Epigenetic effects of early life stress exposure

This 2017 Netherlands review subject was the lasting epigenetic effects of early-life stress:

“Exposure to stress during critical periods in development can have severe long-term consequences..One of the key stress response systems mediating these long-term effects of stress is the hypothalamic-pituitary-adrenal (HPA) axis..early life stress (ELS) exposure has been reported to have numerous consequences on HPA-axis function in adulthood.

ELS is able to “imprint” or “program” an organism’s neuroendocrine, neural and behavioral responses to stress..research focuses along two complementary lines.

Firstly, ELS during critical stages in brain maturation may disrupt specific developmental processes (by altered neurotransmitter exposure, gene transcription, or neuronal differentiation), leading to aberrant neural circuit function throughout life..

Secondly, ELS may induce modifications of the epigenome which lastingly affect brain function..These epigenetic modifications are inducible, stable, and yet reversible, constituting an important emerging mechanism by which transient environmental stimuli can induce persistent changes in gene expression and ultimately behavior.”

In early life, the lower brain and limbic system brain structures are more developed and dominant, whereas the cerebrum and other brain structures are less developed (use the above graphic as a rough guide). Stress and pain generally have a greater impact on the fetus, then the infant, and then the adult.

The reviewers cited 50+ studies from years 2000-2015 in the “Early Life Stress Effects in a “Matching” Stressful Adult Environment” section to argue for the match/mismatch theory:

“Encountering ELS prepares an organism for similar (“matching”) adversities during adulthood, while a mismatching environment results in an increased susceptibility to psychopathology, indicating that ELS can exert either beneficial or disadvantageous effects depending on the environmental context.

Initial evidence for HPA-axis hypo-reactivity is observed for early social deprivation, potentially reflecting the abnormal HPA-axis function as observed in post-traumatic stress disorder.

Interestingly, experiencing additional (chronic) stress in adulthood seems to normalize these alterations in HPA-axis function, supporting the match/mismatch theory.”

Evidence for this theory was contrasted with the allostatic load theory presented in, for example, How one person’s paradigms regarding stress and epigenetics impedes relevant research.

The review mainly cites evidence from rodent studies that mismatched reactions in adulthood may be consequences of early-life events. These events:

“..imprint or program an organism’s neuroendocrine, neural and behavioral responses..leading to aberrant neural circuit function throughout life..which lastingly affect brain function..”

Taking this research to a personal level:

  • Have you had feelings that you were unsafe, although your environment was objectively safe?
  • Have you felt uneasy when people are nice to you?
  • Have you felt anxious when someone pays attention to you, even after you’ve acted to gain their attention?

I assert that mismatched human feelings are one form of mismatched reactions. As such, they may be interpreted as consequences of early-life experiences, and indicators of personal truths.

If researchers can let go of their biases and Advance science by including emotion in research, they may find that human subjects’ feelings produce better evidence for what actually happened during the subjects’ early lives than do standard scientific methods of:

Incorporating this evidence may bring researchers closer to backwardly predicting the major insults to an individual that knocked their development processes out of normally robust pathways and/or induced “persistent changes in gene expression and ultimately behavior.”

https://www.frontiersin.org/articles/10.3389/fncel.2017.00087/full “Modulation of the Hypothalamic-Pituitary-Adrenal Axis by Early Life Stress Exposure”

I discovered this review as a result of it being cited in http://www.sciencedirect.com/science/article/pii/S1084952117302884 “Long-term effects of early environment on the brain: Lesson from rodent models” (not freely available)


A human study of pain avoidance

This 2016 UK human study found:

“People differ in how they learn to avoid pain, with some individuals refraining from actions that resulted in painful outcomes, whereas others favor actions that helped prevent pain.

Learning in our task was best explained as driven by an outcome prediction error that reflects the difference between expected and actual outcomes. Consistent with the expression of such a teaching signal, blood-oxygen level-dependent (BOLD) responses to outcomes in the striatum were modulated by expectation.

Positive learners showed significant functional connectivity between the insula and striatal regions, whereas negative learners showed significant functional connectivity between the insula and amygdala regions.

