Health Soc Work. Author manuscript; available in PMC 2010 September 6.
Published in final edited form as:
Health Soc Work. 2009 August; 34(3): 191–199.
PMCID: PMC2933650
NIHMSID: NIHMS217651
Neuroplasticity, Psychosocial Genomics, and the Biopsychosocial Paradigm in the 21st Century
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Abstract
The
biopsychosocial perspective is a foundation of social work theory and
practice. Recent research on neuroplasticity and psychosocial genomics
lends compelling support to this perspective by elucidating mechanisms
through which psychosocial forces shape neurobiology. Investigations of
neuroplasticity demonstrate that the adult brain can continue to form
novel neural connections and grow new neurons in response to learning or
training even into old age. These findings are complemented by the
contributions of psychosocial genomics, a field of scientific inquiry
that explores the modulating effects of experience on gene expression.
Findings from these new sciences provide external validation for the
biopsychosocial perspective and offer important insights into the
manifold means by which socioenvironmental experiences influence
neurobiological structure and function across the life course.
Keywords: biopsychosocial, neuroplasticity, psychosocial genomics, gene-environment interaction
Introduction
Social work professionals in the 21st
Century have adopted the biopsychosocial paradigm. This paradigm, first
articulated by the physician, George Engel, holds that humans are
dynamic systems whose functioning depends on the holistic integration of
biological, psychological, and social factors (Engel, 1977);
indeed, according to the biopsychosocial model, these factors are
fundamentally interrelated and interdependent. Although Engel rejected
the reductionism of the dominant biomedical model of his era, which
assumed that molecular biological processes (e.g., genes and
biochemistry) immutably dictated physiology and behavior, a
simple-minded biological determinism nonetheless took root and became
widely, if uncritically, accepted. At its inception, there was scant
evidence to support Engel's biopsychosocial perspective; however,
scientific discoveries of the past decade have provided important new
findings validating and elaborating the biopsychosocial paradigm.
Over
the past decade, two fields of empirical investigation, neuroplasticity
and psychosocial genomics, have offered important findings that may
lead to a paradigm shift in our conceptions of psyche and soma and the
modes of their interrelationships. These two fields mutually inform one
another, depicting interpenetrating biopsychosocial relationships on
different scales:
neuroplasticity research describes how neurons within
the brain proliferate and grow new connections across the lifespan,
whereas psychosocial genomics describes the processes by which
psychological and social experiences activate or deactivate genes,
thereby driving the development of new neural pathways.
The interplay of
these sciences reflects a vision of humans as inherently resilient;
psychosocial factors appear to stimulate gene expression within neurons
resulting in alterations to the structure and function of the brain.
Discoveries from both fields reveal that experience and learning can
contribute to positive change, even at the neurobiological and
structural levels.
Social work academicians have embraced
the biopsychosocial perspective; yet, many are perhaps not fully aware
of recent developments in genomic and neurobiological research with
implications for social work and the biopsychosocial perspective. This
research provides insights into the very substrates of biopsychosocial
change. Thus, we review recent neuroplasticity and psychosocial genomics
research and its implications for current understanding and application
of the biopsychosocial perspective.
Neuroplasticity
Basic neurotransmission
The
human brain is a complex, self-organizing, biological system,
consisting of trillions of interconnected nerve cells called neurons.
The operation of neurons results in two distinct forms of information
processing: signaling and integration. Each neuron propagates signals
via action potentials, electrochemical currents that travel the length
of its axon. This current leads to the release of neurotransmitters
which traverse synapses, the gaps between neurons. These chemical
messages are received via specialized receptor cells at the ends of
numerous, tree-like branches of the receiving neuron, called dendrites.
The stimulation of dendritic receptors by neurotransmitters leads to
integration, whereby large amounts of information from many neurons is
summed up before reaching a threshold to fire the action potential down
the next axon. In this manner, perceptual information from the external
environment and the internal milieu of the body is transmitted and
processed in the brain, leading to cognition, emotion, and behavior, the
essence of human experience.
