the Liturgical Brain: Neuroscience of habitBy Daniel Dorman
Your brain is wired for habit. Neuroscientists are discovering the stunning complexity of the brain that predisposes it to develop habits in response to repeated and rewarding experiences. Your brain is also wired by habit. Repeated behaviors physically shape, wire, and rewire the connections between brain cells to become established habits embedded in brain circuits. From the macroscale landscape of brain regions consisting of billions of brain cells to the microscale single branching neuron with its intricate biochemical machinery, neuroscience is revealing the brain circuits that mediate habit formation. Habits, whether mundane or spiritually transformative, whether for good or ill, establish lasting changes in the brain that orient every facet of life.
It does not, of course, take neuroscience to reveal the significance of habits in human life. Biblical and Christian wisdom has long recognized the transformative role that habits of love, prayer, and worship have in renewing the Christian mind. Hence Paul’s injunction, “Do not be conformed to this world, but be transformed by the renewal of your mind…” (Romans 12:2a, ESV). James K. A. Smith’s recent book You Are What You Love makes a compelling argument that we are liturgical beings formed by liturgical practices, and he shows how historical liturgies of Christian worship form the Christian mind (1). What neuroscience adds to the picture is a view of the beautifully complex biology that allows us to be just this—we are liturgical beings in part because we are embodied with liturgical brains.
Because our brains are wired for habits, it should come as no surprise that transformative spiritual practices result in measurable changes in the brain. A recently published study by Andrew Newberg and colleagues found this to be the case (2). In their study, Christians were enrolled in a seven-day Jesuit spirituality retreat. The scientists scanned the participants’ brains before and after the retreat, and for every participant they found measurable, significant changes in regions of the brain called the basal ganglia, which are involved in reward-sensitive learning and habit formation. The PET brain scan used in the study is not sensitive to moment-to-moment fluctuations in brain activity, but rather reflects longer lasting, established characteristics of brain signaling. Therefore, the changes observed in the attendees following the retreat reflected a significant and enduring change in brain activity due to the experience of participating in the spiritual retreat. The scientists also found corresponding improvement in measures of psychological well-being for the attendees. This preliminary study does not indicate which specific practices of the retreat—which included prayer, quiet, scripture meditation, and disconnection from the technologies and stresses of normal life—were most significantly related to the changes in the brain. Nor did it include a control group that did not attend the retreat. Nevertheless, the study strongly indicates that spiritual practices change the activity of the basal ganglia in the brain. How might observed changes in the basal ganglia following a spiritual retreat relate to the neurobiology underlying habit? Human brain scans can give a big picture view of the brain regions that functionally correspond to habits. This macroscale view of the brain, however, cannot record the activity of single neurons or even circuits of neurons to understand how a particular brain region is involved in habit. To resolve the circuit level and single cell details of the brain, neuroscientists turn to more invasive technologies and techniques in animal brains. By combining human and animal studies with a diverse array of scientific techniques, neuroscientists are painting a picture of how the cells and circuits of the mammalian brain are wired by and for habit. How do the brain cells and circuits of the basal ganglia mediate habit formation? The basal ganglia consist of several interconnected nuclei of neurons that are deep in the brain, lying beneath the outer convoluted layers known as the cortex. Each nucleus is a cluster of millions of functionally related and interconnected neurons. Essentially, neurons of the basal ganglia form feedback loops to regulate the activity of neurons in the cortex, which in turn control behavior. Basal ganglia neurons receive input from cortical neurons, and through a series of connections loop back to regulate the output of other cortical neurons. Two pathways with opposite effects on cortical activity loop through the basal ganglia. One pathway excites specific cortical neurons related to a desired or habitual behavior. The second pathway inhibits competing cortical neurons. By selectively activating the patterns of cortical activity necessary to carry out a behavior while simultaneously inhibiting activity that would oppose the desired behavior, the two pathways of the basal ganglia modulate cortical activity to perform desired or habituated behaviors. Activity-dependent modification of the neuron-to-neuron connections from the cortex to the basal ganglia is a form of neuroplasticity that can change the connection strength of neurons in the brain and lead to changed, learned behavior. The basal ganglia can be classified functionally into two systems. The associative system is involved in goal-directed behaviors, while the sensorimotor system is involved in habitual behaviors. Many behaviors that begin as goal-directed, over time, become learned habits. For example, learning to drive a car requires practice and focused mental effort that limits the ability to simultaneously perform other goal-directed tasks, such as planning what you will do at your destination. Once learned, however, the habitual system can carry out the driving with little mental effort, allowing you to plan your workday while you drive to work. This habitual sensorimotor system allows us to flexibly and effortlessly navigate a world that is feeding an overwhelming amount