Chapter 19: Higher mental functions

1. Chapter 19: Higher mental functions • Chris Rorden University of South Carolina Norman J. Arnold School of Public Health Department of Communication Sciences and Disorders University of South Carolina

2. Methods of Study • How do we infer brain function? • Classically, we examined what went wrong when someone had a disorder within the brain and inferred that their injury was crucial for this task. • Example: Patients with left frontal cortex injury have non-fluent speech. • Now we visualize brain structures and localize functional areas using advanced equipment and technology • Example: The left frontal cortex is activated during speech production.

3. Functional Localization (previous lectures) • Frontal Lobe • Executive function • Planning • Sequencing • Initiation – inhibition • Voluntary movements • Working memory • Occipital Lobe • Vision (Field cuts) • Temporal Lobe • Encoding long-term memories • Language comprehension • Hearing • Parietal Lobe • Reading/Writing • Praxis • Spatial processing (neglect)

4. Functional Localization • Functionalization occurs over period of time. Brain becomes more specialized with development • People who suffer brain injury early in life will utilize existing brain regions in novel ways. • Plasticity allows compensation

5. Cerebral Dominance & Functional Specialization • Brain preprogrammed for different uses of right and left hemispheres • Left Hemisphere • Most people have left hemisphere dominant for language • Left hemisphere is called “Dominant” hemisphere • Right handed people have longer planum temporale in left hemisphere which may be biased for use by dominant hemisphere

6. Right hemisphere functions • Right hemisphere involved in visual-spatial and constructional tasks, emotion and emotional intonation of speech and music. • Right hemisphere is often referred to as the “Minor” Hemisphere • Patients with injury to right cortex often exhibit neglect. • Studies of lateralization can include tests such as Wada test – Today most studies use fMRI for this purpose

8. Speech and Language Disorders • Motor Speech Disorders • Dysarthria - Paralysis or Paresis of Muscles • Flaccid – LMN problem – hypernasal, breathy speech and imprecisely articulated consonants • Spastic – UMN – Harsh, strained / strangled speech with slow articulation • Hypokinetic – Basal ganglia – variable rate, excessive variation in loudness and timing with distorted vowels • Mixed – Combination of other dysarthrias • Apraxia of speech - No Paresis, Programming Disorder

9. Language Disorders • Aphasia • Broca’s Aphasia - Broca’s Area • Wernicke’s Aphasia - Wernicke’s Area • Global Aphasia - Wide area • Conduction Aphasia - Angular gyrus or inf. PL • Anomic Aphasia - Angular Gyrus • Transcortical Aphasia • Subcortical Aphasia

10. Language Production • Broca’s Area (1861) • Difficulty in speech production • Loss of ability to repeat speech • Comprehension intact • Foot of 3rd frontal convolution (BA 44) • Left hemisphere (1865) • Except left handers

11. Language Comprehension • Wernicke’s Area (1874) • Normal production (speech sounds and fluent nonsense) • Sounds okay if you do not know the patient’s language (e.g. Chinese Wernicke’s aphasic would sound fine to me) • Unaware of deficit • Impaired comprehension • Left hemisphere • Superior temporal gyrus(BA 42, 22)

12. Wernicke’s prediction • Predicted two language centers: • Broca’s Area: speech articulation. • Wernicke’s Area: language comprehension. • Predicted 3rd Syndrome: • Disconnection syndrome • ‘Conduction aphasia’ • Damage to arcuate fasciculus

13. Conduction aphasia • Can comprehend speech • Difficulty in repeating speech • phonemic paraphasias (substitution errors) • Lesions in Temporal Parietal Junction that knock out underlying white matter • Patients with damage ONLY to the arcuate fasciculus can still generate speech. • Why? Other pathways

14. Wernicke-Lichtheim (1885) Schema • From auditory input (a) to motoric articulation of speech (m) Concepts(Distributed) Broca’s Aphasia Wernicke’s Aphasia Conduction aphasia

15. 4: Transcortical Motor Aphasia • Disconnection of Broca’s from concepts • Speech is slow, terse • Can comprehend speech • Found after damage to the frontal lobes • Unlike Broca’s Aphasics, can repeat phrases when spoken to • direct Wernicke’s to Broca’s pathway intact

16. 6: Transcortical Sensory Aphasia • Disconnection of Wernicke’s from concepts • Can repeat words • Speech is articulate nonsense • Unable to comprehend speech • Found after damage to the posterior language area

17. 7 Pure Word Deafness • Loss of ability to understand spoken speech. • Normal speech, reading, writing • Behaviour and anatomy dissociate from Wernicke’s aphasia • Written comprehension intact, intact written/verbal production.

18. Language Disorders • Alexia • with agraphia - supramarginal or angular gyrus • without agraphia - medial occipital and temporal L. • Aphasic alexia • Deep dyslexia – large mixed lesions • Surface dyslexia – Anterior left hemisphere • Agraphia • Pure agraphia - left superior frontal or parietal regions • Phonological agraphia • Lexical agraphia

19. Alexia without agraphia • Disconnection of angular gyrus from visual inputs • Language outputs intact • Patients cannot read • Writing preserved • Rare: left and right pathways to angular gyrus • Requires damage to • posterior callosum • left occipital lobe • Without damage to left angular gyrus

20. Apraxias • Apraxias (Other than Speech) • Difficulty in carrying out learned voluntary motor acts • Constructional: visual-spatial difficulty from RH • Dressing: Spatial perception of clothing in relationship to body • Oculomotor: Difficulty in gaze • Gait: Problems in walking • Ideomotor: Trouble following commands • Ideational: Trouble with multistep tasks – trouble with use of objects – may confuse objects use • Limb-Kinetic: Trouble with one limb only

21. Aphasia Notes [lcbr.ss.uci.edu]

22. Anatomy of aphasia Conduction Transcortical- motor Anomic Broca’s Global Wernicke’s Transcortical- sensory