The mammalian central nervous system develops through a series of complex cellular
processes which may be grouped into two broad phases (1,2). The first, cytogenesis
and histogenesis, is a phase in which neurons are formed, move to their
correct positions, and elaborate the primary neuritic processes which contribute to
emerging dendritic fields and axon fascicles.
The brain evolves through a series of temporally overlapping stages. Brain malformations
may be analyzed in the context of the stage or stages during which the
pathologic process was judged to be initially and maximally active.
Most viable developmental brain disorders occurring during the second half of
gestation lead to neurological defects that can range from minimal learning or motor
deficits to major motor and cognitive handicaps.
Dr. Sotelo: I should like Dr. Evrard and Dr. Caviness to speculate about the
mechanism of the formation of the gyri. According to Dr. Williams it appears that
cytogenetic problems may be responsible for the absence of gyri, but in your chapter,
Dr. Evrard, it seems that problems in brain vascularization may actually induce
the formation of gyri.
Synaptogenesis is one of the final events during neurogenesis and is preceded by
a series of phenomena (both progressive and regressive) overlapping in time but yet
distinguishable (see Caviness, this volume).
Peroxisomes play a key role in a number of genetic diseases. These include disorders
in which the activity of a peroxisomal enzyme is deficient and an extraordinary
group of diseases in which the formation of the organelle itself is defective (1-3)
Until recently the assertion that mammalian peroxisomes play a role in the development
of the central nervous system was received with incredulity by most investigators
despite the demonstration by Goldfischer et al.
Very accurate gene mapping is essential in both man and laboratory mammals ( 1 -
3). Several techniques have been used over the last 50 years to localize mammalian
genes on the chromosomes of a given species.
Myelination is a major biological event during the early postnatal development of
the mouse brain, yet relatively little is known about the mechanism and regulation
of myelin assembly.
Nerve cells and myelin require an adequate supply of nutrients, particularly lipids,
for their formation and development. This chapter examines the role of nutrition
in the synthesis of myelin lipids.
In spite of the apparent homogeneity of the cerebellar cortex, which is composed
throughout of the same neuronal populations and the same types of afferent and efferent
systems, the anatomical work of Voogd (1) and the electrophysiological studies
of Oscarsson (2)
Monoamines have an important cerebral regulatory function in adult animals. Serotonin
(5-hydroxytryptamine, 5-HT), noradrenalin (NA), and dopamine (DA) are
central neurotransmitters involved in the regulation of major functions such as nociception,
sleeping and waking cycles, thermoregulation, and some types of behavior
(e.g., the 5-HT syndrome evoked by 5-HT agonists, or the turning behavior induced
by DA agonists in rats with a unilateral lesion of the dopaminergic nigrostriatal
The onset of myelination is of great interest in the field of pediatric nutrition because
it is one of the critical periods of brain development during which nutritional
influences may lead to neurological deficiencies.
In the adult, vision is a cortical function and thus it has always been assumed that
this would also hold true for the newborn infant.
In recent years there has been a growing awareness of the significance of hemodynamic
factors in the pathogenesis of perinatal neurologic disorders.
The two major causes of neurological morbidity and mortality related to definable
events in the neonatal period are intraventricular hemorrhage (IVH) with hemorrhagic
intracerebral involvement in the preterm infant, and hypoxic-ischemic encephalopathy
in the asphyxiated term infant.
Dr. Dubowitz: I agree with Dr. Lou that the primary lesions in large intracranial
hemorrhages are ischemic. The demonstration of this is dependent on having a really
good 7 MHz ultrasound scanner which allows you to see ischemic lesions preceding
In exploring the role of psychological factors in neurological development— and
by extension—behavior, we tread firmly on the nature-nurture controversy, an
arena of debate that has ensnarled many bright minds and often generated great heat
but little light.
Arguments concerned with the impact of malnutrition on neurological development
have been a matter of considerable scientific and political interest during the
past two decades.
Ethanol has both pharmacologic and toxic effects in the developing and mature
nervous systems (1). The toxic effects, which are associated with chronic abuse,
may depend on ethanol's pharmacologic actions.
A large number of publications during the last 15 years have addressed the question
of the influence of nutrition, particularly nutritional deprivation, on brain development.
It is generally accepted that the higher functions of the central nervous system are
closely related to association areas of the cerebral cortex. This notion is based on
considerable evidence obtained from studies mainly performed in freely moving
Two questions regarding brain development and nutrition are of particular importance:
How long does brain development (i.e., growth and differentiation) continue?
and What are the effects of malnutrition on neurotransmitter systems? Many
of the research data available today are derived from animal experiments, and the
limitations of animal studies are well known.
biochemical defects in, 67-68
clinical features of, 67
Accessory olive projections, in cerebellum,