Origins of neuroplasticity research
The
brains of infants and children are known to be plastic, undergoing
spurts of neuronal development in response to stimulus exposure during
critical periods (Mundkur, 2005).
This development consists of the genesis of neurons, increased
connectivity between extant neurons, and the routing of new synaptic
connections between previously unrelated neurons. However, before 1998,
it was widely accepted that neuronal connections in the adult brain were
immutable; the neurons that populated a given brain area were thought
to be fixed in accordance with whatever form and function the genetic
code prescribed for that region (Begley, 2006).
In addition, the conventional wisdom at the time--that no new neurons
could be generated after injury or insult to the brain—was held with
conviction on the part of leading neuroscientists.
However,
upon discovery of the growth of new neural tissue, or neurogenesis, in
the adult human hippocampus, a brain region responsible for memory (Eriksson et al., 1998),
the dogma of the “hardwired brain” was formally repudiated. This
finding complemented earlier evidence from primate studies demonstrating
that novel sensory experience and learning new behaviors triggers
neuronal growth in the somatosensory and motor cortices, areas of the
brain subserving tactile perception and limb movement (Jenkins, Merzenich, Ochs, Allard, & Guic-Robles, 1990; Nudo, Milliken, Jenkins, & Merzenich, 1996).
Subsequent to the discovery of neurogenesis in the adult human brain,
neuroscience has pursued this line of investigation with vigor, aided by
advances in brain imaging techniques such as magnetic-resonance
imaging.
Neuroplasticity research findings
The
growth of neurons has been documented in the brains of adults exposed
to a variety of experiences. For instance, violinists evidence neural
growth in the portion of their somatosensory cortex devoted to their
fingering hand through hours of musical practice (Elbert, Pantev, Wienbruch, Rockstroh, & Taub, 1995), as do persons engaged in the practice of juggling (Draganski et al., 2004).
In addition to such physical training, mental practice may promote
neuroplasticity: neurogenesis can occur in the motor cortex just by
imagining playing the piano (Pascual-Leone, Amedi, Fregni, & Merabet, 2005).
Similarly, taxicab drivers develop the areas of their brains involved
in spatial relationships by memorizing the labyrinthine streets and
avenues of the cities in which they work (Maguire et al., 2000).
While the underlying mechanisms are different, neuroplasticity research
suggests that challenging learning experiences can lead to the
development of brain tissue analogous to the way physical exercise can
lead to the development of muscle tissue.
One area of
research that has found significant evidence of mental training leading
to neuroplastic modifications in brain activity focuses on the study of
meditation. Meditation, while greatly varying in technique and purpose
across the diverse spiritual and cultural traditions where it is
employed, may be generally defined as the intentional practice whereby
one grasps “the handle of cognition” to cultivate a competent use of his
or her own mental capacities, gaining agency over thought and emotion (Depraz, Varela, & Vermersch, 2003). Such intentional mental training has been shown to induce functional neurobiological changes.
A
study by Lutz and colleagues found marked alterations in the
synchronization of neurons as an effect of long-term training in
Buddhist loving-kindness meditation, a practice which is thought by some
practitioners to promote a state of unconditional compassion and
benevolence (Lutz, Greischar, Rawlings, Ricard, & Davidson, 2004). Neural synchrony of the type observed in this study may be indicative of coherent and integrated psychological functioning (Williams et al., 2005).
The synchronization of brain activity found in some of the
practitioners sampled, whose experience ranged between 10,000 and 50,000
hours spent in meditation, was higher than any previously reported in
the literature. Such increased neural synchrony was observed not only
during the meditative state, but also when the practitioners were not
meditating, suggesting that long-term mental practice can induce
lasting, trait-level changes possibly mediated by structural
modifications to the brain (Begley, 2006).
