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

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

9. Distribution of receptors

11. 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

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 Contrast Integration over space.

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. Choclear output 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. Each pathway conveys a different “part” of the information. Redundancy…

50. Topographic organization

51. Homonculus

52. Secondary Somatosensory areas

53. How does all this develop? Genetics Experience Flexibility/Plasticity