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Macaca Fascicularis : Alternative epileptic model
Pergamon Press
Life Sciences, Vol . 25, pp . 281-286 Printed in the U.S .A .
MACACA FASCICULARIS :
ALTERNATIVE EPILEPTIC MODEL
A. Basil Harris and Joan S . Lockard Department of Neurological Surgery University of Washington Seattle, Washington 98195 (Received is final form May 31, 1979) Summary In view of the relatively recent Indian embargo on rhesus monkeys . Macaca mulatta), our data indicate that the iris (or crab-eating) macaque fascicularis) is a suitable substitute species ae a model for experimental epilepsy . Seasorimotor intracortical aluminum-hydroxide injections is the iris monkey result in chronic recurring seizures ae readily ae is rhesus . Comparable drug plasma levels and seizure frequency patterns show the former is a reliable alternative epileptic animal model for the latter . Differences between these two species in diet and body size do not require extensive readjustment of housing and maintenance facilities . The hiatochemical findings suggest that the iris monkey might also become an alternative to other experimental animal models for which the rhesus has been used in the health sciences .
L.
The embargo on exportation of M. mulatta imposed by the Indian Government (1) dictates that alternative primates be sought for studies in epilepsy, as well as in many other experimental studies involving multiple body systems and functions. Since Ropeloff's discovery in 1942 (2) that the application of aluminum hydroxide gel to the aensorimotor cortex caused repetititve seizures in rhesus, no other primate has been identified as being equally successful in Our objective was to develop a new mimicing the epileptic condition in man. model where seizure frequencies, electroencephalographic (EEG) paroxysms and drug treatment could be studied is another primate whose population numbers There are an estimated 35,000,000 _M . fascicularis in the wild in are great. several Southeast Asia countries where there are no present exportation problems (3, 4) . This paper details the success of _M . fascicularis as a new experiIa addition to histological comparisons of epileptomental epileptic model . genic foci of rhesus and iris monkeys, seizure frequency during baseline and Plasma aatiepileptic drug administration has been recorded for several yearn . concentrations of 4 anticonvulsante at efficacious doses are reported . Methods and Materiale Seven adult male M. faecicularis monkeys were obtained from Primate Imports (Port Washington, New York) . In the initial studies, alumina injections were made into the aenaorimotor cortex oa either aide of the central fissure ae Seizures and EEG paroxysms developed within 3 shown in Figure 1 (asterisks) . months after the alumina injections . The details of the surgical procedure 0024-3205/79/030281-06$02 .00/0 Copyright (c) 1979 Pergamon Press Ltd
28 2
Alternative Epileptic Model
Vol. 25, No . 3, 1979
FIG. 1 _M . fascicularis left hemisphere lateral oblique view of cortical surface and sites for alumine injection to create epileptogenic foci (asterisks) in the sessorimotor cortex (see text) . Principal eulci are : p, principal ; _a, arcuate ; fir, precentral ; çe, central ; la, lateral (Sylvias) ; t, temporal superior ; iQ, intraparietal; moo, postcentral ; _oi, occipital inferior ; _1, lunate ; and ec, external calcarine (note : adapted from vos Bonis (13)) . Original magnification x 2 . have been outlined in earlier reports on M . mulatta (5, 6, 7, 8) . For the terminal hietochemical studies the animals (6 epileptic, 1 normal) comprised 6 experimental hemispheres and 8 control hemispheres (6 hemispheres contralateral to the epileptogenic foci and both hemispheres of a normal monkey) . Baseline EEGs (Figure 2A) were obtained prior to the alumina injections on all animals . Serial EEG recordings were made after the development of epileptic foci (Figure 2B) . Recordings were obtained using electrode screws into the skull in representative arrays . This method of recording has been As shown in Figure 2B, electrical activity reported and used extensively (9) . from motor cortex is symptomatic of the developed epileptogenic focus (sharp waveforms, less than 80 cosec in duration, over 25 mcV in amplitude and having a segmental velocity of 2 mcV/cosec or greater) . Subsequent to the development of clinical seizures (4-6 months poatalumina injections), 5 of the 6 epileptic monkeys were administered anticonvulsant drugs (phenytoin, phenobarbital, primidose and valproic acid) either separately or in combinations of two drugs for 2-10 weeks, preceded and followed by 2-6 baseline weeks of no drugs. Phenytoin was administered orally (15-60 mg/kg b .i .d .) ; phenobarbital intramuscularly (6-9 mg/kg b .i .d .) ; primidone orally (30 mg/kg b .i .d .) ; and valproic acid by constant-rate istravenoue infusion (76 .8 mg/ml/hr) . Periodic blood samples were assayed by
IIol . 25, No . 3, 1979
Alternative Epileptic Model
w
Trc .
I w ,v
_
w
_
_
_
~
-
w',.,w.~,w~f-~^r~
FIG. 2 Illustrative macaque electroencephalographic (EEG) records prior to (A) and after (B) the development of the epileptogenic (electrode #3) focus . Epileptiform discharges were often associated with discrete right arm jerks .
283
28 4
Alternative Epileptic Model
Vol . 25, No . 3, 1979
gas-liquid chromotography to ascertain the plasma drug concentrations for each animal under each treatment . The experiments were concluded under surital anesthesia . A large segment of calvarium was removed and electrocorticography used to define maximal epileptic focal abnormalities . This procedure was followed by aldehyde intravascular perfusion fixation, excision biopsy of cortex blocks for processing and examination by electron microscopy ; for light microscopy the brain was post fixed in 15X formalin ammonium bromide and 50 u frozen sections were stained by Nissl, Cajal's gold sublimate, and histochemical stain for aluminum (10, 11, 12) . Results and Discussion Histochemical Data . _M . faecicularis brain weight is approximately 2/3 that of M. mulatta . Cortical gyre (Figure 1) are arranged slightly differently but quite similar to the pattern of _M . mulatta (13) . Hiatological studies show cortical changes similar to those in _M . mulatta (5, 10, 11) . The alumina is confined to intracellular inclusions in granuloma macrophages, adjacent pervascular pericytes and occasional astrocytes (11) . No alumina is seen within neurone by histochemistry or electronmicroscopy (11) . Immediately surrounding the granuloma is a dense astrocytic response consisting of increased cellular cytoplasm filled with filaments and a proliferation of cell processes . Beyond this border are gliotic changes in epileptic foci and cortical bands as reported for M. mulatta (10) . Seizure Data . Similar to the rhesus monkey (6, 14), iris monkeys (N = 6) develop recurring spontaneous gross motor seizures which initially involve only the body contralateral to the epileptogenic focus . Within weeks of the first occurrence of these focal seizures (sometimes analogously called partial seizures in man), the epileptic activity encompasses the ipsilateral side as well, in what is termed secondarily generalized tonic-clonic seizures (i .e ., a model for human grand mal seizures) . Thereafter, both categories of seizure phenomena are observed with the more severe activity eventually predominating . Without intervention, stable seizure frequencies ensue of approximately 1-10 in number per day (depending upon individual differences) and continue at that rate for ears . Treatment with standard antiepileptic drugs such as phenytoin (Dilanti~, primidone (Mysolin~, and phenobarbital (Phenobarbital Sodiu~ reduce the number of seizures from 1/3 to 2/3 of baseline frequencies (e .g ., z ~ 2 .85, phenytoin vs . baseline : z = 1.65, p < .05 ; primidoae vs . baseline : p < .002) . These effects are manifested at plasma drug-concentration ranges equivalent to efficacious levels in humans, i.e ., 10-20 (phenytoin), 5-15 (primidone) and 20-40 mcg/ml (phenobarbital) . Newer anticonvulsant drugs such as valproic acid (Depakené~ are at least this effective (baseline vs . drug : z = 3 .71, p < .0001) at plasma levels between 50-100 mcg/ml (Figure 3) Whereas in both and in some monkeys eliminate seizure activity altogether . rhesus and iris monkeys these drugs may be metabolized at a much faster rate than in man (i .e ., the biological half-life of valproic acid in rhesus is 1/2 - 2 hours (15) and approximately 8 hours in man (16), similar blood levels of the drugs in patients and in these monkeys appear to provide comparable pharmacological effects. Both the histochemical and seizure data indicate that _M . faecicularis is a likely substitute species for _M . mulatta as a model for experimental epilepsy . Evaluation of new therapeutic techniques -- e.g ., experimental aaticonvulsants (17), EEG biofeedback (18), cerebellar stimulation (19), pursuance of mechanisms (10, 20) and use for experimental convulsanta (21) -may be continued with the iris macaque to enlarge the understanding of epilepsy in man. The differences between the iris and rhesus monkey in diet
Vol. 25, No . 3, 1979
Alteraative Epileptic Model
285
(iris requires leafy vegetables in addition to fruit and monkey chow) and body size (iris is 1/2 to 2/3 the size of rhesus) do _not require extensive readjustment of housing and maintenance facilities . The similarity of the histochemical findings in these two species also indicates that _M . fascicularis is likely to become an alternative to other experimental animal models for which M. mulatta has been used in the health sciences .
FIG. 3 Seizure frequency during weeks of baseline (saline, 1 ml/hr) and of valproic acid at a constant-rate intravenous solution of 76 .8 mg/ml/hr . Monkey 4, left aide ; Monkey 5, right Bide . Açknowled~~enta This research was funded by NIB Grant No . NS-09037, NS-04053 and NIH Contract No . NO1-NS-1-2282, National Institute of Neurological and Communicative Disorders and Stroke, PHS/DREW . The authors are affiliates of the Child Development and Mental Retardation Center, Seattle, Washington . References 1. 2. 3. 4. 5. 6.
N . WADE, Science 199 280-281 (1978) . L .M . ROPELOFF, S .E . BARRERA and N . ROPELOFF, Amer . J . Psychiat . 98 881-902 (1942) . C .C . WILSON and W.L . WILSON in Contemporary Primatology, S . Rondo, M. Rawai and A. Ehara (Eds .), Rarger Press, Basel, pp . 345-350 (1975) . C . WILSON-CROCKEIT, Personal communication (1978) . A.B . HARRIS, Arch . Neurol . _26 434-449 (1972) . L .M . ROPELOFF, J .G . CHIISID and N. KOPELOFF, Arch . Neurol . Psychiat . 74 523-526 (1955) .
286
7. 8. 9. 10 . 11 . 12 . 13 . 14 . 15 . 16 .
17 . 18 . 19 . 20 . 21 .
Alternative Epileptic Model
Vol . 25, No . 3, 1979
A.A . WARD, JR ., in Experimental Models of Epilepsy , D .P . Purpurs, J .R . Penry, D . Tower, D .M . Woodbury and R. Walter (Eda .), Raven Press, New York, pp . 13-35 (1972) . L .E . WESTRUM, L .E . WBITE and A.A . WARD, JR ., J . Neurosurg . _21 10331046 (1964) . J .S . LOCRARD,R,H. LEVY, I .A . PATEL, L .L . DuCHARME and W .C . CONGDON, in quantitative Analytic Studies _in Epilepsy , P. Rellaway and I. Petersen (Eds .), Raven Press, New York, pp . 147-164 (1976) . A.B . HARRIS, Exp . Neurol . _49 691-715 (1975) . A.B . HARRIS, Exp . Neurol . _38 33-63 (1973) . A .G .E . PEARSE, Hiatochemiatry Theoretical _and Applied, pp . 592-639 and 935-937, Little, Brown, Boston (1961) . G . Von BONIN aad P, BAILEY, _The Naocortex _of Macaca Mulatta , pp . 7-17, University of Illinois Press, Urbana, I11. (1947) . J .S . LOCRARD, W .C . CONGDON, L.L, DuCHARME and B.J . HUNTSMAN, Epilepsia _17 37-47 (1976) . R.H . LEVY, J .S . LOCRARD, I .H . PATEL and A.A . LAI, Epilepsia _18 191-204 (1977) . A.J . ROWAN, C .D . BINNIE, C.A . WARFIELD, and J .W .A . MEYER, pp . 249-254 and A.J . ROWAN et al ., pp . 255-260, in Thirteenth Congress _of _the einst Epilepsy , J .R . Penny (Ed .), Raven Press, International Lea ue New York (1977) . J .S . LOCRARD, R .H, LEVY, L.L . DuCHARME and W.C . CONGDON, Epilepsia (in press, 1979) . J.S . LOCKARD, A .R, WYLER, C .A . FINCH and K .E . HURLBURT, Epilepsia _18 471-479 (1977) . J.S . LOCRARD, G .A . OJEMANN, W.C . CONGDON and L.L . DuCHARME, Epilepsia _20 223-234 (1979) . A.R, WYLER, K.J . BURCHIEL and A .A . WARD, JR ., Epilepsia _19 475-483 (1978) . L .J . WILLMORE, G.W . SYPERT, J .B . MUNSON and R.W . HURD, Science 200 1501-1503 (1978) .
