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