Universidade da Coruña. UDCDspace
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UDCDspace é o repositorio dixital da Universidade da Coruña, un sistema que proporciona de xeito estable e seguro a preservación de documentos dixitais produto da actividade científica e institucional da UDC, e facilita a súa accesibilidade en Internet.
Mostrando recursos 1 - 16 de 16
1.
Invariant computations in local cortical networks with balanced excitation and inhibition - Mariño Alfonso, Jorge; Schummers, James; Lyon, David C.; Schwabe, Lars; Beck, Oliver; Wiesing, Peter; Obermayer, Klaus; Sur, Mriganka
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...
2.
A cortico-subcortical synchronization in the chloralose anesthetized cat - Mariño Alfonso, Jorge; Aguilar Fernández, Jaime; Canedo Lamas, Antonio
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.
3.
Tonic and bursting activity in the cuneate nucleus of the chloralose anesthetized cat - Canedo Lamas, Antonio; Martínez Otero, Luis Miguel; Mariño Alfonso, Jorge
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 projection cells by...
4.
Modelling the circuitry of the cuneate nucleus - Sánchez Vila, Eduardo; Barro Ameneiro, Senén; Mariño Alfonso, Jorge; Canedo Lamas, Antonio; Vázquez Muñíz, Pablo José
Experimental data recorded in cat "in vivo" offer a new picture of the cuneate nucleus. Clasically definied as a simple relay station, the cuneate nucleus is currently seen as a fundamental stage in somatosensory information processing. Intracellular and extracellular recordings have revealed a complex circuitry estabished by cuneothalamic cells, interneurons and afferent fibers from the sensorimotor cortex. As a result of electrophysiological work, some circuits have been hypothesized in order to explain the data. In this paper we present a computational model designed and developed in order to test the validity of the proposed circuit in [15]. The results of...
5.
Coupled slow and delta oscillations between cuneothalamic and
thalamocortical neurons in the chloralose anesthetized cat - Mariño Alfonso, Jorge; Martínez Otero, Luis Miguel; Canedo Lamas, Antonio
Simultaneous recordings were obtained from cuneothalamic (extracellular) and thalamocortical (intracellular) cells in chloralose
anesthetized cats. It was found that cuneothalamic neurons present slow rhythmicity (0.11 Hz) tightly coupled to slow oscillations of
thalamocortical neurons. This coupling was not due to a direct synaptic linkage but rather produced by other (s) structure (s) probably
the cortex. Furthermore, the cuneothalamic neurons also showed delta rhythms (14 Hz) coherently oscillating with the delta rhythms of
thalamocortical cells which suggests that these rhythms are more widespread than previously thought, and may be a general phenomenon
characterizing quiet sleep in multiple structures.
6.
A sensorimotor integration at the dorsal column nuclei - Mariño Alfonso, Jorge; Martínez Otero, Luis Miguel; Canedo Lamas, Antonio
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.
7.
Sensorimotor cortical influences on cuneate nucleus rhythmic activity in the anesthetized cat - Mariño Alfonso, Jorge; Canedo Lamas, Antonio; Aguilar Fernández, Jaime
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
(14 Hz), spindle (515 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...
8.
Lemniscal recurrent and transcortical influences on cuneate neurons - Canedo Lamas, Antonio; Mariño Alfonso, Jorge; Aguilar Fernández, Jaime
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...
9.
A realistic computational model of the local circuitry of the cuneate nucleus - Sánchez Vila, Eduardo; Barro Ameneiro, Senén; Mariño Alfonso, Jorge; Canedo Lamas, Antonio
Intracellular recordings obtained under cutaneous and lemniscal
stimulation show that the afferent fibers can establish excitatory
and inhibitory synaptic connections with cuneothalamic neurons [5]. In
addition, distinct types of recurrent collaterals with the capability of either
exciting or inhibiting both cuneothalamic neurons and interneurons
were also discovered [6]. With these data we have generated hypothesis
about which circuits are implicated and also developed realistic computational
models to test the hypothesis and study the cuneate properties
[17,18]. The results show that the cuneate could perform spatial and
temporal filtering and therefore detect dynamic edges.
10.
La corteza cerebral modula la transmisión cutánea
a través de los núcleos de los cordones posteriores - Mariño Alfonso, Jorge; Aguilar Fernández, Jaime; Soto, C.; Canedo Lamas, Antonio
The mechanisms used by the cerebral cortex to modulate the cutaneous information at prethalamic level
have been scarcely studied. This article reviews experimental evidence leading to a better understanding of this issue at the level
of the cuneate nucleus (Burdach nucleus). Development. The primary afferents and the corticocuneate fibers make synaptic
contact with cuneothalamic neurons and with inhibitory interneurons in the middle cuneate nucleus. By stimulating the skin at
different places while recording the cuneothalamic intracellular activity in anaesthetized animals with the cortex intact, with
the cortex pharmacologically inactivated, or in absence of a cerebral cortex it was possible to ascertain the functional role of
the...
