The artist emerges: Visual art learning alters neural structure and function

Highlights

• Frontal white matter reorganized as art students became more creative.

• Cortical and cerebellar activity patterns changed as drawing skills improved.

• Visual art training did not entail improvements in purely perceptual abilities.

Abstract

How does the brain mediate visual artistic creativity? Here we studied behavioral and neural changes in drawing and painting students compared to students who did not study art. We investigated three aspects of cognition vital to many visual artists: creative cognition, perception, and perception-to-action. We found that the art students became more creative via the reorganization of prefrontal white matter but did not find any significant changes in perceptual ability or related neural activity in the art students relative to the control group. Moreover, the art students improved in their ability to sketch human figures from observation, and multivariate patterns of cortical and cerebellar activity evoked by this drawing task became increasingly separable between art and non-art students. Our findings suggest that the emergence of visual artistic skills is supported by plasticity in neural pathways that enable creative cognition and mediate perceptuomotor integration.

Introduction

Art is a complex and uniquely human phenomenon. The creation of artistic work has historically been a mysterious and poorly understood process, often even by artists themselves (Stiles and Selz, 2012). However, according to central tenets of neuroscience, the work of an artist must be mediated by the brain. How does the brain support the cognitive skills necessary to create art?

Art has appeared in many forms throughout human history. The qualities that distinguish artistic work are thus often difficult to define. For example, while some trompe l'oeil painters such as William Harnett (Frankenstein, 1953) attain an astounding ability to recreate visual scenes accurately, representation for other painters such as abstract expressionist Barnett Newman (Shiff, 2004) is less important than the concepts or processes that their works communicate. Nonetheless, most artists, regardless of their motivation or medium, spend years developing patterns of thought and behavior that lead ultimately to expression in a work of art. Here, we focused narrowly on a single type of artwork: representational, two-dimensional visual depictions created from observation. We necessarily ignored many important factors such as social, cultural, and affective contexts that are vital to the work of many artists (cf. Stiles and Selz, 2012). No single study can address every factor that influences artistic skill. However, the results presented here may provide a window into some of the neural processes that endow humans with a seemingly limitless ability to create new objects, ideas, and processes.

In the current study we investigated how artistic behaviors are learned, focusing on representational visual art and on three areas of cognition that are relevant to many visual artists: creative cognition, visual perception, and perception-to-action (Fig. 1A). We asked how skills associated with each of these three cognitive domains change and how the brain reorganizes as students learn to create visual art. We recruited 35 undergraduate college students for monthly testing; 17 of these participants took a 3-month-long introductory observational drawing or painting course offered by the Studio Art Department at Dartmouth College, while 18 control participants did not study art. All participants attended monthly MRI scanning sessions. Below we introduce the three areas of cognition that we studied and their potential relevance to visual art.

Artists are distinguished by the ability to think in new ways, developing new patterns of and connections between ideas to imagine and create artifacts and processes that have never existed previously. The sources of this creativity are among the least understood and most mythologized aspects of art production (Milbrandt and Milbrandt, 2011, Taylor, 1976). Creative cognition is notoriously difficult to define within a scientific context, partly because creativity can be manifested in myriad domains such as artistic and scientific fields, verbal and visual modalities, and divergent and convergent thought (Dietrich and Kanso, 2010). Many questions about what makes artists creative remain open, especially with respect to the brain's role in these creative processes. Previous neuroscientific studies have used a range of approaches to study the neural basis of creativity in artists, but little consensus about this basis has emerged. For example, Bhattacharya and Petsche (2005) used EEG to study differences in cortical activity between artists and non-artists as both produced drawings of their own choice and found differences in short and long range neural synchronization patterns between the two groups. Kowatari et al. (2009) asked design experts and novice participants to invent a new type of pen while undergoing functional MRI (fMRI) scans and found that creative output was correlated with the degree of dominance of right over left prefrontal cortical activity. Limb and Braun (2008) used fMRI to show that jazz pianists experienced extensive deactivation of prefrontal cortex when they played improvised compared to over-learned musical pieces. Solso (2001), on the other hand, found reduced activity in the parietal cortex in a skilled portrait artist compared to a novice participant as both produced drawings of faces. While little consensus has emerged from such studies, the many emerging findings about both artists and creative cognition more generally have shown that creativity is a complex rather than monolithic process and that researchers must therefore avoid the tendency to reduce creativity to simple conceptual constructs (Arden et al., 2010, Dietrich and Kanso, 2010, Hee Kim, 2006). Thus, in this study we chose assessments of creativity (described below) that measured many aspects of creative ability.

