Papers by Maria V. Sanchez-Vives
Background. The cerebral cortex is permanently active during both awake and sleep states. This on... more Background. The cerebral cortex is permanently active during both awake and sleep states. This ongoing cortical activity has an impact on synaptic transmission and short-term plasticity. An activity pattern generated by the cortical network is a slow rhythmic activity that alternates up (active) and down (silent) states, a pattern occurring during slow wave sleep, anesthesia and even in vitro. Here we have studied 1) how network activity affects short term synaptic plasticity and, 2) how synaptic transmission varies in up versus down states. Methodology/Principal Findings. Intracellular recordings obtained from cortex in vitro and in vivo were used to record synaptic potentials, while presynaptic activation was achieved either with electrical or natural stimulation. Repetitive activation of layer 4 to layer 2/3 synaptic connections from ferret visual cortex slices displayed synaptic augmentation that was larger and longer lasting in active than in silent slices. Paired-pulse facilitation was also significantly larger in an active network and it persisted for longer intervals (up to 200 ms) than in silent slices. Intracortical synaptic potentials occurring during up states in vitro increased their amplitude while paired-pulse facilitation disappeared. Both intracortical and thalamocortical synaptic potentials were also significantly larger in up than in down states in the cat visual cortex in vivo. These enhanced synaptic potentials did not further facilitate when pairs of stimuli were given, thus paired-pulse facilitation during up states in vivo was virtually absent. Visually induced synaptic responses displayed larger amplitudes when occurring during up versus down states. This was further tested in rat barrel cortex, where a sensory activated synaptic potential was also larger in up states. Conclusions/ Significance. These results imply that synaptic transmission in an active cortical network is more secure and efficient due to larger amplitude of synaptic potentials and lesser short term plasticity.
The ferret dorsal lateral geniculate nucleus (LGNd) contains interneurons within the interlaminar... more The ferret dorsal lateral geniculate nucleus (LGNd) contains interneurons within the interlaminar zones situated between the laminae corresponding to the ipsi-and contralateral eyes. We found that a subset of these neurons exhibits electrophysiological properties similar to those previously reported for perigeniculate (PGN) neurons, including the generation of rhythmic sequences of rebound low-threshold Ca 2ϩ spikes at a frequency of 1-4 Hz after the intracellular injection of a hyperpolarizing current pulse. These "PGN-like" interlaminar interneurons innervated restricted regions of the A-laminae, inhibited thalamocortical cells through GABA A , and perhaps GABA B , receptors, and were excited by axon collaterals from thalamocortical cells. This reciprocal relationship is identical to that formed by PGN cells and allowed the PGN-like interlaminar neurons to participate in the generation of spindle waves and other network oscillations. Pharmacologically, PGN-like interlaminar interneurons were also similar to PGN neurons: both generated a prolonged depolarization in response to the local application of serotonin, 1S,3R-ACPD, and CCK8S, and a rapid depolarization followed by a more prolonged hyperpolarization in response to acetylcholine.
Abstract Although telerehabilitation systems represent one of the most technologically appealing ... more Abstract Although telerehabilitation systems represent one of the most technologically appealing clinical solutions for the immediate future, they still present limitations that prevent their standardization.
Abstract In this study, we recorded single unit activity from rat auditory cortex while the anima... more Abstract In this study, we recorded single unit activity from rat auditory cortex while the animals performed an interval-discrimination task. The animals had to decide whether two auditory stimuli were separated by either 150 or 300 ms, and go to the left or right nose poke accordingly. Spontaneous firing in between auditory responses was compared in the attentive versus non-attentive brain states. We describe the firing rate modulation detected during intervals while there was no auditory stimulation.
Abstract When a rubber hand is placed on a table top in a plausible position as if part of a pers... more Abstract When a rubber hand is placed on a table top in a plausible position as if part of a person's body, and is stroked synchronously with the person's corresponding hidden real hand, an illusion of ownership over the rubber hand can occur (Botvinick and Cohen 1998). A similar result has been found with respect to a virtual hand portrayed in a virtual environment, a virtual hand illusion (Slater et al. 2008). The conditions under which these illusions occur have been the subject of considerable study.
Abstract Short-term synaptic depression (STD) is a form of synaptic plasticity that has a large i... more Abstract Short-term synaptic depression (STD) is a form of synaptic plasticity that has a large impact on network computations. Experimental results suggest that STD is modulated by cortical activity, decreasing with activity in the network and increasing during silent states. Here, we explored different activity-modulation protocols in a biophysical network model for which the model displayed less STD when the network was active than when it was silent, in agreement with experimental results.
Abstract In this paper we discuss the use of virtual environments in the understanding of the rol... more Abstract In this paper we discuss the use of virtual environments in the understanding of the role of body image on consciousness of the self. If we consider presence as a restricted form of consciousness in the realm of virtual environments, assesing presence while modifying a virtual body may allow an insight in the impact that body perception has on consciousness of the self. The possibility of using VE for the diagnosis and treatment of body dysmorphias is also considered.