11.
Synaptic integration by V1 neurons depends
on location within the orientation map - Schummers, James; Mariño Alfonso, Jorge; Sur, Mriganka
Neurons in the primary visual cortex (V1) are organized
into an orientation map consisting of orientation domains arranged radially around pinwheel centers at
which the representations of all orientations converge. We have combined optical imaging of intrinsic signals
with intracellular recordings to estimate the subthreshold inputs and spike outputs of neurons located
near pinwheel centers or in orientation domains. We find that neurons near pinwheel centers have subthreshold
responses to all stimulus orientations but spike responses to only a narrow range of orientations.
Across the map, the selectivity of inputs covaries with the selectivity of orientations in the local cortical network,
while the selectivity of spike outputs...
12.
A computational model of cuneothalamic projection
neurons - Sánchez Vila, Eduardo; Barro Ameneiro, Senén; Mariño Alfonso, Jorge; Canedo Lamas, Antonio
The dorsal column nuclei, cuneatus and gracilis, play a fundamental role
in the processing and integration of somesthetic ascending information.
Intracellular and patch-clamp recordings obtained in cat in vivo have shown that
cuneothalamic projection neurons present two modes of activity: oscillatory
and tonic (Canedo et al 1998 Neuroscience 84 60317). The former is the basis
of generating, in sleep and anaesthetized states, slow, delta and spindle rhythms
under the control of the cerebral cortex (Marino et al 2000 Neuroscience 95
65773). The latter is needed, during wakefulness, to process somesthetic
information in real time. To study this behaviour we have developed the
first realistic computational model of the cuneothalamic...
13.
Nitric oxide-mediated cortical activation: a diffuse
wake-up system - Mariño Alfonso, Jorge; Cudeiro Mazaira, Javier
Nitric oxide (NO) has been implicated in some of the central pathways engaged in the regulation of the sleepwake cycle. The existence of
nitric oxide synthase (NOS) in the cholinergic basal forebrain (BF) cells projecting to the cortex suggests a role for NO in the activation
induced by the BF during arousal. We tested, in the anesthetized cat, the hypothesis that inhibition of NOS would decrease the ability of
BFcholinergic fibers to induce cortical activation. In control conditions,BFstimulation evoked an awake-likeEEGpattern (i.e., a decrease
in the low-frequency high-amplitude oscillatory activity and an increase in the high-frequencylow-amplitude activity). After blocking
NOS activity, the capacity of BF...
14.
Combinación de nuevas técnicas electrofisiológicas y de imagen
en el estudio de la función de la corteza visual primaria - Mariño Alfonso, Jorge; Schummers, James; Sur, Mriganka
This work summarizes current research focused on explaining orientation selectivity of primary visual
cortex (V1), and describes the electrophysiological and imaging techniques than are being used. Development. The study of
orientation selectivity in V1 is key to understanding the cortical mechanisms implicated in the processing of sensory information,
but this enterprise has proved more challenging than previously thought and there is no consensus about the best model to explain
V1 neurons activity. Ongoing research is focused on determining the importance of the different inputs that a cortical cell receives
(thalamic and lateral cortical inputs), and their link to cortical architecture. To achieve that, current research...
15.
Sleep and wakefulness in the cuneate nucleus: a
computational study - Sánchez Vila, Eduardo; Barro Ameneiro, Senén; Mariño Alfonso, Jorge; Canedo Lamas, Antonio
We present a computational study about the influence of the
sensorimotor cortex on the processing of the cuneate nucleus during sleep
as well as wakefulness. Realistic computational models were developed
supported by experimental data obtained from intact-brain preparations
in cat. Furthermore, a physiologically plausible circuit is proposed and
predictions under both different cortical stimulation and synaptic configurations are suggested. The computer simulations show that the CN
circuitry (1) under sleep conditions can block the transmission of afferent
sensory information, and (2) under awaking conditions can perform
operations such as filtering and facilitation.
16.
Receptive field structure of burst and tonic firing in feline lateral geniculate nucleus - Rivadulla Fernández, Casto; Martínez Otero, Luis Miguel; Grieve, Kenneth; Cudeiro Mazaira, Javier
Demostración da plasticidade nos campos receptores nos primeirops estadios do procesamento sensorial. Observanse cambios dependendo do estado (desperto-dormido) do animal. Estes cambios poden ter implicacións no funcionamento do sistema visual que se describen no artigo.
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