Neuroaesthetics and the Trouble with Beauty

Neuroscience is increasingly being called upon to address issues within the humanities. We discuss challenges that arise, relating to art and beauty, and provide ideas for a way forward.Musi

Parallel, multi-stage processing of colors, faces and shapes in macaque inferior temporal cortex

Visual-object processing culminates in inferior temporal (IT) cortex. To assess the organization of IT, we measured fMRI responses in alert monkey to achromatic images (faces, fruit, bodies, places) and colored gratings. IT contained multiple color-biased regions, which were typically ventral to face patches and, remarkably, yoked to them, spaced regularly at four locations predicted by known anatomy. Color and face selectivity increased for more anterior regions, indicative of a broad hierarchical arrangement. Responses to non-face shapes were found across IT, but were stronger outside color-biased regions and face patches, consistent with multiple parallel streams. IT also contained multiple coarse eccentricity maps: face patches overlapped central representations; color-biased regions spanned mid-peripheral representations; and place-biased regions overlapped peripheral representations. These results suggest that IT comprises parallel, multi-stage processing networks subject to one organizing principle

Neural basis for unique hues

SummaryAll colors can be described in terms of four non-reducible ‘unique’ hues: red, green, yellow, and blue [1]. These four hues are also the most common ‘focal’ colors — the best examples of color terms in language [2]. The significance of the unique hues has been recognized since at least the 14th century [3] and is universal [4,5], although there is some individual variation [6,7]. Psychophysical linking hypotheses predict an explicit neural representation of unique hues at some stage of the visual system, but no such representation has been described [8]. The special status of the unique hues “remains one of the central mysteries of color science” [9]. Here we report that a population of recently identified cells in posterior inferior temporal cortex of macaque monkey contains an explicit representation of unique hues

Specialized Color Modules in Macaque Extrastriate Cortex

Imaging studies are consistent with the existence of brain regions specialized for color, but electrophysiological studies have produced conflicting results. Here we address the neural basis for color, using targeted single-unit recording in alert macaque monkeys, guided by functional magnetic resonance imaging (fMRI) of the same subjects. Distributed within posterior inferior temporal cortex, a large region encompassing V4, PITd, and posterior TEO that some have proposed functions as a single visual complex, we found color-biased fMRI hotspots that we call “globs,” each several millimeters wide. Almost all cells located in globs showed strong luminance-invariant color tuning and some shape selectivity. Cells in different globs represented distinct visual field locations, consistent with the coarse retinotopy of this brain region. Cells in “interglob” regions were not color tuned, but were more strongly shape selective. Neither population was direction selective. These results suggest that color perception is mediated by specialized neurons that are clustered within the extrastriate brain

Art, Intuition, and Identity in Ramón y Cajal

In the history of neuroscience, Cajal stands tall. Many figures in the late 19th and early 20th centuries made major contributions to neuroscience-Sherrington, Ferrier, Jackson, Holmes, Adrian, and Békésy, to name a few. But in the public mind, Cajal is unique. His application of the Golgi method, with an array of histologic stains, unlocked a wealth of new knowledge on the structure and function of the brain. Here we argue that Cajal's success should not only be attributed to the importance of his scientific contributions but also to the artistic visual language that he created and to his pioneering self-branding, which exploited methods of the artist, including classical drawing and the new invention of photography. We argue that Cajal created his distinctive visual language and self-branding strategy by interweaving an ostensibly objective research product with an intimately subjective narrative about the brain and himself. His approach is evident in the use of photography, notably self-portraits, which furthered broad engagement initially inspired by his scientific drawings. Through his visual language, Cajal made an impact in art and culture far beyond the bounds of science, which has sustained his scientific legacy.</p

Color-tuned neurons are spatially clustered according to color preference within alert macaque posterior inferior temporal cortex