Other
research has documented changes in neurobiological function as a result
of mindfulness meditation, the practice of cultivating a
present-centered, metacognitive awareness, “a naturalistic state wherein
consciousness transcends its content to rest upon the dynamics of its
own processes” (Garland, 2007). A recent study by Slagter et al. (2007)
compared attentional performance of a group of experienced meditators
participating in a 3-month mindfulness meditation retreat to that of a
novice control group who received a 1-hour meditation class and were
asked to meditate 20 minutes daily for one week. Relative to controls,
experienced meditators evidenced significant improvements in attentional
performance that correlated with alterations in brain activity. This
cognitive enhancement was maintained 3 months after formal meditation
practice, providing suggestive evidence that mental training can
stimulate neuroplastic changes in the adult human brain (Slagter et al., 2007).
While
the work of Slagter et al. and Lutz et al. provide tentative support
for meditation-induced neuroplasticity, neither study examined
structural brain changes per se. However, two structural MRI
investigations comparing the brains of experienced meditators to control
subjects matched in sex, age, race, and years of education found that
years of meditation experience correlated with increased cortical
thickness in brain areas where visceral attention (e.g. right anterior
insula) and self-awareness (e.g. left superior temporal gyrus) have been
localized (Holzel et al., 2008; Lazar et al., 2005).
These empirical investigations of meditation suggest that mental
training may stimulate structural alterations reflective of
neuroplasticity.
Clinical implications of neuroplasticity research
The
finding that experience and training can lead to the development of new
neural connections has key implications. For example, persons suffering
from what was once thought to be permanent brain injury can heal
through rehabilitation designed to stimulate the damaged area, such as
in the case of stroke (Taub et al., 2006).
However, although largely speculative, it is possible that
neuroplasticity may undergird not only rehabilitation of physical
illness but that of select psychological disorders as well, mediating
natural recovery from mental illness in some cases as well as
improvements related to psychosocial interventions. At present, it has
been demonstrated that psychotherapy can induce functional changes in
brain activation. For example, a brain imaging study found that persons
with obsessive-compulsive disorder who were treated with a
mindfulness-oriented form of cognitive-behavioral therapy (CBT)
exhibited functional changes in the orbital frontal cortex and striatum,
two brain structures found to be overactive in OCD (Schwartz & Begley, 2002). Other studies have demonstrated psychotherapy-related alterations in brain circuits involved in depression (e.g. Goldapple et al., 2004; Martin, Martin, Rai, Richardson, & Royall, 2001). CBT has also been associated with changes in frontal and temporal brain regions of persons suffering from panic disorder (Prasko et al., 2004).
Such intervention-related changes in both psychosocial function and
neural activity may correlate with neuroplastic alterations to the
brain; critically, a combined functional and structural magnetic
resonance imaging study of practice-induced increases in gray matter
found that increased task-specific brain activation led to the
remodeling of one of the same neural structures (i.e. dorsolateral
occipital cortex) that was activated by the practice and learning of the
task (Ilg et al., 2008).
Neuroplasticity
research of psychosocial interventions has just begun. A recent
longitudinal study of cognitive-behavioral therapy for women with
chronic fatigue syndrome found increases in gray matter of the lateral
prefrontal cortex after 16 sessions of CBT (de Lange et al., 2008).
Increases in gray matter volume correlated with enhanced cognitive
processing speed, suggesting that the neuroplasticity evoked by
psychotherapy played a causal role in rehabilitation of cognitive
performance after cerebral atrophy resulting from chronic fatigue.
Indeed,
neuroplasticity may be the biological mechanism through which
psychosocial interventions exert at least some of their therapeutic
effects. During psychotherapy, when the client recalls negative or
painful life experiences, the clinician may assist in reframing the
context so that the experience gains new meaning (de Shazer, 1988).
For instance, in treating persons who have experienced traumas such as
rape, therapy may help clients to envision themselves as a survivor
rather than as a victim. Such reframing or reappraisal may be a critical
component of successful biopsychosocial outcomes (Folkman, 1997; Penley, Tomaka, & Wiebe, 2002).
