Classics in Psychology

Robert H. Wozniak - Bryn Mawr College

John Hughlings Jackson: Evolution and Dissolution of the NervousSystem (18817; Collected 1932)

In 1824, Marie-Jean-Pierre Flourens provided the first experi-mental demonstration of localization of functionin the brain: a motor center in the medulla oblongata and stability and motor coordination in the cerebellum.By 1842, he had articulated a clear distinction between sensation and perception and localized sensoryfunction in several related sub-cortical structures. For a combination of empirical and philosophical reasons,however, Flourens was firmly opposed to cortical localization of function and committed to a view of the cortexas the unitary, undiffer-entiated seat of higher mental processes. 154 This was a position that was widelyshared.

It was not until the 1870s that views concerning the nature of cortical function began to change. For thischange to occur, the intellectual ground had to be prepared. This involved the abandonment of a fixed facultyapproach to mind in favor of a balanced sensori-motor, evolutionary associationism. These advances camethrough the respective contributions of Alexander Bain and Herbert Spencer. 155 Prior to Bain,associationisms commitment to experience as the source of knowledge led to the neglect of movement infavor of the analysis of sensation. Drawing heavily on the work of physiologists such as Johannes Mller, 156

Bain brought the new physiology of movement into conjunction with an associationist account of mind. Action, he wrote, is a more intimate and inseparable property of our constitution than any of our sensations,and in fact enters as a component part into every one of the senses, giving them the character of compounds. 157

Herbert Spencer offered students of the brain an evolutionary view to which sensori-motor and hierarchicalorganization in the brain as a whole were simple corollaries. For Spencer, evolution consisted of gradual andcontinuous change from homogeneity to heterogeneity, from relative unity and indivisibility to differentiationand complexity, from relative rigidity of organization to relative flexibility. Nowhere in the process of evolutionwere there radical discontinuities; principles describing lower levels of an evolving system were alsocharacteristic of higher levels. And just as evolution was an increase in differentiation, complexity, andflexibility, dissolution involved return to relative lack of differentiation, simplicity, and stereotypy.

The broad implications of these evolutionary conceptions for the theory of brain function were clear. The brainwas the most highly developed physical system known and the cortex the most developed level of the brain.As such, it must be heterogeneous, differentiated, complex, and flexibly organized. Furthermore, if the cortexwas a continuous evolutionary development from sub-cortical structures, the sensori-motor principles thatgoverned sub-cortical localization must hold for the cortex as well. Finally, if higher mental processes werethe end product of a continuous process of development, pathology in higher brain centers could lead todissolution of function.

In the late 1870s and 1880s, these implications were elaborated in striking fashion in a series of paperspublished by John Hughlings Jackson.158 The most famous of these, including Jacksons Croonian Lectureson Evolution and Dissolution of the Nervous System, appeared between 1881 and 1887 and were collectedtogether for the first time in 1932 in the second volume of Jacksons Selected Writings. 159

As Jackson put it in the introduction to the first of these papers, he had long thought that Herbert Spencershypothesis of dissolution( would) enable us to develop a science of disease of the nervous system. 160 Hisgoal, therefore, was to illustrate Spencers doctrines of nervous evolution, by the reverse process of nervousdissolution, as this is effected by pathological processes. 161

And for Jackson, pathology was very broadly construed to include exceptional mental states of any kind, not only cases specially described by alienists, but delirium in acute non-cerebral disease, degrees ofdrunkenness, and even sleep with dreaming. 162 Indeed, it was a hallmark of Jacksons work that his generaltheory of the functional architecture of brain systems could be used to elucidate not only exceptional mentalstates of the sort just listed but even the effects of nervous diseases as varied as muscular atrophy,hemiplegia, paralysis agitans, epilepsy, chorea, and aphasia.

Unfortunately, Jackson never published a systematic account of his theory. The historian of psychology whogoes in search of Jacksons views will find bits and pieces of the theory scattered about among his writings.For the sake of exposition, the major principles will be laid out here with some systematicity; but this was notcharacteristic of Jacksons own work.

