- Birth is a time of peril for the human brain, especially
in pre-term infants. For vulnerable "preemies," biochemical signs of
reduced blood oxygen levels (hypoxia) soon after birth are
associated with lower IQs and language skills. In 2001, premature
babies were 12 percent of U.S. births - the highest level in 20
years, due in part to more multiple pregnancies, induced labor, and
older mothers. The January issue of Neuropsychology, published by
the American Psychological Association (APA) reports on links among
pre-term birth, risk for birth hypoxia and cognitive problems, and
reveals how the risk threshold for brain damage in preterm babies
could be lower than thought.
Psychologists compared the
intellectual and language development of five- and six- year olds,
all of whom had been born prematurely. Half the group were, during
or immediately following birth, at slight to moderate risk for
hypoxia. The other half had no such risk, although they resembled
the risk group on other early risk factors and on socio-demographic
characteristics. Despite the relatively small difference between the
groups in the degree of risk, the authors report that the two groups
"diverged significantly" in their development.
The relationship between
mild to moderate birth hypoxia and later cognitive abilities
contradicts established wisdom that regards severe oxygen
deprivation as the threshold for brain damage in an "all or nothing"
manner. The findings add to other recent evidence of a continuum of
brain injury due to asphyxia around birth.
The researchers, at Wayne
State University, The University of Memphis, and Baptist Memorial
Hospital in Memphis, studied 52 children. All had been born at or
before 36 weeks (normal term is about 40 weeks). Twenty six of the
children were at slight to moderate risk of perinatal hypoxia, as
measured by higher blood acidity within two hours of birth (lower
than normal arterial blood pH). The other 26 children in the
comparison group were at lower perinatal risk.
Hopkins-Golightly, Ph.D., Sarah Raz, Ph.D., and Craig J. Sander,
M.D. tested all 52 children at an average age of six on intelligence
and language (receptive and expressive) skills.
There was a significant
relationship between blood pH soon after birth and later cognitive
and language skills. For example, the pre-term group, with mild to
moderate acidosis, scored about 10 to 11 points lower on verbal and
visuospatial tests than the low-risk pre-term group - a large
discrepancy. Such data, say the authors, reveal that even a minor
risk for hypoxia around birth may have a "discernible influence on
the course of cognitive development."
Says Raz, now at Wayne
State University in Detroit, "most neonatologists would probably not
expect to find a statistically significant relationship between
degree of acidosis measured soon after birth and performance on
cognitive tests in preschool and early school-age children, when
acidosis is only mild to moderate, at worst".
Although it is well-known
that premature babies tend to have more cognitive problems than
full-term infants, scientists want to tease out the specific
complications -- from a host of many - that cause the most trouble.
A good way to do that is to compare two groups of preterm infants,
who share the risks of pregnancy, delivery and the vulnerable
postnatal period, but who differ in terms of one single, special
risk factor (such as birth hypoxia).
Structural or functional
imaging, such as MRI, may shed light on which brain areas are the
most vulnerable to damage by hypoxia in the preterm infant. For now
the authors speculate that, in babies born prematurely, even minor
risk may be associated with damage to the periventricular white
matter, deep inside the brain.
By linking birth
complications to specific cognitive problems occurring later,
scientists hope to understand the brain's vulnerability to insult
during early human development. Furthermore, knowledge of how early
risk factors affect cognitive abilities may help doctors to evaluate
the effectiveness of medical interventions that support preterm
infants during and after birth.
"Influence of Slight to Moderate Risk for Birth Hypoxia on
Acquisition of Cognitive and Language Function in the Preterm
Infant: A Cross-Sectional Comparison With Pre-Term Birth Controls,"
Tracy Hopkins-Golightly, Ph.D., University of Memphis; Sarah Raz,
Ph.D. University of Memphis and Wayne State University; and Craig J.
Sander, M.D., Baptist Memorial Hospital; Neuropsychology, Vol. 17,
A Look Into the Teenage Brain
Scientists used to think
that the teenage brain more closely resembled the adult brain than a
child's brain. Recent studies have indicated that isn't necessarily
the case. The August 9th, 1999, issue of "US News and World Report"
reported on some of the most recent findings.
Most teens don't wear
trench coats and shoot fellow students, but adults have often been
amazed at how teens can seem to be happy-go-lucky, well-adjusted,
seemingly-normal people one minute and ranting, raving lunatics who
are impossible to understand the next.
The single most frustrating
thing to parents of teens is the fact that they can run so hot and
cold. One minute they love you and the next they hate you. The
reason for this seems hidden deep inside the teenage brain.
Since the inception of the
M.R.I. (magnetic resonance imaging) scientists have been able to
study the human brain in ways never thought possible before. Adults
and teens wired for study purposes are given certain stimuli and
certain regions of the brain light up with activity. What puzzled
researchers at first was that adult brains light up in both the
prefrontal cortex and the limbic regions almost simultaneously. Teen
brains only light the limbic region and the prefrontal cortex region
The problem with the fact
that teen prefrontal cortex regions of the brain show practically no
activity is that the prefrontal cortex is like the CEO of the brain.
The limbic region is the seat of the emotions. It is no wonder teens
are so ruled by emotions and seem to be so illogical. The "US News"
article states "the prefrontal cortex is the seat of civilization."
