Language and the Brain
- Gross Anatomy of the Brain
- Language and the Left Hemisphere
- Aphasia
- Right Hemisphere Syndrome
- Cognitive Neuroscience and Language
- Additional Constraints?
Gross Anatomy of the Brian
- The Cortex and Higher Mental Function
- The Hemispheres
- The Corpus Callosum
Language and the Left Hemisphere
- Lateralization of Function
- Dichotic Listening
- Split-Brain Studies
- Hemisphere Removal
- The Wada Test
- Aphasia
Aphasia
- Cognitive Neuropsychology
- Broca’s Aphasia
- Wernicke’s Aphasia
- Double Dissociation?
- Other Aphasias
- The Wernicke-Lichtheim-Geschwind Model
Cognitive Neuropsychology
- Effects of Brain Lesions
- The Locality Assumption
- Modularity
- Functional Subsystems = Anatomical Subsystems
- Karl Lashley’s Laws (1950) of Mass Action and Equipotentiality are wrong!
- Single Dissociations and Double Dissociations
- How representative are the case studies that make it into journals and textbooks?
Broca’s Aphasia
- "Son . . . University . . . Smart . . . Boy . . . Good . . . Good . . . "
Broca’s Aphasia
- Speech is nonfluent, labored, and halting.
- Intonation and stress patterns are deficient.
- Misarticulations are common.
- Speech is "telegraphic".
- Repetition is poor.
- Comprehension is pretty good!
Wernicke’s Aphasia
- "I called my mother on the television and did not understand the door. It was too
breakfast, but they came from far to near. My mother is not too old for me to be
young."
Wernicke’s Aphasia
- Speech is fluent but "empty" (word salad).
- Rate, intonation, and stress are normal.
- Substitutions of one word for another ("telephone" -->
"television") are common.
- Comprehension and repetition are poor.
Double Dissociation?
- Comprehension versus Production
- Broca’s Area is the production module and Wernicke’s Area is the Comprehension
module.
- Caramazza & Zurif (1976) used a sentence/picture matching paradigm to show that
Broca’s aphasics can’t understand reversible sentences.
- Syntax versus Semantics
- Broca’s Area is the syntax module and Wernicke’s Area is the semantics module.
- Bradley, Garrett, & Zurif (1980) found that Broca’s aphasics do not show a
dissociation between open and closed class words in a lexical decision task.
- How could we test this idea further?
Other Aphasias
- Conduction Aphasia
- Transcortical Motor Aphasia
- Subcortical Motor Aphasia
- Transcortical Sensory Aphasia
- Subcortical Sensory Aphasia
- Anomic Aphasia
Conduction Aphasia
- Caused by damage to fibers connecting Wernicke’s and Broca’s areas.
- Speech is fluent.
- Auditory comprehension is good.
- Oral reading is poor.
- Patients are unable to repeat what they hear.
- Transpositions of sounds within a word ("television" -->
"velitision") are common.
Transcortical Motor Aphasia
- Caused by damage to cortical fibers surrounding Broca’s area.
- Auditory comprehension is good.
- So is repetition.
- Speech is fluent and well-articulated, but sparse.
- Most utterances are 1 or 2 words long, complete sentences are rare.
- Patients can repeat long and complex sentences, but can’t initiate them.
Subcortical Motor Aphasia
- Caused by damage to the anterior subcortical region of the left hemisphere.
- Comprehension is intact.
- Spontaneous speech and repetition are limited.
- Word concepts are intact.
- Patients can indicate the number of syllables in a word.
- Hemiplegia (Paralysis of Both Limbs on Right Side)
Transcortical Sensory Aphasia
- Caused by damage to fibers surrounding Wernicke’s area.
- Comprehension is impaired.
- Patients produce long, but empty speech like those with Wernicke’s Aphaisa.
- Unlike patients with Wernicke’s Aphasia, they are able to repeat back what is said
to them.
- Patients sometimes repeat back what is said to them involuntarily (echolalia).
Subcortical Sensory Aphasia
- Caused by damage to the posterior subcortical region of the left hemisphere.
- Repetition and comprehension are impaired.
- Spontaneous speech is normal.
- Sort of like Wernicke’s aphasia with hemiplegia.
Anomic Aphasia
- Caused by damage to specific areas of the left temporal lobe.
- Major symptom is word retrieval difficulties in spontaneous speech and in naming tasks.
- Spontaneous speech is usually fluent and grammatically correct except for word retrieval
problems which lead to pauses, substitution of nonspecific words ("thing") and
"talking around" missing words.
- Does it really exist?
The Wernicke-Lichteim-Geschwind Model
- "A" (Wernicke’s Area) stores information about word sounds.
- "M" (Broca’s Area) is the speech planning and programming area.
- "B" stores conceptual information.
The Wernicke-Lichteim-Geschwind Model
- 1 = Broca’s
- 2 = Wernicke’s
- 3 = Conduction
- 4 = Transcortical Motor
- 5 = Subcortical Motor
- 6 = Transcortical Sensory
- 7 = Subcortical Sensory
- ? = Anomic
Right Hemisphere Syndrome
- Non-Communication
- Denial of Illness (Anosagnosia)
- Left Hemispatial Neglect
- Topographic Impairments and Geographic Disorientation
- Face Recognition Deficits (Prosopagnosia)
- Difficulty Recognizing and Expressing of Emotion
- Communication
- Diminished Speech Prosody
- Anomalous Content and Organization of Connected Speech
- Impaired Comprehension of Narratives and Conversations
- Pragmatic Impairments
Cognitive Neuroscience of Language
- Divided Visual Field Studies
- Functional Imaging
- Electrophysiology
Divided Visual Field Studies
- Information is presented to just one hemisphere.
- Time is required for that information to cross the corpus callosum.
- Dominant RT < Non-Dominant RT
- This technique is useful for determining lateralization of function in normal
populations.
Some Findings
- Word recognition is faster in the left hemisphere.
- RH shows repetition priming only for exact visual form but LH shows repetition priming
regardless of form (Marsolek, et al., 1992).
- LH shows greater associative priming but RH shows greater summation priming (Beeman, et
al., 1994)
- (FOOT + CRY + GLASS --> CUT)
Functional Imaging
- PET and fMRI
- The Subtraction Technique
- Experimental Tasks and Comparison Tasks
- Assumption of Pure Insertion
- The Additive Factors Technique
- Spatial and Temporal Resolution
Some Findings
- Blood flow to Wernicke’s area increases while listening to words.
- Blood flow to Broca’s area increases during:
- Silent Picture Naming (Chertkow, et al, 1993)
- Silent Verb Generation (Wise, et al., 1991)
- Rhyme Judgement (Zatorre, et al., 1993)
- As grammatical complexity increases, blood flow increases in both Broca’s and
Wernicke’s areas (Just, et al., 1996).
Electrophysiology
- EEGs and ERPs
- Averaging and Graphical Presentations of Results
- Components
- Generators and Functional Components
- Subtraction and Additive Factors
- Spatial and Temporal Resolution
Some Findings
- Contextually inappropriate words produce a strong N400 component (Kutas & Hillyard,
1980).
- WINDOW --> NURSE
- DOCTOR --> NURSE
- In sentence contexts, semantic anomalies produce an N400 while syntactic anomalies
produce a P600 (Osterhout, 1994).
- "He spread the warm bread with socks."
- "The broker persuaded to sell the stock."
- Words in a discourse produce a stronger N400 when an appropriate schema is not available
(St. George, et al., 1994).
Additional Constraints?
- Neural Computation
- The 100 Step Maximum
- Symmetry of Connections
The End!
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