Changes in neural readout of response magnitude during auditory streaming do not correlate with behavioral choice in the auditory cortex.

A fundamental goal of the auditory system is to group stimuli from the auditory environment into a perceptual unit (i.e., "stream") or segregate the stimuli into multiple different streams.

Computational and neurophysiological principles underlying auditory perceptual decisions.

A fundamental scientific goal in auditory neuroscience is identifying what mechanisms allow the brain to transform an unlabeled mixture of auditory stimuli into distinct perceptual representations. This transformation is accomplished by a complex interaction of multiple neurocomputational processes, including Gestalt grouping mechanisms, categorization, attention, and perceptual decision-making. Despite a great deal of scientific energy devoted to understanding these principles of hearing, we still do not understand either how auditory perception arises from neural activity or the causal relationship between neural activity and auditory perception.

Sound Frequency Representation in the Auditory Cortex of the Common Marmoset Visualized Using Optical Intrinsic Signal Imaging.

Natural sound is composed of various frequencies. Although the core region of the primate auditory cortex has functionally defined sound frequency preference maps, how the map is organized in the auditory areas of the belt and parabelt regions is not well known. In this study, we investigated the functional organizations of the core, belt, and parabelt regions encompassed by the lateral sulcus and the superior temporal sulcus in the common marmoset ().

Representation of Glossy Material Surface in Ventral Superior Temporal Sulcal Area of Common Marmosets.

The common marmoset () is one of the smallest species of primates, with high visual recognition abilities that allow them to judge the identity and quality of food and objects in their environment. To address the cortical processing of visual information related to material surface features in marmosets, we presented a set of stimuli that have identical three-dimensional shapes (bone, torus or amorphous) but different material appearances (ceramic, glass, fur, leather, metal, stone, wood, or matte) to anesthetized marmoset, and recorded multiunit activities from an area ventral to the superior temporal sulcus (STS) using multi-shanked, and depth resolved multi-electrode array. Out of 143 visually responsive multiunits recorded from four animals, 29% had significant main effect only of the material, 3% only of the shape and 43% of both the material and the shape.

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).

Functional columns in superior temporal sulcus areas of the common marmoset.

Cortical areas in the superior temporal sulcus (STS) of primates have been recognized as a part of the 'social brain'. In particular, biological motion stimuli elicit neuronal responses in the STS, indicating their roles in the ability to understand others' actions. However, the spatial organization of functionally identified STS cells is not well understood because it is difficult to identify the precise locations of cells in sulcal regions.

Indifference of marmosets with prenatal valproate exposure to third-party non-reciprocal interactions with otherwise avoided non-reciprocal individuals.

Autism is characterized by deficits in social interaction and social recognition. Although animal models of autism have demonstrated that model animals engage less in social interaction or attend less to conspecifics than control animals, no animal model has yet replicated the deficit in recognition of complex social interaction as is seen in humans with autism. Here, we show that marmosets discriminated between human actors who reciprocated in social exchanges and those who did not; however, marmosets with foetal exposure to valproic acid (VPA marmosets) did not.

Effects of luminance contrast on the color selectivity of neurons in the macaque area v4 and inferior temporal cortex.

Appearance of a color stimulus is significantly affected by the contrast between its luminance and the luminance of the background. In the present study, we used stimuli evenly distributed on the CIE-xy chromaticity diagram to examine how luminance contrast affects neural representation of color in V4 and the anterior inferior temporal (AITC) and posterior inferior temporal (PITC) color areas (Banno et al., 2011).

Marmoset monkeys evaluate third-party reciprocity.

Many non-human primates have been observed to reciprocate and to understand reciprocity in one-to-one social exchanges. A recent study demonstrated that capuchin monkeys are sensitive to both third-party reciprocity and violation of reciprocity; however, whether this sensitivity is a function of general intelligence, evidenced by their larger brain size relative to other primates, remains unclear. We hypothesized that highly pro-social primates, even with a relatively smaller brain, would be sensitive to others' reciprocity.

Reciprocal connectivity of identified color-processing modules in the monkey inferior temporal cortex.

The inferior temporal (IT) cortex is the last unimodal visual area in the ventral visual pathway and is essential for color discrimination. Recent imaging and electrophysiological studies have revealed the presence of several distinct patches of color-selective cells in the anterior IT cortex (AIT) and posterior IT cortex (PIT). To understand the neural machinery for color processing in the IT cortex, in the present study, we combined anatomical tracing methods with electrophysiological unit recordings to investigate the anatomical connections of identified clusters of color-selective cells in monkey IT cortex.

Color selectivity of neurons in the posterior inferior temporal cortex of the macaque monkey.

We recorded the activities of neurons in the lateral surface of the posterior inferior temporal cortex (PIT) of 3 hemispheres of 3 monkeys performing a visual fixation task. We characterized the color and shape selectivities of each neuron, mapped its receptive field (RF), and studied the distributions of these response properties. Using a set of color stimuli that were systematically distributed in Commission Internationale de l'Eclairage-xy chromaticity diagram, we found numerous color-selective neurons distributed throughout the area examined.