The Neurology of Speech and Language: Avians to Humans

David B. Rosenfield, M.D.Director, Speech/Language CenterDirector, EMG/Motor Control Lab.

Professor of NeurologyWeill Cornell Medical College

Times are Changing for Modeling Language and Speech

•Brain imaging•Analysis of sounds

•Spectral and temporal analysis•Phonemes•Morphemes•Syllables•Phrases

• New approaches in modeling

Language

• Representational System

• Generativity

• Drives the motor system

Speech Motor Control System

• Respiratory

• Articulatory

• Phonatory (e.g., laryngeal)

Mammalian Vocalization Involves Coordination of:

• Respiration - anterior horn cells (cerrvical, thoracic, upper lumbar)

• Laryngeal activity - neurons controlling glottic closure (n. ambiguous)

• Articulatory mechanism (supralaryngeal)– V Motor n.– VII n.– Rostal n. ambiguous– XI n.– Upper cervical anterior horn cells

Neuroanatomy of Language• Two principal regions for language

– Sup. temporal areas adjacent to auditory cortex– Inferior frontal cortex adjacent to articulatory

motor cortex• These two regions connected by several

white matter tracts• Extreme capsule• Uncinate fasciculus• Arcuate fasciculus (well developed in humans)

Areas of Language Function• Pars Triangularis (PTR, #45)

– Heteromodal cortex– Located within inferior frontal gyrus

• Pars Opercularis (POP, #44)• Motor Association Cortex

• Planum Temporale (PT, #22)– Auditory Association Cortex

Broca’s and Wernicke’s Area• No cytoarchitectonic signature• Cannot identify by looking under a microscope• Broca’s Area

– Portions of #44 and of #45• Wernicke’s Area

– Portion of #22

Broca’s and Wernicke’s Area• External brain stimulations:

– While talking > cease talking– While not talking > grunt from Broca’s, nothing from

Wernicke’s• Anatomy BA and WA

• Connections are polysnaptic• Connections are bi-directional• No direct connections to n. ambiguous• None below periaqueductal gray

Non-human Primates v. Humans•Language v. Communication Systems•We learn tens of thousands of words/symbols; NHP <40 signs•Humans learn syntax, gen. grammar•Anatomic differences:

•Association cortex•More fronto-temporal connections

Song Learning in Zebra Finches

Sensory learning

Sensorymotor

60-65dCritical period closes

90dCrystallization

25-40dSinging begins

J. neurosci, February 1, 1997 17(3):1147-1167

HVC

RA

LMAN

Area X

DLM

RA

LMAN

DLM

Parasagittal Section of Male Zebra Finch Brain

NIF

FIELD LLMAN

X

HVC

RA

DM

DLMN XII ts

Ts nerve totrachea and syrinx

Learning songMaintaining song

Comparison between ZF Birdsong and Human Speech

Birdsong Human SpeechOccurs early in life ++++ ++++Dependent on auditory

feedback ++++ ++++Dependent on specialized

brain areas ++++ ++++Spectrally complex ++++ ++++Temporally complex ++++ ++++Hierarchically controlled ++++ ++++Modular* ++++ ++++* (E.g., notes, syllables, phrases, phonemes, words, sentences, paragraphs)

“Domestic”

Normal Song 1

Normal Song 2

Repeater Song 1

Repeater Song 2

Rauschecker and Scott, Nature Neuroscience, 2009

Improved Understanding of Our Knowledge of Language and Speech

•Anatomy•Imaging•Physiology•Greater attention in new clinical domains•stuttering•dysphonia•aphasia•rehabilitation