Arnold L. Towe
Russel W. Morse
Gary W. Harding
Ronald J. Adkins
Judy K. Nyquist
C. Fred Tyner
David Whitehorn
Michael D. Mann
Gernot S. Doetsch
William R. Satterthwaite
Thomas O. Videen
Jefferson C. Slimp
Fred A. Harris
Jane A. Burnham
Jean A. Ennever
Yev Gahery
Terry A. Harrison
Zhengqiu Chen
For acute experiments, adult cats of either sex were anesthetized with 60 mg/kg alpha-Chloralose (some with 35 mg/kg Nembutal) i.p. Supplemental doses of anesthetic were given as needed to maintain anesthesia. With Chloralose anesthesia, the paralyzing agent Syncurine (decamethonium bromide) was administered. Bilateral pneumothorax was performed to reduce cerebral pulsations. The animals were artificially respirated throughout the experiment. In many animals, the medulary pyramids were exposed. The cerebral cortex was exposed in one hemisphere and the animal was placed in a head-holder. A polyethylene sheet cut to fit and with a small hole for microelectrode passage was placed upon the cortex to prevent drying.
Bipolar needle electrodes were placed in all 4 paws (Contralateral Fore Paw, Ipsifore, Contrahind, Ipsihind; CF, IF, CH, IH) and 0.1 ms pulses delivered with a constant-voltage, transformer-isolated stimulator. A small bipolar electrode was placed upon the surface of the ipsilateral pyramidal tract (PY) in some animals and on the surface of the contralateral dorsal columns in one study. Glass microelectrodes filled with 3 M NaCl (or etched tungsten in cases where noted) were used to extracellularly isolate neurons responding to the hunting stimulus. The microelectrodes were oriented perpendicular to the cortical surface and slowly advanced to a depth of 2.5 mm. Depending upon the study, the sites sampled are shown in Figure 1.
Figure 1. Left) Diagram of the left frontal hemisphere showing the sites (1-7) that were sampled. The cytoarchitectonic regions are labeled from left to right. (pcd) - post cruciate dimple. Right) Diagram of cross section of cortex along region labels at left.
When a neuron was isolated, the depth below the pial surface was noted and the stimulus location (CF, IF, CH, IH, PY), CF frequency (1, 2, 4, 6.25, 10/sec; 12V, 0.1 msec pulse) and CF intensity (12, 2, 1V; 1/sec) were manipulated to characterize the behavior of the neuron. In some animals, the pyramidal tract was stimulated (0.1 V, 0.05 msec pulse; 1 and 100/sec) to test for antidromic activation. The IF, CH, and IH locations were tested (12V; 1/sec) and the frequency-following, and intensity thresholds were determined for all locations. Five to 10 trials under each condition were recorded. The sensory modality was determined and the peripheral receptive field was mapped with natural stimulation. Subsequently, spike latencies were measured for each response and averaged and mean spikes per discharge determined.
In some experiments, the optic chyasm, splanchnic nerve, or pudendal nerve or optic nerve was also electrically stimulated. In others, the dorsal columns or medial lemniscus was electrically stimulated or the visual or auditory system was naturally stimulated in addition to the somatosensory periphery. A more detailed account of the rationale behind these experiments can be found at The story behind the data. See References listed below for further methods details. The methods used for the awake experiments are included with that data set.
Under Chloralose anesthesia, neurons in the pericruciate region (sensorymotor area SI, CF sites 1 and 4) showed behaviors that were classified by response as follows: Sa - CF only; M - CF, IF, CH, and IH; Sb - CF and IF only; Sc - CF and CH only; and I - IF, CH, and IH but not CF. Neurons in class Sa were called 'small-field', while those in classes M and I were called 'wide-field' because they responded to somatosensory inputs from all over the body, and often visual, auditory, and visceral inputs as well. Neurons in the other classes did not have wide-field properties. Neurons in classes Sb and Sc were called 'bilateral-field' and 'contralateral-field', respectively. Large numbers of neurons in classes other than Sa were found. At site 3, however, only Sa neurones were found with the distribution at site 2 about halfway between that at sites 1 and 3. The CH cortex at sites 5 and 6 showed a similar pattern for the hindpaw to that seen for the forepaw at sites 1 and 4, respectively. About 50% of M and I neurons sent their axons into the pyramidal tract. Approximately 20% of Sb and Sc neurons did so and only 10% of Sa neurons were antidromically activated by PY stimulation at 100/sec. Site 7 is in somatosensory area SII and the distribution of classes was similar to that at site 3.
