Exophasia = external speech Expression of thought by spoken or written words, comprehension of spoken or written words of others Almost continuous when humans gather

Introphasia = internal speech Silent process of thought and formulation in our minds of unspoken words

connections Arcuate fasciculus connects sensory and motor speech areas Short association fibres connect Broca’s area with lower part of motor cortex that innervates muscles of lips, tongue and pharynx

Perisylvian cortical areas connected to Striatum, thalamus Corresponding areas in non- dominant hemisphere via corpus callosum and anterior commissure

Communication by language involves more than just selecting words and then assembling them according to grammatical rules. Most of the emotional content, and part of the linguistic content as well, is conveyed by varying emphases. This is true of language generally, but especially of spoken language

Cerebral Dominance and Its Relation to Language and Handedness There are many ways of determining that the left side of the brain is dominant by the loss of speech that occurs with disease in parts of the left hemisphere and its preservation with lesions involving corresponding parts of the right hemisphere by preference for and greater facility in the use of the right hand, foot, and eye;

by the arrest of speech with a focal seizure or with electrical or magnetic stimulation of the anterior (left) language area; by dichotic listening, in which different words or phonemes are presented simultaneously to the two ears (yielding a right ear–left hemisphere advantage

by observing increases in cerebral blood flow during language processing by lateralization of speech and language functions following commissurotomy.

anatomic differences between the dominant and the nondominant cerebral hemispheres. Yakovlev and Rakic, in a study of infant brains, observed that the corticospinal tract coming from the left cerebral hemisphere contains more fibers and decussates higher than the tract from the right hemisphere

More pertinent to language, the planum temporale, the region on the superior surface of the temporal lobe posterior to Heschl gyri and extending to the posterior end of the sylvian fissure, is slightly larger on the left in 65 percent of brains and larger on the right in only 11 percent (Geschwind and Levitsky).

LeMay and Culebras noted in cerebral angiograms that the left sylvian fissure is longer and more horizontal than the right and that there is a greater mass of cerebral tissue in the area of the left temporoparietal junction.

Anatomy of language functionsA The conventional teaching, based on correlations between various disorders of language and damage to particular areas of the brain, postulates four main language areas, situated in most persons in the left cerebral hemisphere

The entire language zone that encompasses these areas is perisylvian, i.e., it borders the sylvian fissure. Two language areas are receptive and two are executive, i.e., the latter are concerned with the production (output) of language.

The main receptive area, subserving the perception of spoken and probably of internal language, occupies the posterosuperior temporal area (the posterior portion of area 22) and Heschl gyri (areas 41 and 42).

The posterior part of area 22 in the planum temporale is referred to as Wernicke area. A second receptive area occupies the angular gyrus (area 39) in the inferior parietal lobule, anterior to the visual receptive areas

The supramarginal gyrus, which lies between these auditory and visual language "centers," and the inferior temporal region, just anterior to the visual association cortex, are probably part of the language apparatus as well. Here are located the integrative centers for crossmodal visual and auditory language functions.

The main executive, or output, region, situated at the posterior end of the inferior frontal gyrus (Brodmann areas 44 and 45), is referred to as Broca area and is concerned with motor aspects of speech

These sensory and motor language areas are intricately connected with one another by a rich network of nerve fibers one large bundle of which, the arcuate fasciculus, passes through the isthmus of the temporal lobe and around the posterior end of the sylvian fissure

other connections may traverse the external capsule of the lenticular nucleus (subcortical white matter of the insula). Many additional corticocortical connections lead into the perisylvian zones and project from them to other parts of the brain.

Of special importance for the production of speech are the short association fibers that join the Broca area with the lower rolandic cortex, which, in turn, innervates the muscles of the lips, tongue, pharynx, and larynx

The perisylvian language areas are also connected with the striatum and thalamus and with corresponding areas in the minor (nondominant) cerebral hemisphere through the corpus callosum and anterior commissure

there remains considerable difference of opinion concerning the status of cortical language areas objection has been made to calling them "centers," for they do not represent histologically or circumscribed structures of constant function.

Role of non-dominant hemisphere Modulative aspects of language Prosody Melody of speech Its intonation, inflection, and its pauses All these have emotional overtones Prosody and gestures accompanying them enhance the meaning of spoken word

Speech is endowed with richness and vitality Aprosody is seen in lesions involving inferior division of right Middle cerebral artery

The right hemisphere system for generating and comprehending prosody is apparently organized in a fashion analogous to the left hemisphere system for producing and comprehending language.

That is, the right inferior frontal gyrus is involved in producing prosody, and the right posterior temporoparietal region in comprehending it

One of the first patients described with a deficit related to prosody was a schoolteacher with right frontal damage who began to have difficulty controlling her students because she was unable to convey anger or authority by voice or gesture (even though the feelings were there).

She had motor aprosodia. Patients with more posterior lesions on the right may have sensory aprosodia and have difficulty comprehending the emotional content of the speech or gestures of others.