camille blochet language brain areas implied in language analysis oscillations related to language...

Camille Blochet

LanguageLanguage

Brain areas implied in language analysis

Oscillations related to language and cognitive skills

What is it?

• Ability to associate arbitrary symbols with specific meanings to express thoughts and emotions to ourselves and others by means of spoken and in some culture written language

Components of language• Grammar = obedience to a set of rules

• Syntax = meaning

• Prosody = emotional valence

Aphasia

Broca’s aphasia Wernicke’s aphasia

Halting speech Fluent speech

Tendency to repeat phrases or words Little spontaneaous repetition

Disordered syntax Syntax adequate

Disordered grammar Grammar adequate

Disordered structure of individual words

Contrived or inappropriate words

Comprehension intact Comprehension not intact

Language-related areas

Localization of the brain regions implied in language analysis

Broca’s area: production of language

Wernicke’s area: interpretation of language

Geschwind’s territory: apprehending the multiple properties of words

Language-related regions of the left hemisphere mapped by positron emission tomography (PET) in a normal human subject (Prosner and Raichle, 1994)

Activity in Broca’s and Wernicke’s area and in primary and association sensory and motor areas

Language processing involves many cortical regions in addition to the classic language areas

Sequential processing of lexical, grammatical, and phonological information within Broca’s area.

2009. Ned T. Sahin. Science

Conditions of the experiment

Main resultsSahin (2009)

Additional features of the triphasic waveform support the lexical-inflectional-phonological progressionSahin (2009)

But limitations of this experiment:

• Only 3 patients

• Epileptic patients

• Good resolution but difficult to repeat

Group differences across power spectra increase across age

Early cognitive and language skills are linked to resting frontal gamma power across the first 3 years. 2008.

April A. Benasich. Behavioural Brain Research

Variance test at 5-30 and 31-50 Hz band power

The two groups significantly differ for frequencies within the gamma-range

Correlations between mean gamma power and behavior at 16, 24 and 36 months.

Correlation between mean gamma power and behavioral test

Bootstrap procedure

Bootstrapping is a resampling technique used to obtain estimates of summary statistics.

Post-hoc analysis of electrode-by-electrode

Limitations and questions on this experiment:

• Correlation or causal link?

• Gamma oscillations due to specific attention or language?

• Gamma oscillation in adult?few studies about this phenomenon

Conclusion

• Language is a complex cognitive function

• Lack of animals model but different methods capable of revealing some features

• Complex brain analysis: many cortical regions implied

• Gamma oscillations play an important role