The degree to which a participant tended to learn from success in avoiding than experiencing shocks was predicted by the structure of a participants’ striatum, specifically by higher gray matter density where the response to shocks was consistent with a prediction error signal. Higher gray matter density in the putamen (and lower gray matter density in the caudate) predicted better learning from shocks and poorer learning from success in avoiding shocks.”

The researchers termed the subjects’ pain responses “learning” instead of conditioning. The experiments presented no 100%-certain choices to avoid pain. The experiments were also rigged to force choices at similar rates among subjects because:

“Participants who learned more from painful outcomes developed a propensity to avoid gambling, whereas participants who learned more from success in preventing pain developed a propensity to gamble.”

Human responses to pain don’t arise out of nowhere. The subjects’ pain histories were clearly relevant, but weren’t investigated. The closest the study came to considering the subjects’ histories was:

“Before the experiment, participants completed an 80-item questionnaire composed of several measures of different mood and anxiety traits. Age, sex and mood and anxiety traits did not differ between participants later classified as positive and negative learners.”

Emotional content was neither included nor solicited. Emotions were inferred:

“Participants biased in favor of passive avoidance learning (i.e., learning what gambles should be avoided), striatal response to painful outcomes was consistent with an aversive prediction error, as seen in fear conditioning.”

As a result, there weren’t causal explanations for the subjects’ differing pain responses. How, when, and why did the behavioral, functional, and structural differences develop?

I didn’t see the level of detail needed to characterize striatal regions into the Empathy, value, pain, control: Psychological functions of the human striatum segments. I’d guess that the findings of “higher gray matter density in the putamen (and lower gray matter density in the caudate)” applied to the posterior putamen and the anterior caudate nucleus.

Two of the coauthors were also coauthors of If a study didn’t measure feelings, then its findings may not pertain to genuine empathy. The technique of Why do we cut short our decision-making process? was referenced.

http://www.pnas.org/content/early/2016/04/06/1519829113.full “Striatal structure and function predict individual biases in learning to avoid pain”

The current paradigm of child abuse limits pre-childhood causal research

As an adult, what would be your primary concern if you suspected that your early life had something to do with current problems? Would you be interested in effective treatments of causes of your symptoms?

Such information wasn’t available in this 2016 Miami review of the effects of child abuse. The review laid out the current paradigm mentioned in Grokking an Adverse Childhood Experiences (ACE) score, one that limits research into pre-childhood causes for later-life symptoms.

The review’s goal was to describe:

“How numerous clinical and basic studies have contributed to establish the now widely accepted idea that adverse early life experiences can elicit profound effects on the development and function of the nervous system.”

The hidden assumption of almost all of the cited references was that these distant causes can no longer be addressed. Aren’t such assumptions testable here in 2016?

As an example, the Discussion section posed the top nine “most pressing unanswered questions related to the neurobiological effects of early life trauma.” In line with the current paradigm, the reviewer assigned “Are the biological consequences of ELS [early life stress] reversible?” into the sixth position.

If the current paradigm encouraged research into treatment of causes, there would probably already be plenty of evidence to demonstrate that directly reducing the source of the damage would also reverse the damaging effects. There would have been enough studies done so that the generalized question of reversibility wouldn’t be asked.

Aren’t people interested in human treatments of originating causes so that their various symptoms don’t keep bubbling up? Why wouldn’t research paradigms be aligned accordingly?

The review also demonstrated how the current paradigm of child abuse misrepresents items like telomere length and oxytocin. Researchers on the bandwagon tend to forget about the principle Einstein expressed as:

“No amount of experimentation can ever prove me right; a single experiment can prove me wrong.”

That single experiment for telomere length arrived in 2016 with Using an epigenetic clock to distinguish cellular aging from senescence. The seven references the review cited for telomere length that had “is associated with” or “is linked to” child abuse findings should now be viewed in a different light.

The same light shone on oxytocin with Testing the null hypothesis of oxytocin’s effects in humans and Oxytocin research null findings come out of the file drawer. See their references, and decide for yourself whether or not:

“Claimed research findings may often be simply accurate measures of the prevailing bias.”

http://www.cell.com/neuron/fulltext/S0896-6273%2816%2900020-9 “Paradise Lost: The Neurobiological and Clinical Consequences of Child Abuse and Neglect”

What’s the underlying question for every brain study to answer?

