Chapter 2. Prehension

Chapter 9. Reevaluation and Future Directions
”What do human hands do? Look around you.”
--C. L. MacKenzie and T. Iberall(l994)
329
As we look around, we sit in wonder at the versatility of the
human hand, the greatest tool known to humankind. Yet, as Frederick
Wood-Jones (1920) pointed out, the structure of the human hand and
monkey hand are very similar. Phillips (1986, p. 6) stated that,
“the increasing versatility of hand function as we
ascend the primate scale has been conferred by a
progressive enlargement of cerebral cortex and
cerebellum and a corresponding enrichment of their
intrinsic and extrinsic synaptic connectivity” .
This book has explored two questions: the question of what is the
nature of the human hand and the question of what might be involved
in the CNS as it controls this marvelous tool in prehension. Starting
with the concept of a black box that takes inputs and produces results,
experimental evidence has been examined for data that might suggest
how the CNS selects prehensile behaviors for interacting with objects
for a task, given numerous constraints. Computational models have
been explored that make explicit the issues in motor control. The
underlying theoretical framework was based on the model of the CNS
as a parallel distributed processor using action-oriented perception and
goal-directed movement.
In this chapter, we revisit the issues put forth in Chapter 1,
summarizing key points made through the text. Our goal in writing
this book has been to put forth a comprehensive study of human
prehension, looking in depth at all the factors contributing to our
primate ability to grasp objects. However, the careful reader will note
many missing topics. Therefore, we take the opportunity in this
chapter to outline other issues critical to the understanding of human
prehension .