Some theorists hypothesize that the process of recalling,
reconstructing, and reframing memories of past trauma during
psychotherapy is mediated by the reorganization and genesis of neurons (Centonze, Siracusano, Calabresi, & Bernardi, 2005; E.L. Rossi, 2005).
This hypothesis is founded on evidence that the formation of new
long-term memories results from neuroplastic changes in the brain
structure known as the hippocampus. Hippocampal changes appear within
hours of significant learning experiences (McGaugh, 2000), such as those that can occur during psychotherapy.
Neuroplasticity
is mediated at the cellular level through activity-dependent gene
expression, the mechanism by which neurons secrete growth factors
leading to the “activation of gene transcription in the nucleus that
support[s] synaptic connections…Thus, with every new experience, the
brain slightly rewires its physical structure and this rewiring is
mediated through the signaling cascade” (Mundkur, 2005). Hence, in order to understand neuroplasticity, we must consider the domain of psychosocial genomics.
Psychosocial Genomics
Basic epigenetics
In
the 21st century, there is broad agreement that the genome is the basis
of human life and a precondition for psychosocial experience.
Nevertheless, the question of the respective roles of nature and nurture
in human experience and the manner of their interaction in select
contexts remains contentious, despite the more than half-century that
has transpired since Watson and Crick (1953) identified DNA as the building block of biological processes.
The
DNA code of the human genome does not determine protein synthesis in a
one-toone fashion; instead, genes are subject to epigenetic processes
(i.e. modifications that do not occur due to changes in the basic
genetic sequence of amino acids but that instead result from biological
and environmental influences on the expression of genes as proteins) (Eisenberg, 2004).
During gene expression, the genetic code serves as a “blueprint” that
guides the construction of proteins from amino acids. However, this
construction process is modulated by signals from the internal and
external environments, which steer and modify the manner in which basic
organic molecules are organized into anatomy and physiology. Although
genes prescribe protein synthesis, there is substantial variability in
the manner in which they are expressed.
A single
genotype, the genetic blueprint of an organism, can be expressed in a
multiplicity of distinct physiological and behavioral forms, known as
phenotypes. This is evident in Eisenberg's (2004)
example of phenylketonuria, a disorder that when untreated may lead to
severe mental retardation, psychosis, and seizures. If children with
this genetic abnormality are kept on a postnatal diet low in the amino
acid phenyalanine, they do not develop these disorders. Hence, although
the genotype for phenylketonuria does not change, its phenotypic
expression is modified by the environment (i.e., nutrition) to which the
individual has been exposed. The mechanisms by which such different
phenotypes are expressed are just beginning to be understood, but appear
to involve the regulatory effect of internal and external environmental
signals on stress hormones, which in turn modify gene transcription
processes (Kandel, 1998; E. L. Rossi, 2004).
Learning and other psychosocial experiences may modulate gene expression
In addition to physical environmental forces, learning experiences in the social environment can alter gene expression (McCutcheon, 2006).
The bi-directional relationship of nature and nurture, genes and
environment, was first demonstrated in a series of path-breaking studies
of maternal care in rats (Francis, Champagne, Liu, & Meaney, 1999; Liu et al., 1997).
In these studies, an inverse relationship was found between the number
of stress hormone receptors in a rat's hippocampus and its tendency to
exhibit stress reactions. The number of these receptors is dictated by
the genotype of the rat. Highly stress-reactive rats give low levels of
maternal care to their offspring, who, in turn, exhibit high stress
reactivity and later provide low levels of maternal care to their
offspring. However, these studies revealed that hormonal and behavioral
stress reactions of rat pups as well as the number of their stress
hormone receptors are modulated by the licking, grooming, and nursing
behaviors of their mothers. Even if a rat were born with a genotype
coding for fewer stress hormone receptors, if it was reared by an
adoptive mother providing high levels of maternal care, the rat's genes
produced more stress receptors, making it calmer, less reactive to
stressors, and more apt to provide maternal care to its offspring. These
findings offer some evidence that social behavior may be inherited and
transduced via gene expression into neuroplastic alterations in brain
structure, leading to psychobiological learning and change.