Life Sciences, Vol . 25, pp . 281-286 Printed in the U.S .A .
MACACA FASCICULARIS :
ALTERNATIVE EPILEPTIC MODEL
A. Basil Harris and Joan S . Lockard Department of Neurological Surgery University of Washington Seattle, Washington 98195 (Received is final form May 31, 1979) Summary In view of the relatively recent Indian embargo on rhesus monkeys . Macaca mulatta), our data indicate that the iris (or crab-eating) macaque fascicularis) is a suitable substitute species ae a model for experimental epilepsy . Seasorimotor intracortical aluminum-hydroxide injections is the iris monkey result in chronic recurring seizures ae readily ae is rhesus . Comparable drug plasma levels and seizure frequency patterns show the former is a reliable alternative epileptic animal model for the latter . Differences between these two species in diet and body size do not require extensive readjustment of housing and maintenance facilities . The hiatochemical findings suggest that the iris monkey might also become an alternative to other experimental animal models for which the rhesus has been used in the health sciences .
L.
The embargo on exportation of M. mulatta imposed by the Indian Government (1) dictates that alternative primates be sought for studies in epilepsy, as well as in many other experimental studies involving multiple body systems and functions. Since Ropeloff's discovery in 1942 (2) that the application of aluminum hydroxide gel to the aensorimotor cortex caused repetititve seizures in rhesus, no other primate has been identified as being equally successful in Our objective was to develop a new mimicing the epileptic condition in man. model where seizure frequencies, electroencephalographic (EEG) paroxysms and drug treatment could be studied is another primate whose population numbers There are an estimated 35,000,000 _M . fascicularis in the wild in are great. several Southeast Asia countries where there are no present exportation problems (3, 4) . This paper details the success of _M . fascicularis as a new experiIa addition to histological comparisons of epileptomental epileptic model . genic foci of rhesus and iris monkeys, seizure frequency during baseline and Plasma aatiepileptic drug administration has been recorded for several yearn . concentrations of 4 anticonvulsante at efficacious doses are reported . Methods and Materiale Seven adult male M. faecicularis monkeys were obtained from Primate Imports (Port Washington, New York) . In the initial studies, alumina injections were made into the aenaorimotor cortex oa either aide of the central fissure ae Seizures and EEG paroxysms developed within 3 shown in Figure 1 (asterisks) . months after the alumina injections . The details of the surgical procedure 0024-3205/79/030281-06$02 .00/0 Copyright (c) 1979 Pergamon Press Ltd
28 2
Alternative Epileptic Model
Vol. 25, No . 3, 1979
FIG. 1 _M . fascicularis left hemisphere lateral oblique view of cortical surface and sites for alumine injection to create epileptogenic foci (asterisks) in the sessorimotor cortex (see text) . Principal eulci are : p, principal ; _a, arcuate ; fir, precentral ; çe, central ; la, lateral (Sylvias) ; t, temporal superior ; iQ, intraparietal; moo, postcentral ; _oi, occipital inferior ; _1, lunate ; and ec, external calcarine (note : adapted from vos Bonis (13)) . Original magnification x 2 . have been outlined in earlier reports on M . mulatta (5, 6, 7, 8) . For the terminal hietochemical studies the animals (6 epileptic, 1 normal) comprised 6 experimental hemispheres and 8 control hemispheres (6 hemispheres contralateral to the epileptogenic foci and both hemispheres of a normal monkey) . Baseline EEGs (Figure 2A) were obtained prior to the alumina injections on all animals . Serial EEG recordings were made after the development of epileptic foci (Figure 2B) . Recordings were obtained using electrode screws into the skull in representative arrays . This method of recording has been As shown in Figure 2B, electrical activity reported and used extensively (9) . from motor cortex is symptomatic of the developed epileptogenic focus (sharp waveforms, less than 80 cosec in duration, over 25 mcV in amplitude and having a segmental velocity of 2 mcV/cosec or greater) . Subsequent to the development of clinical seizures (4-6 months poatalumina injections), 5 of the 6 epileptic monkeys were administered anticonvulsant drugs (phenytoin, phenobarbital, primidose and valproic acid) either separately or in combinations of two drugs for 2-10 weeks, preceded and followed by 2-6 baseline weeks of no drugs. Phenytoin was administered orally (15-60 mg/kg b .i .d .) ; phenobarbital intramuscularly (6-9 mg/kg b .i .d .) ; primidone orally (30 mg/kg b .i .d .) ; and valproic acid by constant-rate istravenoue infusion (76 .8 mg/ml/hr) . Periodic blood samples were assayed by
IIol . 25, No . 3, 1979
Alternative Epileptic Model
w
Trc .
