Neurophysiology of language

Vijay kumar

Language is the ability to encode ideas into signals which will be streamed as speech.

It is one of the important cognitive ability humans have.

Language is different from thinking or thought.

It involves usage of words which links sounds to the meaning.

Syntax : rules for combining words into phrases and sentences & determining relations among words.

Phonology : rules combining sounds into a consistent pattern in language.

Grammer: system specifying how vocabulary units can be combined into words,phrases & sentences .

Descartes gave his description on language 1637

Meynert, Hughling jackson

Paul broca – Broca’s motor speech area 1861

Carl Wernicke – Wernicke’s area for comprehension in 1874.

Noam chomsky – Father of modern linguistics.

Marc D. Hauser et al Science 298,(2002).

Marc D. Hauser et al Science 298,(2002).

Language implementation system:- Broca’s area (Broadmann area no 44)- Wernicke’s area(Broadmann area no 22)- Insular cortex- Basal ganglia

Mediational system:Regions in temporal ,parietal & frontal association

cortices.

Conceptual system: Higher order association cortices.

Marc D. Hauser et al Science 298,(2002).

Angela D. Friederici, Trends in Cognitive Sciences 2009

Lesion studies done by Broca and Wernicke helped to identify the centers of language.

Later critical analysis of patients using new techniques changed this view.

Sign language also stimulates the same brain areas which are stimulated by verbal stimuli.

Left cerebral hemisphere is dominant in right handed individual.

Right cerebral hemisphere is for colouring of language i.e. adding of emotional intonation for spoken words.

Language centers are more prominent in left hemisphere.

Arcuate fasciculus was the only link between Wernicke’s area & Broca’s area.

Due to Functional MRI, MEG,Diffusion tensor imaging tractography neural networks involved in language processing can be dileneated.

Dorothee Saur et al, PNAS 2008

Dorsal stream: Responsible for repetition of speech.

Ventral stream: Listening to meaningful speech

Gregory Hickok Phys Life Rev. 2009

Dorothee Saur et al, PNAS 2008

Linguistic genes:FOXP2 gene mutation in KE family with Specific

language impairment.Quantitative trait loci – set of genes which are

critical for language function.

Critical period for language acquisition: Time window during which proper input signals

are necessary for activation of the genetic programs underlying the normal development of brain structures and their functions.

Yuri I. Arshavsky, Brain research review 2009

At birth infants exhibits a universal capacity to detect differences b/w phonetic contrasts used in world’s language.

Native language phonetic abilities significantly increase.

Infants make language like sounds at 5-7 months

Babble in syllables at 7-8 months

Patricia Kuhl et al Annu. Rev. Neurosci. 2008

Form sentence like streams by first year.

By the end of first year infant brain is primed for language which it is exposed.

First words are spoken around first birthday.

Patricia Kuhl et al Annu. Rev. Neurosci. 2008

Patricia Kuhl et al Annual. Rev. Neurosci. 2008

Definition: Aphasias are language

disorders which are caused by focal brain lesions due to stroke or head injury.

Medical physiology, Ganong 22 nd edition

Principles of neuroscience,4th edi ,Kandel

Principles of neuroscience,4th edi ,Kandel

Principles of neuroscience,4th edi ,Kandel

Thank you