Neuroanatomy of Language and Attention

Broca’s area

in frontal lobe (dorsal portion of inferior frontal gyrus) of dominant (L) hemisphere; motor planning region for speech

Wernicke’s area

at junction of temporal and parietal lobes; processes and interprets speech

arcuate fasciculus

neurons connecting Wernicke’s area to Broca’s area

classical model of language

primary auditory cortex → Wernicke’s area → arcuate fasciculus → Broca’s area → primary motor cortex

dual stream model of language

ventral stream and dorsal stream

ventral stream

bilateral; language comprehension

dorsal stream

L hemisphere; language production

dysarthria

lack motor control of speech muscles; involves lower motor neurons or corticobrainstem neurons

Broca’s aphasia (nonfluent, expressive, motor aphasia)

grammatical omissions and errors, short phrases, effortful speech; involves Borca’s area (L hemisphere0

Wernicke’s aphasia (fluent, sensory, receptive aphasia)

cannot comprehend language, speaks fluently but unintelligibly; involves Wernicke’s area (L hemisphere)

conduction aphasia (disconnection aphasia)

can understand language, language output unintelligible; involves neurons connecting Wernicke’s area with Broca’s area (arcuate fasciculus)

global aphasia

cannot speak fluently, cannot communicate verbally, cannot understand language; involves both Wernicke’s and Broca’s areas, and the intervening cortical and subcortical areas

arousal

awake vs. asleep

attentiveness

inattentive vs. attentive

selective attention

ignore vs. attend

5 levels of attention

1. focused

2. sustained

3. selective

4. alternating

5. divided

focused attention

ability to respond discretely to specific visual, auditory, or tactile stimuli

sustained attention

ability to maintain a consistent behavioral response during continuous or repetitive activity

selective attention

ability to maintain a cognitive set which requires activation and inhibition of responses dependent on discrimination of stimuli

alternating attention

capacity for mental flexibility which allows for moving between tasks having different cognitive requirements

divided attention

ability to simultaneously respond to multiple tasks

bottom-up control

“grabbing” attention; high salience

top-down control

voluntary, goal-directed; can override high salient stimuli

overt attention

eyes focused on target of attention

covert attention

eyes focused on target different from target of attention

dorsal attention network

bilateral; spatial attention; voluntary, goal-directed control of attention; “decide’ attention focus

involves superior prefrontal and posterior parietal cortices

ventral attention network

R hemisphere; non-spatial attention; stimulus-driven control of attention; “grabs” attention focus, novel and unexpected stimuli

involves tempoparietal junction and ventral frontal cortex in R hemisphere

attentional control subcortical network

superior colliculi and pulvinar of thalamus

hemispatial neglect

attention bias in direction of lesion (neglect contralateral side)

neglect of extrapersonal space

correctly identifies all items in ipsilesional extrapersonal space, ignores any item in contralesional space

e.g. lesions to inferior parietal lobule and temporoparietal junction

object-centered neglect

neglect for contralesional side of each object, but can see items in contralesional space

e.g. lesion to superior temporal gyrus