Neural foundations of creativity: A systematic review

Abstract

When considering the importance of the human cognitive function of creativity, we often overlook the fact that it is due to human creativity and to the constant search for new sensory stimuli that our world has, throughout the years, been one of innovation in every aspect of our existence—in the sciences, the humanities, and the arts. Almost everything that surrounds us is the result of human creativity, therefore it is not difficult to understand that although neuroscientific research has led to valuable perceptions into the probable underpinnings of this multifaceted ability, the precise neurological substrates that underlie creativity are yet to be determined. Despite the establishment of a strong link between creativity and divergent thinking, other brain networks have been implicated in this mental process. The following review underlines recent studies on the neural foundations of creativity. A comprehensive analysis of the upmost important facts will be presented, with emphasis on concepts, tests, and methods that have been used to study creativity, and how they have outlined a pathway to the key understanding of this unique human ability.

Resumen

Al considerar la importancia de la creatividad en la función cognitiva humana, sucede con frecuencia y pasamos por alto el hecho de que es precisamente debido a la creatividad humana que a través de los años nuestro mundo ha estado en constante innovación en cada aspecto de nuestra existencia: en la ciencia, las humanidades y las artes. Casi todo lo que nos rodea se debe a la creatividad humana; por lo tanto, no es difícil entender que, aunque la investigación neurocientífica ha conducido a percepciones valiosas sobre los fundamentos probables de esta capacidad multifacética, estos estudios no han permitido conclusiones claras y tienen todavía mucho por determinar para comprenderla mejor. A pesar de que se ha establecido un fuerte vínculo entre la creatividad y el pensamiento divergente, científicos han identificado otras redes cerebrales implicadas en este proceso mental. La presente revisión subraya los estudios recientes sobre los fundamentos neuronales de la creatividad. Se presenta un análisis comprensivo con énfasis en los conceptos, las pruebas y los métodos que se han utilizado para estudiar la creatividad y la forma en que han proyectado una vía para la comprensión fundamental de esta capacidad humana única.

Introduction

In the last decade, although studies in neuroscience have provided important insights about the neural basis of creativity, these studies have not yet led to clear assumptions regarding neural correlates due to the complicated construct of the topic.¹ Neural correlates in the fundamental human capacity of creativity have become increasingly important in research,² albeit hard to document and replicate due to their abstract and multiform definitions which are likely to involve other cognitive brain processes.³ Therefore, although specific neural processes are assumed to mediate creativity, their scientific exploration has been extremely challenging.⁴ There is no single measure method that can apprehend the multifactorial complexity of this cognitive function. Research on creativity is puzzling for a number of reasons; more specifically, the study of creativity becomes complicated when identifying tasks that will be able to measure creativity without other cognitive processes that can trigger brain responses.⁵ For example, rather than being yes or no answer tasks,⁶ creativity tasks involve verbal or written/drawing responses that may lead to brain activity related to working memory, attention and language.⁷ Furthermore, there is also a problem due to the conceptual meaning of creativity and the difficulties overcoming the fact that creativity is not predictable and cannot be prompted volitionally.

The problem can be approached at the level of large-scale systems using neuroimaging methods and standardised psychometric tests.^8,9. Brain imaging methods including positron emission tomography (PET), functional magnetic resonance imaging (fMRI) and electroencephalography (EEG and event-related potentials [ERP]) have provided important implications regarding the neural basis of creativity.^10,11 Notwithstanding the lack of consensus, developing literature and neuroimaging studies has prompted the suggestion that divergent thinking is a neural correlate of creativity and a central component of the ability.¹² Specifically, these studies provide information on the role of the prefrontal cortex, the default mode network and central executive processes associated with internally-directed attention and spontaneous cognition.¹³

This review discusses definitions and evidence regarding the neural basis of creativity in an attempt to explain the neural mechanisms underlying this mental process, elucidating the current difficulties and the need to study other approaches and reveal how functionally-linked neural areas may contribute to the production thereof. By reviewing creativity, this article hopes to clarify that this cognitive process is one that cannot be completely apprehended by current theoretical proposals.

