Neuroplasticity, Therapeutic Action, and Change
Although William James, Sigmund Freud, and Santiago Ramon у Cajal introduced formulations of neuroplasticity in their accounts of the brain toward the end of the 19th century, modern neuroscientists came to believe that the core structures of the brain are “hardwired,” fixed in accordance with the form and function of genetic codes, immutable by adulthood. Over the last two decades, however, researchers have rediscovered the ways in which the brain remains elastic and flexible, capable of change and growth across the course of life. Experience—patterns of activation—changes the brain.
The pioneering research of Eric Kandel, documenting the fundamental role of learning in gene expression and the development of neural structures in the marine snail aplysia californiai, deepens our understanding of the dynamics of neuroplasticity and the ways in which the experiential opportunities of psychotherapy potentially expand and strengthen the networks that form the neural substrate of mind.
Kandel completed training in psychiatry and had planned to practice psychoanalysis before he decided to pursue a research career in neuroscience, and he began to explore the clinical implications of neuroplasticity decades before he received the Nobel Prize for his studies of the cellular mechanisms of learning and memory in 2000. Drawing on Cajal’s theory that learning modifies the strength of synaptic connections between neurons, he proposed that different forms of learning generate different patterns of neural activity that change the strength of synaptic connections in particular ways. In 1979, in his account of “Psychotherapy and the single synapse,” he explored the relevance of neuroplasticity for clinical practice, framing psychotherapy as a psychological and social influence that changes the brain. “It is only insofar as our words produce changes in each other’s brains,” Kandel proposed, “that psychotherapeutic intervention produces changes in patients’ minds. From this perspective, the biological and psychological approaches are joined” (1979, p. 1037).
He had chosen the sea slug for his research because the neural memory' structure of the snail is observable to the naked eye, allowing Kandel and his collaborators to map a series of networks and functions that they manipulated in classic conditioning experiments. In his studies of the snail, carried out over three decades, he found that the number of synapses doubles or triples as a result of learning.
Although the anatomical connections between neurons develop according to a definite plan, the strength and effectiveness of the connections are not fully determined by' template genes. They' can be altered by experience. In Kandel’s account of neural development, experience activates the transcription of certain genes that facilitate the synthesis of proteins instrumental in the development of neural structures. Gene transcription mediates the ongoing growth of neurons, altering the structure and function of the cell. Experiential learning in the social surround continues to shape the development of the brain, modifying the molecular mechanisms that govern gene expression, determining when genes express themselves through the process of protein synthesis (Kandel, 1998, 2006, 2018). Nature and nurture, genetic action and experience, shape the development of the brain.
Kandel continued to explore the ways in which the experiential opportunities of psychotherapy potentially' expand and strengthen the networks that form the neural substrate of mind. In an influential article, “A new intellectual framework for psychiatry,” he proposed that the experiential learning that occurs over the course of psychotherapy carries the potential to bring about the comparable degrees of growth in neuronal and synaptic functioning that he had documented in his studies of the sea slug.
When psychotherapy brings about change and growth, he argued, “it presumably does so through learning, by producing changes in gene expression
Neuroscience and Therapeutic Action 59 that alter the strength of synaptic connections, and structural changes that alter the anatomical patter of interconnections between nerve cells of the brain” (Kandel, 1998, p. 460). The interactive experience of psychotherapy, engaging the mental processes of mind, carries the potential to change the physical processes of the body.
The “regulation of gene expression by social factors makes all bodily functions, including all functions of the brain, susceptible to social influences,” Kandel explains. “These social influences will be biologically incorporated in the altered expressions of specific genes in specific nerve cells in specific regions of the brain” (1998, p. 461).
When a therapist speaks to a patient and the patient listens, the therapist is not only making eye contact and voice contact, but the action of neuronal machinery in the therapist’s brain is having an indirect, and, one hopes, long-lasting effect on the neural machinery' in the patient’s brain and quite likely, vice versa. Insofar as our words produce changes in our patient’s mind, it is likely' that these psychotherapeutic interventions produce changes in the patient’s brain. From this perspective, the biological and the sociopsychological approaches are joined.
(1998, p. 466)
Kandel believes that psychological and social domains of understanding remain crucial as we continue to shape the science of mind, and he attributes causal factors to the dynamics of mental life and interactive experience in accord with the principles of non-reductive materialism, offering an integrative biopsychosocial perspective (see Kandel, 1999). The structure and function of the brain are shaped by' experience unique to each individual, dependent on the person’s particular experiential history' (Milner, Squire & Kandel, 1998, p. 463).
Drawing on Kandel’s research, clinical scholars in the field of interpersonal neurobiology have emphasized the recursive dynamics of the development of brain and mind across the life course (Howe & Lewis, 2005; Kandel, 2018). Our behavior shapes genetic expression and regulation, creating patterns of activation and neural connections that, in turn, influence how we feel, think, and act. As Siegel explains: “Experience, gene expression and gene regulation, mental activity', behavior, and continued interactions with the environment (experience) are tightly linked in a transactional set of processes” (2020, pp. 50-51). Genes and experience, nature and nurture, shape the development of the brain and mind. The structural changes may encompass the genesis of new neural tissue and expanded arborization of neurons, enhancing synaptic connectivity'.
The transcription function of genes underlies our capacity' for neuroplasticity' across the course of life, and our conceptions of Hebbian learning and longterm potentiation provide heuristics for understanding the ways in which the core conditions of the therapeutic relationship and the experiential opportunities of help and care potentially promote the growth of neurons and expansion of neural networks, changing the structure and function of the brain.