How some of these data were used to model the behavior of neuronal circuits can be found at Modeling Examples.
Under Nembutal anesthesia, the vast majority of neurons were Sa at sites 1, 2, and 3; very few neurons in the other classes were found. At site 4, there were very few neurons found. Sites 5 and 6 were not tested under Nembutal.
In awake cats, many more sites were sampled and neuronal behaviors were often complex. In general, everything seen under Chloralose and Nembutal was seen (depending upon the animal's state of alertness) as well as much more. These results are included with that data set.
Contralateral Forepaw (CF) Cortex (Chloralose)
Contralateral Forepaw (CF) Cortex (Nembutal)
Contralateral Hindpaw (CH) Cortex (Chloralose)
Contralateral Sigmoid Gyrus Cortex (Awake)
The chloralose and nembutal samples cannot be directly compared with the awake samples because the methods were quite different. However, the chloralose and nembutal samples taken in the cats that were also done awake provide clues as to how the samples differ. For example, consider the average number of cells found per electrode track:
Number of cells per track Site | 1 2 3 4 -------------------------------------------- Chloralose | 3.2 2.5 3.4 3.1 Nembutal | 1.2 2.1 3.5 0.3 Awake | 8.7 11.3 13.8 11.1
Adkins, R. J., R. W. Morse and A. L. Towe. 1966. Control of somatosensory input by cerebral cortex. Science 153:1020-1022.
Chen, Z. and A. L. Towe. 1985. Influence of molecular layer on pyramidal tract neurons. Exp. Neurol. 88:215-228.
Chen, Z., G. W. Harding and A. L. Towe. 1983. Effect of strychnine on the cutaneous responsiveness of wide-field cerebral neurons after depression by pentobarbital. Exp. Neurol. 81:770-775.
Doetsch, G. S. and A. L. Towe. 1976. Response properties of distinct neuronal subsets in hindlimb sensorimotor cerebral cortex of the domestic cat. Exp. Neurol. 53:520-547.
Ennever. J. A. and A. L. Towe. 1974. Response of somatosensory cerebral neurons to stimulation of dorsal and dorsolateral spinal funiculi. Exp. Neurol. 43:124-142.
Gehary, Y. and A. L. Towe. 1993. Effect of optic nerve stimulation on neurons in pericruciate cortex of cats. Exp. Brain Res. 94:272-278.
Harding, G. W. and A. L. Towe. 1976. An on-line real-time laboratory for single neuron studies. Comput. Biomed. Res. 9:471-501.
Harding, G. W., R. M. Stogsdill and A. L. Towe. 1979. Relative effects of pentobarbital and chloralose on the responsiveness of neurons in sensorimotor cerebral cortex of the domestic cat. Neuroscience 4:369-378.
Harris, F. A. and A. L. Towe. 1976. Effects of topical bicuculline on primary evoked responses in pericruciate and precoronal cortex of the domestic cat. Exp. Neurol. 52:227-241.
Harris, F. A. and A. L. Towe. 1978. Effects of topical application of diphenylhydantoin on gross evoked responses and single-neuron activity in pericruciate and precoronal cerebral cortex of the domestic cat. Exp. Neurol. 62:521-538.
Harrison T. A. and A. L. Towe. 1986. Antidromic response to medulary pyramid stimulation in rats and its relation to that in cats. Brain Behav. Evol. 29:143-161.
Kennedy, T. T. and A. L. Towe. 1962. Identification of a fast lamnisco-cortical system in the cat. J. Physiol. (London) 160:535-547.
Mann, M. D. 1979. Sets of neurons in somatic cerebral cortex of the cat and their ontogeny. Brain Res. Rev. 1:3-45.
Mann, M. D., W. S. Holt and A. L. Towe. 1977. Afferent modulation of the excitability of pyramidal tract fibers. Exp. Neurol. 55:414-435.
Mann, M. D., and A. L. Towe. 1974. Effect of strychnine on single neurons of the pericruciate cerebral cortex. Exp. Neurol. 42:388-411.
Morse, R. W. and R. A. Vargo. 1970. Functional neuronal subsets in the forepaw focus of somatosensory area II of the cat. Exp. Neurol. 27:125-138.
Morse, R. W., R. J. Adkins and A. L. Towe. 1965. Population and modality characteristics of neurons in the coronal region of somatosensory area I of the cat. Exp. Neurol. 11:419-440.