A recent study by Jung et al. (2010) investigated the relationship between white matter organization and creative cognitive ability using diffusion tensor imaging (DTI). They found an inverse correlation in the frontal lobes between fractional anisotropy (FA; a measure of the directionality of water diffusion in white matter) and both divergent thinking and openness, such that more creative individuals as measured by these traits tended to have lower frontal white matter FA. While FA is often associated with myelination of axons, several other properties such as axon count, axon packing, and crossing fibers can affect the anisotropy of water diffusion in the brain as well. While the exact neural correlates of FA are not determined precisely, DTI nonetheless provides a non-invasive means of investigating longitudinal changes in the structure of white matter. Several recent studies have shown that diffusion tensor imaging (DTI) is an effective tool for tracking learning-related changes in the white matter organization of the brain in as little as six weeks or as long as nine months (May, 2011, Schlegel et al., 2012, Scholz et al., 2009). Even shorter term changes (in as little as five days) have been observed in brain structure using other imaging modalities (Ditye et al., 2013, Driemeyer et al., 2008).

The visual system is organized to recover intrinsic properties of perceived objects such as size and reflectance. It therefore often counteracts context-dependent aspects of objects such as distance from the observer and ambient luminance (Todorović, 2002). In other words, the brain constructs our perception of the world not necessarily in accordance with the physical stimulation, but rather as it infers things to be intrinsically. For instance, a white flower still appears white in a blue-lit room, even though the flower reflects only blue light in such a room. While such inferences on the part of the visual system permit us to perceive intrinsic properties of objects (e.g. size, shape, or pigment), they can also lead to illusory percepts such as the Craik-O'Brien-Cornsweet and Müller-Lyer illusions (Figs. 1C & D) (Müller-Lyer, 1889, Todorović, 1987).

One skill acquired by many visual artists is the ability to create precise, realistic representations of the world. For these representations to appear realistic, they must reflect accurately the physical, rather than the inferred, properties of the observed environment. A representational artist may therefore need to counteract these inferences. Otherwise, the brain's corrections would propagate to the artwork and result in incorrect depictions of the subject matter (e.g. in a painting of a white flower in a blue-lit room, the flower would look whiter than in real life). How do representational artists learn to bypass these seemingly automatic inferential processes? Do their brains reorganize so as to perceive the true physical properties of stimuli directly, or do artists use other cognitive strategies such as correcting inaccuracies in an artwork by comparing the actual stimulus with an initial attempt at its representation? Previous studies have presented conflicting findings in this regard. Graham and Meng (2011) reported that professional painters were less susceptible than non-artists to the Craik–O'Brien–Cornsweet effect, suggesting that these artists' direct perceptual experience of luminance had changed as a result of training and practice. However, Perdreau and Cavanagh (2011) found no differences between the abilities of visual artists and non-artists to overcome luminance and size constancy operations. Drawing ability, rather than artistic ability more generally, has been shown to affect size constancy processes (Ostrofsky et al., 2012), integration of object information (Perdreau and Cavanagh, 2013), and encoding of object structure (Perdreau and Cavanagh, 2014). Several other scholars have argued both for and against differences between the perceptual abilities of artists and non-artists (Fry, 1920, Gombrich, 1960, Kozbelt and Seeley, 2007, Ruskin, 1857, Thouless, 1932). How representational artists can create faithful depictions of environments that are filtered through perception is therefore still an open question.

No matter the style or medium in which they work, artists must develop the ability to translate thoughts and perceptual experiences into skilled actions; in this case, drawing and painting. Here we conceive of perception-to-action as encompassing those cognitive processes that involve close interactions between perceptual and motor processes, broadly defined. Relevant perceptual processes could include visual perception of the subject of an art work or of the artist's own hand, or proprioceptive feedback from hand and arm as a drawing is created. Relevant motor processes could include both the hand and arm movements that create the art work and the eye movements that direct attention over the subject.

Previous studies have investigated how the drawing habits and abilities of artists differ from those of non-artists. Kozbelt (2001) found that artists' superior skills in perception, motor actions, and perceptuomotor integration contribute to their advantage in drawing ability. His data indicated additionally that the perceptual advantages among artists had developed largely to serve drawing skills. Providing further evidence for a tight integration between perception and action among artists, Cohen (2005) found that artists shift their eyes between the drawing and its subject more frequently and that this gaze frequency correlates with drawing accuracy. He suggested that frequent eye gaze shifts to update the contents of perception allow artists to reduce the amount of (possibly inaccurate) information held in working memory. Glazek (2012) found additionally that artists engage more efficient visual encoding and motor output mechanisms when drawing. These results may also relate to Perdreau and Cavanagh's (2011) argument that artists overcome constancy operations essentially by trial and error: drawing a subject and then making corrections after comparing the drawing to the subject. If this is the case, one aspect of becoming skilled in drawing may be development of the ability to compare drawing and subject while creating an artwork.

An influential model of the visual system proposes that visual information processing can be divided primarily along two neural pathways or processing streams (Goodale and Milner, 1992, Mishkin and Ungerleider, 1982). The ventral or vision for perception stream is responsible for recovering information about object identity and tracks features such as size, shape, and color. The dorsal or vision for action stream is responsible for spatial awareness and the guidance of movements such as the strokes of a paintbrush. Since artists' perceptual skills exist to subserve skilled movements, it is possible that a representational visual artist's training can target the functions of the vision for action stream over those of the vision for perception stream. If so, finding evidence of differences between the perceptual skills of artists and non-artists may depend on whether the tests of those skills target purely perceptual or perception-to-action pathways.

In the current study we investigated behavioral and neural changes in creative cognition, visual perception, and perception-to-action as follows. First, in behavioral sessions at the beginning and end of the study, participants completed the Torrance Tests of Creative Thinking Figural Form A (TTCT; Fig. 1B) (Torrance, 1969). The TTCT tests for the ability to think creatively as defined by several factors such as fluency, originality, abstractness of thought, the ability to depict complex systems compellingly, and the creative use of imagery and language. The test yields a single composite creativity index (CI) as well as submeasures that separately assess many aspects of creative ability. Although the painting and drawing courses completed by the participants were not designed explicitly to improve the creative qualities measured by the TTCT, we hypothesized that training in painting and drawing would transfer to improvements in some or all of these qualities. Because of the finding of Jung et al. (2010) we hypothesized additionally that any changes we observed in the creative thinking abilities of our experimental group would correlate with corresponding changes in prefrontal white matter organization.

Second, in order to track the development of perceptual abilities in our visual art students and test whether improvements in these abilities entail changes in the activity of the brain's perceptual pathways, we acquired a series of functional scans in each session while participants judged properties of illusory visual stimuli. For illusory stimuli we used the Craik–O'Brien–Cornsweet illusion (Fig. 1C) and the Müller–Lyer illusion (Fig. 1D). We chose these two classic visual illusions because they are cognitively impenetrable. Previous neuroimaging studies have shown that brain areas implicated in early and mid-level visual processing underlie the illusory effects (Perna et al., 2005, Plewan et al., 2012). If perceived strengths and neural correlates of these visual illusions change as students become artists, it would suggest neural plasticity at perceptual processing levels. However, no changes in earlier levels of processing would suggest that artists may have learned to interpret the outputs of early processing differently.

Finally, to assess learning-related changes in perception-to-action pathways, we acquired a functional scan during each session in which participants made quick, 30 second gesture drawings based on observation of human figures (Fig. 1E). Gesture drawing is a technique often used among representational artists to develop more direct translation of visual observation to hand and arm movements. In creating gesture drawings, one is often discouraged from devoting attention to the art work itself, focusing more on translating directly from the perceived form and gesture to motor actions that faithfully capture those aspects of the subject on the canvas. This was especially true in the current study, since participants lay with their heads still in the scanner and had little opportunity to see the drawings as they were produced. If visual art training targets perception-to-action, we hypothesized that changes in neural activity would be observed in the corresponding perceptuomotor pathways among our art students.

Until recently, plastic reorganization of the brain was thought to occur mainly during childhood and adolescence, leaving adults with limited means to learn new skills. Research in the last two decades has convincingly overturned this belief, revealing a brain that remains able to reorganize with learning well beyond early developmental periods (Draganski et al., 2004, Lövdén et al., 2010, May, 2011, Schlegel et al., 2012, Scholz et al., 2009, Taubert et al., 2010). Structural changes in the adult brain have been observed with interventions lasting as little as six weeks (Draganski et al., 2004). Our previous work has shown that novel insights can be gained into the neural processes underlying specific behaviors by studying how the adult brain changes as those behaviors are learned (Schlegel et al., 2012). Thus, studying how the brain changes as students become artists may reveal insights into how the brain mediates artistic work.