Large islands of extrastriate cortex that are enriched for color-tuned neurons have recently been described in alert macaque using a combination of functional magnetic resonance imaging (fMRI) and single-unit recording. These millimeter-sized islands, dubbed “globs,” are scattered throughout the posterior inferior temporal cortex (PIT), a swath of brain anterior to area V3, including areas V4, PITd, and posterior TEO. We investigated the micro-organization of neurons within the globs. We used fMRI to identify the globs and then used MRI-guided microelectrodes to test the color properties of single glob cells. We used color stimuli that sample the CIELUV perceptual color space at regular intervals to test the color tuning of single units, and make two observations. First, color-tuned neurons of various color preferences were found within single globs. Second, adjacent glob cells tended to have the same color tuning, demonstrating that glob cells are clustered by color preference and suggesting that they are arranged in color columns. Neurons separated by 50 μm, measured parallel to the cortical sheet, had more similar color tuning than neurons separated by 100 μm, suggesting that the scale of the color columns is <100 μm. These results show that color-tuned neurons in PIT are organized by color preference on a finer scale than the scale of single globs. Moreover, the color preferences of neurons recorded sequentially along a given electrode penetration shifted gradually in many penetrations, suggesting that the color columns are arranged according to a chromotopic map reflecting perceptual color space

Temporal dynamics of the neural representation of hue and luminance contrast

Hue and luminance contrast are the most basic visual features, emerging in early layers of convolutional neural networks trained to perform object categorization. In human vision, the timing of the neural computations that extract these features, and the extent to which they are determined by the same or separate neural circuits, is unknown. We addressed these questions using multivariate analyses of human brain responses measured with magnetoencephalography. We report four discoveries. First, it was possible to decode hue tolerant to changes in luminance contrast, and luminance contrast tolerant to changes in hue, consistent with the existence of separable neural mechanisms for these features. Second, the decoding time course for luminance contrast peaked 16-24 ms before hue and showed a more prominent secondary peak corresponding to decoding of stimulus cessation. These results are consistent with the idea that the brain uses luminance contrast as an updating signal to separate events within the constant stream of visual information. Third, neural representations of hue generalized to a greater extent across time, providing a neural correlate of the preeminence of hue over luminance contrast in perceptual grouping and memory. Finally, decoding of luminance contrast was more variable across participants for hues associated with daylight (orange and blue) than for anti-daylight (green and pink), suggesting that color-constancy mechanisms reflect individual differences in assumptions about natural lighting

Parallel, multi-stage processing of colors, faces and shapes in macaque inferior temporal cortex