The
notion that social experience can lead to changes in gene expression
was voiced most prominently by Nobel laureate, Eric Kandel, who regarded
this observation as the core component of a new paradigm for psychiatry
(1998). Kandel summarized the current state of biological thinking with
regard to the relation between social experiences and neurobiology,
observing that:
This powerful claim, while supported by over a decade of rigorous research, has rarely been directly tested. However, advances in psychoendoneuroimmunology, the study of how mental processes affect the immune system, have clearly shown the effects of psychological and social factors on human physiological functions that indirectly involve the genetic replication of cells (Ray, 2004). Such alterations of biological function may be mediated through experience-dependent gene expression, the process whereby social-environmental signals turn genes “on” and “off,” leading to alterations in protein synthesis which ultimately result in physiological changes (Pinaud, 2004).The regulation of gene expression by social factors makes all bodily functions, including all functions of the brain, susceptible to social influences. These social influences will be biologically incorporated in the altered expressions of specific genes in specific nerve cells of specific regions of the brain. These socially influenced alterations are transmitted culturally (Kandel, 1998, p. 461).
Psychosocial genomic hypotheses
Although
our genes provide a basic outline for development, environmental
influences such as social experiences shape gene expression and
ultimately make us unique individuals. This interaction is the essence
of what Rossi (2002)
has termed “psychosocial genomics,” the interdisciplinary study of the
processes by which gene expression is modulated by psychological,
social, and cultural experiences. Practitioners might profit from
knowing more about this new science, for according to Kandel:
Insofar as psychotherapy or counseling is effective and produces long-term changes in behavior, it presumably does so though learning, through producing changes in gene expression that alter the strength of synaptic connections and structural changes that alter the anatomical pattern of nerve cells of the brain (Kandel, 1998, p. 460)
Thus,
it is conceivable that psychosocial interventions, the tools of social
work practice, may produce alterations in gene expression leading, in
some cases, to measurable neurobiological changes. Since can stress
affect neurogenesis through alterations in gene expression and
transcription (Glaser et al., 1990; Warner-Schmidt & Duman, 2006), ultimately leading to dysregulation of affect (Post, 1992),
psychosocial interventions designed to reduce distress and improve mood
may affect brain structure and function through this pathway. Muenke (2008)
has recently suggested that the therapeutic effects of stress-reduction
techniques might be mediated by changes in gene expression. In line
with this hypothesis, a recent study of a meditative breathing practice
found increased gene expression of the immune factors glutathione
S-transferase, Cox-2, and HSP-70 in practitioners relative to controls (Sharmaa et al., 2008).
While this study supports the psychosocial genomic hypothesis, its
cross-sectional design does not allow for confident inferences vis-à-vis
causality. However, in light of this potential shortcoming, a
longitudinal study examined gene expression before and after exposure to
eight weeks of meditation training (Dusek et al., 2008),
and found alterations in the expression of 1561 genes after the
intervention. Among these changes were increases in the expression of
genes associated with the stress response, suggesting that learning to
engage the relaxation response through meditation may attenuate the
deleterious impact of stress on cellular processes.
Although
controlled psychosocial genomic research is uncommon, there are a
growing number of psychosocial intervention studies that do measure
physiological outcomes such as blood levels of cortisol or immune
factors. For instance, stress reduction interventions have been shown to
increase numbers of immune cells and decrease numbers of cells
associated with allergic reactivity (Castes et al., 1999), and improve antibody response to the flu vaccine (Davidson et al., 2003). Intervention-related changes in such biological markers may serve as indirect measures of alterations in gene expression.
