Neuroscientists from the RIKEN Brain Science Institute, Wako, and New York University have used functional magnetic resonance imaging (fMRI) to study the organization of neurons in the primary visual cortex (V1) of humans and establish that the temporal frequency of a stimulus activates specific V1 neurons.
The V1 is an area at the back of the brain where the first stage of visual processing takes place. Although this is one of the most heavily studied parts of the visual cortex, little is known about how its neurons are arranged. In general, neurons with similar selectivity for visual stimuli cluster together. For example, V1 neurons that process stimuli from each eye are grouped into pillars, called ocular dominance columns.
V1 neurons are highly sensitive to the contrast, orientation, and spatio-temporal frequency of a visual stimulus. Temporal frequency is an important determinant of how moving images are processed by the brain and is a measure of how often an image appears in the visual field. This attribute is also of particular interest to RIKEN researcher Pei Sun and his team, headed by Keiji Tanaka and Kang Cheng, who have determined that images appearing less frequently over time are handled by neurons that arrange themselves differently to those that are activated by more frequently appearing images.
The fMRI technique allows the function and anatomical structure of the brain to be studied live and works by measuring the level of oxygen in the blood immediately after a neuron has been active, giving a pattern of which neurons have been triggered by a stimulus.
The team has shown that separate domains in human V1 respond preferentially to low- and high-temporal frequencies. The former appear to be continuous, whereas the latter seem to be more like isolated islands with no particular orientation (Fig. 1).
This study provides direct physiological evidence that different temporal frequencies are preferentially processed by spatially segregated streams in human V1. The work recently published in Nature Neuroscience (1) is the first to show neuronal organization specific to temporal frequency in primate V1.
Evidence of these separate neural regions will assist further study into human perception of moving images and help to develop a map of the neural architecture of the brain. Pei plans to develop the fMRI technique as “it could link animal and human behavioral studies, giving a better picture of how information is processed by the brain,” he says.
1. Sun, P., Ueno, K., Waggoner, R.A., Gardner, J.L., Tanaka, K. & Cheng, K. A temporal frequency-dependent functional architecture in human V1 revealed by high-resolution fMRI. Nature Neuroscience 10, 1404–1406 (2007).
Saeko Okada | ResearchSEA
Innovative genetic tests for children with developmental disorders and epilepsy
11.07.2018 | Christian-Albrechts-Universität zu Kiel
Oxygen loss in the coastal Baltic Sea is “unprecedentedly severe”
05.07.2018 | European Geosciences Union
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences