An evoked potential mapping of transcallosal projections in the cat

Cukiert, A.; Timo-Iaria, C.

doi:10.1590/S0004-282X1989000100001

Abstracts

In ten adult cats anesthetized with ketamine hydrochloride the neocortex was exposed and rectangular pulses (1msec, 0.5 Hz and variable intensity) were applied to discrete points of one side and transcallosal evoked potentials were recorded from the other. The stimulation and recording positions were determined on a cartesian map of most of the exposable neocortical areas and the potentials were analysed as to their components, voltage and latency. Passive spread and electrotonic potentials and the effects of increasing frequency were also analysed. The results showed large transcallosal potentials in some areas and an increase of potentials in the caudorostral direction, attaining the highest values in anteromedial areas of the suprasylvian gyrus. Confirming anatomical studies, a few silent spots were found in the motor and somesthetic cortex and in restricted posterior regions of the visual cortex, where small or zero voltages occurred. While causing weak contralateral potentials, stimulation of some posterior sites provoked high voltage potentials in anterior regions of the side being stimulated and in the corresponding area of the opposite site. These posterior sites are. poorly interconnected by the corpus callosum. The L-shaped indirect connection described in this work may be involved in some types of epilepsy and may explain the effectiveness of partial callosotomy in their treatment.

Em dez gatos anestesiados com cetamina (Ketalar) o neocórtex foi exposto e pulsos retangulares (1 ms, 0,5Hz e intensidade variável) foram aplicados a pontos discretos de um lado enquanto se registravam os potenciais evocados no outro lado. As posições de estimulação e registro eram determinadas em mapa cartesiano que abrangia quase todo o neocórtex. Os potenciais foram analisados quanto aos seus componentes, voltagem e latência. A difusão passiva, potenciais eletrotônicos e os efeitos do incremento da frequência de estimulação sobre os vários componentes foram analisados. Os resultados mostram a presença de grandes potenciais evocados transcalosos em algumas regiões, com incremento de sua amplitude no sentido caudo-rostral, sendo máximos em áreas anteromediais do giro suprasilviano. Confirmando estudos anatômicos, em algumas regiões do córtex soma-tomotor e visual foram registrados potenciais bastante reduzidos ou ausentes. A estimulação de algumas áreas posteriores causava o aparecimento de pequenos potenciais em sua área homóloga contralateral ao mesmo tempo em que grandes potenciais eram registrados em áreas anteriores ipsi- e contralateralmente, constituindo uma conexão em L ainda não descrita. É possível que tal conexão esteja implicada em alguns tipos de epilepsia e possa explicar em parte a eficácia de calosotomias parciais para seu tratamento.

An evoked potential mapping of transcallosal projections in the cat

Mapeamento por potencial evocado das projeções transcalosas no gato

A. Cukiert^I; C. Timo-Iaria^II

^ILaboratory of Functional Neurosurgery, School of Medicine University of São Paulo, Resident in Neurosurgery

^IILaboratory of Clinical Physiology, School of Medicine University of São Paulo, Full Professor of Physiology

SUMMARY

In ten adult cats anesthetized with ketamine hydrochloride the neocortex was exposed and rectangular pulses (1msec, 0.5 Hz and variable intensity) were applied to discrete points of one side and transcallosal evoked potentials were recorded from the other. The stimulation and recording positions were determined on a cartesian map of most of the exposable neocortical areas and the potentials were analysed as to their components, voltage and latency. Passive spread and electrotonic potentials and the effects of increasing frequency were also analysed. The results showed large transcallosal potentials in some areas and an increase of potentials in the caudorostral direction, attaining the highest values in anteromedial areas of the suprasylvian gyrus. Confirming anatomical studies, a few silent spots were found in the motor and somesthetic cortex and in restricted posterior regions of the visual cortex, where small or zero voltages occurred. While causing weak contralateral potentials, stimulation of some posterior sites provoked high voltage potentials in anterior regions of the side being stimulated and in the corresponding area of the opposite site. These posterior sites are. poorly interconnected by the corpus callosum. The L-shaped indirect connection described in this work may be involved in some types of epilepsy and may explain the effectiveness of partial callosotomy in their treatment.

RESUMO

Em dez gatos anestesiados com cetamina (Ketalar) o neocórtex foi exposto e pulsos retangulares (1 ms, 0,5Hz e intensidade variável) foram aplicados a pontos discretos de um lado enquanto se registravam os potenciais evocados no outro lado. As posições de estimulação e registro eram determinadas em mapa cartesiano que abrangia quase todo o neocórtex. Os potenciais foram analisados quanto aos seus componentes, voltagem e latência. A difusão passiva, potenciais eletrotônicos e os efeitos do incremento da frequência de estimulação sobre os vários componentes foram analisados. Os resultados mostram a presença de grandes potenciais evocados transcalosos em algumas regiões, com incremento de sua amplitude no sentido caudo-rostral, sendo máximos em áreas anteromediais do giro suprasilviano. Confirmando estudos anatômicos, em algumas regiões do córtex soma-tomotor e visual foram registrados potenciais bastante reduzidos ou ausentes. A estimulação de algumas áreas posteriores causava o aparecimento de pequenos potenciais em sua área homóloga contralateral ao mesmo tempo em que grandes potenciais eram registrados em áreas anteriores ipsi- e contralateralmente, constituindo uma conexão em L ainda não descrita. É possível que tal conexão esteja implicada em alguns tipos de epilepsia e possa explicar em parte a eficácia de calosotomias parciais para seu tratamento.

Full text available only in PDF format.

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This research was supported by the State of São Paulo Research Foundation (FAPESP, grants 84/1078-9 and 85/3531-5), FINEP (grant 43.86.0222.00) and Institute of the Laboratories of Medical Research (LIM-74-45).

Laboratório de Fisiologia Clínica, Faculdade de Medicina USP - Caixa Postal 2921 - 01051 São Paulo SP - Brasil

1. Avila JO, Radvany J, Huck FR, Fires de Camargo CH, Marino RJr, Ragazzo PC, Riva D - Anterior callosotomy as a substitute for hemispherectomy. Acta Neurochir, suppl, 30:137, 1980.
2. Chang HT - Cortical response to activity of callosal neurons. J Neurophysiol 16:117, 1953.
3. Chang HT - Interaction of evoked cortical potentials. J Neurophysiol 16:133, 1953.
4. Curtis HJ - Intercortical connections uf corpus callosum as indicated by evoked potentials. J Neurophysiol 3:405, 1940.
5. Curtis HJ - An analysis of cortical potentials mediated by the corpus callosum. J Neurophysiol 3:414, 1940.
6. Ebner FF, Myers RE - Distribution of corpus callosum and anterior commissure in cat and racoon. J Comp Neurol 124:353, 1965.
7. Gates JR, Maxwell R, Leppik IE, Gumnit RJ - Electroencephalographic and clinical effects of total corpus callosotomy. In Reeves AG (ed): Epilepsy and the Corpus Callosum. Plenum Press, New York, 1965, pg 315.
8. Hubel DH, Wiesel TN - Cortical and callosal connections concerned with the vertical meridian of visual fields in the cat. J Neurophysiol 30:1561, 1967.
9. Huck FR, Radvany J, Avila JO, Pires de Camargo CH, Marino RJr, Ragazzo PC, Riva D - Anterior callosotomy in epileptics with multiform seizures and bilateral synchronous spike and wave EEG pattern. Acta Neurochir, suppl, 30:127, 1980.
10. Imig TJ, Brugge JF - Sources and terminations of callosal axons related to binaural and frequency maps in primary cortex of the cat. J Comp Neurol 182:637, 1978.
11. Isaacson RL, Schwartz H, Persoff N - The role of corpus callosum in the establishment of areas of secondary epileptiform activity. Epilepsia 12:133, 1971.
12. Ivy GO Killackey HP - The ontogeny of the distribution of callosal projection neurons in the rat parietal cortex. J Comp Neurol 195:367, 1981.
13. Jacobson S, Trojanowsky JQ - Prefrontal granular cortex of the Rhesus monkey: II. Interhemispheric cortical afferents. Brain Res 132:209, 1977.
14. Jones EG, Burton H, Porter R - Commissural and corticocortical columns in the somatic sensory cortex of primates. Science 190:572, 1975.
15. Jones EG, Coulter JD, Wise SP - Commissural columns in the sensory motor cortex of monkeys. J Comp Neurol 188:133, 1979.
16. Luessenhop AJ - Interhemispheric commissurotomy. Am Surg 36:265, 1970.
17. Marcus EM, Watson CW - Bilateral synchronous spike and wave electrographic patterns in the cat. Arch Neurol 14:601, 1966.
18. Marcus EM - Generalized seizure models and the corpus callosum. In Reeves AG (ed): Epilepsy and the Corpus Callosum. Plenum Press, New York, 1985, pg 131.
19. Mares P - Symmetrical epileptogenic foci in cerebral cortex of immature rat. Epilepsia 14:422, 1973.
20. Musgrave J, Gloor P - The role of corpus callosum in bilateral interhemispheric synchrony of spike and wave discharges in feline generalized penicilin epilepsy. Epilepsia 21:369, 1980.
21. Mutani R, Durell L - Mechanisms of interaction of asymmetrical bilateral epileptogenic foci in neocortex. Epilepsia 21:549, 1981.
22. Ottino CA, Meglio M, Rossi GF - An experimental study of the structures mediating bilateral synchrony of epileptic discharges of cortical origin. Epilepsia 12:299, 1971.
23. Pandya DN, Heilbrown D - The topographic distribution of interhemispheric projections in the corpus callosum of the Rhesus monkey. Brain Res 32:31, 1971.
24. Poljak S - An experimental study of the association callosal and projection fibers of the cerebral cortex of the cat. J Comp Neurol 44:197, 1927.
25. Schwartzkroin PA, Futamachi KJ, Noebels JL - Transcallosal effects of a cortical epileptiform focus. Brain Res 55:59, 1975.
26. Tomasch J - Size, distribution and number of fibers in the human corpus callosum. Anat Rec 119:119, 1954.
27. Van Wagenen WP, Harren RY - Surgical division of commissural pathways in the corpus callosum. Arch Neurol Psychiat 44:740, 1940.
28. Wilson DH, Reeves A, Gazzaniga M - Cerebral commissurotomy for control of intractable seizures. Neurology 27:708, 1977.

Publication Dates

Publication in this collection
06 June 2011
Date of issue
Mar 1989

This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

[1] 1. Avila JO, Radvany J, Huck FR, Fires de Camargo CH, Marino RJr, Ragazzo PC, Riva D - Anterior callosotomy as a substitute for hemispherectomy. Acta Neurochir, suppl, 30:137, 1980.

[2] 2. Chang HT - Cortical response to activity of callosal neurons. J Neurophysiol 16:117, 1953.

[3] 3. Chang HT - Interaction of evoked cortical potentials. J Neurophysiol 16:133, 1953.

[4] 4. Curtis HJ - Intercortical connections uf corpus callosum as indicated by evoked potentials. J Neurophysiol 3:405, 1940.

[5] 5. Curtis HJ - An analysis of cortical potentials mediated by the corpus callosum. J Neurophysiol 3:414, 1940.

[6] 6. Ebner FF, Myers RE - Distribution of corpus callosum and anterior commissure in cat and racoon. J Comp Neurol 124:353, 1965.

[7] 7. Gates JR, Maxwell R, Leppik IE, Gumnit RJ - Electroencephalographic and clinical effects of total corpus callosotomy. In Reeves AG (ed): Epilepsy and the Corpus Callosum. Plenum Press, New York, 1965, pg 315.

[8] 8. Hubel DH, Wiesel TN - Cortical and callosal connections concerned with the vertical meridian of visual fields in the cat. J Neurophysiol 30:1561, 1967.

[9] 9. Huck FR, Radvany J, Avila JO, Pires de Camargo CH, Marino RJr, Ragazzo PC, Riva D - Anterior callosotomy in epileptics with multiform seizures and bilateral synchronous spike and wave EEG pattern. Acta Neurochir, suppl, 30:127, 1980.

[10] 10. Imig TJ, Brugge JF - Sources and terminations of callosal axons related to binaural and frequency maps in primary cortex of the cat. J Comp Neurol 182:637, 1978.

[11] 11. Isaacson RL, Schwartz H, Persoff N - The role of corpus callosum in the establishment of areas of secondary epileptiform activity. Epilepsia 12:133, 1971.

[12] 12. Ivy GO Killackey HP - The ontogeny of the distribution of callosal projection neurons in the rat parietal cortex. J Comp Neurol 195:367, 1981.

[13] 13. Jacobson S, Trojanowsky JQ - Prefrontal granular cortex of the Rhesus monkey: II. Interhemispheric cortical afferents. Brain Res 132:209, 1977.

[14] 14. Jones EG, Burton H, Porter R - Commissural and corticocortical columns in the somatic sensory cortex of primates. Science 190:572, 1975.

[15] 15. Jones EG, Coulter JD, Wise SP - Commissural columns in the sensory motor cortex of monkeys. J Comp Neurol 188:133, 1979.

[16] 16. Luessenhop AJ - Interhemispheric commissurotomy. Am Surg 36:265, 1970.

[17] 17. Marcus EM, Watson CW - Bilateral synchronous spike and wave electrographic patterns in the cat. Arch Neurol 14:601, 1966.

[18] 18. Marcus EM - Generalized seizure models and the corpus callosum. In Reeves AG (ed): Epilepsy and the Corpus Callosum. Plenum Press, New York, 1985, pg 131.

[19] 19. Mares P - Symmetrical epileptogenic foci in cerebral cortex of immature rat. Epilepsia 14:422, 1973.

[20] 20. Musgrave J, Gloor P - The role of corpus callosum in bilateral interhemispheric synchrony of spike and wave discharges in feline generalized penicilin epilepsy. Epilepsia 21:369, 1980.

[21] 21. Mutani R, Durell L - Mechanisms of interaction of asymmetrical bilateral epileptogenic foci in neocortex. Epilepsia 21:549, 1981.

[22] 22. Ottino CA, Meglio M, Rossi GF - An experimental study of the structures mediating bilateral synchrony of epileptic discharges of cortical origin. Epilepsia 12:299, 1971.

[23] 23. Pandya DN, Heilbrown D - The topographic distribution of interhemispheric projections in the corpus callosum of the Rhesus monkey. Brain Res 32:31, 1971.

[24] 24. Poljak S - An experimental study of the association callosal and projection fibers of the cerebral cortex of the cat. J Comp Neurol 44:197, 1927.

[25] 25. Schwartzkroin PA, Futamachi KJ, Noebels JL - Transcallosal effects of a cortical epileptiform focus. Brain Res 55:59, 1975.

[26] 26. Tomasch J - Size, distribution and number of fibers in the human corpus callosum. Anat Rec 119:119, 1954.

[27] 27. Van Wagenen WP, Harren RY - Surgical division of commissural pathways in the corpus callosum. Arch Neurol Psychiat 44:740, 1940.

[28] 28. Wilson DH, Reeves A, Gazzaniga M - Cerebral commissurotomy for control of intractable seizures. Neurology 27:708, 1977.