Showing papers by "Rodrigo Quian Quiroga published in 2012"

Concept cells: the building blocks of declarative memory functions

Abstract: Intracranial recordings in subjects suffering from intractable epilepsy — made during their evaluation for an eventual surgical removal of the epileptic focus — have allowed the extraordinary opportunity to study the firing of multiple single neurons in awake and behaving human subjects. These studies have shown that neurons in the human medial temporal lobe respond in a remarkably selective and abstract manner to particular persons or objects, such as Jennifer Aniston, Luke Skywalker or the Tower of Pisa. These neurons have been named 'Jennifer Aniston neurons' or, more recently, 'concept cells'. I argue that the sparse, explicit and abstract representation of these neurons is crucial for memory functions, such as the creation of associations and the transition between related concepts that leads to episodic memories and the flow of consciousness.

Imaging Brain Function With EEG: Advanced Temporal and Spatial Analysis of Electroencephalographic Signals

Abstract: Electroencephalography.- Frequency analysis.- Time-frequency analysis.- Wavelets.- Single-trial evoked potentials: Wavelet denoising.- Basic concepts for spatial analysis.- Image sampling based on spatiotemporal spectral analysis.- Allocortical ECoG images formed by learning.- Neocortical ECoG images formed by learning.- ECoG and EEG images in higher cognition.- Synthesis.

Fixation-related potentials in visual search: a combined EEG and eye tracking study.

Abstract: We report a study of concurrent eye movements and electroencephalographic (EEG) recordings while subjects freely explored a search array looking for hidden targets. We describe a sequence of fixation-event related potentials (fERPs) that unfolds during ∼ 400 ms following each fixation. This sequence highly resembles the event-related responses in a replay experiment, in which subjects kept fixation while a sequence of images occurred around the fovea simulating the spatial and temporal patterns during the free viewing experiment. Similar responses were also observed in a second control experiment where the appearance of stimuli was controlled by the experimenters and presented at the center of the screen. We also observed a relatively early component (∼150 ms) that distinguished between targets and distractors only in the freeviewing condition. We present a novel approach to match the critical properties of two conditions (targets/distractors), which can be readily adapted to other paradigms to investigate EEG components during free eye-movements.

Borges and Memory: Encounters with the Human Brain

Abstract: Imagine the astonishment felt by neuroscientist Rodrigo Quian Quiroga when he found a fantastically precise interpretation of his research findings in a story written by the great Argentinian fabulist Jorge Luis Borges fifty years earlier. Quian Quiroga studies the workings of the brain -- in particular how memory works -- one of the most complex and elusive mysteries of science. He and his fellow neuroscientists have at their disposal sophisticated imaging equipment and access to information not available just twenty years ago. And yet Borges seemed to have imagined the gist of Quian Quiroga's discoveries decades before he made them. The title character of Borges's "Funes the Memorious" remembers everything in excruciatingly particular detail but is unable to grasp abstract ideas. Quian Quiroga found neurons in the human brain that respond to abstract concepts but ignore particular details, and, spurred by the way Borges imagined the consequences of remembering every detail but being incapable of abstraction, he began a search for the origins of Funes. Borges's widow, Maria Kodama, gave him access to her husband's personal library, and Borges's books led Quian Quiroga to reread earlier thinkers in philosophy and psychology. He found that just as Borges had perhaps dreamed the results of Quian Quiroga's discoveries, other thinkers -- William James, Gustav Spiller, John Stuart Mill -- had perhaps also dreamed a story like "Funes." With Borges and Memory, Quian Quiroga has given us a fascinating and accessible story about the workings of the brain that the great creator of Funes would appreciate.

Iterative Feedback Tuning for the joint controllers of a 7-DOF Whole Arm Manipulator

Abstract: This paper presents the tuning of the Proportional Integral Derivative (PID) controllers of the joints of a 7 degrees of freedom (DOF) manipulator with friction using the Iterative Feedback Tuning method In the procedure both experimental data and model simulations are used and two different approaches to the approximation of the Hessian are tested Friction identification is also performed for the implementation of friction compensation over the pre-configured joint Proportional Derivative (PD) control of the manipulator The responses of the system when using joint PID control and joint PD control with gravity and friction compensation are compared

Dynamic Model of a 7-DOF Whole Arm Manipulator and Validation from Experimental Data

Abstract: Abstract: The present paper describes the design of the dynamic model of a 7 degrees of freedom whole arm manipulator implemented in SimMechanics. The friction phenomena of the manipulator is identified, represented through a fitted model and included in the system model with the aim of increment the accuracy of the model with respect to the real system. The characteristics of the model make it suitable to test and design control strategies for motion and friction compensation in MATLAB/Simulink.