of sensory information to our brains. This system is also to blame when you habitually turn your car in the direction of work on a day off. Competition and cooperation between the two systems is important for learning goal-directed skills, transferring them to habits, and in replacing unwanted habits. Distinct patterns of brain wiring underlie the difference between the goal-directed and habitual systems. The associative (goal-directed) system receives cortical input from brain areas such as the prefrontal cortex that are involved in setting goals and regulating behavior. The sensorimotor system primarily receives cortical input from sensory and motor regions of the cortex. The two systems are intrinsically very similar, but the difference in their inputs and outputs enables them to mediate both goal-directed learning and habit formation. The goal-directed system is fast, while the habit-forming system is slow. While you are learning a new skill, such as playing the piano, both systems are learning in parallel, but the fast goal-directed system learns first so that you can play a chord with mental effort before you can play it habitually. As the skill becomes engrained in the habitual system, neuronal connections in the goal-directed system are weakened as it becomes less involved in the task. In the habit-forming sensorimotor system, repeated patterns of sensory and motor activity become associated, establish changes in the basal ganglia, and lead to the reinforcement of specific motor responses to the same sensory context. Though slower to form, brain changes in the sensorimotor system enable independent execution of habits in response to sensory context that become difficult to change. Changing habits likely requires the goal-directed system to learn and maintain counter-habits while the old habits of the sensorimotor system become weakened with disuse. Both systems of the basal ganglia are activated by the reward neurotransmitter dopamine. Dopamine molecules are released in response to rewarding stimuli or experiences, and dopamine binds to its target neurons to trigger physiological changes that can result in neuroplasticity. The basal ganglia integrate contextual information from the cortex with reward information transmitted by dopamine. If a certain action performed in a certain context is rewarding (such as playing the right chord in a piece of music), the basal ganglia reinforces the cortical activity associated with that action. Over time, many repetitions lead to strongly reinforced actions that become habits. Neuroscientists are also discovering how single neurons function within habit-forming systems. A single neuron of the basal ganglia receives inputs from thousands of different cortical neurons as well as input from dopamine-releasing neurons. Active cortical neurons excite basal ganglia neurons, while dopamine modulates their excitability. A significant number of cortical inputs must be active nearly simultaneously to activate a basal ganglia neuron. If a specific sensory context is represented in the simultaneous activation of thousands of cortical neurons, a basal ganglia neuron that receives those inputs will sense the specific context. However, cortical activation alone does not rewire basal ganglia connections; it must be closely followed by dopamine activation. Cortical and dopamine signaling interdependently trigger biochemical responses inside basal ganglia neurons that can lead to long-lasting changes in their structure and function. In this way, a single neuron can compute the association between a sensory context (represented by its total cortical input) and a rewarding outcome that triggers a dopamine response. Across millions of neurons, these small changes in single neurons change the activity patterns of brain circuits and lead to the development of long-lasting learned and habituated behavior. There is an astounding degree of detail and complexity to the brain that enables it to sense repeated experiences, change in response to those repeated experiences, modify its activity until its actual behavior matches a desired behavior, and maintain behaviors as enduring habits. The biology of our brain is tuned to reinforce our practices and behaviors. As Christians, this can lead us to marvel at how God has created us as embodied beings and breathed into us the dynamic biological forms that enable us to worship and invoke the image of our Creator through the cultivation of spiritual habits. It can also make us aware of how sinful habits can be strongly reinforced in our brains, but also how God in his grace has created our brains with the ability to change. Liturgically formative practices transform us by renewing our minds through the work of the Holy Spirit. And, as neuroscience is discovering, spiritual disciplines physically renew our minds by rewiring our brains. With the Psalmist we can proclaim, “I praise you, for I am fearfully and wonderfully made. Wonderful are your works; my soul knows it very well.” (Psalm 139:14) (1) Smith, James KA. You are what you love: the spiritual power of habit. Brazos Press, 2016. (2) Newberg, Andrew B. et al. “Effect of a One-Week Spiritual Retreat on Dopamine and Serotonin Transporter Binding: A Preliminary Study.” Religion, Brain & Behavior 0.0 (2017): 1–14. 
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Daniel Dorman is a PhD Candidate in the Interdisciplinary Neuroscience Program at George Mason University in Fairfax, Virginia, where his research focuses on mechanisms of plasticity in brain cells that underlie the learning and performance of goal-directed and habitual behaviors. He is broadly interested in computational and theoretical approaches to neuroscience that integrate the microscale functions of individual brain cells with mental processes such as learning, memory, and cognition. As a Christian, Daniel is also interested in integrating a Christian view of the human person with the neuroscientific evidence linking brain processes to human experience.
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