The
new scientific paradigm outlined above provides a perspective on how
the biopsychosocial constitutions of practitioners and clients might
interact in the act of therapy:
The union of neuroplasticity and psychosocial genomics research represents a synthesis of the social and biological sciences that is non-reductive: it does not dismiss human experience as the product of a neural machine, pre-determined by its genetic blueprint. Instead, it is integrative, inclusive, and holistic; this unitary approach reveals the power of thought and emotion, society and culture to affect not only our phenomenological experience but our very neurobiological structure and function. In sharp contrast to genetic determinism, this new paradigm envisions individuals as having the innate potential for agency over the tripartite dimensionality of their biopsychosocial selves.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 neuronal 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 sociopsychological approaches are joined. (Kandel, 1998, p. 466)
Implications for Social Work
The
social work profession's historical emphasis on the social environment
as the context for individual well-being is supported by research over
the past decade. Neuroplasticity and psychosocial genomic research
indicate that socioenvironmental forces have the potency to alter human
well-being through their effects on neurobiology. Social experience may
be transduced through the activation of neurons, leading to
modifications in the phenotypic expression of genes and eventuating in
structural changes to the brain. While genes and neurobiology may be the
substrates of vulnerability to environmental stressors, they are also,
in all likelihood, the substrates of resilience (D Cicchetti, 2003; D. Cicchetti & Blender, 2006).
The
sciences of neuroplasticity and psychosocial genomics may provide new
empirical bases for social work interventions. Biological measures of
change can and should be used to enhance the evaluation of social
intervention research. Given the current funding climate and priorities
of the National Institutes of Health, research programs designed to
evaluate social work practice might be more likely to obtain grant
support if interventions studied were evaluated with physiological
outcome measures including those assessing gene expression and
neuroplasticity. In time, a given practice may be deemed
“evidence-based” when, among other criteria, it is shown to result in
plastic brain changes or altered gene expression associated with
improved biopsychosocial functioning.
Currently, there is
a paucity of empirical support for this new paradigm in studies with
humans. An abundance of research on higher mammals indicates that
experience can trigger gene expression leading to neuroplasticity. As
referenced earlier in this paper, several studies on humans indicate
that learning and training led to neurogenesis and the reorganization of
neural networks. Despite developments in these lines of research,
science has only begun to examine the effects of psychosocial
interventions on brain structure and function. More research must be
conducted in this emerging field, and the social work profession, with
its expertise in addressing social problems and enhancing human
well-being, can make a vital contribution to this endeavor.
Brain
imaging and gene assays may be utilized to detect the neuroplastic and
genomic effects of psychosocial interventions. Technologies such as
magnetic resonance imaging (MRI), functional magnetic resonance imaging
(fMRI) and positron emission tomography (PET) are capable of assessing
the neurophysiological changes associated with psychosocial
interventions (Kumari, 2006).
Reductions in psychiatric symptoms may be reflected in the alterations
in brain metabolism and structure revealed by these imaging
technologies. DNA microarray technologies, which can evaluate messenger
RNA production in cells and thereby determine which genes are activated (Mirnics, Middleton, Lewis, & Levitt, 2001; Raychaudhuri, Sutphin, Chang, & Altman, 2001), have been used to assess alterations in gene expression related to post-traumatic stress disorder (Segman et al., 2005), social aggression (Berton et al., 2006), and depression (Evans et al., 2004).
DNA microarrays may become more widely used to measure biological
effects of psychosocial interventions in the not-too-distant future (E. L. Rossi, 2005).
Nevertheless,
the funding and specialized training necessary to perform brain imaging
and DNA microarrays decreases the likelihood that social work
researchers working in isolation could leverage these technologies for
biopsychosocial research. Consequently, future psychosocial intervention
research could involve interdisciplinary teams of social workers,
neuroscientists, and molecular biologists, where data from the
biological sciences could be complemented by the insights of social work
research. Alternatively, other more accessible biological markers, such
as stress hormone levels in saliva, could be measured as a proxy for
physiological change induced by psychosocial interventions. For example,
salivary cortisol assays are a relatively inexpensive form of
assessment that can be done by many university laboratories. Social work
investigators could add this measure to their intervention research
protocols.
