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Fotos de la obra teatral representada por "Centro Dramático Galego" en el año 2002
Interaction among primary afferents, corticofugal fibers, and intrinsic elements
allows for sensorimotor integration at the dorsal column nuclei. The interneurons
permit the spatial localization, the recurrent collaterals synchronize the
activity of projecting cells with overlapping receptive fields, and the corticofugal
fibers induce a central zone of activity surrounded by a peripheral
zone of inhibition.
The spontaneous and paroxysmal cerebral cortical synchronized
activity was used as reference to study the cortical
impact exerted on subcortical neurons. The sensorimotor
cortical synchronized activity spread down to subcortical
structures receiving direct cortical input, including neuronal
populations that originate descending rubrospinal, tectospinal
and reticulospinal motor axons, and to a somatosensory
relay station, the cuneate nucleus. Lesion of the pyramidal
tract abolished the cortically induced synchronization of the
activity of contralateral cuneate nucleus neurons.
This work aimed to study whether the sensorimotor cerebral cortex spreads down its rhythmic patterns of activity to the
dorsal column nuclei. Extracellular and intracellular recordings were obtained from the cuneate nucleus of chloralose-anesthetized
cats. From a total of 140 neurons tested (106 cuneolemniscal), 72 showed spontaneous rhythmic activity within the slow (,1 Hz), d
(1–4 Hz), spindle (5–15 Hz) and higher frequencies, with seven cells having the d rhythm coupled to slow oscillations. The spindle
activity recorded in the cuneate was tightly coupled to the thalamo-cortico-thalamic spindle rhythmicity. Bilateral or contralateral
removal of the frontoparietal cortex abolished the cuneate slow and spindle oscillations. Oscillatory paroxysmal activity generated
by fast electrical stimulation (50–100 Hz/1–2 s) of the sensorim...
Whole-cell recordings were obtained from cuneate neurons in anesthetized, paralysed cats.
Stimulation of the contralateral medial lemniscus permitted us to separate projection cells from presumed
interneurons. Pericruciate motor cortex electrical stimulation inhibited postsynaptically all the projection
cells (n=57) and excited all the presumed interneurons (n=29). The cuneothalamic cells showed an
oscillatory and a tonic mode of activity. Membrane depolarization and primary afferent stimulation
converted the oscillatory to the tonic mode. Hyperpolarizing current steps applied to projection neurons
induced a depolarizing sag and bursts of conventional spikes in current-clamp records. This indicates the
probable existence of low-threshold and hyperpolarization-activated inward currents. Also, the hyperpolarization
induced on pro...
Intracellular recordings were obtained from cuneate neurons of chloralose-anesthetized, paralysed cats to study the
synaptic responses induced by electrical stimulation of the contralateral medial lemniscus. From a total of 178 cells sampled, 109
were antidromically fired from the medial lemniscus, 82 of which showed spontaneous bursting activity. In contrast, the great
majority (58/69) of the non-lemniscal neurons presented spontaneous single spike activity. Medial lemniscus stimulation induced
recurrent excitation and inhibition on cuneolemniscal and non-lemniscal cells. Some non-lemniscal neurons were activated by
somatosensory cortex and inhibited by motor cortex stimulation. Some other non-lemniscal cells that did not respond to medial
lemniscus stimulation in control conditions were transcortically affected by stimulating t...
Cortical computations critically involve local neuronal circuits. The computations are often invariant across a cortical area yet are carried out by networks that can vary widely within an area according to its functional architecture. Here we demostrate a mechanism by which orientation selectivity is computer invariantly in cat primary visual cortex across an orientation preference map that provides a wide diversity of local circuits. Visually evoked excitatory and inhibitory synaptic conductances are balanced exquisitely in cortical neurons and thus keep the spike response sharply tuned at all map locations. This functional balance derives from spatially isotropic local connectivity of both excitatory and inhibitory cells. Modeling results demostrate that such covariation is a signature of recurrent rather than purely feed-forward pr...
1 lám. (cartel) col. ;68 x 48 cm
1 lám. (cartel) col. ;29 x 21 cm
