AssociationCortices2022.pptx

Association Cortices and Complex Brain Functions Dr Natasha Sigala [email protected] Module 202 Neuroscience & Behaviour Outline •Hierarchical Organization •Three main multimodal association areas •Principles of function •Executive functions •Language 2 Learning Outcomes • Explain the conce...

Association Cortices and Complex Brain Functions Dr Natasha Sigala [email protected] Module 202 Neuroscience & Behaviour Outline •Hierarchical Organization •Three main multimodal association areas •Principles of function •Executive functions •Language 2 Learning Outcomes • Explain the concept of hierarchical organisation in the cortex • Give examples of multimodal association cortical areas, along with their function • Define prosopagnosia, visual agnosia, anosognosia, apperceptive and associative agnosia, aphasia • Give examples of serial and parallel processing of information in the brain • Name and localise the main cortical areas involved in language processing, explain their respective function • Describe the Wada procedure and its use • Explain the contribution of split brain studies in the study of language processing 3 Dr John Hughlings Jackson, FRS founder of British Neurology (1835 – 1911) 4 Example processes 7H15 M355463 53RV35 70 PR0V3 H0W 0UR M1ND5 C4N D0 4M4Z1N6 7H1N65! 1MPR3551V3 7H1N65! 1N 7H3 B361NN1NG 17 W45 H4RD BU7 N0W, 0N 7H15 L1N3 Y0UR M1ND 15 R34D1N6 17 4U70M471C411Y W17H 0UT 3V3N 7H1NK1N6 4B0U7 17. 5 Hierarchical organization of sensory systems Association cortex Secondary sensory cortex Primary sensory cortex Thalamic relay nuclei Receptors 6 Hierarchical organization of sensory systems Association cortex: •Unimodal association areas (single modality) •Multimodal association areas (>1 modalities) •Multimodal sensory association areas project to multimodal motor association areas (rostral to M1) • Primary sensory area: initial stage of processing, •Primary motor area: final stage for cortical processing of motor commands 7 Example hierarchical network: visual system Van Essen et al, 1992, Science, 255, 419-423 8 Three main multimodal association areas 1. Posterior association area (perception, language) 2. Temporal association area (emotion, memory) 3. Prefrontal association area (executive functions) Approximate locations of the primary, secondary and tertiary sensory and motor cortices Source: http://users.fmrib.ox.ac.uk/~stuart/thesis/chapter_3/sec tion3_2.html 9 10 Prosopagnosia, visual agnosia, anosognosia (agnosia for own illness) 11 Personality changes. Long term planning and judgment. Working memory. Phineas Gage, 1848 Continuity of behavioural planning (stored program of action). Anxiety for the future? 12 Information converges from unimodal to multimodal areas Jones & Powell, 1970, Brain 93: 793-820 13 Serial and Parallel processing of sensory information Agnosia: •Apperceptive •Associative Purves, Neuroscience 14 Sequence of information processing is reversed in the motor system Motor planning: General outline of behaviour -> concrete motor responses Frontal cortex: individual neurons fire for a range of related behaviours (not specific motor responses). Movements and complex actions result from patterns of firing of large networks of neurons in the frontal lobe. The premotor cortex generates motors programs and the neurons are active during preparation of movement. Motor cortex neurons mainly fire to produce movements in particular directions around specific joints. 15 Specialised language areas in the brain Aphasia Paul Broca, 1824-1880 Region of dominant left frontal lobe, articulate speech Karl Wernicke, 1848-1905 16 Asymmetrical language processing Wada Procedure Used to determine hemisphere dominant for speech 17 Aphasia Broca’s, motor, nonfluent aphasia Wernicke’s aphasia- fluent speech, poor comprehension Aphasia in bilinguals (order, fluency, use of language) Aphasia and sign language 18 James: I need to tell you something. You see, for past many days, everything so unclear, you see, I have to say, I went out, I got up, I felling, every go around but clamp. I try best. 19 Sophie: Eric, where do you work and do you enjoy your job? Eric: I work as a fro...no...hotel..I mean...des. . you know... Sophie: You work at the front-desk in a hotel, right? Eric: Yes. The job is er...you know...I mean... 20 Asymmetrical language processing – split brain studies 21 Asymmetrical language processing – split brain studies 22 Which brain area is important for word processing and comprehension of speech? Answers A. Broca’s area B. Brodmann’s area C. Papez area D. Wada’s area E. Wernicke’s area Reading materials Kandel, Chapter 19 Bear, Chapters 20, 21 The man who mistook his wife for a hat: https://web.arch.virginia.edu/arch5420/docs/reading/sackspdf/ sacksvl.pdf 24