The part of the brain that will later balance the emotions with
reason and common sense is sadly asleep at the wheel until long
The limbic region, found
deep within the brain, is the source of raw emotions such as anger.
Unfortunately, the limbic region goes into hyperdevelopment mode
during the teen years. The raw emotions are tempered in adult brains
by signals from the prefrontal cortex. According to Karl Pribriam,
director of the Center for Brain Research and Informational Sciences
at Radford University in Virginia, "the prefrontal cortex is in
charge of `executive functions.' "These include the brain's ability
to handle ambiguous information and make decisions, to coordinate
signals in different regions of the brain, and to tamp down or
prolong emotions generated in the limbic system."
"In an adult, for instance,
an overheard insult might arouse a murderous rage, until the
prefrontal cortex figures out that the comment was meant for
somebody else and tells the limbic system to pipe down."
Teens shown pictures of
faces with certain strong emotions were almost never able to tell
what emotion was being expressed. Adults shown the same pictures
almost always knew what emotion was being shown. This reveals yet
another piece of the puzzle in trying to understand teenagers.
The gist of the "US News"
seemed to be that teenagers are much like a computer. You can pump
good information into them, but if the hardware is incapable of
processing it therein lies the problem. The hardware in the teen
brain is pretty much incapable of maturely processing information
until the early twenties.
"The teenage tendency to
leap before looking is compounded by the fact that adolescence is a
time for seeking out new experiences, including some that are
dangerous. `I think all people do stupid things sometimes. It just
seems like teenagers do it more often,' says Rachel Fisher, an
18-year-old senior from Lakewood, Colo. That's an understatement.
Driving without a seatbelt, getting tattooed, smoking cigarettes,
shoplifting-the list of foolish things kids do is longer than most
parents really want to know."
The good news for parents
seems to be "that the vast majority of kids will make it through
adolescence with few permanent scars, except for the occasional hole
through a belly button. New research shows that most children emerge
from adolescence physically and emotionally intact-although their
parents will probably never be the same."
It probably won't help
parents to tell their teenagers that we know their brains are a work
in progress. It might help parents to realize that teen brains are
incapable of processing information the same way adult brains do. So
next time your teen looks at you in that certain way only a teenager
can, just look back at them and smile, realizing full well that
his/her brain is only half there for a few more
HYPERBARIC OXYGEN IMPROVES PERIPHERAL
Several studies have documented the effectiveness of
hyperbaric oxygen in models of acute and delayed crush injury.
Intermittent exposure to hyperbaric hyperoxia serves to interrupt
the injury cycle of edema, ischemia and tissue necrosis(1), as well
as hemorrhagic hypotension(2), which in turn leads to former edema
and ischemia. Tissue ischemia is countered by the ability of
hyperbaric doses of oxygen to elevate tissue oxygen tensions(3).
Furthermore, edema is reduced, secondary to hyperoxia-induced
arteriolar vasoconstriction(4), leading to improved tissue
viability, thereby reducing necrosis(1). Hyperbaric oxygen has also
been studied in models of peripheral nerve injury(5).
Researchers from the US Air Force School Aerospace Medicine
and Louisiana State University recently sought to determine what, if
any, morphologic changes are associated with hyperbaric oxygen
treated peripheral nerve injury(6). Their model involved a crushed
sciatic nerve in the rabbit.
Exposure to hyperbaric oxygen across the range of current
clinical dose schedules was compared to untreated, and pressure
(hyperbaric air) controls. The extent of nerve regeneration was
documented via morphologic analysis of electron micrographs, by a
pathologist blinded as to group.
All of the animals exposed to hyperbaric doses of oxygen were
reported to demonstrate advanced stages of a healed nerve, in
contrast to both control groups.
this research was limited to a determination of regeneration of
morphology, the exact effects of hyperbaric oxygen were not known.
The authors speculate, however, that there may be several suggesting
increased myelination, decreased edema, reduced internal collagen
and improvements in neurofilamentous material density.
They conclude that this study provides additional evidence of
a link between tissue oxygen levels and the health of peripheral
... all animals exposed to hyperbaric oxygen
"demonstrated characteristics expected of in the advanced stages of
a healed nerve"
- Strauss MB et al.: Delayed use of hyperbaric oxygen for
treatment of a model anterior compartment syndrome. Journal of
Orthopedic Research 1986; 4:108-111.
- Skyhar MJ et al.: Hyperbaric oxygen reduces edema and
necrosis of skeletal muscle in compartment syndromes associated
with hemorrhagic hypotension. Journal of Bone and Joint Surgery
- Nylander G: Tissue ischemia and hyperbaric oxygen
treatment. Scand 1986; suppl. 533.
- Nylander G et al.: Reduction of postischemic edema with
hyperbaric oxygen. Plastic and Reconstructive Surgery
- Zamboni WA et al.: Functional evaluation of
peripheral-nerve repair and the effect of hyperbaric oxygen.
Journal of Reconstructive Microsurgery 1995; 11:27-29.
- Bradshaw PO, et al.: Effect of hyperbaric oxygenation on
peripheral nerve regeneration in adult male rabbits. Undersea and
Hyperbaric Medicine 1996; 23(2): 107-113.