Results 1 - 10
of
19
Dynamical changes and temporal precision of synchronised spiking activity in monkey motor cortex during movement preparation
- Journal of Physiology
, 2000
"... Abstract -Movement preparation is considered to be based on central processes which are responsible for improving motor performance. For instance, it has been shown that motor cortical neurones change their activity selectively in relation to prior information about movement parameters. However, it ..."
Abstract
-
Cited by 23 (6 self)
- Add to MetaCart
(Show Context)
Abstract -Movement preparation is considered to be based on central processes which are responsible for improving motor performance. For instance, it has been shown that motor cortical neurones change their activity selectively in relation to prior information about movement parameters. However, it is not clear how groups of neurones dynamically organize their activity to cope with computational demands. The aim of the study was to compare the firing rate of multiple simultaneously recorded neurones with the interaction between them by describing not only the frequency of occurrence of epochs of significant synchronization, but also its modulation in time and its changes in temporal precision during an instructed delay. Multiple single-neurone activity was thus recorded in monkey motor cortex during the performance of two different delayed multi-directional pointing tasks. In order to detect conspicuous spike coincidences in simultaneously recorded spike trains by tolerating temporal jitter ranging from 0 to 20 ms and to calculate their statistical significance, a modified method of the 'Unitary Events' analysis was used. Two main results were obtained. First, simultaneously recorded neurones synchronize their spiking activity in a highly dynamic way. Synchronization becomes significant only during short periods (about 100 to 200 ms). Several such periods occurred during a behavioural trial more or less regularly. Second, in many pairs of neurones, the temporal precision of synchronous activity was highest at the end of the preparatory period. As a matter of fact, at the beginning of this period, after the presentation of the preparatory signal, neurones significantly synchronize their spiking activity, but with low temporal precision. As time advances, significant synchronization becomes more precise. Data indicate that not only the discharge rate is involved in preparatory processes, but also temporal aspects of neuronal activity as expressed in the precise synchronization of individual action potentials. © 2000 É ditions scientifiques et médicales Elsevier SAS monkey / motor cortex / multiple single-neurone recordings / precise spike coincidences / cell assemblies
Multiple movement representations in the human brain: an event-related fMRI study
- J. Cogn. Neurosci
, 2002
"... & Neurovascular correlates of response preparation have been investigated in human neuroimaging studies. However, conventional neuroimaging cannot distinguish, within the same trial, between areas involved in response selection and/ or response execution and areas specifically involved in respon ..."
Abstract
-
Cited by 21 (5 self)
- Add to MetaCart
& Neurovascular correlates of response preparation have been investigated in human neuroimaging studies. However, conventional neuroimaging cannot distinguish, within the same trial, between areas involved in response selection and/ or response execution and areas specifically involved in response preparation. The specific contribution of parietal and frontal areas to motor preparation has been explored in electrophysiological studies in monkey. However, the asso-ciative nature of sensorimotor tasks calls for the additional contributions of other cortical regions. In this article, we have investigated the functional anatomy of movement represen-tations in the context of an associative visuomotor task with instructed delays. Neural correlates of movement representa-tions have been assessed by isolating preparatory activity that
Moving on time: brain network for auditory-motor synchronization is modulated by rhythm complexity and musical training
- Journal of Cognitive Neuroscience
, 2008
"... & Much is known about the motor system and its role in simple movement execution. However, little is understood about the neural systems underlying auditory–motor integration in the context of musical rhythm, or the enhanced ability of musicians to execute precisely timed sequences. Using functi ..."