Whether the impact of psychosocial
interventions can be traced at the neuronal, genomic, or grosser levels
of physiological response, biological markers will only be meaningful as
a complement to self-report and collateral measures of change. Indeed,
Engel's biopsychosocial paradigm is rooted in the philosophical
principle of complementarity (Freedman, 1995);
instead of the “either/or” mentality of dualistic reductionism,
biopsychosocial research should embrace a “both/and” logic, where
reports of subjective experience garnered through validated instruments
and qualitative interviews are correlated with biological and behavioral
data. Such research can add value to Social Work as a primary mental
health and allied-health profession and lead to the implementation of
interventions with demonstrable physiological, psychological, and
behavioral benefits.
Conclusion
Over
the past decade neuroplasticity research has enriched the
biopsychosocial perspective by demonstrating that psychosocial
experiences not only influence neurobiological processes but may
actually change the structure of the adult brain. These structural
changes consist of increased arborization of neurons, enhanced synaptic
connectivity, and even the genesis of new neural tissue. Although
neuroplasticity research is in its infancy, recent findings suggest that
the effects of psychosocial experiences such learning and mental
training on cognitive, emotional, and behavioral functions may be
mediated by alterations to the architecture of the brain.
In
turn, experience-dependent modifications to neural tissue may be driven
by epigenetic processes (i.e., changes in gene expression produced by
environmental determinants). The human environment is constantly
conditioned by social experiences, which, when transduced by the nervous
system into electrochemical signals, may modulate protein synthesis in
the nuclei of nerve cells, ultimately leading to changes in the
replication and growth of neurons. Social experience can change gene
expression, leading to the restructuring of the brain through
neuroplasticity. While tentative at present, empirical investigations of
the psychosocial genomic hypothesis will likely proliferate over the
next decade.
These new biopsychosocial sciences are
consistent with a view of human beings as holistic, recursive systems
structurally coupled with their environments in a process of mutual
change (Maturana & Varela, 1987).
Intentionality and volition can generate changes in the structure of
the brain, the very organ assumed to produce such mental phenomena (Schwartz & Begley, 2002).
With this finding it is evident that human experience is not driven
solely from the bottom-up by neurobiology and genetics. Instead, there
is growing evidence that psychosocial experience can exert a
macrodeterministic, top-down force upon our biology. In the philosophy
of emergent interactionism, Roger Sperry, Nobel laureate neuroscientist,
described macrodeterminism as a higher-order, molar level of
organization that determines and conditions the activity of lower-order,
nested sub-components (Sperry, 1987).
Hence, human beings, who are at one level assemblies of organ systems
comprised of aggregates of cells, in turn composed of organic molecules
made up of sub-atomic particles, are not merely the summation of these
physical elements. Instead, the consciousness that emerges from the
interaction of these components can act back upon its physical
substrate. Thought, emotion, and action trigger neural activity, which
can lead to a re-organization of the brain, shaping future psychosocial
experience. From this perspective, we are not the passive products of
neurophysiology and heredity; rather, through our behavior in the social
environment, we become active agents in the construction of our own
neurobiology, and ultimately, our own lives.
This new
paradigm may reveal the empirical foundation of that most central of
social work principles, the idea that people have the power to transcend
and transform their limitations into opportunities for growth and
well-being.
Acknowledgments
ELG was supported by Grant Number T32AT003378 from the National Center for Complementary and Alternative Medicine.
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Although we generally experience our bodies as being biologically stable across time and situations, an emerging field of research is demonstrating that external social conditions, especially our subjective perceptions of those conditions, can influence our most basic internal biological processes—namely, the expression of our genes. This research on human social genomics has begun to identify the types of genes that are subject to social-environmental regulation, the neural and molecular mechanisms that mediate the effects of social processes on gene expression, and the genetic polymorphisms that moderate individual differences in genomic sensitivity to social context. The molecular models resulting from this research provide new opportunities for understanding how social and genetic factors interact to shape complex behavioral phenotypes and susceptibility to disease. This research also sheds new light on the evolution of the human genome and challenges the fundamental belief that our molecular makeup is relatively stable and impermeable to social-environmental influence.
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