This document provides an overview of neuroscience concepts related to language processing in the brain. It discusses what neuroscience is, the basic functional units of neurons, and key brain regions involved in language like Broca's area, Wernicke's area, the primary motor cortex, and primary auditory cortex. The document also covers divisions of the nervous system, gray and white matter, anatomical orientation terms, and development of the brain through synaptogenesis and neuroplasticity.

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CSD 333 Oral Language
Development
Week 7
Oct. 6 - 10, 2014
The brain and language
• Overview of neuroscience concepts
• Brain regions involved in speech-language
processing
What is neuroscience?
1) Study of brain mechanisms that allow
acquisition and regulation of higher mental
functions and production of basic and skilled
actions
2) Study of the nervous system, from
perspectives of biology, chemistry, medicine,
speech & hearing sciences, and others

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Studying the nervous system
• Biology (biochemistry): allows study of the
smallest functional units of the nervous
system, i.e., neurons
• Chemistry: communication in the nervous
system is electrochemical
• Speech-language pathology and psychology:
the nervous system can be understood in the
context of function and pathology
Studying the brain and language
• In the past: lesion studies from post-mortem
examination of stroke victims, TBI (traumatic
brain injury) patients…
• Now: Various neuroimaging techniques such
as CT, PET, MRI
• It’s possible to study not only structure
(anatomy), but also how the brain works in
(almost) real-time through PET, fMRI
Neuroscience and speech-language
• Work by physician Paul Broca on
language impairment and the brain laid
foundations for neuroscience study
– Confirmed that function could be localized
to brain structure
Bear et al., 2006

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Basic functional units
• What is the smallest functional unit of the
brain?
– Neurons!
• Neurons are the information bearing cell of
the nervous system
• Types and sub-types of neurons exist but
there are basic common cellular structures
Neurons
• 15 billion + neurons with CNS that
function as populations to serve all
brain functions: sensation,
movement, cognition …
–With trillions of synapses!!!
Neurons
• Neurons communicate by means of
electrochemical nerve impulses called
action potentials
• Action potentials are either excitatory
(increasing activation) or inhibitory
(decreasing activation)

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The typical neuron
Synapse
Cell body
Presynaptic Postsynaptic
Bhatnagar, 2002
• Terminal structure is the synapse
• Bouton at end of neuron that releases neurotransmitters
• Synaptic cleft between 2 communicating neurons
• Neurotransmitters travel across cleft to affect receptor
structures on communicating neuron
Divisions of the Nervous System
Blumenfeld, 2002
• Central nervous
system (CNS): The
brain and spinal cord
• Peripheral nervous
system (PNS): cranial
and spinal nerves
– 12 pairs of cranial nerves
provide sensory, motor
function to head and neck

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Afferent vs. efferent
• Afferent means toward the brain
– Afferent neurons carry nerve impulses from
receptors (sense organs) to the brain
• Efferent means away from the brain
– Efferent neurons carry commands from the
brain to e.g., muscles

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Gray / White Matter
• Typically, cell bodies and
dendrites are distinctively
gray in dissections
• Axons are white due to
myelin
– Myelin insulates axon
allowing for rapid conduction
Blumenfeld, 2002
Gray / White Matter
• White matter affects how
the brain learns and
functions, relaying action
potentials among brain
regions
• Gray matter is associated
with processing and
cognition
Blumenfeld, 2002
Gray-White matter in the cerebrum

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White matter fibers in the brain shown
with diffusion tensor imaging
Rostral / Caudal Orientation
Bhatnagar, 2002
Rostral
Caudal
Rostral
Cortex
Caudal
Spinal
Cord
“toward the head”
“toward the tail”
Proximal / Distal
Bhatnagar, 2002
Proximal
Distal
Proximal: Relatively
closer to the
anatomical site of
reference in the
nervous system
Distal: Relatively
further from the
anatomical site of
reference in the
nervous system

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Anatomical Orientation
Major brain divisions
(Adj: “cerebral”)
Major brain divisions
• Cerebrum serves higher mental
functions
• Cerebellum: helps coordinate
movements and regulates balance
• Brainstem: contains the cranial nerve
cell bodies (nuclei); regulates
respiration, phonation, and heart beat

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Gross anatomy
of the CNS
Cortex: outer layer of the
cerebrum
• Composed of folded gray
matter
• Plays an important role in
consciousness
Brain hemispheres
• The cerebrum is divided into two
hemispheres, left and right
• Two key language regions, Broca’s area
and Wernicke’s area, are located in the
left hemisphere in most people
– Wada test is used to establish which
hemisphere is used for language

