Brain Development: Normal Processes and the Effects of Alcohol ...

a Swedis h sample ha d visual impairment, an d >10 %
showed sever e acuity problems (Strômland , 1985 , in
Strômland an d Pinazo-Durân , 2002) . This findin g
indicates tha t prenata l alcoho l exposur e ha s detri -
mental consequence s o n th e developin g visua l system,
a conclusion corroborate d b y ERG results . Ten
of 1 1 subject s i n th e stud y b y Hu g an d colleague s
(2000) ha d abnorma l ER G results , attributabl e t o a
lack o f sufficient retina l sensitivity . Data fro m oph -
thalmological studie s o f FA S subject s sugges t tha t
ocular deficits should be considered amon g the con -
stellation o f presentin g symptom s o f a n alcohol -
exposed individual . Thus, a n ey e examinatio n ma y
be o f diagnosti c us e i n identifyin g individuals wit h
prenatal alcoho l exposur e (Strômlan d an d Pinazo -
Durân, 2002).
OTHER IMAGING APPROACHES
Ultrasonography
In ultrasonography, sound wave s are recorded t o produce
image s of internal organs and body tissues. This
imaging modality 7 has been use d to examine the con -
sequences o f prenatal alcoho l exposur e o n th e feta l
development o f the fronta l cortex (Was s et al., 2001).
The sampl e consist s o f 16 7 women , almos t hal f o f
whom consume d varyin g amounts o f alcohol whil e
pregnant. Result s from thi s stud y represen t th e spec -
trum of fetal alcohol exposure effects; the prospectively
identified sampl e relie s o n neithe r spontaneousl y
aborted fetuse s nor severel y affected childre n identi -
fied throug h retrospectiv e methods , scenario s tha t
overrepresent case s o f heav y exposure . Th e fronta l
lobe measuremen t wa s operationalized a s the linear
distance fro m th e posterio r cavu m septu m pellu -
cidum to the inner surface of the calvarium. It should
be note d tha t this measurement i s logically less com -
prehensive and precise than area or volume measure -
ments o f brai n structure . Regressio n analyse s wer e
used t o determine whic h o f several variable s studie d
were predictiv e of i n viv o feta l fronta l lob e size . I n
general, alcohol exposur e i s a significant predictor of
reduced fronta l lob e size . Interestingly , other brai n
measurements taken fro m th e ultrasonographs , suc h
as th e distanc e betwee n th e posterio r thalamu s an d
the inner calvarium, are less sensitive to alcohol exposure
than th e frontal cortex .
There is an interaction between the effect of alcohol
exposure on the developing frontal corte x and maternal
ALCOHOL AND THE DEVELOPIN G HUMAN BRAI N 14 9
age (Was s e t al. , 2001) . Withi n th e alcohol-expose d
women, a maternal age of greater than 30 years old increases
the ris k of a fetus having a significantly smaller
frontal lobe . Thi s findin g i s consistent wit h previou s
research identifyin g advance d materna l ag e a s a ris k
factor for having a child born with FAS (May and Gos -
sage, 2001) . Thus , i t appears tha t th e deleteriou s ef -
fects o f alcoho l exposur e o n th e developin g fronta l
cortex are exacerbated with increased materna l age.
Emission Computed Tomography
Emission compute d tomograph y (CT ) technologies ,
such a s positron emissio n tomograph y (PET ) an d single
photon emissio n computed tomograph y (SPECT),
can be used t o measure cerebra l metabolism . Accord -
ingly, a radiotracer is injected int o a subject's body an d
images o f a nonsedate d individual , wh o migh t b e
asked to perform a behavioral task, are taken. The im -
ages are reconstructed t o appreciate the activity within
nuclei o f the brain . Fo r the purpose s o f the researc h
discussed i n th e presen t chapter , measurement s ob -
tained in this way are a proxy for brain function in that
increased metaboli c rate s within a brain regio n indi -
cate more neural activity in that region.
The effec t o f prenatal alcoho l exposur e o n brai n
function wa s assesse d vi a PE T analysi s i n 1 9 youn g
adults diagnose d wit h FA S (Clark et al, 2000). Glu -
cose metabolis m i n subcortica l areas , includin g th e
thalamic an d caudat e nuclei , i s decreased . I n th e
most severe situations, ethanol causes gross structural
deficits, wherea s othe r case s sho w subtl e effect s tha t
vary b y region o r cel l type . These change s ar e remi -
niscent o f ethanol-induced reductions i n glucose uti -
lization amon g specifi c subcortical structure s i n th e
rat brai n (Vinga n e t al. , 1986 ; Mille r an d Dow -
Edwards, 1993) . Thus , fetal alcoho l exposur e cause s
a continuum o f damage to the developing brain.
SPECT has been used to evaluate the brain function
o f 1 1 children (mea n age , 8. 6 years ) wit h FA S
(Riikonen e t al., 1999) . Thes e children exhibi t mod -
erate decrease s i n cerebra l bloo d flo w i n th e lef t
parieto-occipital region . Thi s i s consisten t wit h th e
abnormalities identified by structural MRI studies. Altered
functio n withi n thi s regio n ma y b e relate d t o
difficulties tha t childre n wit h FA S have wit h arith -
metic an d speech . Additionally , th e sampl e o f chil -
dren wit h FA S show s a n asymmetrica l patter n o f
frontal lob e perfusion, or the patter n i n which th e radiotracer
i s incorporate d b y th e tissue . Specifically,
the righ t frontal region showed sligh t hyperperfusio n