I w ,v
_
w
_
_
_
~
-
w',.,w.~,w~f-~^r~
FIG. 2 Illustrative macaque electroencephalographic (EEG) records prior to (A) and after (B) the development of the epileptogenic (electrode #3) focus . Epileptiform discharges were often associated with discrete right arm jerks .
283
28 4
Alternative Epileptic Model
Vol . 25, No . 3, 1979
gas-liquid chromotography to ascertain the plasma drug concentrations for each animal under each treatment . The experiments were concluded under surital anesthesia . A large segment of calvarium was removed and electrocorticography used to define maximal epileptic focal abnormalities . This procedure was followed by aldehyde intravascular perfusion fixation, excision biopsy of cortex blocks for processing and examination by electron microscopy ; for light microscopy the brain was post fixed in 15X formalin ammonium bromide and 50 u frozen sections were stained by Nissl, Cajal's gold sublimate, and histochemical stain for aluminum (10, 11, 12) . Results and Discussion Histochemical Data . _M . faecicularis brain weight is approximately 2/3 that of M. mulatta . Cortical gyre (Figure 1) are arranged slightly differently but quite similar to the pattern of _M . mulatta (13) . Hiatological studies show cortical changes similar to those in _M . mulatta (5, 10, 11) . The alumina is confined to intracellular inclusions in granuloma macrophages, adjacent pervascular pericytes and occasional astrocytes (11) . No alumina is seen within neurone by histochemistry or electronmicroscopy (11) . Immediately surrounding the granuloma is a dense astrocytic response consisting of increased cellular cytoplasm filled with filaments and a proliferation of cell processes . Beyond this border are gliotic changes in epileptic foci and cortical bands as reported for M. mulatta (10) . Seizure Data . Similar to the rhesus monkey (6, 14), iris monkeys (N = 6) develop recurring spontaneous gross motor seizures which initially involve only the body contralateral to the epileptogenic focus . Within weeks of the first occurrence of these focal seizures (sometimes analogously called partial seizures in man), the epileptic activity encompasses the ipsilateral side as well, in what is termed secondarily generalized tonic-clonic seizures (i .e ., a model for human grand mal seizures) . Thereafter, both categories of seizure phenomena are observed with the more severe activity eventually predominating . Without intervention, stable seizure frequencies ensue of approximately 1-10 in number per day (depending upon individual differences) and continue at that rate for ears . Treatment with standard antiepileptic drugs such as phenytoin (Dilanti~, primidone (Mysolin~, and phenobarbital (Phenobarbital Sodiu~ reduce the number of seizures from 1/3 to 2/3 of baseline frequencies (e .g ., z ~ 2 .85, phenytoin vs . baseline : z = 1.65, p < .05 ; primidoae vs . baseline : p < .002) . These effects are manifested at plasma drug-concentration ranges equivalent to efficacious levels in humans, i.e ., 10-20 (phenytoin), 5-15 (primidone) and 20-40 mcg/ml (phenobarbital) . Newer anticonvulsant drugs such as valproic acid (Depakené~ are at least this effective (baseline vs . drug : z = 3 .71, p < .0001) at plasma levels between 50-100 mcg/ml (Figure 3) Whereas in both and in some monkeys eliminate seizure activity altogether . rhesus and iris monkeys these drugs may be metabolized at a much faster rate than in man (i .e ., the biological half-life of valproic acid in rhesus is 1/2 - 2 hours (15) and approximately 8 hours in man (16), similar blood levels of the drugs in patients and in these monkeys appear to provide comparable pharmacological effects. Both the histochemical and seizure data indicate that _M . faecicularis is a likely substitute species for _M . mulatta as a model for experimental epilepsy . Evaluation of new therapeutic techniques -- e.g ., experimental aaticonvulsants (17), EEG biofeedback (18), cerebellar stimulation (19), pursuance of mechanisms (10, 20) and use for experimental convulsanta (21) -may be continued with the iris macaque to enlarge the understanding of epilepsy in man. The differences between the iris and rhesus monkey in diet
Vol. 25, No . 3, 1979
Alteraative Epileptic Model
285
(iris requires leafy vegetables in addition to fruit and monkey chow) and body size (iris is 1/2 to 2/3 the size of rhesus) do _not require extensive readjustment of housing and maintenance facilities . The similarity of the histochemical findings in these two species also indicates that _M . fascicularis is likely to become an alternative to other experimental animal models for which M. mulatta has been used in the health sciences .
