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Sensory systems basics

Sensory systems basics. Sensing the external world. Sensory transduction. Transforming external physical forces/energy into electrical impulses that are mediated by neural spikes. Neural “encoding”. Encoding stimulus amplitude. Responses of a photoreceptor to light at different intensities.

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Sensory systems basics

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  1. Sensory systems basics

  2. Sensing the external world

  3. Sensory transduction Transforming external physical forces/energy into electrical impulses that are mediated by neural spikes. Neural “encoding”

  4. Encoding stimulus amplitude Responses of a photoreceptor to light at different intensities. Information is encoded by both amplitude and length of the response.

  5. Encoding stimulus location The location of the stimulus in space is encoded by the identity of responding receptors.

  6. Encoding stimulus location

  7. Encoding stimulus location

  8. Distribution of receptors Different organs (or organ locations) contain different amounts and types of receptors.

  9. Distribution of receptors

  10. Distribution of receptors

  11. Sensory pathways

  12. Sensory pathways

  13. Central nervous system

  14. Vision

  15. Topographical organization Photoreceptors responding to the left visual field innervate the right LGN.

  16. Topographical organization Both the thalamus and early visual cortices contain retinotopic maps of visual space.

  17. Occular dominance Information from the left and right eyes remains segregated in the LGN.

  18. Occular dominance Also in primary visual cortex.

  19. Cortical magnification

  20. Cortical magnification

  21. Acuity

  22. Columnar organization

  23. Selectivity to stimulus attributes Spatial receptive fields Contrast Luminance Spatial frequency Orientations Colors Movement direction and/or speed Textures Shapes

  24. Receptive field Many visual neurons have excitatory and inhibitory parts to their receptive field. Examples of retinal and LGN cells.

  25. Retino-topic mapping

  26. Luminance & Contrast

  27. Orientation selectivity Orientation selectivity in primary visual cortex.

  28. Orientation selectivity Pinwheels (only in primates)

  29. Hierarchy and integration LGN V1 Neurons

  30. Invariance and Gain Contrast invariant orientation tuning. Response gain

  31. Spatial frequency Integration over space. Contrast Spatial frequency

  32. Movement direction Integration over time. Overlapping representations of orientations and directions

  33. Hierarchy and integration Low, mid, and high level vision

  34. Functional specialization

  35. Face selectivity

  36. Invariance (abstractness) Is this vision or abstract memory?

  37. Audition

  38. Choclearoutput Selectivity to specific frequencies. Louder stimuli generate less selective responses.

  39. Sound localization Interaural time differences (ITD)

  40. Sound localization Brainstem areas: Olivary nuclei Colliculus

  41. Sound localization

  42. Auditory brainstem response

  43. Tonotopy But no spatial encoding…

  44. Language system Lateralized!

  45. Language structure Phonetics: ‘ba’, ‘da’, ‘pa’ Words, Grammar, Intonation How is all this encoded? Language hierarchy? Invariance across hearing and reading?

  46. Specific white matter tracts Aphasias

  47. Somatosensation

  48. Parallel pathways

  49. Parallel pathways Each pathway conveys a different “part” of the information. Redundancy…

  50. Topographic organization

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