Language and the Brain I Gareth O Price

So far … Language as a fairly abstract phenomenon (except, perhaps, for the biology of phonetics) Structures, systems, theories … what do they tell us? Problem? Language is in here as well as out there (and may even be more in here) If language is in here, where is it?

Language and the Brain Useful here to illuminate some ideas about semantics and syntax (and morphology and phonology) More properly, language and (in?) the brain = neurolinguistics Language acquisition (and storage, processing) = psycholinguistics

Neurolinguistics vs Psycholinguistics Neurolinguistics: whats under the hood (the engine, fuel pump, transmission, etc.) – real areas of the brain – engineering Psycholinguistics: how the car performs (mpg, top speed, cornering, etc.) – theoretical processes in the brain – reverse-engineering In practice, the two are linked (with neurolinguistics drawing from psycholinguistics, as well as biology, neurobiology, cognition studies, etc.)

However … We dont actually know very much about language and the brain, even the real neurolinguistic bits We know even less about the psycholinguistic aspects of it (such as storage, processing etc.) as these are not directly observable, but only experimentally testable In fact, we know very little about the brain … Epistemological vs. ontological problems (That is, we know we know things … we dont really know how we know them!)

The brain and lateralisation The left side of the brain is generally the dominant side for language However, right-brain does take over some language functions … intuition about speaker intent, emotion; possibly intonation, prosody, etc. – music? The dichotomy between language and creativity seems problematic … … but then language being on the same side as science difficult to solve language as a scientific puzzle?!

The brain and lateralisation Left-handedness doesnt mean that you have the language faculty in the right brain … … but there may be a correlation: perhaps 95% of right-handers use the left side, around 70% of left-handers.

Evidence for lateralisation? Split-brain studies – Surgical removal of the corpus collossum (treatment for epilepsy) – right eye/hand (left brain): could name an object, but not explain what it was used for – left eye/hand (right brain): could explain and demonstrate use, but not name object

Evidence for lateralisation? Brain pathology: – Post-mortem examination of brains of subjects with language impairment (and assessment of physical damage) – Generally showed damage on the left side (trauma, disease, stroke etc.) – Earliest were Brocas Area and Wernickes Area (late 19 th century) – Problems: it could take years until you got your data!

The Brain

Evidence for lateralisation? Anaesthesia – to either the right/left carotid artery can numb either hemisphere (invasive) Electrical Stimulation – can temporarily disrupt production or perception of language, in specific places (partly invasive, ethically dubious) fMRI / positron scans – can show blood-oxygen level dependent (BOLD) flow in real time while subjects perform language tasks (non-invasive)

Brain regions with significant activity during color discrimination. Tan L H et al. PNAS 2008;105: ©2008 by National Academy of Sciences

Brain activations elicited by color perception and explicit color naming. Tan L H et al. PNAS 2008;105: ©2008 by National Academy of Sciences