Visual-object processing culminates in inferior temporal cortex (IT). To assess the organization of IT, we measured functional magnetic resonance imaging responses in alert monkeys to achromatic images (faces, fruit, bodies and places) and colored gratings. IT contained multiple color-biased regions, which were typically ventral to face patches and yoked to them, spaced regularly at four locations predicted by known anatomy. Color and face selectivity increased for more anterior regions, indicative of a broad hierarchical arrangement. Responses to non-face shapes were found across IT, but were stronger outside color-biased regions and face patches, consistent with multiple parallel streams. IT also contained multiple coarse eccentricity maps: face patches overlapped central representations, color-biased regions spanned mid-peripheral representations and place-biased regions overlapped peripheral representations. These results show that IT comprises parallel, multi-stage processing networks subject to one organizing principle. © 2013 Nature America, Inc. All rights reserved. advance online publication nature neurOSCIenCe a r t I C l e S Functional architecture for color Using fMRI, we determined the functional architecture for color and related it to the functional landmarks of the face-patch system. We defined color-biased regions as those showing stronger activation to drifting equiluminant colored gratings than to achromatic gratings The locations of the color-biased regions were generally symmetric across hemispheres in a given monkey and somewhat stereotyped IT IT * * © 2013 Nature America, Inc. All rights reserved. nature neurOSCIenCe advance online publication a r t I C l e S across the two monkeys (M1 and M2; The color-biased activity in central and anterior IT was more distinct than we found previously 12,13 (see Online Methods). At the same time, the pattern of color-biased activity in V4 and surrounding areas (including V2; The pattern of color-biased regions in IT is consistent with the general location of color-selective cells identified in microelectrode studies of monkey visual cortex. The location of ALc corresponds to a rich pocket of color-tuned neurons 27,28 , a region that has also been identified with fMRI 14 and positron emission tomography r t I C l e S Relationship between color architecture and face patches We compared the responses to color with the responses to achromatic images of faces, objects (fruits and vegetables) and places in the same subjects. As in previous reports, the fMRI maps showed three prominent clusters of face patches: PL, ML/MF, AL/AF 2 and several other less prominent face patches, including one at the anterior-ventral pole of the temporal lobe (AM) 4,31 The color and face regions were defined independently; thus, it is possible for the two sets of regions to overlap completely. Despite this possibility, the two sets of regions showed little overlap nature neurOSCIenCe advance online publication a r t I C l e S the luminance dependence of face processing 32 . Moreover, the color selectivity increased for color regions at more anterior locations, consistent with the hypothesis that these regions constitute a hierarchy of processing stages similar to the hierarchy described among face patches To quantify the spatial relationship of face and color regions, we constructed a three-dimensional volume of IT and volumes corresponding to the regions defined by stringent threshold criteria that yielded roughly the same number of face-selective and color-selective voxels in each hemisphere Responses to non-face objects In addition to faces, we mapped the response to other types of objects (bodies and body parts, vegetables and fruit, places; In addition, we found that highly significant place-biased responses tended to be ventral (and dorsal) to face patches and color-biased regions. Place-biased regions were also more prominent in PIT. The maps generated by some stimulus contrasts also showed activation in the superior temporal gyrus We quantified the magnitude of the responses to the different stimuli in regions of interest (ROIs) along the posterior-anterior axis These results indicate that, to a substantial extent, color and object-shape information is carried by segregated channels through IT: color-biased regions showed strong responses to color and modest responses to object shape, and regions outside of the color-biased regions showed substantially stronger responses to object shape. But the extent to which non-face object-shape information is segregated into discrete channels for different object classes is less clear. The regions showing the strongest activation to bodies versus scrambled bodies were not the same as those showing preferential activation to bodies over other objects such as vegetables and fruit ( © 2013 Nature America, Inc. All rights reserved. advance online publication nature neurOSCIenCe a r t I C l e S for faces: regions showing strongest activation to intact faces were also the same regions that showed activation to faces versus any of the other stimuli used, including bodies, which share the most similarity to faces. The face selectivity of face patches is underscored by maps of responses to all non-face objects versus scrambled non-face objects, which showed substantial activation throughout most of IT except conspicuous islands that correspond to the face patches Eccentricity maps in IT Functional imaging of humans shows an eccentricity bias in IT Finally, we quantified the responses to different images nature neurOSCIenCe advance online publication a r t I C l e S representation, a clear increase in modulation to place stimuli in the peripheral representation, and an intermediate response to non-face and non-place images in the mid-peripheral representation, confirming results obtained in humans DISCUSSION We addressed the functional organization of IT by measuring fMRI responses to colored gratings, achromatic images (faces, vegetables and fruit, body parts, and places) and retinotopic checkerboard stimuli in two monkey subjects. Color-biased regions and face patches were mostly non-overlapping, consistent with