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The Neural Basis of Body Form and Body Action Agnosia

The Neural Basis of Body Form and Body Action Agnosia. Valentina Moro, Cosimo Urgesi, Simone Pernigo, Paola Lanteri, Mariella Pazzaglia, and Salvatore Maria Aglioti. Evidence for body selective neural mechanisms. 1. Single unit recording and fMRI in monkeys.

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The Neural Basis of Body Form and Body Action Agnosia

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  1. The Neural Basis of Body Form and Body Action Agnosia Valentina Moro, Cosimo Urgesi, Simone Pernigo, Paola Lanteri, Mariella Pazzaglia, and Salvatore Maria Aglioti

  2. Evidence for body selective neural mechanisms 1. Single unit recording and fMRI in monkeys 2. Intracranial recordings in humans 3. Evoked potentials in humans 4. fMRI in humans 5. TMS in humans 6. Lesions in humans – this experiment

  3. Single unit recording and fMRI in monkeys Neurons in inferior temporal cortex (IT) respond selectively to human/monkey bodies and body parts. Other neurons in IT respond selectively to faces but not to hands. from Peelem & Downing, 2007 שיטות

  4. Intracranial recordings in humans Extrastriate visual cortex N230 - hand selective from Peelem & Downing, 2007 שיטות

  5. Evoked potentials in humans N170 (face selective) and N190 (body selective) have distinct lateral occipitotemporal Sources (according to source localization) from Peelem & Downing, 2007 שיטות

  6. fMRI in humans Extrastriate body area (EBA) - posterior inferior temporal sulcus/middle temporal gyrus - Body parts. Fusiform body area (FBA) – Whole bodies. from Peelem & Downing, 2007 שיטות

  7. TMS in humans EBA - 150–250 ms after stimulus onset - impaired performance on a delayed match-to-sample task involving images of body parts, but not face or motorcycle parts.

  8. Body in the Brain so far Extrastriate body area (EBA) Static bodies Dynamic displays of bodies Body parts Body forms but not actions Not faces Fusiform body area (FBA) Whole body Body parts Ventral Premotor cortex (vPMc) Body actions but not form שיטות

  9. This experiment - neuropsychological evidence Patientswith anterior (n=14) and posterior (n=14) lesions. No visual agnosia Study 1– face parts vs. body parts vs. objects Study 2– Body Form vs. Body Action

  10. Study 1: Face, Body & Object OFA & FFA LOC EBA & FBA

  11. Study 1 Task: Two choice matching to sample visual discrimination *In a separate experiment with controls: inverted and upright stimuli inversion effect for faces only (configural processing for faces)

  12. Behavioural results - Accuracy Group (anterior, posterior, control) X Category (body, face, object) Posterior patients perform worse than controls and anterior patients in discriminating body and face parts. Body Face

  13. Voxel-based Lesion Symptom Mapping (VLSM) Relationship between injury andbehavior on a voxel-by-voxel basis • In this experiment: • For each patient T1 weighted MRI • Each lesion was superimposed onto a standard brain • To identify the voxels that are associated with the three categories, three VLSM analyses were conducted. • The predictors were: • % correct responses of the for body • % correct responses for face • % correct responses for object • (Individual % CR of each category were entered)

  14. VLSM Results Impaired body discrimination – bilateral inferior and middle Occipitotmeporal & left STS lesions. EBA FBA

  15. Study 2: Body form & Body action

  16. Study 2: Body form & Body action Task: two choice matching to sample visual discrimination (action or form) Form discrimination: Different models, same action Action discrimination: Same model, different action.

  17. Behavioural results - Accuracy Group (anterior, posterior, control) X Type (action, form) Anterior patients – worse for actions Posterior patients – worse for form / identity Double dissociation between action & form and anterior posterior - Independent from lateralization

  18. VLSM Analysis Predictors: % CR in Action/% CR in Form % CR in Form/% CR in Action Body form - Lateral occipitotemporal (bilatetral) - (BA 19,37) – EBA Left inferior occipital (BA 19). same size & location as in study 1 Body action – left vPMC, a little bit right as well.

  19. Conclusions Selective deficits for bodies at the perceptuallevel Study 1: Body agnosia 1. Face & body - Ventromedial, occipitotemporal (FBA). 2. Body only - Extrastriate body area (EBA). Study 2: body form and body action agnosias. 3. Double dissociation: Bodyform - EBA & FBA Body action - ventral premotor cortex (vPMc).

  20. What's new about this research? Selective deficits for bodies at the perceptuallevel Neural substrates for form and body action agnosias that are Double dissociated. Left and right ventral premotor are causatively associates with Action perception. Diagnostic tools for clinical assessment.

  21. Why can't we find body agnostics? • We need sensitive tests (The Posterior patients did not report having difficulties in recognizing bodies in daily life). • 2. Body selective areas are small and sometimes overlap with object, face and motion areas. Maybe motion agnosia masks body agnosia? • 3. Body deficits may be compensated by other body selective areas • (ipsilateral or contralaetral)

  22. The End

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