Nyquist, J. K. and A. L. Towe. 1970. Neuronal activity evoked in cat precruciate cerebral cortex by cutaneous stimulation. Exp. Neurol. 29:494-512.
Patton, H. D., A. L. Towe, and T. T. Kennedy. 1962. Activation of pyramidal tract neurons by ipsilateral cutaneous stimuli. J. Neurophysiol. 25:501-514.
Satterthwaite, W. R. 1976. Feline pericruciate cerebral neurons activated by electrical stimulation of the ventral medulla. PhD Dissertation, University of Washington. 251pp.
Satterthwaite, W. R., J. A. Burnham, and A. L. Towe. 1978. Wide-field conditioning effects on small-field neurons in the posterior sigmoid gyrus of domestic cats. Exp. Neurol. 60:603-613.
Slimp, J. C. and A. L. Towe. 1977. Characteristics of somatic receptive fields of neurons in postcruciate cerebral cortex in awake-restrained and two anesthetic conditions in the same cat. Neurosci. Abs. 2:492.
Slimp, J. C. and A. L. Towe. 1980. Effects of pudendal nerve stimulation on neurons in pericruciate cerebral cortex of male domestic cats. Exp. Neurol. 67:181-204
Slimp, J. C. and A. L. Towe. 1990. Spatial distribution of modalities and receptive fields in sensorimotor cortex of awake cats. Exp. Neurol. 107:78-96.
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Towe, A. L. 1968. Neuronal population behavior in the somatosensory systems. pp. 552--574. In D. R.- Kenshalo (ed.) "The Skin Senses". Thomas, Springfield, Illinois.
Towe, A. L. 1975. Notes on the hypothesis of columnar organization in somatosensory cerebral cortex. Brain Behav. Evol. 11:16-47.
Towe, A. L. and G. W. Harding. 1970. Extracellular microelectrode sampling bias. Exp. Neurol. 29:366-381.
Towe, A. L. and T. T. Kennedy. 1961. Response of cortical neurons to variation of stimulus intensity and locus. Exp. Neurol. 3:570-587.
Towe, A. L. and R. W. Morse. 1962. Dependence of the response characteristics of somatosensory neurons on the form of their afferent input. Exp. Neurol. 6:407-425.
Towe, A. L., M. D. Mann, and G. W. Harding. 1981. On the currents that flow during the strychnine spike. Elecroenceph. clin. Neurophysiol. 51:306-327.
Towe, A. L., H. D. Patton, and T. T. Kennedy. 1963. Properties of the pyramidal system in the cat. Exp. Neurol. 8:220-238.
Towe, A. L., H. D. Patton, and T. T. Kennedy. 1964. Response properties of neurons in the pericruciate cortex of the cat following electrical stimulation of the appendages. Exp. Neurol. 10:325-344.
Towe, A. L. and J. C. Slimp. 1977. Organization of postcruciate neurons with respect to somatic modality and receptive field in a awake-restrained cat. Neurosci. Abs. 3:493.
Towe, A. L., C. F. Tyner, and J. K. Nyquist. 1976. Facilitatory an inhibitory modulation of wide-field neuron activity in postcruciate cerebral cortex of the domestic cat. Exp. Neurol. 50:734-756.
Towe, A. L., D. Whitehorn, and J. K. Nyquist. 1968. Differential activity among wide-field neurons of the cat postcruciate cerebral cortex. Exp. Neurol. 20:497-521.
Tyner, C. F. 1975. The naming of neurons: Application of taxonomic theory to the study of cellular populations. Brain Behav. Evol. 12:75-96.
Tyner, C. F. 1979. Splanchnic nerve activation of single cells in the cat's postcruciate motorsensory cortex. Exp. Neurol. 63:76-93.
Tyner, C. F. and M. G. Miller. 1977. Selective inhibition of some wide-field sensorimotor cortex neurons by high intensity skin stimuli. Neurosci. Abs. 3:72.
Tyner, C. F. and A. L. Towe. 1970. Interhemispheric influences on sensorimotor neurons. Exp. Neurol. 28:88-105.
Videen, T. 0. 1981. Visual input to small-field and wide-field neurons in the postcruciate cortex of domestic cat. Exp. Neurol. 71:341-355.
Whitehorn, D. and A. L. Towe. 1968. Postsynaptic potential patterns evoked upon cells in sensorimotor cortex of cat by stimulation at the periphery. Exp. Neurol. 22:222-242.