neurophysiological and psychophysical evidence suggesting that color and faces are processed by largely independent networks 38,39 . Faces and colors share little low-level similarity, so the limited overlap may not be surprising. However, color-biased regions appeared to be yoked to face patches, with color-biased regions typically being ventral to face patches. Clusters of color-biased regions and face patches were located at four main sites along the posterior-anterior axis of IT Although anatomical evidence suggests the stages are not linked in a strictly feedforward fashion 18 (and the functional data are not inconsistent with a rich set of interconnections between stages and pathways), we found that color selectivity increased for more anterior regions advance online publication nature neurOSCIenCe a r t I C l e S The findings have implications for understanding how IT evolved and shed light on a neurological puzzle, as discussed below. Responses to images of non-face objects were significant across much of IT, but were greatest in regions outside of face patches and color-biased regions; moreover, place-biased activation was strongest in regions outside of body-biased, face-biased and color-biased regions. These results provide additional support for the notion of several parallel routes through IT. We acknowledge, however, that one might not expect the multi-stage conception of IT to manifest as three or four patches of activation to every image class tested-other factors, such as the nature of the computations performed in each stage and contextual interactions 9 , will influence the degree to which a given stage is activated. Nonetheless, regions showing response biases to images of bodies/body parts were found in three main clusters, overlapping and adjacent to face patches Color is an important component of objects; the extent to which color and form are processed by the same neural circuits has been a long-standing question in visual neuroscience In humans, object-processing cortex is organized according to a coarse map of eccentricity, an extension of the retinotopic map in early visual cortex 23 . It has not been clear whether this principle applies across primates. Our results provide fMRI confirmation of electrophysiological evidence 13,24,25 for a retinotopic map in PIT; moreover, we found additional representations of the visual field in CIT and AIT The results of our eccentricity mapping experiment are surprising because IT in monkeys is not thought to be organized retinotopically. Experiments in humans have shown that the eccentricity representation in IT may reflect an organization for the real-world size; the region in IT that is activated by images of large objects is offset from the region activated by images of small objects, even when the images themselves occupy the same fraction of the visual field Our results may shed light on the evolutionary mechanisms that brought about the expansion of cerebral cortex. The eccentricity map in human IT suggests that this region initially arose by extension of retinotopic cortex 23 . The multi-stage functional organizational scheme uncovered here may reflect the process by which IT subsequently expanded during evolution. The alternating pattern of horizontal and vertical meridian representations that define early retinotopic visual areas The historically minded reader may recall the theory that V4 is the &apos;color area&apos; . The seminal neurophysiology 46 underlying this idea led to the notion that acquired cerebral achromatopsia comes about because of a lesion of the human homolog of monkey V4 (for a review, see ref. 12). This deceptively simple interpretation has been complicated by three observations. First, V4 is not a homogenous area and is not uniquely specialized for processing color METhODS Methods and any associated references are available in the online version of the paper. nature neurOSCIenCe advance online publication a r t I C l e S scripts compiled by S. Moeller (RWTH Aachen University). We thank J. Maunsell, D. Hubel and M. Livingstone for research space, helpful discussions and assistance with animal protocols. A. Rehding, N. Kanwisher, J. DiCarlo and P. Mayo provided valuable comments on the manuscript. B.R.C. gratefully acknowledges seminal conversations that took place with D. Tsao, with whom the idea to map multiple stimulus dimensions in IT was conceived and initially begun. We thank Y. Liu for implementing the simulation shown i

Color naming across languages reflects color use

What determines how languages categorize colors? We analyzed results of the World Color Survey (WCS) of 110 languages to show that despite gross differences across languages, communication of chromatic chips is always better for warm colors (yellows/reds) than cool colors (blues/greens). We present an analysis of color statistics in a large databank of natural images curated by human observers for salient objects and show that objects tend to have warm rather than cool colors. These results suggest that the cross-linguistic similarity in color-naming efficiency reflects colors of universal usefulness and provide an account of a principle (color use) that governs how color categories come about. We show that potential methodological issues with the WCS do not corrupt information-theoretic analyses, by collecting original data using two extreme versions of the color-naming task, in three groups: the Tsimane’, a remote Amazonian hunter-gatherer isolate; Bolivian-Spanish speakers; and English speakers. These data also enabled us to test another prediction of the color-usefulness hypothesis: that differences in color categorization between languages are caused by differences in overall usefulness of color to a culture. In support, we found that color naming among Tsimane’ had relatively low communicative efficiency, and the Tsimane’ were less likely to use color terms when describing familiar objects. Color-naming among Tsimane’ was boosted when naming artificially colored objects compared with natural objects, suggesting that industrialization promotes color usefulness.National Science Foundation (U.S.) (Award 1534318