An approach to unravelling the meaning of creativity

Over the years there have been many definitions of creativity. Wallas¹⁴ proposed that creativity was a mental process that included phases such as preparation, incubation, illumination and verification. Torrance¹⁵ defined creativity as “a process of becoming sensitive to problems, deficiencies, gaps in knowledge, missing elements, disharmonies, and so on; identifying the difficulty; searching for solutions, making guesses, or formulating hypotheses about the deficiencies: testing and retesting these hypotheses and possibly modifying and retesting them; and finally communicating the results.” Bronowski¹⁶ defined creativity as the ability to find unity in what appears to be diverse or finding the thread that unites. Moreover, Boden¹⁷ formalised a mathematical Creative Systems Framework based on creative conceptualisation and process. Heilman¹⁸ defined creativity as “the ability to understand, develop and express in a systematic fashion, novel orderly relationships”. Lastly, Schmidhuber¹⁹ proposes a model founded on intrinsic motivation and creativity based on maximising intrinsic reward for the active creation of innovating sequences that allow for prediction.

It is important to understand that creativity is influenced by the development of new social institutions, economic growth²⁰ and time. Creative potential exists in everyone, but is greatly influenced by experiences and social and environmental contexts.²¹ Curiosity, experience and the senses are all key in the construct of creativity.²² Experience can be considered as a basis through which us humans more effectively influence the world we live in by constantly creating new and different ways of sensing our environment.²³ Considering the relationship between sensory-driven information and mind-driven information²⁴, it can be stated that creativity is a multimodal process that comprises sensory areas such as visual, tactile, olfactory, auditory, gustatory, physical and also cognitive, emotional and verbal information.²⁵

There is a general consensus that creativity is a multifaceted phenomenon²⁶ that involves the ability to create or work on something that is innovative, beneficial, practical and generative.²⁷ However, creativity can be also observed, considered and studied as a part of a process, rather than a mere ability.²⁸ Creativity in the brain does appear to work in a series of cognitive function networks such as attention, flexibility and cognitive control.^29,30 As mentioned, an increasing body of research around divergent thinking proposes an interest in the cognitive basis of creative thought. Defined as the ability to generate a variety of solutions to an open ended problem (Guilford, 1967), divergent thinking was taken up to pinpoint one of the main problems regarding creativity's complex and multi-layered nature.¹²

Cognitive neuroscience in creativity: psychometric standardised tests

One of the challenges to investigating creativity lies in the widespread use of qualitative approaches. This has led to the development of several metrics in an attempt to investigate brain correlations in a quantitative or semi-quantitative manner.^31,32 At the present time, it is important to understand the terms convergent and divergent thinking and their definitions.²⁰ While convergent thinking leads to conventional ideas and solutions, divergent thinking leads to originality, which—we can now agree—is the central feature of creativity.³³ Taking this into account, most measures involve divergent thinking, and look at fluency, originality, flexibility and elaboration.^34,35 Fluency considers the ability and fluency of an individual to provide a large number of organised ideas. Originality is based on innovation and frequency. Flexibility leads to diverse ideas, and elaboration to an associative pathway followed by an individual.³³ What follows is a further overview on some of the most commonly used measures for creativity research.

Guildford's divergent thinking test 1967 (DTT)

During this test individuals list as many uses for common objects as possible. Scoring is comprised of four basic components: originality, fluency, flexibility and elaboration.³⁶

Structure of the intellect (SOI) divergent production test

This test is based on Guildford's DTT (1967) and considers an individual's potential for divergent creations in numerous areas such as semantic systems, figural systems and symbolic units. The test has a scoring criteria which is also based on fluency, flexibility, originality and elaboration.²⁶

Wallach–Kogan test of creative thinking (WKCT)

WKCT is based on the associative notion of creativity; the performance of this task is then scored on the number of related responses and uniqueness generated under several contexts.²⁶

Torrance tests of creative thinking (TTCT) (1966)

