Author
T Trinath
Bio: T Trinath is an academic researcher from Max Planck Society. The author has contributed to research in topics: Visual cortex & Macaque. The author has an hindex of 11, co-authored 19 publications receiving 6927 citations.
Papers
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TL;DR: These findings suggest that the BOLD contrast mechanism reflects the input and intracortical processing of a given area rather than its spiking output, and that LFPs yield a better estimate of BOLD responses than the multi-unit responses.
Abstract: Functional magnetic resonance imaging (fMRI) is widely used to study the operational organization of the human brain, but the exact relationship between the measured fMRI signal and the underlying neural activity is unclear. Here we present simultaneous intracortical recordings of neural signals and fMRI responses. We compared local field potentials (LFPs), single- and multi-unit spiking activity with highly spatio-temporally resolved blood-oxygen-level-dependent (BOLD) fMRI responses from the visual cortex of monkeys. The largest magnitude changes were observed in LFPs, which at recording sites characterized by transient responses were the only signal that significantly correlated with the haemodynamic response. Linear systems analysis on a trialby-trial basis showed that the impulse response of the neurovascular system is both animal- and site-specific, and that LFPs yield a better estimate of BOLD responses than the multi-unit responses. These findings suggest that the BOLD contrast mechanism reflects the input and intracortical processing of a given area rather than its spiking output.
6,140 citations
01 Jan 2002
TL;DR: Watanabe et al. as mentioned in this paper used MRI contrast to evaluate the specificity of the former by tracing in the optic tract, as well as in the contralateral superior the neuronal connections of the basal ganglia of the colliculus.
Abstract: nin conjugated to horseradish peroxidase (WGA-HRP) of the eye. After 24 hr, they found signal enhancement to evaluate the specificity of the former by tracing in the optic tract, as well as in the contralateral superior the neuronal connections of the basal ganglia of the colliculus. The time course of the enhanced MRI contrast monkey. Mn 2 and WGA-HRP yielded remarkably simi- indicated that Mn 2 was being transported at approxilar and highly specific projection patterns. By showing mately 2 mm/hr, consistent with fast axonal transport. the sequential transport of Mn 2 from striatum to pal- Intraocular injection of MnCl2 has also been applied in lidum-substantia nigra and then to thalamus, we dem- the rat where labeling was detected in the retina, optic onstrated MRI visualization of transport across at least nerve, chiasm, and contralateral optic tract, as well as one synapse in the CNS of the primate. Transsynaptic in a number of central structures including the dorsal tract tracing in living primates will allow chronic stud- and ventral lateral geniculate nucleus and the superior ies of development and plasticity and provide valuable colliculus (Watanabe et al., 2001). anatomical information for fMRI and electrophysiolog- Axonal transport of radioactive manganese ( 54 Mn 2 ) ical experiments in primates.
212 citations
TL;DR: Experiments simultaneously tracing manganese chloride and wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) to evaluate the specificity of the former by tracing the neuronal connections of the basal ganglia of the monkey yielded remarkably similar and highly specific projection patterns.
204 citations
TL;DR: Using fMRI in anesthetized monkeys, this study investigates how the primate visual system constructs representations of three-dimensional (3D) shape from a variety of cues, suggesting multiple uses for 3D shape representation in perception, recognition, and action.
170 citations
TL;DR: In this article, the authors presented a novel technique that yields high-resolution structural and functional images of the monkey brain with small, tissue-compatible, intraosteally implantable radiofrequency coils.
159 citations
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TL;DR: The major concepts and results recently achieved in the study of the structure and dynamics of complex networks are reviewed, and the relevant applications of these ideas in many different disciplines are summarized, ranging from nonlinear science to biology, from statistical mechanics to medicine and engineering.
9,441 citations
TL;DR: These findings suggest that the BOLD contrast mechanism reflects the input and intracortical processing of a given area rather than its spiking output, and that LFPs yield a better estimate of BOLD responses than the multi-unit responses.
Abstract: Functional magnetic resonance imaging (fMRI) is widely used to study the operational organization of the human brain, but the exact relationship between the measured fMRI signal and the underlying neural activity is unclear. Here we present simultaneous intracortical recordings of neural signals and fMRI responses. We compared local field potentials (LFPs), single- and multi-unit spiking activity with highly spatio-temporally resolved blood-oxygen-level-dependent (BOLD) fMRI responses from the visual cortex of monkeys. The largest magnitude changes were observed in LFPs, which at recording sites characterized by transient responses were the only signal that significantly correlated with the haemodynamic response. Linear systems analysis on a trialby-trial basis showed that the impulse response of the neurovascular system is both animal- and site-specific, and that LFPs yield a better estimate of BOLD responses than the multi-unit responses. These findings suggest that the BOLD contrast mechanism reflects the input and intracortical processing of a given area rather than its spiking output.
6,140 citations
TL;DR: It is argued that the most plausible candidate is the formation of dynamic links mediated by synchrony over multiple frequency bands.
Abstract: The emergence of a unified cognitive moment relies on the coordination of scattered mosaics of functionally specialized brain regions. Here we review the mechanisms of large-scale integration that counterbalance the distributed anatomical and functional organization of brain activity to enable the emergence of coherent behaviour and cognition. Although the mechanisms involved in large-scale integration are still largely unknown, we argue that the most plausible candidate is the formation of dynamic links mediated by synchrony over multiple frequency bands.
4,485 citations
TL;DR: It is hypothesized that neuronal communication is mechanistically subserved by neuronal coherence, and a flexible pattern of coherence defines a flexible communication structure, which subserves the authors' cognitive flexibility.
3,862 citations
TL;DR: This work explores the possibility that there might be a baseline or resting state of brain function involving a specific set of mental operations, including the manner in which a baseline is defined and the implications of such a baseline for the understanding ofbrain function.
Abstract: Functional brain imaging in humans has revealed task-specific increases in brain activity that are associated with various mental activities. In the same studies, mysterious, task-independent decreases have also frequently been encountered, especially when the tasks of interest have been compared with a passive state, such as simple fixation or eyes closed. These decreases have raised the possibility that there might be a baseline or resting state of brain function involving a specific set of mental operations. We explore this possibility, including the manner in which we might define a baseline and the implications of such a baseline for our understanding of brain function.
3,285 citations