Last Lecture Dichotic Listening Dichotic Listening The corpus callosum & resource allocation The corpus callosum & resource allocation Handedness Handedness Broca’s Aphasia Broca’s Aphasia

This Lecture Wernicke’s aphasia Wernicke’s aphasia The Wernicke-Geschwind Model The Wernicke-Geschwind Model Category-specific semantic deficits and the representation of meaning Category-specific semantic deficits and the representation of meaning Introduction to the Frontal Lobes Introduction to the Frontal Lobes

Remember the Wernicke-Geschwind model? Broca’s area: forms detailed coordinated plans for language production (speech, writing, covert/rehearsal) Broca’s area: forms detailed coordinated plans for language production (speech, writing, covert/rehearsal) Explains dysfluency and poor articulation in Broca's aphasics. Explains dysfluency and poor articulation in Broca's aphasics. But comprehension is not perfect... Poor syntax comprehension Poor syntax comprehension Broca's aphasics poor at judging grammaticality Broca's aphasics poor at judging grammaticality Active: The horse kicked the cow. Passive: The cow was kicked by the horse.

Agrammatism Disproportional difficulty reading and producing function words. Disproportional difficulty reading and producing function words. Difficulty using & understanding grammar Difficulty using & understanding grammar Modification to Wernicke-Geschwind model Broca's area: Plan for coordinating language production Plan for coordinating language production Understanding and using syntax. Understanding and using syntax.

Wernicke's aphasia Examiner: Can you tell me a little bit about why you’re here? Patient: Sine just don’t know why, what is really wrong, I don’t know, cause I can eaten treffren eatly an everythin like that I’m all right at home. (Excerpt from Kertesz, 1980; quoted by Carlson, 1994)

Symptoms of Wernicke's aphasia Speech: phonetically & grammatically normal but meaningless. Speech: phonetically & grammatically normal but meaningless. generally fluent, unlabored, well articulated. generally fluent, unlabored, well articulated. normal intonation (prosody). normal intonation (prosody). words used inappropriately words used inappropriately nonsense words (neologisms) --> "word salad" nonsense words (neologisms) --> "word salad" meaning expressed in roundabout way (circumlocution). meaning expressed in roundabout way (circumlocution). Comprehension: severely impaired. Comprehension: severely impaired.

According to Wernicke-Geschwind model Wernicke's Area... DOES NOT STORE MEANING! DOES NOT STORE MEANING! stores memories of sound sequences that constitute words. stores memories of sound sequences that constitute words. translates auditory input into phonological forms that can then access semantics. translates auditory input into phonological forms that can then access semantics.

Interpretation of Wernicke's area in action Understanding spoken language: Primary auditory cortex (41/42) -> Wernicke's A. (22) -> semantic networks distributed throughout the brain. Primary auditory cortex (41/42) -> Wernicke's A. (22) -> semantic networks distributed throughout the brain. Spontaneous speech: "cognitive" areas send input to Wernicke's area: Cognition -> Wernicke's A. (22) -> arcuate fasciculus -> Broca's A. (44)-> Primary motor cortex Cognition -> Wernicke's A. (22) -> arcuate fasciculus -> Broca's A. (44)-> Primary motor cortex

PET activation during listening

According to the Wernicke-Geschwind model... Wernicke’s A. essential for reading... Visual processing --> Angular g. --> Wernicke's a.--> Semantics Angular gyrus (39) translates visual code to a form accessible by Wernicke’s a. Angular gyrus (39) translates visual code to a form accessible by Wernicke’s a. grapheme --> phoneme translation grapheme --> phoneme translation Wernicke’s a. translates to a form that can access meaning. Wernicke’s a. translates to a form that can access meaning. Implication: Reading requires phonological recoding via Wernicke’s A. Implication: Reading requires phonological recoding via Wernicke’s A.

Where is meaning stored? Wernicke’s area does not store meaning, so where is it stored? Wernicke’s area does not store meaning, so where is it stored? Meaning is represented across a network of brain areas Meaning is represented across a network of brain areas Different brain areas contribute to different kinds of knowledge Different brain areas contribute to different kinds of knowledge

How do we know this? Loss of SEMANTIC KNOWLEDGE: can’t recognize, describe from memory, or answer questions about objects. can’t recognize, describe from memory, or answer questions about objects. Category -specific deficits: Some patients cannot recognize living things (plants/animals) but can recognize man-made things (tools/instruments) Some patients cannot recognize living things (plants/animals) but can recognize man-made things (tools/instruments) Opposite pattern also reported (non-living things-impairment) Opposite pattern also reported (non-living things-impairment) Double dissociation: separable representations for difference categories of knowledge.

PET evidence: Category-specific activations (Martin et al., 1996) Subjects identified pictures of animals and tools Subjects identified pictures of animals and tools Certain visual areas more active for animals Certain visual areas more active for animals Left premotor area more active for tools. Left premotor area more active for tools. Semantic representation: - tools represented by function. - living things represented by visual/sensory features.

The Role of Language Language ability sets us apart from other animals. Language ability sets us apart from other animals. Is language what makes us uniquely human? Is language what makes us uniquely human?

Phineas Gage Railroad worker who experienced head trauma. Railroad worker who experienced head trauma. He survived. He survived. Drastically changed his personality. Drastically changed his personality. “Gage was no longer Gage,” according to his friends. “Gage was no longer Gage,” according to his friends.

The Frontal Lobes Claim: The frontal lobes mediate those abilities that make us uniquely human. Herein lies the riddle... What makes us uniquely human? Herein lies the riddle... What makes us uniquely human?

The Frontal Lobes 3 natural boundaries 3 natural boundaries posterior: central sulcus posterior: central sulcus inferior: Sylvian fissure (lateral fissure) inferior: Sylvian fissure (lateral fissure) medial/inferior: corpus callosum medial/inferior: corpus callosum

Major Subdivisions Precentral (motor cortex): Area 4 Premotor: Areas 6 and 8 (including supplementary motor) Areas 6 and 8 (including supplementary motor) 44 (Broca’s area) 44 (Broca’s area)Prefrontal: dorsolateral: Areas 46, 45, 9, 10 dorsolateral: Areas 46, 45, 9, 10 ventrolateral: Areas 11, 47 ventrolateral: Areas 11, 47 orbital: 11 orbital: 11 Anterior Cingulate: medial: Areas 24, 25, 32 medial: Areas 24, 25, 32