Brain hemispheres

Differing characteristics of languages shape people’s brains differently

gettingwell4 2-3 stars Required further work, Brain development, Brain hemispheres, Cerebrum

This 2015 Chinese study found that the differing characteristics of the Chinese and English languages shape people’s brains differently:

“Our results revealed that, although speech processing is largely carried out in the common left hemisphere classical language areas (Broca’s and Wernicke’s areas) and anterior temporal cortex, speech comprehension across different language groups depends on how these brain regions interact with each other.”

For an informed discussion of the study and related issues, visit http://languagelog.ldc.upenn.edu/nll/?p=17949 and comments.

We can infer from the Would you deprive your infant in order to be in a researcher’s control group? study that this shaping process begins during womb life.

http://www.pnas.org/content/112/10/2972.full “Cross-language differences in the brain network subserving intelligible speech”

New role discovered for a speech area of the human prefrontal cortex

gettingwell4 2-3 stars Required further work, Brain hemispheres, Cerebrum

This 2015 human study found that an area in the left hemisphere of the prefrontal cortex involved with speech has characteristics not previously known:

“Broca’s area coordinates the transformation of information across large-scale cortical networks involved in spoken word production.”

The study found that this area:

“Disengages when we actually start to utter word sequences.”

It was previously thought that the Broca’s area was active during speech.

I looked throughout the study, footnotes and references, and couldn’t find the list of words that were used. The study would have shown more promise if the researchers had made an effort to include words with emotional content. For example, it’s possible that the Broca’s area may have different activation patterns when speaking with emotional content, or that it may account for part of the slowdown that normally occurs when we speak with feeling.

http://www.pnas.org/content/112/9/2871.full “Redefining the role of Broca’s area in speech”

Research on brain areas involved when we imagine people, places, and pleasantness

gettingwell4 2-3 stars Required further work, Amygdala, Beliefs, Brain hemispheres, Cerebrum, Hippocampus, Limbic system, Thalamus ,

This highly jargoned 2014 Harvard study was on how people imagine that they’ll feel in the future.

One of the researchers was an author of:

I was surprised that this study also didn’t ignore the limbic system to the point to where the researchers wouldn’t even bother to measure important areas.

Limbic system areas that process people were different than those that process places. For example, the data in Table S4 showed that the subjects’ left amygdala and hippocampus were more activated when simulating future familiar people, whereas their right hippocampus was more activated when simulating future familiar places.

The researchers may have improved the study’s findings if they were informed by studies such as the Hippocampus replays memories and preplays to extend memories into future scenarios, which found that “place” cells in the CA1 segment of the hippocampus preplay events that imagine future scenarios of:

“Novel spatial experiences of similar distinctiveness and complexity.”

Such information may have helped to disambiguate one of the study’s findings in Table S5, that both sides of the subjects’ hippocampus were more activated than other brain regions when simulating both familiar people and places.

The researchers got a little carried away in broadly attributing most of the study’s findings to the ventromedial prefrontal cortex. For example, the data in Table S6 showed that the thalamus was more activated when the subjects anticipated positive pleasantness, but not when negative effects were anticipated.

We know from Thalamus gating and control of the limbic system and cerebrum is a form of memory that this is normally how the thalamus part of the limbic system actively controls and gates information to and from the cerebrum. Their data showed thalamic gating in operation:

  • Active when passing along pleasantness to cerebral areas, and
  • Passive when blocking unpleasantness from cerebral areas.

Also, I didn’t see how the researchers differentiated some of their findings from a placebo effect. For example, Using expectations of oxytocin to induce positive placebo effects of touching is a cerebral exercise found:

“Pain reduction dampened sensory processing in the brain, whereas increased touch pleasantness increased sensory processing.”

This was very similar to the above finding involving the thalamus.

http://www.pnas.org/content/111/46/16550.full “Ventromedial prefrontal cortex supports affective future simulation by integrating distributed knowledge”

Using expectations of oxytocin to induce positive placebo effects of touching

gettingwell4 2-3 stars Required further work, Amygdala, Beliefs, Brain hemispheres, Limbic system, Neurochemicals, Oxytocin, Thalamus

This 2013 Scandinavian study detailed which brain structures were involved when fooling oneself about actual sensations in favor of expected sensations.

