Point
4
Intro
Pathway
Deficit
Note
Overview
Problems
Contents
Anatomy
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You may remember that there is a somatotopic
representation of the body in the dorsal columns (fasciculus
gracilis and fasciculus cuneatus). Caudal (sacral and
lumbar) body parts are represented medially, while
the rostral segments (upper thoracic and cervical)
are represented laterally. Nucleus gracilis receives
its input from about T7 and downward, while nucleus cuneatus
receives its input from spinal levels above this.
There is also a somatotopic organization
within the medial lemniscus. For instance, in the medullary
segment of the medial lemniscus the body is represented in
an upright position, so that the legs are ventral and
the arms dorsal. Within the pontine portion of the medial
lemniscus there is a rotation, so that the arms are
represented medially and the legs laterally. Finally, in the
midbrain portion of the medial lemniscus the arms are
represented ventrally while the legs are represented
dorsally.
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