Is it:

  • How do our brains internally represent the external world?

Is it:

  • How did we learn what we know?
  • How do we forget or disregard what we’ve learned?
  • What keeps us from acquiring and learning newer or better information?

How about:

  • What affects how we pay attention to our environments?
  • How do our various biochemical states affect our perceptions, learning, experiences, and behavior?
  • How do these factors in turn affect our biology?

Or maybe:

  • Why do we do what we do?
  • How is our behavior affected by our experiences?
  • How did we become attracted and motivated toward what we like?
  • How do we develop expectations?
  • Why do we avoid certain situations?

Not to lose sight of:

  • How do the contexts affect all of the above?
  • What happens over time to affect all of the above?

This 2015 UCLA paper reviewed the above questions from the perspective of Pavlovian conditioning:

“The common definition of Pavlovian conditioning, that via repeated pairings of a neutral stimulus with a stimulus that elicits a reflex the neutral stimulus acquires the ability to elicit that the reflex, is neither accurate nor reflective of the richness of Pavlovian conditioning. Rather, Pavlovian conditioning is the way we learn about dependent relationships between stimuli.

Pavlovian conditioning is one of the few areas in biology in which there is direct experimental evidence of biological fitness.”

The most important question unanswered by the review is:

  • How can its information be used to help humans?

How does Pavlov conditioning answer:

  • What can a human do about the thoughts, feelings, behavior, epigenetic effects – the person – that they’ve been shaped into?

One relevant hypothesis of Dr. Arthur Janov’s Primal Therapy is that a person will continue to be their conditioned self until they address the sources of their pain. A corollary is that addressing symptoms will seldom address causes.

How could it be otherwise? A problem isn’t cured by ameliorating its effects.

As an example, the review pointed out in a section about fear extinction that it doesn’t involve unlearning. Fear extinction instead inhibits the symptoms of fear response. The fear memory is still intact, awaiting some other context to be reactivated and expressed.

How can that information be used to help humans?

  • Is inhibiting the symptoms and leaving the fear memory in place costless with humans?
  • Or does this practice have both potential and realized adverse effects?
  • Where’s the human research on methods that may directly address a painful emotional memory?

http://cshperspectives.cshlp.org/content/8/1/a021717.full “The Origins and Organization of Vertebrate Pavlovian Conditioning”

Empathy, value, pain, control: Psychological functions of the human striatum

This 2016 US human study found:

“A link between existing data on the anatomical and physiological characteristics of striatal regions and psychological functions.

Because we did not limit our metaanalysis to studies that specifically targeted striatal function, our results extend previous knowledge of the involvement of the striatum in reward-related decision-making tasks, and provide a detailed functional map of regional specialization for diverse psychological functions, some of which are sometimes thought of as being the exclusive domain of the PFC [prefrontal cortex].”

The analysis led to dividing the striatum into five segments:

Ventral striatum (VS):

  • Stimulus Value
  • Terms such as “reward,” “losses,” and “craving”
  • The most representative study reported that monetary and social rewards activate overlapping regions within the VS.
  • Together with the above finding of a reliable coactivation with OFC [orbitofrontal cortex] and ventromedial PFC, this finding suggests a broad involvement of this area in representing stimulus value and related stimulus-driven motivational states.

Anterior caudate (Ca) Nucleus:

  • Incentive Behavior
  • Terms such as “grasping,” “reaching,” and “reinforcement”
  • The most representative study reported a stronger blood-oxygen level-dependent (BOLD) response in this region during trials in which participants had a chance of winning or losing money in a card guessing game, in comparison to trials where participants merely received feedback about the accuracy of their guess.
  • This result suggests a role in evaluating the value of different actions, contrasting with the above role of the VS in evaluating the value of stimuli.

Posterior putamen (Pp):

  • Sensorimotor Processes
  • Terms such as “foot,” “noxious,” and “taste”
  • The most representative study reported activation of this region in response to painful stimulation at the back of the left hand and foot of participants. Anatomically, the most reliable and specific coactivation is with sensorimotor cortices, and the posterior and midinsula and operculum (secondary somatosensory cortex SII) in particular, some parts of which are specifically associated with pain.
  • Together, these findings suggest a broad involvement of this area in sensorimotor functions, including aspects of their affective qualities.

