Abstract: IT WAS OUR PURPOSE in the studies described in the intact, behaving organism are therefore this paper to combine two experimental of the first importance for sensory neurophysdesigns which differ remarkably in method, iology, for they establish: 7) the dynamic and in their historical and conceptual derange required of the input on the afferent side of the system to account for the output-the measured sensory capacities; 2) the information about the stimulus which must be preserved in the initial encoding to account for the over-all information transmitting capacity of the nervous system in a particular sensory sphere; and 3) a basis for determining which of the many codes available to the pulse-operated input sys tern may be of functional significance in the sensory performance measured. It is thought that a continued correlation of the results of these two types of studies will set the limits and establish some of the parameters to be expected of that higher order neural mechanism intervening between initial cortical display and sensory experience, referred to above. mechanisms (30). Electrophysiological studies, particularly with the method of singleunit analysis, can now provide precise measures of the neural encoding in first-order nerve fibers of the parameters of peripheral stimuli, and of the successive relay and transformation of that neural replication from periphery to cerebral cortex. They have so far provided little understanding of those cerebral mechanisms which, operating upon the transformed replication of the peripheral event in the primary receiving areas of the cerebral cortex, are thought to lead to subjective sensory experience and its overt behavioral counterparts. Psychophysical studies, on the other hand, seek to establish Ideally, the two types of observation should be made in the same organism at the same lawful relations between those experiences time. Given the demands of the single-unit and certain physical aspects of the stimuli method when applied in its quantitative which evoke them. The results of these quantiform, and particularly the desired level of tative measures of the sensory performance of control of stimulus parameters, this is not vet possible for somesthesis. For the present Received for publication August 24, 1967. l This study was supported by Public Health &e Ahave made the assumption thai what Service Grants NB-1045 and NB-06828, Air Force monkeys and humans feel with their hands Contract no. 49 (638) 1305. is in principle the same, and that neuro2 Visiting Lecturer in Physiology, 1966, from the physiological observations made in the one School of Physiology, University of New South Wales, New South Wales, Australia. may with some validity be correlated with 3 Foreign Fellow of the Public Health Service, psychophysical measures in the other, given 1965-1966, from the University of Freiburg im Breisa precise identity of experimental design in gau, Germany. the two cases.