Cerebro-cerebellar interactions in nonhuman primates examined by optogenetic functional magnetic resonance imaging.

Functional magnetic resonance imaging (fMRI) is a promising approach for the simultaneous and extensive scanning of whole-brain activities. Optogenetics is free from electrical and magnetic artifacts and is an ideal stimulation method for combined use with fMRI. However, the application of optogenetics in nonhuman primates (NHPs) remains limited.

Structure and function of neural circuit related to gloss perception in the macaque inferior temporal cortex: a case report.

The inferior temporal (IT) cortex of the macaque monkey plays a pivotal role in the visual recognition of objects. In the IT cortex, a feature-selective network formed by connecting subregions specialized for common visual features seems to be a basic strategy for processing biologically important visual features. Gloss perception plays an important role in the judgment of materials and conditions of objects and is a biologically significant visual function.

Neural Mechanisms of Material Perception: Quest on Shitsukan.

In recent years, a growing body of research has addressed the nature and mechanism of material perception. Material perception entails perceiving and recognizing a material, surface quality or internal state of an object based on sensory stimuli such as visual, tactile, and/or auditory sensations. This process is ongoing in every aspect of daily life.

Dependence of behavioral performance on material category in an object-grasping task with monkeys.

Material perception is an essential part of our cognitive function that enables us to properly interact with our complex daily environment. One important aspect of material perception is its multimodal nature. When we see an object, we generally recognize its haptic properties as well as its visual properties.

Crossmodal Association of Visual and Haptic Material Properties of Objects in the Monkey Ventral Visual Cortex.

Just by looking at an object, we can recognize its non-visual properties, such as hardness. The visual recognition of non-visual object properties is generally accurate [1], and influences actions toward the object [2]. Recent studies suggest that, in the primate brain, this may involve the ventral visual cortex, which represents objects in a way that reflects not only visual but also non-visual object properties, such as haptic roughness, hardness, and weight [3-7].

Mirror Neurons in a New World Monkey, Common Marmoset.

Mirror neurons respond when executing a motor act and when observing others' similar act. So far, mirror neurons have been found only in macaques, humans, and songbirds. To investigate the degree of phylogenetic specialization of mirror neurons during the course of their evolution, we determined whether mirror neurons with similar properties to macaques occur in a New World monkey, the common marmoset (Callithrix jacchus).

Perceptual gloss parameters are encoded by population responses in the monkey inferior temporal cortex.

There are neurons localized in the lower bank of the superior temporal sulcus (STS) in the inferior temporal (IT) cortex of the monkey that selectively respond to specific ranges of gloss characterized by combinations of three physical reflectance parameters: specular reflectance (ρs), diffuse reflectance (ρd), and spread of specular reflection (α; Nishio et al., 2012). In the present study, we examined how the activities of these gloss-selective IT neurons are related to perceived gloss.

Audiovisual integration in the human perception of materials.

Interest in the perception of the material of objects has been growing. While material perception is a critical ability for animals to properly regulate behavioral interactions with surrounding objects (e.g.

Representation of the material properties of objects in the visual cortex of nonhuman primates.

Information about the material from which objects are made provide rich and useful clues that enable us to categorize and identify those objects, know their state (e.g., ripeness of fruits), and properly act on them.

Selective responses to specular surfaces in the macaque visual cortex revealed by fMRI.

The surface properties of objects, such as gloss, transparency and texture, provide important information about the material characteristics of objects in our visual environment. However, because there have been few reports on the neuronal responses to surface properties in primates, we still lack information about where and how surface properties are processed in the primate visual cortex. In this study, we used functional magnetic resonance imaging (fMRI) to examine the cortical responses to specular surfaces in the macaque visual cortex.

Neural selectivity and representation of gloss in the monkey inferior temporal cortex.

When we view an object, its appearance depends in large part on specific surface reflectance properties; among these is surface gloss, which provides important information about the material composition of the object and the fine structure of its surface. To study how gloss is represented in the visual cortical areas related to object recognition, we examined the responses of neurons in the inferior temporal (IT) cortex of the macaque monkey to a set of object images exhibiting various combinations of specular reflection, diffuse reflection, and roughness, which are important physical parameters of surface gloss. We found that there are neurons in the lower bank of the superior temporal sulcus that selectively respond to specific gloss.

Transformation from image-based to perceptual representation of materials along the human ventral visual pathway.