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Some functions of lobes
• Frontal lobe: reasoning, planning,
problem solving; pragmatics
• Parietal lobe: integrating sensory
information
• Temporal lobe: sense of sound
• Occipital lobe: sense of sight
– All four lobes are involved in processing
language!
Speech, language, hearing
• Primary auditory cortex
• Primary motor cortex
• Primary somatosensory cortex
• Broca’s area
• Wernicke’s area
Structures in the brain
• Sulcus (plural: sulci): Depression or
groove in cerebral cortex
• Gyrus (plural: gyri): Ridge on the
cerebral cortex

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Important gyri and sulci
• Sulci
– Lateral sulcus
– Central sulcus
• Gyri
– Precentral gyrus
– Postcentral gyrus
– Inferior frontal gyrus
– Superior temporal gyrus

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Primary auditory cortex
• Responsible for perception of sound
• Important for phonology
• Located in the lateral sulcus and on
superior temporal gyrus
• Shows a tonotopic organization
– Frequency sensitive regions are arranged
from lower to higher, anterior to posterior
Primary auditory cortex
Primary motor cortex
• Responsible for planning and executing
movement along with supplementary
motor area (SMA), premotor area (PMA)
• Located in precentral gyrus (posterior
frontal lobe just anterior to central sulcus)
• Organized according to a homunculus
(“little man”), reflecting arrangement of
motor neurons controlling body parts

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• Primary motor cortex is Frontal lobe
housed within the precentral
gyrus
• Premotor motor area (PMA)
and supplementary motor
areas (SMA) is anterior to the
primary motor cortex
Primary motor cortex
Primary somatosensory cortex
• Main sensory receptive area for sense
of touch
• Located in postcentral gyrus

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Somatotopic mapping in human somatosensory
41
and motor cortex
Blumenfeld, 2002
Broca’s area
• Characterized by Paul Broca
• Important for language production
• Important for syntactic comprehension

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Broca’s area
• Broca’s area is in the inferior frontal
gyrus (generally in left hemisphere)
– Pars opercularis and pars triangularis parts
of the inferior frontal gyrus
• Damage to Broca’s area leads to
Broca’s aphasia (or expressive aphasia)
– Characterized by loss of ability to produce
language; speech is nonfluent and halting,
and language is disjointed
Broca’s area
Broca’s aphasia
(Gardner, 1975)

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Wernicke’s area
• Involved in the understanding of spoken
and written language
• Located in posterior section of superior
temporal gyrus
Wernicke’s area
Wernicke’s aphasia
• In Wernicke’s aphasia, speech sounds
normal but meaning and language are
impaired
Examiner: Tell me the names of each of these.
Patient:
[cigarette] This is a cigarette.
[comb] a wongt.
[fork] a fillt.
[key] a wote.
[knife] a mergiss…

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Brodmann areas
• Scientist Korbinian Brodmann used
Nissl staining technique to map groups
of similar neurons
• A Brodmann area is a region of
cerebral cortex defined based on cell
organization
Korbinian Brodmann
(1868-1918)
Franz Nissl
(1860-1919)

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Types of neurons
Brodmann’s maps
Brodmann’s areas
• Primary auditory cortex: Brodmann area
41 & 42 and part of 22
• Primary motor cortex: Brodmann area 4
• Primary somatosensory cortex:
Brodmann areas 3, 1, and 2
• Broca’s area: Brodmann area 44 & 45
• Wernicke’s area: Brodmann area 22

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Contralateral Control
• Anatomical terminology:
– Contralateral: opposite side
– Ipsilateral: same side
• In general, the left side
of the brain controls the
right side of the body
(“contralateral control”)
– Also vice versa
– A few exceptions
Bhatnagar, 2002
The developing brain
• New synaptic connections are forged
among neurons during development
• Synaptogenesis refers to formation of
synaptic connections
– Driven by sensory and motor experiences
• Infants’ brains at 1 year contain about
2x as many synapses as adults
– Synaptic pruning: elimination of synapses
Neuroplasticity
• Neuroplasticity means changing of neurons,
the organization of their networks, and their
function via new experiences
• Infants (but not adults) with left hemisphere
damage can achieve typical or near-typical
language function
• Plasticity is possible at any age to some
degree
– Significant implications for assessment, therapy,
rehabilitation