This 2014 human study provided additional details on the specialized brain circuits we have for recognizing faces.
Damage to the hippocampus didn’t impair recognition of new faces, “..but only at a short retention interval. Recognition memory for words, buildings, famous faces, and inverted faces was impaired.”
http://www.pnas.org/content/111/27/9935.full “When recognition memory is independent of hippocampal function”
This 2014 human study showed that:
“Item memories are weakened when they are mispredicted by their context..weakening of the synapses that support the item’s representation in memory.
Note that our use of the term “pruning” is not meant to imply that traces are being deleted completely from memory.“
Connecting the dots, two studies showed that our memories are formed within specific contexts and that our memories have contexts with specific places and times.
http://www.pnas.org/content/111/24/8997.full “Pruning of memories by context-based prediction error”
This 2014 human study involved the subjects replaying hippocampal memories in the limbic system while in a restful state.
The researchers found that intentional replaying made memories stronger, and improved understanding of future related material.
However, the researchers excluded emotional memories from this study. See the human Emotional memories and out-of-body–induced hippocampal amnesia study as an example of why emotional memories are necessary in order to properly study the hippocampus. Also see Problematic research on memory for why excluding emotional memories yields questionable findings.
http://www.pnas.org/content/111/44/15845.full “Memory reactivation during rest supports upcoming learning of related content”
Ever wonder how someone could become attached to their early childhood abuser?
Ever wonder what underlying neurobiological conditions may account for the popularity of Fifty Shades of Grey?
This 2014 rodent study “Enduring good memories of infant trauma” linked below showed how trauma changed infants’ limbic system and lower brains. As adults, they derived a neurochemical benefit from re-experiencing the traumatic conditions:
“Trauma and pain experienced in infancy clearly led to higher rates of adult rat depression-like behavior..(but) the infant brain has limited ability to link trauma to fear areas in the brain, such as the amygdala.
These results are surprising because cues associated with trauma experienced as adults provoke fear and do not rescue depressive behavior.
It is possible that giving SSRI medications to children could be detrimental to mental health in adulthood,” Dr. Sullivan says. “We believe that our research offers the first evidence for the impact of serotonin pathways.
The infant trauma increases serotonin to produce brain programming of later life depression, and the infant trauma cue increases serotonin to alleviate the adult depressive like symptoms.”
As the study may apply to humans, let’s say that as an infant, someone was traumatized by a caregiver who, for example, bound them too tightly and left them alone for too long. What adult behaviors and other symptoms may develop as results? The person may:
Isn’t it curious that this acting-out behavior – driven by unconscious memories of traumatic conditions – is a subject for popular entertainment? It may have resonated with personal experiences of the people who read the books and watched the movie.
What about people who want to be relieved of their symptomatic behavior? Is it a justifiable practice:
A principle of Dr. Arthur Janov’s Primal Therapy is that people are capable of treating their own originating neurobiological conditions. One of the therapeutic results is that the patient is relieved of being caught in endless circles of acting-out behavior.
That way we can have our own lives, and not be driven by what happened during early stages of our lives.
http://www.pnas.org/content/112/3/881.full “Enduring good memories of infant trauma: Rescue of adult neurobehavioral deficits via amygdala serotonin and corticosterone interaction”
This 2013 Harvard human study investigated brain areas that stabilized and updated memories when reactivated:
“The timing of neural recruitment and the way in which memories were reactivated contributed to differences in whether memory reactivation led to distortions or not.
Stronger reliving improved memory.”
However, like researchers often do, they stripped all emotional memory content out of the study, presumably because messy feelings would confound their conclusions. The study used non-emotional pictures only.
The researchers wanted to apply this study to eyewitness accounts. What are the chances that an eyewitness to a murder or a violent accident or crime would have a non-emotional memory of the event?
The study’s exclusion of emotional memories called into doubt that the finding “stronger reliving improved memory” also applied to reliving emotional memories. The categorical statements the researchers claimed about memory, in particular about the hippocampus – the center of emotional memories – weren’t shown to be applicable to emotional memories.
Also, the researchers didn’t include areas of the limbic system, other than the hippocampus, that would likely participate in the reliving of emotional memories. The Making lasting memories: Remembering the significant summary study cited many studies that provided evidence of other brain areas’ involvement.
The researchers had too narrow a basis for a finding that applied across the spectrum of what can be termed memory.
http://www.pnas.org/content/110/49/19671.full “Neural mechanisms of reactivation-induced updating that enhance and distort memory”
This 2013 article summarized 158 studies related to the roles of regions in the limbic system and memory:
“Episodic memory is the capacity to recall specific experiences and to re-experience individual events.
The findings of both animal and human studies provide compelling evidence that stress-induced activation of the amygdala and its interactions with other brain regions involved in processing memory play a critical role in ensuring that emotionally significant experiences are well-remembered.”
http://www.pnas.org/content/110/Supplement_2/10402.full “Making lasting memories: Remembering the significant”
This 2013 UK human study provided details of the growths of infants’ cerebral and limbic system structures. With 55 of the 65 infants in the study born prematurely, the UK researchers found:
“Rapidly developing cortical microstructure is vulnerable to the effects of premature birth, suggesting a mechanism for the adverse effects of preterm delivery on cognitive function.”
The infants’ first set of measurements were taken from 27 to 46 weeks after birth. Follow-up measurements were taken when the infants were two years old.
Only the politically-correct adverse effects on brain development were included in the study, which led to the researchers making only politically-correct findings. Is this what we want from publicly funded scientific research?
Further, was this all we should expect from the peer review process? The data was presumably there for the reviewers to go back to the researchers and suggest analysis of something other than the predetermined agenda.
http://www.pnas.org/content/110/23/9541.full “Development of cortical microstructure in the preterm human brain”
Here are some 2014 ruminations by Joseph LeDoux, the grandfather of studies of the amygdala. He attempted to disambiguate feeling brain structures’ activations and responses from ideas of what feelings are, specifically regarding fear:
“Damage to the hippocampus in humans disrupts explicit conscious memory of having been conditioned but has no effect on fear conditioning itself, whereas damage to the amygdala disrupts fear conditioning but not the conscious memory of having been conditioned.
Conscious mental states should not, in the absence of direct evidence, be the first-choice explanation of behavior.
Neither amygdala activity nor amygdala-controlled responses are telltale signatures of fearful feelings.
Conscious fear can cause us to act in certain ways, but it is not the cause of the expression of defensive behaviors and physiological responses elicited by conditioned or unconditioned threats.”
http://www.pnas.org/content/111/8/2871.full “Coming to terms with fear”
Surface Your Real Self 