Dopamine

Why do we cut short our decision-making process?

gettingwell4 5+ stars Premium, Beliefs, Cerebrum, Dopamine, Limbic system, Memory, Neurochemicals, Serotonin , , ,

This 2014 Zurich study found that people adapt their goal-directed decision-making processes in certain ways.

First, the researchers found that the subjects usually acted as though the computational cost of evaluating all outcomes became too high once the process expanded to three or more levels. Their approach to a goal involved developing subgoals. For example, for a three-level goal:

“Level 3 was most frequently decomposed into a tree of depth 2 followed by a depth-1 tree.”

A level 3 tree had 24 potential outcomes (24 outcomes = 3*2x2x2) whereas a level 2 tree followed by a level 1 tree had 10 potential outcomes (10 outcomes = 2*2×2 + 1*2).

Second, the subjects memorized and reused subgoals after their initial formation. The researchers found that this practice didn’t produce results significantly different than the optimal solutions, but that could have been due to the study’s particular design. The design also ensured that the subjects’ use of subgoals wasn’t influenced by rewards.

Further:

“It is known that nonhuman primate choices, for instance, depend substantially on their own past choices, above and beyond the rewards associated with the decisions. Similar arguments have been made for human choices in a variety of tasks and settings and have been argued to be under dopaminergic and serotonergic control.”

Third, ALL 37 subjects were unwilling to evaluate decisions that had initial large losses, even if they could see that the path to reach the optimal solution went through this loss outcome! The researchers termed this behavior “pruning” and stated:

“Pruning is a Pavlovian and reflexive response to aversive outcomes.”

The lead author relied on a previous study he coauthored to elaborate on the third finding. One statement in the previous study was:

“This theory predicts excessive pruning to occur in subjects at risk for depression, and reduced pruning to occur during a depressive episode.”

The current study’s subjects were screened out for depressive conditions, though. They were somewhat conditioned by the study design, but not to the extent where their behavior could be characterized as Pavlovian responses.

Fourth, the subjects’ use of larger subgoals wasn’t correlated to their verbal IQ.

So, what can we make of this research?

  1. Are shortcuts to our decision processes strictly a cerebral exercise per the first and second findings?
  2. Do we recycle our decision shortcuts like our primate relatives, uninfluenced by current rewards?
  3. Or is it rewarding to just not fully evaluate all of our alternatives?
  4. Do all of us always back away from decisions involving an initial painful loss, even when we may see the possibility of gaining a better outcome by persevering through the loss?
  5. Is it true that we excessively cut decision processes too short – such that many of our decisions are suboptimal – when we’re on our way to becoming depressed?
  6. Are we overwhelmed when depressed such that we don’t summon up the effort to cut short or otherwise evaluate decisional input?

Let me know your point of view.

http://www.pnas.org/content/112/10/3098.full “Interplay of approximate planning strategies”

Pulling on the chain of causes and effects with insulin resistance

gettingwell4 0-1 star Wasted resources, Cortisol, Dopamine, Neurochemicals, Stress , , ,

This 2015 Harvard rodent study found multiple undesirable symptoms and attributed the cause to insulin resistance, which is itself a symptom.

Humans most often develop the symptom of insulin resistance due to causes other than genetics, such as a result of abnormal eating behaviors, which are symptoms of other causes.

Use of insulin-resistant-due-to-genetics mice may have misdirected the researchers to lose focus that their ultimate task was to find ways that their research can help humans. If helping humans was the researchers’ focus, it may have occurred to them to develop evidence for how “something” caused symptoms such as abnormal eating behaviors, that in turn caused a symptom of insulin resistance.

The study’s unexamined causes included why genetically insulin-resistant mice developed symptoms of anxiety and depressive-like behaviors between early adulthood and late middle age. Examples of undesirable symptoms described in the supplementary material included:

  • Higher body weight in late middle age, especially in females;
  • Depressive-like behavior in both sexes by late middle age;
  • Higher corticosterone levels in both sexes by late middle age, even when unstressed; and
  • Higher corticosterone levels in late middle age when stressed, especially in males.

It’s remarkable how researchers consistently get caught in a loop of studying only symptoms, paying little attention to studying causes, then suggesting various medications and treatments to suppress the studied symptoms.

It’s not surprising then that there’s no explanation of why and how symptoms develop. The study designs seldom include trying to show causes for the effects in the first place!

http://www.pnas.org/content/112/11/3463.full “Insulin resistance in brain alters dopamine turnover and causes behavioral disorders”

A biologically relevant event can drive long-term memory in a single training session

gettingwell4 2-3 stars Required further work, Brain development, Dopamine, Epigenetics, Memory, Neurochemicals

This 2014 fruit fly study found:

“A biologically relevant event such as finding food under starvation conditions or being poisoned can drive long-term memory in a single training session.”

I don’t think that we need to discover at these extremes, though, whether or not the finding has human applicability.

We do know from the Dutch hunger winter of 1944 study referenced in the Non-PC alert: Treating the mother’s obesity symptoms positively affects the post-surgery offspring study that prenatal exposure to famine had lifelong ill effects on the children. The exposed children had epigenetic DNA changes – a form of long-term memory – from their mothers’ starvation, which resulted in relative obesity compared with their unexposed siblings.

http://www.pnas.org/content/112/2/578.full “Distinct dopamine neurons mediate reward signals for short- and long-term memories”

What is the purpose of music? A review of evolutionary and pleasurable research findings

gettingwell4 2-3 stars Required further work, Amygdala, Anterior cingulate cortex, Cerebrum, Dopamine, Hippocampus, Hypothalamus, Limbic system, Lower brain, Neurochemicals

Ever wonder what happens in your brain and body when you get chills from a musical performance?

This 2013 summary review of 126 studies provided details of brain areas that contribute to our enjoyment of music.

Much of the review addressed Darwin’s observation that music had no readily apparent functional consequence and no clear-cut adaptive function. The researchers noted that:

“There is scant evidence that other species possess the mental machinery to decode music in the way humans do, or to derive enjoyment from it.”

The reasons why different types of music affect us differently are similar to the findings of the Reciprocity behaviors differ as to whether we seek cerebral vs. limbic system rewards study.

Here are the “We seek limbic system rewards” similarities:

“The nucleus accumbens played an important role with both familiar and novel music. In the case of familiar music, hemodynamic activity in the nucleus accumbens was associated with increasing pleasure, and maximally expressed during the experience of chills, which represent the peak emotional response; these were the same regions that showed dopamine release. The nucleus accumbens is tightly connected with subcortical limbic areas of the brain, implicated in processing, detecting, and expressing emotions, including the amygdala and hippocampus. It is also connected to the hypothalamus, insula, and anterior cingulate cortex, all of which are implicated in controlling the autonomic nervous system, and may be responsible for the psychophysiological phenomena associated with listening to music and emotional arousal.”

Here is the “We seek cerebral rewards” part.

“Finally, the nucleus accumbens is tightly integrated with cortical areas implicated in “high-level” processing of emotions that integrate information from various sources, including the orbital and ventromedial frontal lobe. These areas are largely implicated in assigning and maintaining reward value to stimuli and may be critical in evaluating the significance of abstract stimuli that we consider pleasurable.”

http://www.pnas.org/content/110/Supplement_2/10430.full “From perception to pleasure: Music and its neural substrates”