TRED 256 Class 3
February 7, 2005
Brain & Language
Neurolinguistics:
the
study of the biological and neural foundations of language
Cortex: surface of the brain "gray matter" 
white matter: connecting fibers
beneath the cortex
(http://www.bic.mni.mcgill.ca/cgi/brainweb1)
cerebral hemispheres:
left/right halves of the brain
corpus callosum: network of 2
million fibers connecting the hemispheres
contralateral brain function: left
side of brain controls functioning
of right side of body and right hemisphere of brain controls left side
of body.
Modularity of the Brain
First indications came from phrenology - practice of determining
personality traits and abilities based on reading the bumps on the
skull. Proposed by Franz Joseph Gall in early 1800s. Phrenology has
been discarded but Gall's concept of modularity
has been upheld.
Paul Broca - 1864: related
language to the left side of the brain, based on autopsies of people
who had language deficits and damage to the left frontal lobes of
brian. This area came to be called Broca's
area
Broca's Aphasia: language disorder that results from injury to
Broca's area
Aphasia: any language disorder
that results from brain damage caused by disease or trauma
Carl
Wernicke - 1874 - identified aphasia in patients with
damage to the back left portion of brain. (Wernicke's
area)
Wernicke's
aphasia: patients who spoke fluently but had
numerous lexical errors; using jargon and nonsense words. Had
difficulty in comprehending speech.
Does everyone have language functions in the left side of their
brains? How
about right-handed people?
Discussion: is there an
evolutionary purpose for lateralization? What do you think could be the
reason behind it?
New ways to discover brain functioning:
MRI
(Magnetic Resonance
Imaging): Magnetic Resonance Imaging (MRI) is a
noninvasive method which utilizes the properties of magnetism to create
nondestructive, three dimensional, internal images of the soft tissues
of the body, including the brain, spinal cord and muscle. (
How MRI works)
PET (Positron Emission Tomography): shows metabolic activity of
the
brain (How PET
works)
Images
from PET scans
SPECT/CT
scans: SPECT studies combine nuclear medicine (the use
of radioisotopes in the diagnosis of disease) with computed
tomography. In this technique, the patient either swallows
or is injected with a radioisotope, which travels to a target
organ. Concentrating in the target organ, the radioisotope
emits radiation, which is detected by a gamma camera that rotates
around the patient. The information obtained via the gamma
camera is analyzed by a computer, which creates a cross-sectional image
of the target organ. SPECT scans are frequently used
to determine if a specific area of the body is receiving
adequate blood flow.
Childhood brain lesions
Hemiplegic children: have lesions on
one side of the brain; shows differing cognitive abilities
Split brains
surgical severing of the corpus
callosum - no communication between two side of brain
Dichotic Listening
contralateral
stimuli (opposite side) outweigh ipsilateral stimuli
reason: stimuli don't have to cross the corpus callosum
(Discussion: Does this make
sense? signals from
right ear go directly to left side of brain, not through right side of
brain; How about your use of the phone - do you hold it to your left
ear or your right war?)
EEG -
based evidence: Event-related Brain Potentials (ERPs)
Cognitive neurophysiology
is the study of changes in brain function and the relationship of such
changes to thought processes. The primary physiological signal that we
measure is the electroencephalogram or EEG. The EEG reflects summated
potentials generated by the electrochemical signaling processes by
which networks of neurons process information. The EEG changes in
predictable ways as a function of level of alertness, type and/or
intensity of mental activity, and particular forms of brain pathology.
We record the EEG by arrays of electrodes attached with conductive gel
to many locations across the scalp. Similar sensors are attached to the
face in the region of the eyes to record the electro-oculogram or EOG,
that is, the electrical potentials generated by eye movements and
blinks. The EOG can also provide useful information about mental state.
(
Gevins 1997)
For a more in-depth explanation of ERPs: Coles & Rugg 1995
Other interesting applications of ERPs:
Brain
Fingerprinting for Counter-Terrorism
Language
Perception & learning strategies
Neural
basis of musicality
Historical Evidence for Brain
Modularity: Studies of Aphasia
Carl Linnaeus (1745) studied jargon
aphasia, a disease in which the patient substitutes a
semantically similar word for the intended word.
Johannes Gesner (1770) attributed language difficulties to specific
impairment of language memory. He observed bilingual asymmetry in which an
abbot who had brain damage could read Latin but not German.
Broca's aphasics - agrammatic aphasia:
utterances without function words, problems understanding
syntactic structure
Wernicke's aphasics - may
produce fluent but unintelligible speech, substitute one sound for
another (table -> sable) or one word for another. (chair ->
table) Also jargon
aphasia.
One way that has been tried to help such patients communicate is to
have them write the words they want to communicate. In England a Lightwriter has been
used to help aphasic patients communicate. Words can be typed and show
up on two screens, one for the writer and one for the person they want
to communicate with.
Acquired dyslexics: people who
lose the ability to read after brain damage
Genetic Evidence for Language Autonomy
Linguistic savants: individuals who are
handicapped in certain spheres but remarkably talented in others
Specific
Language Impairment: Seems to have genetic basis, affect identical
twins - support modular view of language facility
FoxP2 is
the first identified gene that is specifically involved in speech and
language development in humans (not in book)
Language and Brain Development
The Critical Period: period
from birth to puberty when language acquisition proceeds easily
evidence: "wild" children, Genie,
Chelsea
Bird Songs: some species learn calls, like these:
Male Chaffinch: 
Female
Chaffinch: 
But the
other's calls, like that of the cuckoo, seem to be biologically
determined
Origins of Human Language
Problem: spoken language existed long before written records are
preserved.
Beliefs cloud the topic: monogenetic - belief that all langauges
originated from a single source (Tower of Babel story)
Exercises:
1. Roger
Sperry biography
Eccles
biography
Fun with
electrodes! Probe the brain
References:
for your reference in doing papers that use online sources: see the APA's guide to online
source citation
Coles, M.G.H., Rugg, M.D. (1995). Event-related
brain potentials: An introduction. In M. Rugg, M. Coles (Eds.),
Electrophysiology of Mind. Oxford University Press: Oxford, U.K. (PDF)
Accessed February 6, 2005 at http://whalen.psych.udel.edu/667/1.What_is_ERP/ColesRugg1995chpt1.pdf
Gevins, A. (1997) Neural Signals of Cognition
During Computer Use. Accessed February 6, 2005 at http://cslu.cse.ogi.edu/nsf/isgw97/reports/gevins.html