Anterior putamen (Pa):

  • Social- and Language-Related Functions
  • Terms such as “read,” “vocal,” and “empathic”
  • The most representative study partially supports a role of this area in social- and language-related functions; it reported a stronger activation of the Pa in experienced singers, but not when novices were singing.
  • It is coactivated with frontal areas anterior to the ones coactivated with the Pp, demonstrating topography in frontostriatal associations. These anterior regions have been implicated in language processes.

Posterior caudate (Cp) Nucleus:

  • Executive Functions
  • Terms such as “causality,” “rehearsal,” and “arithmetic”
  • The representative study reported this region to be part of a network that included dorsolateral PFC and ACC, which supported inhibitory control and task set-shifting.
  • These results suggest a broad, and previously underappreciated, role for the Cp in cognitive control.

The authors presented comparisons of the above striatal segments with other analyses of striatal zones.

One of the coauthors was the lead researcher of the 2015 Advance science by including emotion in research. The current study similarly used a coactivation view rather than a connectivity paradigm of:

“Inferring striatal function indirectly via psychological functions of connected cortical regions.”

Another of the coauthors was a developer of the system used by the current study and by The function of the dorsal ACC is to monitor pain in survival contexts, and he provided feedback to those authors regarding proper use of the system.

The researchers’ “unbiased, data-driven approach” had to work around the cortical biases evident in many of the 5,809 human imaging studies analyzed. The authors referred to the biases in statements such as:

“The majority of studies investigating these psychological functions report activity preferentially in cortical areas, except for studies investigating reward-related and motor functions.”

The methods and results of research with cortical biases influenced the study’s use of:

“Word frequencies of psychological terms in the full text of studies, rather than a detailed analysis of psychological tasks and statistical contrasts.”

http://www.pnas.org/content/113/7/1907.full “Regional specialization within the human striatum for diverse psychological functions”

Advance science by including emotion in research

This 2015 analysis of emotion studies found:

“Emotion categories [fear, anger, disgust, sadness, and happiness] are not contained within any one region or system, but are represented as configurations across multiple brain networks.

For example, among other systems, information diagnostic of emotion category was found in both large, multi-functional cortical networks and in the thalamus, a small region composed of functionally dedicated sub-nuclei.

The dataset consists of activation foci from 397 fMRI and PET [positron emission tomography] studies of emotion published between 1990 and 2011.”

From the fascinating Limitations section:

“Our analyses reflect the composition of the studies available in the literature, and are subject to testing and reporting biases on the part of authors. This is particularly true for the amygdala (e.g., the activation intensity for negative emotions may be over-represented in the amygdala given the theoretical focus on fear and related negative states). Other interesting distinctions were encoded in the thalamus and cerebellum, which have not received the theoretical attention that the amygdala has and are likely to be bias-free.

Some regions—particularly the brainstem—are likely to be much more important for understanding and diagnosing emotion than is apparent in our findings, because neuroimaging methods are only now beginning to focus on the brainstem with sufficient spatial resolution and artifact-suppression techniques.

We should not be too quick to dismiss findings in ‘sensory processing’ areas, etc., as methodological artifacts. Emotional responses may be inherently linked to changes in sensory and motor cortical processes that contribute to the emotional response.

The results we present here provide a co-activation based view of emotion representation. Much of the information processing in the brain that creates co-activation may not relate to direct neural connectivity at all, but rather to diffuse modulatory actions (e.g., dopamine and neuropeptide release, much of which is extrasynaptic and results in volume transmission). Thus, the present results do not imply direct neural connectivity, and may be related to diffuse neuromodulatory actions as well as direct neural communication.”

Why did the researchers use only 397 fMRI and PET studies? Why weren’t there hundreds or thousands of times more candidate studies from which to select?

The relative paucity of candidate emotion studies demonstrated the prevalence of other researchers’ biases for cortical brain areas. The lead researcher of the current study was a coauthor of the 2016 Empathy, value, pain, control: Psychological functions of the human striatum, whose researchers mentioned that even their analyses of 5,809 human imaging studies was hampered by other imaging-studies researchers’ cortical biases.

