Taku Banno

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). The activities of single neurons were recorded from monkeys performing a visual fixation task, and the effects of luminance contrast on the color selectivity of individual neurons and their population responses were systematically examined by comparing responses to color stimuli that were brighter or darker than the background. We found that the effects of luminance contrast differed considerably across V4 and the PITC and AITC. In both V4 and the PITC, the effects of luminance contrast on the population responses of color-selective neurons depended on color. In V4, the size of the effect was largest for blue and cyan, whereas in the PITC, the effect gradually increased as the saturation of the color stimulus was reduced, and was especially large with neutral colors (white, gray, black). The pattern observed in the PITC resembles the effect of luminance contrast on color appearance, suggesting PITC neurons are closely involved in the formation of the perceived appearance of color. By contrast, the color selectivities of AITC neurons were little affected by luminance contrast, indicating that hue and saturation of color stimuli are represented independently of luminance contrast in the AITC.

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. We found that a color cluster in AIT received projections from a color cluster in PIT as well as from discrete clusters of cells in other occipitotemporal areas, in the superior temporal sulcus, and in prefrontal and parietal cortices. The distribution of the labeled cells in PIT closely corresponded with that of the physiologically identified color-selective cells in this region. Furthermore, retrograde tracer injections in the posterior color cluster resulted in labeled cells in the anterior cluster. Thus, temporal lobe color-processing modules form a reciprocally interconnected loop within a distributed network.

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. Here, using a small New World monkey, the common marmoset (Callithrix jacchus) that has a lissencephalic brain, we investigated the spatial organization of the cells responsive to other’s actions in STS. The neural responses to movies showing several types of other’s actions were recorded with multicontact linear-array electrodes that had four shanks (0.4 mm spacing), with eight electrode contacts (0.2 mm spacing) for each shank. The four shanks were penetrated perpendicular to the cortical surface. We found that STS cells significantly responded to other’s goal-directed actions, such as when an actor marmoset was reaching for and grasping a piece of food. The response profiles to the movies were more similar between the vertically positioned electrodes than horizontally positioned electrodes when the distances between electrodes were matched. This indicates that there are functional columns in the higher-order visual areas in STS of the common marmoset.

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. In the reciprocal condition, two actors exchanged food equally, while in the non-reciprocal condition, one actor (non-reciprocator) ended up with all food and the other actor with none. After observing these exchanges, the control marmosets avoided receiving food from the non-reciprocator in the non-reciprocal condition. However, the VPA marmosets did not show differential preferences in either condition, suggesting that the VPA marmosets did not discriminate between reciprocal and non-reciprocal interactions. These results indicate that normal marmosets can evaluate social interaction between third-parties, while the VPA marmosets are unable to recognize whether an individual is being reciprocal or not. This test battery can serve as a useful tool to qualify primate models of autism.

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

The common marmoset (Callithrix jacchus) 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. Furthermore, we found neuronal cluster(s), in which most cells: (1) showed a significant main effect in material appearance; (2) the best stimulus was a glossy material (glass or metal); and (3) had reduced response to the pixel-shuffled version of the glossy material images. The location of the gloss-selective area was in agreement with previous macaque studies, showing activation in the ventral bank of STS. Our results suggest that perception of gloss is an important ability preserved across wide range of primate species.

Inputs to areas around the superior temporal cortex of marmosets

Areas in and around superior temporal sulcus (STS) are thought to be important to social behavior (e.g., recognizing other’s action and intention). Although new-world monkey marmosets have strong pro-social nature, data related connection of STS is scanty. We performed retrograde tracer (CTB-Alexa 488 or 555) injection around superior temporal cortex of the marmosets. So far, we have made three injections into dorsal and ventral parts of middle STS and dorsal part of caudal STS. We found each injection resulted in unique input pattern, like macaque monkey (Selzer and Pandya, 1994). But, in general, areas around STS receive strong projection form multiple sources (insular, parietal cortex, frontal and occipital cortices), as expected as its multi-modal nature. Based on these results, we will discuss the subdivision of the marmoset areas around STS, by combining with electrophysiology and cytoarchitectures. Research fund: KAKENHI (22300104).

Anatomical connectivity of color-processing modules in monkey inferior temporal cortex

O2-8-3-1 Anatomical connectivity of color-processing modules in monkey inferior temporal cortex Taku Banno 1,2 , Noritaka Ichinohe 3,5, Kathleen S. Rockland 4,5, Hidehiko Komatsu 1,2 1 Division of Sensory and Cognitive Information, NIPS, Okazaki, Japan 2 SOKENDAI 3 Department of Neuroanat, Hirosaki Univ, Hirosaki, Japan 4 RIKEN-MIT Center for Neural Circuit Genetics, MIT, USA 5 Lab for Cort Org System, BSI, RIKEN, Wako, Japan

Non-uniform distribution of color selective cells in macaque area TEO

in a face-selective region macaque IT cortex using chronically implanted multiple electrode-array. The array consisted of 16 electrodes spaced 350 m apart, covering 1.05 × 1.05 mm region. We recorded the neural responses to human and monkey face pictures taken from various view-angles. We will discuss whether the identification of each face can be decoded from the population activity view-invariantly.

Neural responses selective for the orientation of the luminance gradient in the inferior temporal cortex of the monkey

It is well known that stimuli presented outside the classical receptive field (CRF) of a visual cortical neuron suppress its activities. This effect has traditionally been considered as providing auxiliary modulations to the properties determined by the CRF. However, its roles and the spatial organization of this suppressive effect have not been clear. We have recently developed a new method for reconstructing the details of the CRF (center) and surround structures simultaneously. Based on the twodimensional maps obtained by this method, we tested an idea that these structures constitute next-stage processing units suitable for encoding high-order contours such as contrast or texture boundaries. The majority of the center-surround maps showed a variety of oriented organizations, and cell responses were selective for orientation of high-order contours. These results indicate that a population of neurons with surround suppression is able to represent higher-order forms defined by contrast or texture borders.