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Psychology 210

Psychology 210. Lecture 5 Kevin R Smith. Today. The Auditory system The Somatosensory system The chemical systems. Properties of sounds. Sounds are waves Amplitude: loudness Frequency: pitch. Audible Sound. The ear. The ear. Outer ear Pinna Auditory canal. Anatomy of the ear.

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Psychology 210

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  1. Psychology 210 Lecture 5 Kevin R Smith

  2. Today • The Auditory system • The Somatosensory system • The chemical systems

  3. Properties of sounds • Sounds are waves • Amplitude: loudness • Frequency: pitch

  4. Audible Sound

  5. The ear

  6. The ear • Outer ear • Pinna • Auditory canal

  7. Anatomy of the ear • Middle ear • Tympanic membrane: Ear drum • Oscicles • Malleus (Hammer) • Incus (Anvil) • Stapes (Stirrup) • Oval Window

  8. Anatomy of the ear • Inner ear • Semicircular canals • Cochlea • Basilar membrane • Hair cells

  9. The basilar membrane • Hair cells translate vibrations from the sound waves into frequencies • Higher pitches are processed closer to the base • Lower pitches are processed closer to the apex • Tonotopic organization

  10. The hair cells move Opens Ca channels Leads to the perception of a signal Different hair cells move depending on the frequency of the incoming sound Transduction

  11. Hair cells • Hair cell damage • Noise, infections, genetic diseases, aging • Higher frequencies are harder to hear as you age • Regeneration • Can occur in birds and some invertebrates • Generally does not occur in humans

  12. The Pathway to the brain • The auditory nerve • Cochlear nucleus • Superior olivary nucleus • The inferior colliculus • Thalamus (medial geniculate nucleus) • Primary auditory cortex

  13. In the superior olivary nucleus • Information from the ears is first combined here • May have some role in localization of sounds • Tonotopically organized

  14. Organization of the MGN • Similar to the LGN for vision • Different layers have different inputs • Tuning curves become more specific • Tonotopically organized

  15. Organization of A1 • Tonotopically organized • Just like the cochlea, superior olivary nucleus, and MGN, different tones are processed in different locations

  16. After A1 • Like vision: A2, A3, A4… • Two pathways • Dorsal “where” pathway • Ventral “what” pathway • Researchers try and relate auditory systems to visual systems • Some similarities have been found, but nothing is certain

  17. Is the auditory system contralaterally organized? • Somewhat • 80% of incoming information into each auditory cortex is from the contralateral ear and 20% is from the ipsilateral ear • Why the combining of the incoming information from the two ears?

  18. Spatial cues • We need information from both ears to locate where a sound is in space • Two main cues • Interaural intensity (level) difference (IID or ILD) • Interaural time difference (ITD) • Also our pinna provides information about how vertical a sound is

  19. Interaural Intensity Differences • The ear that is closer to the sound hears a louder sound than the ear that is farther from the sound • The difference in loudness here is a difference in intensity • Our head provides a shadow effect over the far ear • Based upon the difference in intensity, our brain can calculate where the sound was

  20. Interaural Time Differences • The ear that is closer to the sound hears the sound earlier than the ear that is farther from the sound • Based upon the difference in time, our brain can calculate where in space the sound was

  21. IIDs and ITDs

  22. IIDs and ITDs • Only provide information about where a sound is along the horizontal • We use our pinnas to locate where a sound is vertically • Head related transfer functions

  23. Changing the shape of the pinna change localization abilities Eventually subjects learn to localize sounds properly Interesting Note

  24. The somatosensory system • The Vestibular System • Touch • Temperature • Pain

  25. The Vestibular System • Fluid filled cavaties • Semicircular canals • Otoliths • Saccule • Utricle • Found near the ear and auditory structures

  26. How the vestibular system works • Fluid filled cavities • Contain hair cells • Sensitive to direction of movement • Either hyperpolarize or depolarize • Provide information about the location in space of the head • Semicircular canals • Provide more information about the rotation of the head

  27. How the vestibular system works

  28. Pathway to the brain • Auditory nerve • Pons, medulla, cerebellum • Vestibular nuclei • Ventral posterior thalamus • Primary somatosensory cortex and primary motor cortex

  29. The vestibular system • Information is highly integrated with information from the visual cortex • Also, projects to the spinal cord for feedback regarding posture

  30. Touch • The Sensory inputs • Meissner’s corpuscles • Pacinian corpuscles • Merkel’s disks • Ruffini’s endings • Free nerve distributions • Hair follicle receptors

  31. Differences between receptors • Size of receptive field • Small • Meissner’s corpuscles • Merkel’s disks • Large • Pacinian corpuscles • Ruffini’s endings

  32. Differences between receptors • Rate of adaptation • Fast • Meissner’s corpuscles • Pacinian corpuscles • Slow • Merkel’s disks • Ruffini’s endings

  33. Differences between receptors • Location • Shallow in the skin • Meissner’s corpuscles • Merkel’s disks • Deep in the skin (digestive tracts, joints) • Pacinian corpuscles • Ruffini’s endings

  34. Differences between receptors • Type of information processed • Pressure • Meissner’s corpuscles • Merkel’s disks • Pressure and vibrations • Pacinian corpuscles • Stretch • Ruffini’s endings • Pain and temperature • Free nerve endings

  35. Meissner’s Corpuscles

  36. Pacinian corpuscles

  37. Pathway to the brain • Spinal cord • Medial lemniscus • Ventral posterior nucleus of the thalamus • S1

  38. Organization of S1 • Somatotopically organized • Cortical magnification • The amount of cortex devoted to your hand is more than the amount of cortex devoted to your torso, even though your torso is larger • Why?

  39. Somatotopy • Your hand is much more sensitive to touch than your back • Same with face, mouth, eyes, etc…

  40. Homunculus

  41. Other types of receptors • Free Nerve Ending Receptors • Thermoreceptors • Respond to warmth or cold • Nociceptors • Respond to mechanical pain, extreme heat, or both

  42. The chemical senses • Senses that use chemical receptors • Olfaction: Smell • Olfactory epithelium detects molecules in the air • Taste • Saliva dissolves food into molecules

  43. Smelling….. • 1000 different smell receptors • Each receptor detects a broad range of smells • Based upon the combination of activity from the receptors, our brain constructs the smell

  44. The olfactory system • The nose • Olfactory epithelium • Olfactory receptor cells synapse onto olfactory nerves within the olfactory bulb

  45. The olfactory system • Pathway to the brain • Olfactory bulb axons form the olfactory tract • Olfactory cortex • Thalamus: Medial dorsal nucleus • Projects to all over the brain • Various frontal areas

  46. Taste • The tongue • Four different taste buds • Sweet, sour, salty, bitter • Umami: savory • Possibly a fifth type of taste bud • Papilla • Bumps on the tongue • Each contains up to 100 taste buds

  47. The Tongue

  48. Pathway to the brain • Tongue: taste fibers – cranial nerves –Thalamus: ventral posterior medial nucleus – parietal lobe

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