Abstract
-
Cited by 17 (1 self)
- Add to MetaCart
& Much is known about the motor system and its role in simple movement execution. However, little is understood about the neural systems underlying auditory–motor integration in the context of musical rhythm, or the enhanced ability of musicians to execute precisely timed sequences. Using functional mag-netic resonance imaging, we investigated how performance and neural activity were modulated as musicians and nonmusicians tapped in synchrony with progressively more complex and less metrically structured auditory rhythms. A functionally con-nected network was implicated in extracting higher-order fea-tures of a rhythm’s temporal structure, with the dorsal premotor cortex mediating these auditory–motor interactions. In contrast to past studies, musicians recruited the prefrontal cortex to a greater degree than nonmusicians, whereas secondary motor regions were recruited to the same extent. We argue that the superior ability of musicians to deconstruct and organize a rhythm’s temporal structure relates to the greater involvement of the prefrontal cortex mediating working memory. &
Sequence learning is preserved in individuals with cerebellar degeneration when the movements are directly cued
- Journal of Cognitive Neuroscience
, 2009
"... & Cerebellar pathology is associated with impairments on a range of motor learning tasks including sequence learning. How-ever, various lines of evidence are at odds with the idea that the cerebellum plays a central role in the associative processes underlying sequence learning. Behavioral studi ..."
Abstract
-
Cited by 2 (1 self)
- Add to MetaCart
& Cerebellar pathology is associated with impairments on a range of motor learning tasks including sequence learning. How-ever, various lines of evidence are at odds with the idea that the cerebellum plays a central role in the associative processes underlying sequence learning. Behavioral studies indicate that sequence learning, at least with short periods of practice, in-volves the establishment of effector-independent, abstract spa-tial associations, a form of representation not associated with cerebellar function. Moreover, neuroimaging studies have failed to identify learning-related changes within the cerebellum. We hypothesize that the cerebellar contribution to sequence learning may be indirect, related to the maintenance of stimulus–response associations in working memory, rather than through processes directly involved in the formation of sequential predictions. Con-sistent with this hypothesis, individuals with cerebellar pathol-ogy were impaired in learning movement sequences when the task involved a demanding stimulus–response translation. When this translation process was eliminated by having the stimuli di-rectly indicate the response location, the cerebellar ataxia group demonstrated normal sequence learning. This dissociation pro-vides an important constraint on the functional domain of the cerebellum in motor learning. &
Visuo-motor integration in humans: cortical patterns of response lateralisation and functional connectivity
- Neuropsychologia
, 2009
"... a b s t r a c t Purpose: We assessed response and functional connectivity patterns of different parts of the visual and motor cortices during visuo-motor integration with particular focus on the intraparietal sulcus (IPS). Methods: Brain activity was measured during a visuo-motor task in 14 subject ..."
Abstract
-
Cited by 1 (0 self)
- Add to MetaCart
a b s t r a c t Purpose: We assessed response and functional connectivity patterns of different parts of the visual and motor cortices during visuo-motor integration with particular focus on the intraparietal sulcus (IPS). Methods: Brain activity was measured during a visuo-motor task in 14 subjects using event-related fMRI. During central fixation, a blue or red target embedded in an array of grey distractors was presented for 250 ms in either the left or right visual hemifield. After a delay, the subjects were prompted to press the upper or lower response button for targets in the upper and lower hemifield with the left or right thumb for blue and red targets, respectively. The fMRI responses were evaluated for different regions of interests (ROIs), and the functional connectivity of the IPS subregions with these ROIs was quantified. Results: In an anterior IPS region and a region in the anterior premotor cortex, presumably the frontal eye fields (FEF), visually driven responses were dominant contralateral to both visual stimulus and effector. Thus, the anterior IPS combines, in contrast to the posterior IPS and the occipital cortex, response properties of cortex activated by visual input and by motor output. Further, functional connectivity with the motor areas was stronger for the anterior than for the posterior IPS regions. Discussion: Anterior IPS and FEF appear to be of major relevance for relating visual and effector information during visuo-motor integration. Patient studies with the devised paradigm are expected to uncover the impact of pathophysiologies and plasticity on the observed cortical lateralisation patterns.
© 2006 Federation of European Psychophysiology Societies Differences Between Intention-Based and Stimulus-Based Actions
"... Abstract. Actions carried out in response to exogenous stimuli and actions selected endogenously on the basis of intentions were compared in terms of their behavioral (movement timing) and electrophysiological (EEG) profiles. Participants performed a temporal bisection task that involved making left ..."
