Abstract
When using a tool it becomes an extension of the hand both physically and perceptually—the tool is incorporated into our body image, or body schemata. We have shown in monkeys that, visual receptive fields of bimodal (tactile and visual) neurons were altered to include the entire length of the rake to represent neural correlates for assimilation of the tool into our own body-image. Also, we showed the evidence that these neurons can also code the body-image projected onto the video monitor, perhaps corresponding to its “iconic” representation. When above described representations were further advanced, it would become totally free from physical constraints of the actual world to become a (pre-) symbolic one to represent evolutionary precursors of higher cognitive functions such as using tools, and eventually leads to evolution of human language or to metaphysical thoughts.
