restoration of hearing. If the surgery is performed too late, there will
be no, or limited, restoration of hearing.
Touch
This sensing pathway also appears to have a critical or sensitive pe-
riod for development. This pathway affects a number of different
neurological and biological pathways. Touch has a very significant ef-
fect on development of the limbic-hypothalamic-pituitary-adrenal
gland (LHPA) axis, or stress pathway.
Scientists’ understanding of the development of the sensing pathways
has led to considerable interest in the plasticityof neurons and neu-
ronal pathways throughout life and in the concept of critical and sensi-
tive periodsduring the early development of the sensory pathways.Wiring and Sculpting of Neuronal Pathways
The neurons in the brain that translate the signals that come from
the sensing pathways have to interact with the other pathways in the
brain that affect emotion, behavior, language and literacy, speech,
cognition, and the biological pathways that affect physical and men-
tal health. These neural pathways influence how we cope with the
everyday challenges of life. They have sensitive periods for develop-
ment, but are more plastic than the primary sensing pathways.
The LHPA, or stress, pathway is a critical pathway that is affected
by stimuli sensed through the sensing pathways. This pathway is con-
nected to a number of circuits in the brain. It responds to the daily
experience of individuals, and it relates to emotion, fear, and re-
sponse to threats. It influences, for example, cardiovascular function,
behavior, cognition, and immune function.
We now have a better understanding about how the pathways de-
velop in respect to language and literacy. The development of these
different brain pathways can be thought of as a hierarchy in develop-
ment. Pathways that develop early may be difficult to change in later
stages of development, whereas those that develop later may be more
plastic in terms of changing their function. It is generally accepted
50 J. Fraser Mustard