Published online by Cambridge University Press: 23 December 2009
Summary
Our knowledge about an object small enough to be grasped with the hand usually begins first with a visual appreciation of its size and shape. However, in the dark or when searching a deep pocket or purse, vision is impossible. Consequently a haptic exploration procedure is the only course of action and scanning an object's surface with the fingertips provides information about friction, shape, compliance, temperature and friction that is unattainable by visual inspection. This initial information is of particular importance to subsequent object manipulation and dexterous handling. Both exploratory hand movements and object manipulation make efficient use of specialized low-threshold mechanoreceptors in the skin which are selectively sensitive to both normal and tangential (shearing) forces as well as slip on the skin. This cutaneous feedback guides the exploratory movements and provides a signal of when a tactile target is encountered. These primary afferent signals are subsequently transformed by cell assemblies in the somatosensory cortex to generate central representations or internal models of the object's salient physical features. Neuronal signals encoding the internal model of shape, friction and center of mass are then relayed directly by cortico-cortical projections from the somatosensory cortex to motor cortex. The subsequent dexterous object manipulation is driven by anticipatory motor control strategies based on the internal model of the object's features which are used to direct grip forces and finger positions.
To save this book to your Kindle, first ensure [email protected] is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Find out more about the Kindle Personal Document Service.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.