Figure11 is a diagram of the auditory pathway from
the cochlear nerve in the lower brainstem to the
temporal lobes of the cerebral cortex.  The inferior
colliculi are the posterior pair of "hills" (Latin colliculi)
in the midbrain tectum.  Figure 12 is an autoradiogram
from the investigations of Landau et al. (1955) on
cerebral blood flow [1]; it shows the greatest uptake of
radioactive tracer in the inferior colliculi.  Figure 12
can be compared with figure 11 for location of the
inferior colliculi, the superior olives, and the lateral
lemniscal tracts connecting these important way
stations in the brainstem auditory pathway.  The
dramatic autoradiographic picture in figure 5 is from a
paper by Kety (1962), who was director of the group
that first used radioactive tracers to study blood flow
in the brain [2].

Figure 6 from observations of myelination by Yakovlev
and Lecours (1967) shows that the greatest degree of
myelin development in a human fetus at 29 weeks
gestation is in the same structures with highest blood
flow, the inferior colliculi and the lateral lemniscal tract
connections to it from the superior olives [3].  
Myelination is an important measure of maturation,
and the study by Yakovlev and Lecours confirmed
earlier research by Langworthy (1933) who also found
the auditory system of the brain among the earliest to
mature [4].  Langworthy's data is shown in figure 7.  
Confirmation of early myelination and function of the
auditory system can be found in the paper by Moore
et al. (1995) [5].

Early maturation of the auditory system suggests its
possible involvement in stimulating growth of later
developing areas of the cerebral cortex.  Growth of
the auditory receptive areas of the temporal lobes and
speech motor areas in the frontal lobes are likely
dependent at least in part on neurotransmissions from
the brainstem auditory system.  Neurotransmission
does not necessarily require acoustic stimulation;
development of the temporal and frontal lobes takes
place normally in children born deaf, but their
deafness is due to impairment within the lower
auditory system, not the inferior colliculi and thalamic
auditory nuclei.
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Fig 11
Fig 3
Fig 6
Fig 7
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4 – Early maturation and stimulation of cortical growth
  1. Landau WM et al (1955) The
    local circulation of the living
    brain; values in the
    unanesthetized and
    anesthetized cat.
  2. Kety SS (1962) Regional
    neurochemistry and its
    application to brain function.
  3. Yakovlev PI, Lecours A-R
    (1967) The myelogenetic
    cycles of regional maturation
    of the brain.
  4. Langworthy OR (1933)
    Development of behavior
    patterns and myelinization of
    the nervous system in the
    human fetus and infant.
  5. Moore JK, Perazzo LM, Braun
    A (1995). Time course of
    axonal myelination in the
    human brainstem auditory
    pathway.
References
Full References
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Figure 11 -

Diagram of the
auditory system.
Figure 3 -

Blood flow and metabolism
are not uniform throughout
the brain.  The same nuclei
in the brainstem auditory
pathway that are first to
become myelinated during
prenatal life also have the
highest blood flow and
metabolism.
Figure 6 - From Yakovlev & Lecours (1967)
showing prominent myelination in the inferior
colliculus (ICOL) at 25 gestational weeks
(below) and 29 gestational weeks (right).
Figure 7 - From Langworthy (1933) myelination of the acoustic colliculus at 28 weeks gestation
  1. Landau WM, Freygang WH, Rowland LP, Sokoloff L, Kety SS (1955) The local circulation
    of the living brain; values in the unanesthetized and anesthetized cat.  Transactions of the
    American Neurological Association 1955-1956;(80th Meeting):125-129.
  2. Kety SS (1962) Regional neurochemistry and its application to brain function. In French,
    JD, ed, Frontiers in Brain Research. New York: Columbia University Press, pp 97-120.
  3. Yakovlev PI and Lecours A-R (1967) The myelogenetic cycles of regional maturation of the
    brain.  In A. Minkowski (Ed.), Regional Development of the Brain in Early Life (pp. 3-70).  
    Oxford: Blackwell Scientific Publications.
  4. Langworthy OR (1933) Development of behavior patterns and myelinization of the nervous
    system in the human fetus and infant. Contributions to Embryology, no. 139 24:1-57.
  5. Moore JK, Perazzo LM, Braun A (1995). Time course of axonal myelination in the human
    brainstem auditory pathway.  Hearing Research 87:21-31, 91:208-209.