Experiments were made on the posterior parietal association cortical areas 5 and in 17 hemispheres of 11 monkeys, 6 M. mulatta and 5 M. arctoides. The electrical signs of the activity of single cortical cells were recorded with microelectrodes in waking animals as they carried out certain behavioral acts in response to a series of sensory cues. The behavioral paradigms were one for detection alone, and a second for detection plus projection of the arm to contact a stationary or moving target placed at arm's length. Of the 125 microelectrode penetrations made, 1,451 neurons were identified in terms of the correlation of their activity with the behavioral acts and their sensitivity or lack of it to sensory stimuli delivered passively; 180 were studied quantitatively. The locations of cortical neurons were identified in serial sections; 94 penetrations and 1,058 neurons were located with certainty. About two-thirds of the neurons of area 5 were activated by passive rotation of the limbs at their joints; of these, 82% were related to single, contralateral joints, 10% to two or more contralateral joints, 6% to ipsilateral, and 2% to joints on both sides of the body. A few of the latter were active during complex bodily postures. A large proportion of area 5 neurons were relatively insensitive to passive joint rotations, as compared with similar neurons of the postcentral gyrus, but were driven to high rates of discharge when the same joint was rotated during an active movement of the animal...

Posterior parietal association cortex of the monkey: command functions for operations within extrapersonal space

The problem discussed is the relationship between the firing of single neurons in sensory pathways and subjectively experienced sensations. The conclusions are formulated as the following five dogmas:To understand nervous function one needs to look at interactions at a cellular level, rather than either a more macroscopic or microscopic level, because behaviour depends upon the organized pattern of these intercellular interactions.The sensory system is organized to achieve as complete a representation of the sensory stimulus as possible with the minimum number of active neurons.Trigger features of sensory neurons are matched to redundant patterns of stimulation by experience as well as by developmental processes.Perception corresponds to the activity of a small selection from the very numerous high-level neurons, each of which corresponds to a pattern of external events of the order of complexity of the events symbolized by a word.High impulse frequency in such neurons corresponds to high certainty that t...

Single units and sensation: a neuron doctrine for perceptual psychology?

1. Single unit impulses were recorded with percutaneously inserted tungsten needle electrodes from the median nerve in conscious human subjects. 2. A sample of 334 low threshold mechanoreceptive units innervating the glabrous skin area of the hand were studied. In accordance with earlier investigations, the units were separated into four groups on the basis of their adaptation and receptive field properties: RA, PC, SA I and SA II units. 3. The locations of the receptive fields of individual units were determined and the relative unit densities within various skin regions were calculated. The over-all density was found to increase in the proximo-distal direction. There was a slight increase from the palm to the main part of the finger and an abrupt increase from the main part of the finger to the finger tip. The relative densities in these three regions were 1, 1.6, 4.2. 4. The differences in over-all density were essentially accounted for by the two types of units characterized by small and well defined receptive fields, the RA and SA I units, whereas the PC and SA II units were almost evenly distributed over the whole glabrous skin area. 5. The spatial distribution of densities supports the idea that the RA and SA I units account for spatial acuity in psychophysical tests. This capacity is known to increase in distal direction along the hand. 6. On the basis of histological data regarding the number of myelinated fibres in the median nerve, a model of the absolute unit density was proposed. It was estimated that the density of low threshold mechanoreceptive units at the finger tip is as high as 241 u./cm2, whereas in the palm it is only 58 u./cm2.

https://physoc.onlinelibrary.wiley.com/doi/pdf/10.1113/jphysiol.1979.sp012619

Tactile sensibility in the human hand: relative and absolute densities of four types of mechanoreceptive units in glabrous skin.

Quantitative sensory testing: a comprehensive protocol for clinical trials

The Sensory Neurons of Touch

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.

H H Kornhuber

Papers

The sense of flutter-vibration: comparison of the human capacity with response patterns of mechanoreceptive afferents from the monkey hand.