Diencephalon
Sensorimotor integrator and gateway for information to the forebrain
Parts of the Diencephalon
Thalamus, epithalamus, hypothalamus, subthalamus
Thalamus
- Channel projections of sensory (pain, taste, temperature, audition, vision) information
- Integrate sensorimotor information and project afferents from the basal ganglia, limbic system and cerebellum to the primary and premotor cortices
- Regulate functions of the associational cortex and cortically mediated cognition
Planum Temporale
- larger in left hemisphere
- one of the most important functional areas for language
Broca’s Aphasia
- Nonfluent, telegraphic, poorly articulated verbal output in which meaning is conveyed by content or information–carrying words
- Deficient naming
- Deficits in comprehension, especially of multistep commands or sentences with complex syntax
- Halting, dysfluent repetition
- Reading comprehension and writing parallel auditory comprehension and spoken language, respectively
Wernicke’s Aphasia
- Fluent, effortless, but relatively meaningless, spontaneous speech and repetition
- Paraphasias, neologisms, jargon
- Overuse of social phrases, fillers
- Impaired comprehension at the word, sentence, and discourse levels
- Melodic contour of spoken language is often preserved, initially giving listeners the impression that output is intact
Global Aphasia
- Lesions of left MCA territory
- Severe impairment of all language modalities
- Spontaneous verbal output may be restricted to single words, nonwords, or undifferentiated phonation
- Evolve to Broca’s aphasia
Conduction Aphasia
- Relatively fluent, although paraphasic, spontaneous speech, intact auditory comprehension
- Disproportionately impaired repetition
Anomic Aphasia
- Impaired word retrieval = primary feature
- Relatively well-preserved function in other realms
- Circumlocutions for targets, protracted pauses, use of fillers
- Empty or low-content verbal output
- Residual language deficit in recovery
- Least reliably localized aphasia
Transcortical Motor Aphasia
Shares many characteristics of Broca’s aphasia, but has the distinctive feature of fluent, grammatical repetition
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Transcortical Sensory Aphasia
Similar to Wernicke’s aphasia, except for the presence of accurate repetition
Mixed Transcortical Aphasia
Analogous to global aphasia, with reduced or absent spontaneous speech, severely impaired language comprehension, and preserved repetition with consequent echolalia
Subcortical Aphasias
- Preservation of repetition common to all three subtypes; features specific to each
- Striato-capsular
- Thalamic aphasia
Striato-capsular aphasia and aphasia with white matter paraventricular lesions
Impairment of fluency, semantic paraphasias, generally preserved comprehension
Thalamic aphasia
Impaired comprehension and naming with fluent output containing predominantly semantic paraphasias
Dual Stream Model
Dorsal stream
Ventral stream
Dorsal stream
-Superior division of left MCA
-Broca’s aphasia
-Maps motor speech representations onto auditory speech representations
-Auditory-motor integration
Essential for speech development and production
-Strongly left dominant
Ventral Stream
- Inferior division of the left MCA
- Wernicke’s aphasia
- Mediates relationship between sound and meaning for perception and production
- Sound-meaning interface
- Responsible for processing speech signals for comprehension
- Bilaterally organized
