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Actividad neuronal en el sistema auditivo: potenciales provocados y unidades

Actividad neuronal en el sistema auditivo: potenciales provocados y unidades. Prof. Ricardo A. Velluti MD, DSc Neuro-Otología Experimental y Sueño Otorrinolaringología (ORL), Hospital de Clínicas

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Actividad neuronal en el sistema auditivo: potenciales provocados y unidades

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  1. Actividad neuronal en el sistema auditivo: potenciales provocados y unidades Prof. Ricardo A. VellutiMD, DSc Neuro-Otología Experimental y Sueño Otorrinolaringología (ORL), Hospital de Clínicas Programa de Desarrollo de Ciencias Básicas (Pedeciba) y ANII. Universidad de la República. Montevideo, Uruguay ricardo.velluti@gmail.com

  2. Shannon, 1948; 1949Informationtheorymakessenseonlyifthe “receiver” of signalsknowsthe full range of possibilities. (Informationtransmitted in Morse code can beusefullonlyifthe “receiver” knowsthatcode)

  3. Information is carried out by :1. Amplitude and waveform of evoked activity 2. Neuronal firing rate (how the brain can measure “the firing rate”? 3. A response to a transient stimulus my be carried out by the first spike or two 4. Temporal distribution of the neuronal firing, pattern of discharge 5. Relationships with other brain rhythms

  4. Information Processing Cell Assemblies/Neuronal Networks

  5. La actividad neuronal puede expresarse a través de diversas tecnologías • 1. Registro de la actividad de campo cercano: - Potenciales Provocados - Potenciales Provocados de campo lejano • 2. Descargas neuronales: - con registros intracelulares - con registros extracelulares • 3. Magnetoencefalografía (MEG) Actividad provocada • 4. Resonancia Magnética Funcional (fMRI) • 5. Tomografía por Emisión de Positrones (PET)

  6. Averaged Human Auditory Evoked Potentials • Wakefulness • B. Sleep El sistema Auditivo Funciona 24 horas. García-Austt et al. 1961

  7. AuditorynervecompoundactionpotentialsHABITUATION Buño, Velluti, Handler, García-Austt, 1966

  8. Vía Auditiva Ascendente

  9. Vía Auditiva Descendente (Eferente)

  10. Cochlearnucleus post-stimulus time histograms

  11. Histogramas Post Estímulos

  12. Cortical Auditory Evoked Potentials in Rat Hall and Borbély, 1970

  13. Local-field and Far-fieldauditoryevokedpotentials Velluti 2008 Velluti, Galambos 1967

  14. Guerit 1993

  15. Tumor de Fosa Posterior derecha, Bulbo y Protuberancia Guerit, 1993

  16. Potenciales Provocados de Tronco CerebralMuerte cerebral Chiappa 1997

  17. …butthe brain is also able to be in different states – called asleep, awake, or dreaming – involving changes like receiving sensory information that are not necessarily structural, rather functional. Thus, it is still possible that learning mechanisms are ascribed to the dynamic, emergent properties of neural ensembles. We have more neurons than proteins, and perhaps the former can carry out a good job without the need of any structural modifications of their already sophisticated connectivity. Why, then, do most neuroscientists prefer to lean on neural plasticity rather than on neural functional states? J.M. Delgado García, 2008 In: Velluti, 2008 The Auditory System in Sleep, pp 135-136.

  18. A HUB neuron:In adults tends to inhibit the activity of the recipient neuron, though in developing networks, GABA has excitatory effects.  They also have very extensive axonal arborisations – they project over larger distances and make a greater number of and stronger synaptic connections than non-hub neurons. Finally, they are also more responsive to inputs and quicker to fire action potentials themselves, placing them in a position to orchestrate the responses of the entire network. Though hub neurons have so far only been observed in the hippocampus it seems almost certain that they will also be found in the cortex, where their effects may be fundamental for the information processing capabilities of the brain.  Bonifazi, P., Goldin, M., Picardo, M., Jorquera, I., Cattani, A., Bianconi, G., Represa, A., Ben-Ari, Y., &Cossart, R. (2009). GABAergic Hub Neurons Orchestrate Synchrony in Developing Hippocampal Networks Science, 326 (5958), 1419-1424 DOI

  19. AuditoryCortexfMRI(Portas et al. 2005)

  20. Magnetoencephalography Cortical Auditory Evoked Activity Kakigi et al. 2003

  21. Redes Neuronales, Sueño y Audición Getting 1989 MAGNETOENCEPHALOGRAPHIC EVOKED ACTIVITY Kakigi et al. SleepMed. (2003)

  22. Pre-Optic Region Unit Cortical auditoryunits McGinty 2005 Peña et al. 1999; Velluti, 2005

  23. Events - related potentials to words Bastuji and García-Larrea, 2005

  24. Wave P300 Wakefulness Sleep stages Bastuji, Garcia-Larrea 2005

  25. “Mismatch Negativity (MMN)” MMN is a negative potential appearing between 100 and 200 ms as a consequence of any variation in a repetitive stream of stimuli. Its generators are in the superior temporal plane of the auditory cortex (review, Alho et al., 1995) with the addition of a frontal component (Giard et al., 1990).

  26. Extracellular recording system during Wakefulness and Sleep Guinea pig partially restrained ready for recording

  27. Auditory Cortical (A1) Neuron Velluti, Peña, Pedemonte, 2000

  28. Cortical influenceson Inferior ColliculusAuditoryNeuron Goldstein-Daruech, Pedemonte, Inderkum, Velluti Hearing Res. 2002

  29. Normal and Inverted Guinea Pig Natural CallStimuli Auditory Cortical (A1) Recording Pérez-Perera, Velluti. Actas de Fisiología 2001

  30. Actividad Neuronal Unitaria Intracelular Inferior ColliculusAuditoryNeuron

  31. FunctionalMagneticResonanceImaging (fMRI) • When elements as the Hydrogen is exposed to a strong static magnetic field, the nuclei develop a net alignement in the direction of the applied field • A brief pulse of radio waves provide energy then the nuclei emit radio waves • The resonating nuclei thus became radio waves transmitters • The frequency of the radio waves is different in different chemical or physical environment

  32. Positron Emission Tomography (PET) Imaging of Brain Activity • A radioactivesolutionisintroducedintothebloodstream • Theradioactivesubstanceemitpositrons (electronspositivelycharged) producingphotons of light • Neuronsnormally use glucose in theirmetabolism. The 2-deoxyglucose istaken and itsamountisproportionaltotheiracyivity • Thus, thenumber of positronemissionsindicatetheneuron´slevel of activity • Limitations: spatialresolutionisonly 5-10 mm; takesfrom 1 tomany minutes toobtain; shows theactivity of manythousands of neurons

  33. Phrenology(Gall 1792) • Phrenology is based on the concept that the brain is the organ of the mind, and that certain brain areas have localized, specific functions or modules • 2.Phrenologists believed that the mind has a set of different mental faculties, with each particular faculty represented in a different area of the brain. • …so that a person's capacity for a given personality trait could be determined simply by measuring the area of the skull that overlies the corresponding area of the brain.

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