This test provides a tool that can evaluate an individual's creative potential and can accommodate their demographic properties. The test has a figural and verbal component, each with different tasks. The first scores an individual's originality and elaboration potential, picture completion, fluency and flexibility. The verbal task scores for fluency, flexibility and originality.³⁷

Remote associate test (RAT)

The RAT is a test of creative potential and is based on associations and convergence. The questions presented consist of three common stimulus words that can be linked to a fourth word. This test is a verbal task of a certain degree of complexity, involving creative thought and intelligence.³⁸

Consensual assessment technique (CAT)

The CAT was developed to evaluate the perceived creativity of finished items or pieces. During this test, creativity researchers rate a set of products that include stories, poems and other items.³⁹

Brain imaging in creativity

There are several cognitive neuroscience methodologies that provide a basis for understanding the neural correlates of creativity.⁴⁰ Brain imaging technologies are essential in order to identify the areas of the brain that are associated with creativity and the processes related thereto.⁸ Many of these studies shed light and reveal information on areas of the brain that are involved in divergent thinking and the relationship with the Default Mode Network.

Electroencephalography

EEG measures electromagnetic electric fields generated by neuronal activity through sensors that are placed on the patient's scalp.⁸ The method detects neural activity in the dendrites and an electromagnetic field is created if a sufficient number of neurons are receiving signals at the same time.⁴¹ EEG is usually used to measure an event-related potential; this means that information is recorded after the presentation of a stimulus. These studies have revealed that brain patterns are due to different types of cognitive thinking tasks such as mathematical or language processing tasks.²⁷ EEG can be quantified using many different techniques that have proved effective in creativity studies.³¹ Data is reported in ranges of frequency: delta activity is associated with deep sleep and reflects a low neuron firing rate; theta waves are associated with drowsiness; alpha activity can be evidenced with minimal arousal; beta waves occur during active thinking; and finally, gamma activity is associated with perceptual information.¹² In neuroimaging creativity, EEG studies include tests and tasks such as RAT insight problems,¹² GDTT stories,⁴² divergent thinking with closed eyes⁴³ and mentally creating a drawing while looking at a white wall.⁴⁴

Functional magnetic resonance imaging

Neuronal activation results in a local increase in blood supply to the active area of the brain, which induces a change in the relative concentration of oxyhaemoglobin and deoxyhaemoglobin.⁴⁵ fMRI uses a magnetic field to measure these relative changes in the oxy- and deoxyhaemoglobin concentration by using a technique known as the blood-oxygen-level (BOLD) dependent signal. Sites with increased activity receive more blood, which in turn increases the BOLD signal.⁴⁶ fMRI captures these signals and provides images of areas of brain activation.⁸ There are several studies on neural correlates of creativity using fMRI, and tasks such as the three-word remote associates test⁴⁷ match problems, divergent thinking,⁴⁸ story generation task,⁴⁹ processing novel metaphors⁵⁰ and Rorschach-ambiguous figures.⁵¹ In most of these studies, the significant associations are in brain regions unique to each study due to the sensitivity of functional imaging and the differences in experimental design structure.

Positron emission tomography

When neurons are firing rapidly, there is an elevated neuronal activation leading to an increase to their blood supply that matches the increase in oxygen demand.⁸ By introducing a radioactive tracer into the blood stream, PET measures the differences in regional cerebral blood flow (rCBF). Where there is more blood flow to a specific location, a larger amount of the radioactive tracer accumulates in the vascular beds of tissue, resulting in increased radiation emissions from that particular location.⁸ The patient is given a cognitive task and the associated brain regions are then activated. The scanner is thus able to measure brain activity.⁸ Several tests have been conducted using PET. Some of these include a creative functioning test,⁶ which involves creating a story using easy or hard words presented on a screen,⁵² and a creative and two control tasks.⁵³ These studies presented some evidence that, when undertaking cognition tasks involving creativity, creative people show greater activation in the bilateral prefrontal regions. Less creative subjects presented rises in the left prefrontal region when performing a creative cognition task.⁴⁵ Concordantly, studies using PET reveal the activation of the prefrontal regions during creative tasks.

