1 / 91

Plasticity in sensory systems

Plasticity in sensory systems. Jan Schnupp on the monocycle. Activity and size of auditory cortex…. Schneider et al. Nat. Neurosci. 2003. …Are correlated…. …and correlated with musical abilities.

gella
Download Presentation

Plasticity in sensory systems

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Plasticity in sensory systems

  2. Jan Schnupp on the monocycle

  3. Activity and size of auditory cortex… Schneider et al. Nat. Neurosci. 2003

  4. …Are correlated…

  5. …and correlated with musical abilities

  6. Is musical practice increasing the size of auditory cortex, or do people with large auditory cortex become musicians?

  7. What do we learn when we learn a new skill?

  8. Nat. Neurosci. 2006

  9. Pressure ratio between softest and loudest sounds… • Frequency differences • Hair motion at absolute threshold… Human psychoacoustical performance

  10. Learning protocol

  11. Perceptual learning • Partially non-specific • Playing tetris improves frequency discrimination • Partially due to passive exposure • But also to some extent requires active task performance

  12. Animal models of auditory plasticity • Classical conditioning • Fear conditioning: associating a sound with a foot shock • Environmental enrichment and relatives • Manipulating the environment can have both beneficial and disruptive effects on the auditory system • Spatial hearing

  13. Nat. Rev. Neurosci. 2004

  14. Fear conditioning…

  15. …changes cortical neurons

  16. Brain Research 2007

  17. Environmental enrichment…

  18. Environmental enrichment…

  19. Environmental enrichment…

  20. Plasticity in auditory enriched environments

  21. Auditory plasticity requires stimuli but not interaction

  22. Just noticeable differences in azimuthat the center, tone stimuli

  23. Interaural Time Differences (ITDs) Interaural Level Differences (ILDs) Binaural Cues for Localising Sounds in Space amplitude time

  24. ITD Interaural Time Difference (ITD) Cues ITDs are powerful cues to sound source direction, but they are ambiguous (“cones of confusion”)

  25. ILD • ITD Binaural disparities in humans

  26. Disambiguating the cone of confusion • Sounds on the median plane (azimuth 0, different elevations) have zero binaural disparities • This is a special case of the cone of confusion • Nevertheless, humans and other animals can determine the elevation of a sound source

  27. Spectral information about space

  28. The barn owl…

  29. Binaural Cues in the Barn Owl Barn owls have highly asymmetric outer ears, with one ear pointing up, the other down. Consequently, at high frequencies, barn owl ILDs vary with elevation, rather than with azimuth (D). Consequently ITD and ILD cues together form a grid specifying azimuth and elevation respectively.

  30. Phase locking at highfrequencies in the barn owl C. Köppl, 1997

  31. Processing of Interaural Time Differences To the Inferior Colliculus Contra- lateral side Sound on the ipsilateral side MSO neuron response Interaural time difference Medial superior olive

  32. Preservation of Time Cues in AVCN • Auditory Nerve Fibers connect to spherical and globular bushy cells in the antero-ventral cochlear nucleus (AVCN) via large, fast and secure synapses known as “endbulbs of Held”. • Phase locking in bushy cells is even more precise than in the afferent nerve fibers. • Bushy cells project to the superior olivary complex. sphericalbushycell endbulbof Held VIII nervefiber

  33. Left MSO The coincidence detection model of Jeffress (1948) is the widely accepted model for low-frequency sound localisation Right Ear Left Ear

  34. Response 0 Interaural Time Difference Right CN Left MSO Left CN

  35. Response 0 Interaural Time Difference Right CN MSO Left CN

  36. 1 ms 1 ms Interaural Phase Sensitivity in the MSO to 1000 Hz Yin and Chan (1988)

  37. Processing of Interaural Level Differences To the Inferior Colliculus Sound on the ipsilateral side Contralateral side LSO neuron response I > C C > I Interaural intensity difference Lateral superior olive

  38. The Calyx of Held • MNTB relay neurons receive their input via very large calyx of Held synapses. • These secure synapses would not be needed if the MNTB only fed into “ILD pathway” in the LSO. • MNTB also provides precisely timed inhibition to MSO.

More Related