FIG. 3 Seizure frequency during weeks of baseline (saline, 1 ml/hr) and of valproic acid at a constant-rate intravenous solution of 76 .8 mg/ml/hr . Monkey 4, left aide ; Monkey 5, right Bide . Açknowled~~enta This research was funded by NIB Grant No . NS-09037, NS-04053 and NIH Contract No . NO1-NS-1-2282, National Institute of Neurological and Communicative Disorders and Stroke, PHS/DREW . The authors are affiliates of the Child Development and Mental Retardation Center, Seattle, Washington . References 1. 2. 3. 4. 5. 6.
N . WADE, Science 199 280-281 (1978) . L .M . ROPELOFF, S .E . BARRERA and N . ROPELOFF, Amer . J . Psychiat . 98 881-902 (1942) . C .C . WILSON and W.L . WILSON in Contemporary Primatology, S . Rondo, M. Rawai and A. Ehara (Eds .), Rarger Press, Basel, pp . 345-350 (1975) . C . WILSON-CROCKEIT, Personal communication (1978) . A.B . HARRIS, Arch . Neurol . _26 434-449 (1972) . L .M . ROPELOFF, J .G . CHIISID and N. KOPELOFF, Arch . Neurol . Psychiat . 74 523-526 (1955) .
286
7. 8. 9. 10 . 11 . 12 . 13 . 14 . 15 . 16 .
17 . 18 . 19 . 20 . 21 .
Alternative Epileptic Model
Vol . 25, No . 3, 1979
A.A . WARD, JR ., in Experimental Models of Epilepsy , D .P . Purpurs, J .R . Penry, D . Tower, D .M . Woodbury and R. Walter (Eda .), Raven Press, New York, pp . 13-35 (1972) . L .E . WESTRUM, L .E . WBITE and A.A . WARD, JR ., J . Neurosurg . _21 10331046 (1964) . J .S . LOCRARD,R,H. LEVY, I .A . PATEL, L .L . DuCHARME and W .C . CONGDON, in quantitative Analytic Studies _in Epilepsy , P. Rellaway and I. Petersen (Eds .), Raven Press, New York, pp . 147-164 (1976) . A.B . HARRIS, Exp . Neurol . _49 691-715 (1975) . A.B . HARRIS, Exp . Neurol . _38 33-63 (1973) . A .G .E . PEARSE, Hiatochemiatry Theoretical _and Applied, pp . 592-639 and 935-937, Little, Brown, Boston (1961) . G . Von BONIN aad P, BAILEY, _The Naocortex _of Macaca Mulatta , pp . 7-17, University of Illinois Press, Urbana, I11. (1947) . J .S . LOCRARD, W .C . CONGDON, L.L, DuCHARME and B.J . HUNTSMAN, Epilepsia _17 37-47 (1976) . R.H . LEVY, J .S . LOCRARD, I .H . PATEL and A.A . LAI, Epilepsia _18 191-204 (1977) . A.J . ROWAN, C .D . BINNIE, C.A . WARFIELD, and J .W .A . MEYER, pp . 249-254 and A.J . ROWAN et al ., pp . 255-260, in Thirteenth Congress _of _the einst Epilepsy , J .R . Penny (Ed .), Raven Press, International Lea ue New York (1977) . J .S . LOCRARD, R .H, LEVY, L.L . DuCHARME and W.C . CONGDON, Epilepsia (in press, 1979) . J.S . LOCKARD, A .R, WYLER, C .A . FINCH and K .E . HURLBURT, Epilepsia _18 471-479 (1977) . J.S . LOCRARD, G .A . OJEMANN, W.C . CONGDON and L.L . DuCHARME, Epilepsia _20 223-234 (1979) . A.R, WYLER, K.J . BURCHIEL and A .A . WARD, JR ., Epilepsia _19 475-483 (1978) . L .J . WILLMORE, G.W . SYPERT, J .B . MUNSON and R.W . HURD, Science 200 1501-1503 (1978) .