It was hilarious how the researchers used studies of oxytocin to create expectations in the subjects:

“To induce expectation of intranasal oxytocin’s beneficial effects on painful and pleasant touch experience, participants viewed a 6-min locally developed video documentary about oxytocin’s putative prosocial effects such as involvement in bonding, love, grooming, affective touch, and healing. As all of the material was based on published research, there was no deception. The video concluded that a nasal spray of oxytocin might enhance the pleasantness of:

  • (i) stroking and
  • (ii) warm touch, and
  • (iii) reduce the unpleasantness of pain.”

Other items:

  • Only the placebo effects for the warm and pain-reducing touches were statistically significant, not the stroking touch;
  • The a priori brain areas monitored in the “sensory circuitry” included the thalamus and were all in the right brain hemisphere;
  • The a priori brain areas monitored in the “emotional appraisal circuitry” included the amygdala.

One way the researchers summarized the study was:

“Pain reduction dampened sensory processing in the brain, whereas increased touch pleasantness increased sensory processing.”

This finding demonstrated how the thalamus part of the limbic system actively controls and gates information to and from the cerebrum, similar to the Thalamus gating and control of the limbic system and cerebrum is a form of memory study.

There was a terminology problem in the study, evidenced by statements such as:

“We induced placebo improvement of both negative and positive feelings (painful and pleasant touch).”

Touch is a sensation, not a feeling or emotion. This placebo study created expectations of sensations in the subjects’ cerebrums, not expectations of emotions.

Also, including parts of the limbic system such as the amygdala in the “emotional appraisal circuitry” didn’t mean that the researchers studied feelings or emotions. We know from research summarized in the Conscious mental states should not be the first-choice explanation of behavior study that:

“Neither amygdala activity nor amygdala-controlled responses are telltale signatures of fearful feelings.“

The current study cast additional light on the dubious Problematic research on human happiness study. Those researchers were fooled by a positive placebo effect!

http://www.pnas.org/content/110/44/17993.full “Placebo improves pleasure and pain through opposite modulation of sensory processing”

Is oxytocin why more women than men like horror movies?

gettingwell4 2-3 stars Required further work, Amygdala, Brain hemispheres, Limbic system, Neurochemicals, Oxytocin, Serotonin

This 2014 human study showed how oxytocin regulates serotonin with the involvement of the right part of the amygdala.

The following passage caught my eye as a possible explanation of why more women than men prefer horror movies: oxytocin?

“We have chosen to enroll male subjects only to avoid the confounding effects linked to sex and a possible interaction with gonadal steroids. Indeed, as shown by previous studies, oxytocin modulates brain activity differently in male and female subjects.

For instance, oxytocin suppresses amygdala response to emotionally threatening stimuli in males but enhances the same response in females.“

http://www.pnas.org/content/111/23/8637.full “Switching brain serotonin with oxytocin”

Teenagers value rewards more and are more sensitive to punishments than are adults

gettingwell4 2-3 stars Required further work, Beliefs, Brain development, Brain hemispheres, Cerebrum, Limbic system

This 2013 human study found that adolescents placed more value on rewards than did adults. Adolescents were also more sensitive to punishments than were adults.

Cerebral areas increased activity when the expected value of the reward increased. Limbic system areas increased activity when the expected value of the reward decreased.

The left ventral striatum was the brain area that had the most increase in activity in adolescents compared with adults when the expected value of the reward increased. This brain area is usually not fully developed until people are in their mid 20s.

As the researchers noted as a limitation of the study:

“Without including preadolescents it is not possible to say with certainty whether the observed difference is a uniquely adolescent sensitivity to expected value or part of an ongoing developmental trajectory.”

Another limitation of the study was that it studied only 22 teens aged 13 to 17. Nineteen adults were studied with an average age of 28.

http://www.pnas.org/content/111/4/1646.full “Neural representation of expected value in the adolescent brain”

What are the facts about the left-brain/right-brain characterizations?

gettingwell4 4-5 stars Advanced knowledge, Brain development, Brain hemispheres

This 2013 human study added to the existing understanding of how our brain hemispheres work.

“The main contribution of our study is to demonstrate, at a whole-brain scope, the qualitative differences between the hemispheres in their within- and between-hemisphere interactions. The correlations with behavioral ability really hammer this distinction home, since one needed to use the appropriate metric – that is, segregation versus integration – to see these correlations.

..the left hemisphere showing a preference to interact more exclusively with itself, particularly for cortical regions involved in language and fine motor coordination. In contrast, right-hemisphere cortical regions involved in visuospatial and attentional processing interact in a more integrative fashion with both hemispheres.

The degree of lateralization present in these distinct systems selectively predicted behavioral measures of verbal and visuospatial ability, providing direct evidence that lateralization is associated with enhanced cognitive ability.”