Every object in the world has its own surface quality that is a reflection of the material from which the object is made. We can easily identify and categorize materials (wood, metal, fabric etc.) at a glance, and this ability enables us to decide how to interact appropriately with these objects.

Mechanisms underlying the representation of angles embedded within contour stimuli in area V2 of macaque monkeys.

We previously found that surprisingly many V2 neurons showed selective responses to particular angles embedded within continuous contours [M. Ito & H. Komatsu (2004)Journal of Neuroscience, 24, 3313-3324].

Distribution of colour-selective activity in the monkey inferior temporal cortex revealed by functional magnetic resonance imaging.

Previous electrophysiological, neuroimaging and lesion studies have suggested that the anterior part of the monkey inferior temporal (IT) cortex, or area TE, plays an important role in colour processing. However, little is known about how colour information is distributed in these cortical regions. Here, we explored the distribution of colour-selective activity in alert macaque monkeys using functional magnetic resonance imaging (fMRI) with two types of stimuli: a multicoloured ('Mondrian') pattern and an isoluminant colour grating.

The effects of feature attention on prestimulus cortical activity in the human visual system.

Covert attention affects prestimulus activity in the visual cortex. Although most studies investigating neural mechanisms of attention have focused on the effects of spatial attention, attention can also be directed to particular features. To investigate the spatiotemporal nature of feature attention, we measured subjects' brain activity using magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI) while subjects attended to color or motion of a stimulus based on a visual cue, which was presented 1 s before the stimulus onset.

Estimation of the timing of human visual perception from magnetoencephalography.

To explore the timing and the underlying neural dynamics of visual perception, we analyzed the relationship between the manual reaction time (RT) to the onset of a visual stimulus and the time course of the evoked neural response simultaneously measured by magnetoencephalography (MEG). The visual stimuli were a transition from incoherent to coherent motion of random dots and an onset of a chromatic grating from a uniform field, which evoke neural responses in different cortical sites. For both stimuli, changes in median RT with changing stimulus strength (motion coherence or chromatic contrast) were accurately predicted, with a stimulus-independent postdetection delay, from the time that the temporally integrated MEG response crossed a threshold (integrator model).

Anterior and superior lateral occipito-temporal cortex responsible for target motion prediction during overt and covert visual pursuit.

In smooth-pursuit eye movements (SPEM) with gain close to one, SPEM should be controlled mainly by prediction of target motion because retinal slip is nearly zero. We investigated the neural mechanisms of visual-target prediction by the three fMRI experiments. (1) Overt pursuit task: subjects pursued a sinusoidally moving target which blinked (blink condition) or did not blink (continuous condition).

Attentional shifts towards an expected visual target alter the level of alpha-band oscillatory activity in the human calcarine cortex.

Neuronal operations associated with the top-down control process of shifting attention from one locus to another involve a network of cortical regions, and their influence is deemed fundamental to visual perception. However, the extent and nature of these operations within primary visual areas are unknown. In this paper, we used magnetoencephalography (MEG) in combination with magnetic resonance imaging (MRI) to determine whether, prior to the onset of a visual stimulus, neuronal activity within early visual cortex is affected by covert attentional shifts.

Task-specific disruption of perceptual learning.

For more than a century, the process of stabilization has been a central issue in the research of learning and memory. Namely, after a skill or memory is acquired, it must be consolidated before it becomes resistant to disruption by subsequent learning. Although it is clear that there are many cases in which learning can be disrupted, it is unclear when learning something new disrupts what has already been learned.

Hierarchical Bayesian estimation for MEG inverse problem.

Source current estimation from MEG measurement is an ill-posed problem that requires prior assumptions about brain activity and an efficient estimation algorithm. In this article, we propose a new hierarchical Bayesian method introducing a hierarchical prior that can effectively incorporate both structural and functional MRI data. In our method, the variance of the source current at each source location is considered an unknown parameter and estimated from the observed MEG data and prior information by using the Variational Bayesian method.

Attentional modulation of oscillatory activity in human visual cortex.

The effects of attentional modulation on activity within the human visual cortex were investigated using magnetoencephalography. Chromatic sinusoidal stimuli were used to evoke activity from the occipital cortex, with attention directed either toward or away from the stimulus using a bar-orientation judgment task. For five observers, global magnetic field power was plotted as a function of time from stimulus onset.