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: what’s 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 don’t 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 don’t 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 doesn’t 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 Broca’s Area and Wernicke’s Area (late 19th century)

– Problems: it could take years until you got your data!

The Brain

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;105:4004-4009

©2008 by National Academy of Sciences

Brain activations elicited by color perception and explicit color naming.

Tan L H et al. PNAS 2008;105:4004-4009

©2008 by National Academy of Sciences