Divergent thinking and the default mode network

Behavioural evidence of the cognitive processes related to divergent thinking has been supported by EEG and fMRI studies that report task-related activation in regions of the brain associated with creative cognition.³⁴ Such studies compare neuronal activation and brain activity patterns in individuals with high vs. low levels of creativity, proving that highly creative people show stronger prefrontal brain activation.³¹ Among the most strongly activated regions during divergent thinking is the inferior prefrontal cortex (IPC). Conversely, neuroimaging studies have also reported activation in brain regions within the default mode network, which includes the medial temporal lobe (MTL), the ventral and dorsomedial prefrontal cortex (PFC), the posterior cingulate cortex (PCC), the inferior parietal lobule and the hippocampal formation. Creativity researchers have hypothesised that the DMN underlies processes such as internally-directed attention and selective retention processes during divergent thinking.³⁴

Further evidence of the DMN's role in divergent thinking can be evidenced though resting state fMRI (rs-fMRI), which has enabled functional communication between brain regions to be examined by investigating their level of co-activation at rest.^12,13,34 Regions of the DMN show activation during resting states and their activation is reduced during demanding cognitive tasks. This has led researchers to suggest that divergent thinking reflects an attentional focus shift from spontaneous cognition (regions associated with the DMN) and cognitive control (PFC).^12,34

EEG studies could support the notion that DMN regions show activation during resting states and with minimal arousal. A psychometric review on neuroimaging creativity by Arden et al.⁴⁵ reported that virtually all of the EEG studies in neuroimaging creativity used measures of divergent thinking. Moreover, most of these EEG studies indicate alpha band synchronisation changes linked to creative task performance in the centro-parietal brain regions. This is a focus of interest since the increase in power and synchrony at this frequency wave indicates low levels of cortical arousal and defocused attention. Nevertheless, there is significant heterogeneity of outcomes across EEG studies on creative cognition,⁴⁵ thus making it somewhat difficult to obtain strong conclusions about the impact of alpha activity, power and the location of these factors within neural activity on a particular task.⁴⁵

Conclusions

In conclusion, a broad review of the literature indicates that important progress has been made over the last decade; however the neural basis of creativity is still puzzling. Although measures, tests and neuroimaging methods provide researchers with important information regarding creative underpinnings in the brain, it is essential to understand that these methodologies have both strengths and weaknesses. Regardless of this fragmentation, we can draw some conclusions from the existing information:

• 1.

  There appears to be consensus on the brain activity in the prefrontal cortex⁴⁵ during divergent thinking tasks; however, it is unclear which cortices are in involved. Studies have shown activation of the ventrolateral prefrontal cortex, the right ventromedial prefrontal cortex, right premotor region, left dorsolateral prefrontal area and supplementary motor area.

• 2.

  A growing body of evidence suggests that divergent thinking is related to regions associated with internally-directed attention and spontaneous cognition, indicating a functional link to the DMN.^34,42,43

• 3.

  Creativity cannot be localised to a single part of the brain due to its implicit and multifaceted nature. This means that the underlying characteristics of creativity are not dependent on a particular mental process or brain region; rather, they depend on a network of different brain regions. Divergent thinking is broadly distributed and does not involve a specific set of processes and thus a specific brain region. It is the construct of these processes that result in different patterns of brain activation that make creativity such a fascinating human skill.⁵⁴

• 4.

  Although there is a tendency to believe that creativity is a function strictly related to the right hemisphere, neuroimaging results indicate that divergent thinking, and thus creativity, require the activation of different areas involving both hemispheres of the brain.⁴⁵

The most direct inference that can be made from this review is that there is no current notion that is able to capture the neural mechanisms underlying creativity. Such a broad pattern of processes requires a comprehensive framework in order to pursue greater understanding. There is a long road ahead in order to validate current models of measures and methods in creative processes. Further studies would prove valuable by examining whether the involvement of neural substrates underpinning control processes also diverges according to the content of creativity.

Conflicts of interest

The author has no conflicts of interest to declare.