Abstract
- Add to MetaCart
Abstract. Actions carried out in response to exogenous stimuli and actions selected endogenously on the basis of intentions were compared in terms of their behavioral (movement timing) and electrophysiological (EEG) profiles. Participants performed a temporal bisection task that involved making left or right key presses at the midpoint between isochronous pacing signals (a sequence of centrally-presented letters). In separate conditions, the identity of each letter either (1) prescribed the location of the subsequent key press response (stimulus-based) or (2) was determined by the location of the preceding key press, in which case participants were instructed to generate a random sequence of letters (intention-based). The behavioral results indicated that stimulus-based movements occurred earlier in time than intention-based movements. The EEG results revealed that activity reflecting stimulus evaluation and response selection was most pronounced in the stimulus-based condition, whereas activity associated with the general readiness to act was strongest in the intentionbased condition. Together, the behavioral and electrophysiological findings provide evidence for two modes of action planning, one mediated by stimulus-response bindings and the other by action-effect bindings. The comparison of our results to those of an earlier study (Waszak et al., 2005) that employed spatially congruent visuo-motor mappings rather than symbolic visuo-motor mappings suggests that
HUMAN MOTOR CONTROL THROUGH ELECTROCORTICOGRAPHIC BRAIN MACHINE INTERFACES By
, 2008
"... This dissertation has been twenty one years in the making. I remember the first day my father dropped me off at school. The year was 1987 and I have been in school ever since that September morning. For the past twenty one years, therefore, I have been gathering the knowledge and skills that have en ..."
Abstract
- Add to MetaCart
(Show Context)
This dissertation has been twenty one years in the making. I remember the first day my father dropped me off at school. The year was 1987 and I have been in school ever since that September morning. For the past twenty one years, therefore, I have been gathering the knowledge and skills that have enabled me to write this dissertation. I have met many many people along the way whom I am indebted to, yet I will only have the chance to thank a handful. I would like to start by thanking my undergraduate advisor Dr. Aydan Erkmen for persuading me to earn my doctorate’s degree. Without her encouragement and contagious idealism, this dissertation would not have happened. I would also like to thank my master’s advisor Dr. Hamid Krim for giving me the opportunity to pursue my graduate studies in the United States. It has been an honor for me to work with Dr. Jose C. Principe, who for the past four years has guided me with uncanny wisdom, endless patience and witty humor. He always reminded me that knowledge is not a static entity that you put into boxes in your brain and close the lid once you are done using it, rather knowledge is dynamic. I hope
unknown title
, 2007
"... The neural substrate of the ideomotor principle: An event-related fMRI analysis ..."
Abstract
- Add to MetaCart
The neural substrate of the ideomotor principle: An event-related fMRI analysis
Neuron Article Context-Dependent Changes in Functional Circuitry in Visual Area MT
"... Animals can flexibly change their behavior in response to a particular sensory stimulus; the mapping between sensory and motor representations in the brain must therefore be flexible as well. Changes in the correlated firing of pairs of neurons may provide a metric of changes in functional circuitry ..."
Abstract
- Add to MetaCart
Animals can flexibly change their behavior in response to a particular sensory stimulus; the mapping between sensory and motor representations in the brain must therefore be flexible as well. Changes in the correlated firing of pairs of neurons may provide a metric of changes in functional circuitry during behavior. We studied dynamic changes in functional circuitry by analyzing the noise correlations of simultaneously recorded MT neurons in two behavioral contexts: one that promotes cooperative interactions between the two neurons and another that promotes competitive interactions. We found that identical visual stimuli give rise to differences in noise correlation in the two contexts, suggesting that MT neurons receive inputs of central origin whose strength changes with the task structure. The data are consistent with a mixed feature-based attentional strategy model in which the animal sometimes alternates attention between opposite directions of motion and sometimes attends to the two directions simultaneously.