Functional MRI signals depend on the changes in blood flow that follow changes in brain activity. Study designers intentionally limit their findings when they scan brain areas and circuits that are possibly activated by human emotions, yet exclude emotional content that may activate these areas and circuits.

Here are a few examples of limited designs that led to limited findings when there was the potential for so much more:

It’s well past time to change these practices now that we’re in 2016.

This study provided many methodological tests that should be helpful for research that includes emotion. It showed that there aren’t impenetrable barriers – other than popular memes, beliefs, and ingrained dogmas – to including emotional content in studies.

Including emotional content may often be appropriate and informative, with the resultant findings advancing science. Here are a few recent studies that did so:

http://journals.plos.org/ploscompbiol/article?id=10.1371%2Fjournal.pcbi.1004066 “A Bayesian Model of Category-Specific Emotional Brain Responses”

A problematic study of beliefs and dopamine

This 2015 Virginia Tech human study found:

“Dopamine fluctuations encode an integration of RPEs [reward prediction errors, the difference between actual and expected outcomes] with counterfactual prediction errors, the latter defined by how much better or worse the experienced outcome could have been.

How dopamine fluctuations combine the actual and counterfactual is unknown.”

From the study’s news coverage:

“The idea that “what could have been” is part of how people evaluate actual outcomes is not new. But no one expected that dopamine would be doing the job of combining this information in the human brain.”

Some caveats applied:

  • Measurements of dopamine were taken only from basal ganglia areas. These may not act the same as dopamine processes in other brain and nervous system areas.
  • The number of subjects was small (17), they all had Parkinson’s disease, and the experiment’s electrodes accompanied deep brain stimulation implantations.
  • Because there was no control group, findings of a study performed on a sample of people who all had dysfunctional brains and who were all being treated for neurodegenerative disease may not apply to a population of people who weren’t similarly afflicted.

The researchers didn’t provide evidence for the Significance section statement:

“The observed compositional encoding of “actual” and “possible” is consistent with how one should “feel” and may be one example of how the human brain translates computations over experience to embodied states of subjective feeling.”

The subjects weren’t asked for corroborating evidence about their feelings. Evidence for “embodied states of subjective feeling” wasn’t otherwise measured in studied brain areas. The primary argument for “embodied states of subjective feeling” was the second paragraph of the Discussion section where the researchers talked about their model and how they thought it incorporated what people should feel.

The study’s experimental evidence didn’t support the researchers’ assertion – allowed by the reviewer – that the study demonstrated something about “states of subjective feeling.” That the model inferred such “findings” along with the researchers’ statement that it “is consistent with how one should “feel” reminded me of a warning in The function of the dorsal ACC is to monitor pain in survival contexts:

“The more general message you should take away from this is that it’s probably a bad idea to infer any particular process on the basis of observed activity.”

The same researcher who hyped An agenda-driven study on beliefs, smoking and addiction that found nothing of substance was back again with statements such as:

“These precise, real-time measurements of dopamine-encoded events in the living human brain will help us understand the mechanisms of decision-making in health and disease.”

It’s likely that repeated hubris is one way researchers respond to their own history and feelings, such as their need to feel important as mentioned on my Welcome page.

The Parkinson’s patients were willing to become lab rats with extra electrodes that accompanied brain implantations to relieve their symptoms. Findings based on their playing a stock market game didn’t inform us about “mechanisms of decision-making in health and disease” in unafflicted humans. As one counter example, what evidence did the study provide that’s relevant to healthy humans’ decisions to remain healthy by taking actions to prevent disease?

The unwarranted extrapolations revealed a belief that the goal of research should be to explain human actions by explaining the actions of molecules. One problem caused by the preconceptions of this widespread belief is that it leads to study designs and models that omit relevant etiologic evidence embedded in each of the subjects’ historical experiences.

This belief may have factored into why the subjects weren’t asked about their feelings. Why didn’t the study’s design consider as relevant subject-provided evidence for feelings? Because the model already contrived explanations for feelings underlying the subjects’ actions.

http://www.pnas.org/content/113/1/200.full “Subsecond dopamine fluctuations in human striatum encode superposed error signals about actual and counterfactual reward”