A paraphrase of this last sentence may be that our overall cognitive ability is enhanced when we develop the functional specializations of both brain hemispheres.

http://www.pnas.org/content/110/36/E3435.full “Two distinct forms of functional lateralization in the human brain”

Early human brain development can be greatly modified by environmental factors

gettingwell4 4-5 stars Advanced knowledge, Brain development, Brain hemispheres, Epigenetics , , ,

This 2014 Brazilian human study found that the brains of people born without the corpus callosum, the major connection between brain hemispheres, adapted to this loss:

“The authors believe that the development of alternative pathways results from the brain’s ability for long-distance plasticity and occurs in the utero during embryo development, which indicates that connections formed in the human brain early in development can be greatly modified, and most likely by environmental or genetic factors.”

BRAVO! MORE STUDIES LIKE THIS ONE!

People have limited capability to adapt later in life to corpus callosum injuries or to brain hemisphere disconnection.

http://www.pnas.org/content/111/21/7843.full “Structural and functional brain rewiring clarifies preserved interhemispheric transfer in humans born without the corpus callosum”

Problematic research on hardwired differences in human male and female brains

gettingwell4 < 0 Detracted from science, Brain development, Brain hemispheres, Epigenetics

At the risk of wading into a quagmire, it’s hard to take this 2013 Pennsylvania study’s findings seriously, that there were new and significant hardwired differences in human male and female brains in addition to what we already knew. The authors didn’t explain all the factors involved in why they found what they did.

For example, can we raise kids in our culture along typical gender roles and biases, then at ages 12-14, say that the differences in their brains are solely due to their genders? To do so would be to ignore what’s known about epigenetic and environmental influences in shaping the brain.

Here’s an ancient (2011), 90-minute, poor-quality-of-science panel discussion of the subject that included the author of Is the purpose of research to define opportunities for interventions?

Kevin Mitchell had the last word in his 2017 post Debunking the male-female brain mosaic where he both exposed this and other conceptual fallacies, and explained how framing and data cherry-picking can mislead accurate analysis. Feel free to apply what he said to the above video and to the below study.

http://www.pnas.org/content/111/2/823.full “Sex differences in the structural connectome of the human brain”

Our early experiences are maintained and unconsciously influence us for years, if not indefinitely

gettingwell4 4-5 stars Advanced knowledge, Brain development, Brain hemispheres, Memory , , , ,

This 2014 Montreal study provided more evidence of critical periods during human development:

“Clearly illustrates that early acquired information is maintained in the brain and that early experiences unconsciously influence neural processing for years, if not indefinitely.

We show that internationally adopted children (aged 9–17 years) from China, exposed exclusively to French since adoption (mean age of adoption, 12.8 mo), maintained neural representations of their birth language despite functionally losing that language and having no conscious recollection of it.

We show that neural representations are not overwritten and suggest a special status for language input obtained during the first year of development.”

YES! GIVE US MORE STUDIES LIKE THIS ONE!

http://www.pnas.org/content/111/48/17314.full “Mapping the unconscious maintenance of a lost first language”

The same brain areas are used for spontaneous and rehearsed speech

gettingwell4 4-5 stars Advanced knowledge, Brain hemispheres, Primal Therapy

This 2014 human study found:

“..(brain) areas that respond reliably during spontaneous and rehearsed speech production of the same real-world story are the same.”

This finding highlighted the difficulty a therapist or researcher may encounter in objectively determining another person’s reality.

If the listener relied solely on words and speech, they may not be able to tell whether what’s heard was a planned narrative or if the speech had some other origin. That’s why in Dr. Arthur Janov’s Primal Therapy, for example, the therapist is trained to look beyond the patient’s words to ascertain the feeling being expressed.

Also:

“Production of a real-life narrative is not localized to the left hemisphere but recruits an extensive bilateral network.”

http://www.pnas.org/content/111/43/E4687.full “Coupled neural systems underlie the production and comprehension of naturalistic narrative speech”

Left–right dissociation of hippocampal memory processes in mice

gettingwell4 2-3 stars Required further work, Brain hemispheres, Hippocampus, Limbic system, Memory

This 2014 rodent study provided more details on the CA3 segment of the hippocampus:

“Silencing of either the left or right CA3 was sufficient to impair short-term memory…

Only left CA3 silencing impaired performance on an associative spatial long-term memory task, whereas right CA3 silencing had no effect.”

http://www.pnas.org/content/111/42/15238.full “Left–right dissociation of hippocampal memory processes in mice”