In a previous paper (Proceedings of the World Congress on Neuroinformatics (2001)) the authors ap... more In a previous paper (Proceedings of the World Congress on Neuroinformatics (2001)) the authors applied the so-called Lempel–Ziv complexity to study neural discharges (spike trains) from an information-theoretical point of view. Along with other results, it is shown there that this concept of complexity allows to characterize the responses of primary visual cortical neurons to both random and periodic stimuli. To this aim we modeled the neurons as information sources and the spike trains as messages generated by them.
We review several applications of Lempel–Ziv complexity to the characterization of neural respons... more We review several applications of Lempel–Ziv complexity to the characterization of neural responses. In particular, Lempel–Ziv complexity allows to estimate the entropy of binned spike trains in an alternative way to the usual method based on the relative frequencies of words, with the definitive advantage of no requiring very long registers. We also use complexity to discriminate neural responses to different kinds of stimuli and to evaluate the number of states of neuronal sources.
The cerebral cortex generates spontaneous activity organized in up and down states (< 1 Hz) while... more The cerebral cortex generates spontaneous activity organized in up and down states (< 1 Hz) while in vitro [1]. This activity is similar to the cortical activity occurring during anesthesia and slow wave sleep [2]. Different studies have found that there is a delicate balance of excitation and inhibition during up states. Here we describe the effect of progressive blockade of inhibition on up states.
Abstract Place cells are located in the hippocampus of the brain and play an important role for s... more Abstract Place cells are located in the hippocampus of the brain and play an important role for spatial navigation. In this study neural spike activity of freely moving rats along with the position of the rats was acquired. The study was performed to investigate if position reconstruction is possible if the rat is freely moving in open arenas with and without barriers of different rectangular sizes based on neural recordings.
Recent studies have shown that a fake body part can be incorporated into human body representatio... more Recent studies have shown that a fake body part can be incorporated into human body representation through synchronous multisensory stimulation on the fake and corresponding real body part–the most famous example being the Rubber Hand Illusion. However, the extent to which gross asymmetries in the fake body can be assimilated remains unknown. Participants experienced, through a head-tracked stereo head-mounted display a virtual body coincident with their real body.
ABSTRACT The “rubber hand illusion” allows the study of the mechanisms that support multisensory ... more ABSTRACT The “rubber hand illusion” allows the study of the mechanisms that support multisensory integration and self-representation of the own body image. In previous studies, we have shown that the incorporation of virtual parts to our body image by means of a correct multisensory stimulation is a versatile tool for the study of the self-body image generation.
In recent years, there has been in easing interest in determining the statistics of firing in loc... more In recent years, there has been in easing interest in determining the statistics of firing in local networks that generate self-sustained activity, and its mechanistics bstrate. Two phenomena thought to be generated by reverberation in the local recurrent circuitry are persistent activity underlying working memory and slow oscillatory activity during slow-wave sleep or anaesthesia.
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Consider the set of waveforms of distances between rat and robot for each participant and trial (... more Consider the set of waveforms of distances between rat and robot for each participant and trial (for example, as shown in Figure 7 for one participant and trial). Of particular interest is the proportion of time (that is the proportion of samples) where the distance between rat and robot fell below a threshold, indicating a close approach, and whether this differed between the conditions of rat (trial 1) or supposed human opponent (trial 2).
ABSTRACT It is well known that the theta band (4-12 Hz) is a brain rhythm associated to the self-... more ABSTRACT It is well known that the theta band (4-12 Hz) is a brain rhythm associated to the self-movement of the animal [1] as well as to several cognitive functions [2]. The aim of this study has been to determine the possible modulation of this rhythm in relation to dynamic cues. With that purpose we employed an e-puck robot as a dynamic cue in contrast to the few precedent studies where dynamic stimuli were presented in a screen [4].
ABSTRACT In the present study our aim was to spatially characterize the electrocardiogram (ECG) d... more ABSTRACT In the present study our aim was to spatially characterize the electrocardiogram (ECG) during the free navigation of rats in an open space via 2D maps. The development of the necessary tools (hardware, analytical) to carry out this mapping should allow us in the future to obtain a physiological correlate of different behaviours. With that purpose, we recorded the ECG from Lister Hooded rats with three superficial electrodes while the rat was being tracked during free navigation in an 80x80 open field.
Page 1. MUTUAL INFORMATION AND REDUNDANCY IN CORTICAL SPIKE TRAINS DURING THE AWAKE STATES J Szcz... more Page 1. MUTUAL INFORMATION AND REDUNDANCY IN CORTICAL SPIKE TRAINS DURING THE AWAKE STATES J Szczepanski1, MM Arnold2, E Wajnryb1, MV Sanchez-Vives2 1 Institute of Fundamental Technological Research,Polish Academy of Sciences, Warsaw, Poland 2 Instituto de Neurociencias de Alicante, Universidad Miguel Hernandez-CSIC, San Juan de Alicante,Spain.
Immersive virtual reality (IVR) typically generates the illusion in participants that they are in... more Immersive virtual reality (IVR) typically generates the illusion in participants that they are in the displayed virtual scene where they can experience and interact in events as if they were really happening. Teleoperator (TO) systems place people at a remote physical destination embodied as a robotic device, and where typically participants have the sensation of being at the destination, with the ability to interact with entities there. In this paper, we show how to combine IVR and TO to allow a new class of application.
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Papers by Maria V. Sanchez-Vives