[Todos] Recordatorio Simposio Circuitos Neuronales Lunes 21 Nov-Fund Leloir

[Paula Felman]

>Simposio sobre Circuitos Neuronales
>21 de Noviembre 2011 de 9:30-13 hs
>Auditorio Fundación Instituto Leloir
>Av. Patricias Argentinas 435
>
>9:30 Gabriel Mindlin, Departamento de Física, FCEN, UBA
>Neurons tuning to a synthetic birdsong
>
>10:30 Juan Goutman, INGEBI, CONICETFacilitation and depression determine
>timing of synaptic responses atthe Inner Hair Cell ribbon synapse
>
>11:00 Coffee Break
>
>11:30 Francisco Urbano, IFIBYNE, UBA-CONICET
>T-type calcium channels play a key role in GABAergic thalamocortical
>alterations mediated by cocaine administration
>
>12:00 Massimo Scanziani, Section of Neurobiology, University of California
>San Diego, USA
>Addressing cortical processing by perturbing the activity of individual
>layers
>
>ABSTRACS
>
>Gabriel Mindlin
>Neurons tuning to a synthetic birdsong
>
>Abstract: Song birds, like humans, use learned signals to communicate.
>These are acquired from tutors during a specific time window by a process
>that includes vocal imitation. It is natural then to choose birdsong as a
>suitable animal model for the study of learned complex behavior, and it is
>also reasonable that much of the study of vocal behavior has focused on
>its neural control. Yet, behavior emerges from the interaction between a
>nervous system, a peripheral set of devices and environment, and therefore
>it is pertinent to study the interplay between central mechanisms of motor
>control and the peripheral systems. These interactions are particularly
>important in birdsong, where neural instructions drive a highly nonlinear
>physical system. On the other hand, are the simplifications usual in
>physics and nonlinear dynamics capable of leading towards biologically
>pertinent synthetic outputs? In order to address this issue, we compare
>the neural responses of a bird to both synthetic and natural songs.
>Neurons in the birdsong system exhibit strong selective responses to
>acoustic broadcast of the bird's own song (BOS), exhibiting stronger
>responses to BOS than tones, noises, and even conspecific songs or
>slightly modified BOS. These responses have been intensively studied as a
>window into, and part of the mechanism of, sensorimotor vocal learning.
>BOS responses are strongest in sleeping birds, emerge early in
>sensorimotor learning, and their prevalence may vary with species-specific
>patterns of learning. Despite their potential importance, the extreme
>response selectivity of song system neurons have made them difficult to
>study with traditional sensory physiological approaches. I will present a
>line of work in which a low dimensional model for zebra finch song
>production was used to generate synthetic outputs. The model includes a
>description of the sound source and vocal tract where some mathematical
>parameters can be linked to physiological properties observed during
>singing. We propose the hypothesis that changes in parameters in the model
>correspond to changes in motor control parameters birds actually use to
>control song output. To date we have seen that complete models elicit
>neuronal responses in the HVC (a sensorimotor nucleus) strikingly similar
>to BOS responses, eliciting the same phasic-tonic features and somewhat
>lower magnitude of response. Progressively including the oropharyngeal
>cavity into the model, by changing its dissipation, allowing it to
>progressively include its filtering influence into the sound, or
>increasing the intrinsic noise in the activity of the syringeal muscles
>results in systematic increase of response magnitude but not a change in
>phasic/tonic activity patterns. These results demonstrate that a low
>dimensional model representing an approximation of peripheral mechanics is
>sufficient to capture behaviorally relevant features of song.
>This work has been done in collaboration with Ana Amador, Dan Margoliash
>and Yonatan Sanz Perl.
>
>Juan Goutman
>Facilitation and depression determine timing of synaptic responses at the
>Inner Hair Cell ribbon synapse
>
>Abstract: The auditory system analyzes time and intensity to code location
>of a sound source. These parameters are preferentially processed in
>different brainstem nuclei and so must be independently detected in the
>periphery and transmitted to the brain. In the first synapse of the
>hearing pathway, between inner hair cells and boutons of auditory nerve
>neurons, analog signals are converted into a pattern of action potentials.
>By performing simultaneous pre- and post-synaptic recordings at this
>synapse, we investigated how the temporal structure and intensity of a
>stimulus are encoded. Cyclic stimuli such as trains of depolarizations to
>different potentials, were presynaptically applied, trying to mimic
>acoustic stimuli of different intensities. Synaptic responses elicited by
>these trains presented constant first latencies (or phase) within each
>cycle, even comparing different levels of depolarizations. In contrast, in
>single depolarizations, synaptic responses proved to have a
>voltage-(Ca2+-) dependence on timing. Interestingly, short-term
>facilitation partially compensated for changes in latencies (and also
>reducing jitter) in these single pulses. We also showed that synaptic
>depression delayed release, offsetting any remaining differences in timing
>caused by different synaptic drives. Finally, we propose that an
>equilibrium would be established between each stimuli level and the degree
>of synaptic depression, determining that in trains of stimuli the average
>phase was conserved.
>
>Francisco Urbano
>T-type calcium channels play a key role in GABAergic thalamocortical
>alterations mediated by cocaine administration
>
>Abstract: Acute cocaine exposure has been shown to induce locomotor
>activity and GABAergic thalamic alterations. After systemic (i.p.)
>pre-administration of either T-type calcium channel blockers mibefradil
>(20 mg/kg) or 2-octanol (0.5 mg/kg and 0.07 mg/kg) significantly prevented
>cocaine-induced hyperlocomotor activity in vivo as well as GABAergic mini
>frequencies onto VB neurons. Thus, strongly suggesting that T-type calcium
>channels play a key role in cocaine-mediated GABAergic thalamocortical
>alterations, and further propose T-type channel blockers as potential
>targets for future pharmacological strategies aimed at treating cocaine's
>deleterious effects on physiology and behavior
>
>Massimo Scanziani
>Addressing cortical processing by perturbing the activity of individual
>layers
>
>Abstract: The cortex of the brain is responsible for sensations, thoughts,
>and other cognitive functions. It is composed of six layers of
>microcircuits stacked on top of each other but we know little about the
>function of these layers in the processing of sensory information. Using a
>combination of optogenetic approaches and transgenic mouse-lines my lab is
>systematically addressing how each of these layers contributes to the
>response of the cortex to sensory stimuli. I will present data showing
>that layer 6 in visual cortex performs a fundamental computation known as
>gain control. Through gain control layer 6 can act as a volume knob to
>increase or decrease sensory evoked neuronal activity in all other layers.
>Because layer 6 receives convergent inputs from several brain areas, it
>may represent a node through which these various areas regulate the
>earliest steps of cortical visual processing.
>
>
>--
>Contacto: Antonia Marin Burgin, PhD
>Fundacion Instituto Leloir
>Av. Patricias Argentinas 435
>Buenos Aires 1405
>Argentina
>Phone (5411) 5238 7500 int 2307
>Fax (5411) 5238 7501
>
>
>
>Francisco J. Urbano, PhD.
>IFIBYNE-CONICET
>Intendente Güiraldes 2160
>Facultad Ciencias Exactas
>Pabellon 2- Piso 2
>Ciudad Universitaria
>(C1428EGA) Buenos Aires
>ARGENTINA
>Phone: (+54)-11-4576 3368
>Fax: (+54)-11-4576 3321
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