The first principle of Jacksons theory was continuity of sensori-motor function at all levels of the nervoussystem. As Jackson put it, the cerebral centres are, like all lower centres, reflex. The more recent doctrinesof evolution of necessity imply that all nervous centres, even the highestthe substrata of consciousnessare (also) sensori-motor. 163

The second principle was that of the evolution and dissolution of brain systems. One of the best statements ofthis principle appeared in Jacksons Croonian Lectures: Evolution, he wrote, is a passage from the most tothe least organised; that is to say, from the lowest, well organised, centres up to the highest, least organised,centresfrom centres comparatively well organised at birthto thosewhich are continually organisingthrough lifeEvolution is a passage from the most simple to the most complexa passage from the mostautomatic to the most voluntarythe highest centresare the least organised, the most complex, and themost voluntaryDissolutionis a process of undevelopmentfrom the least organised, from the mostcomplex and most voluntary, towards the most organised, most simple, and most automatic. 164

According to the third principle, the nervous system is a representing system.165 Parts of the body wererepresented by different centers. In keeping with the sensori-motor hypothesis, Jackson argued that Even thecentres for mind represent parts of the bodyThe whole nervous system is a sensori-motor mechanism, acoordinating system from top to bottom. 166

The fourth principle, which followed directly from the second and third, was that of the hierarchy of cerebralcenters, divided into lowest, middle, and highestto indicate different evolu-tionary levels. 167 A lowestcentre, in Jacksons view, is one which represents some limited part of the body most nearly directlyAmiddle centre represents over again inmore complexcombinations what many or all of the lowest haverepresented in comparatively simple combinationsThe middle centres are re-representativeThe highestcentresrepresent over again in more complexcombinations, the parts which all the middle centres havere-represented, and thus they represent the whole organism; they are re-re-representative. 168 A corollary ofthis principle was that the depth of dissolution in pathology would reflect the hierarchical level of the affectedcenter.

How this effect was manifested, however, would depend not only on depth of dissolution (severity of thepathology) but on whether the symptomatology was viewed in terms of its negative or positive aspect. Andhere we have the last of Jacksons major principles, that of the fundamental duality of all pathological states.Each such state, in Jacksons view, was characterized by both negative and positive symptoms. Negativesymptoms were those directly caused by the pathological condition as it worked its effect in higher centers;positive symptoms were those indirectly caused by removal of the influence of the higher centres. 169

The source of this duality, of course, was the nature of patho-logical dissolution itself. When the influence ofhigher brain centers was removed (through disease, injury, exhaustion, temporary inhibition), the activity of thenext lower centers, normally under the control of the higher centers, was liberated. This led, in Jacksonsphrase, to a reduction to a more automatic condition 170 frequently characterized by overactivity of the lowercenters.

Jacksons most famous application of his evolutionary theory of brain systems was to the analysis of the post-seizure disorders of epilepsy; and for the purpose of illustrating his theory, this application will be brieflydescribed. For Jackson, the epileptic discharge (a sudden and excessive discharge of certain nervousarrangements, the cells of which are abnormally highly unstable 171 ) led to temporary exhaustion ofassociated nerve fibers in the highest centers of the brain. Depending on the strength and rapidity of theepileptic discharge and the consequent exhaustion of the relevant higher centers, three degrees of depth ofnervous dissolution might be observed.

In the least severe condition, the positive symptom was epileptic ideation, a somewhat dream-like state ofreverie. The negative symptom, attending the ideation, was a certain mental confusion and removal ofconsciousness from reality. The patient as Jackson put it, tells us that he becomes dim to his surroundings172 . In moderately severe dissolution, the positive symptom was action of different kinds and of differentdegrees of elaborateness; 173 the negative symptom was loss of consciousness. The patient in this conditionexhibited a behavior pattern somewhat akin to somnambulism. Finally, in the most severe cases ofdissolution, the patient continued to exhibit the operation of vital processes such as respiration and circulation(the positive symptom) but persisted in a coma (the negative symptom). While the patho-logical discharge ofepilepsy directly produced the negative symptoms, it had, as Jackson wrote, done nothing to the nervous

arrangements concerned in the positive state, except in the indirect way of removing controlby exhaustingtheir higher, or controlling, nervous arrangements. 174

While Jacksons specific contributions to our understanding of the etiology, course, and treatment ofneurological disorders such as epilepsy were of great importance, it was his evolutionary, hierarchical,systemic, sensori-motor conception of cerebral function that was of greatest interest. How influential it was inits day is somewhat difficult to say. In his discussion of perception in The Principles of Psychology, WilliamJames, always alive to evolutionary, systemic thinking, referred to Jacksons theory as masterly and asinvolving principles exactly like those which I am bringing forward here; 175 but for most late 19th centurypsychologists, still burdened with a mechanistic metaphor for both the nervous system and consciousness,Jacksons views may well have been hard to fathom.

154 Flourens, M-J-P. (1824). Recherches exprimentales sur les proprits et les fonctions du systmenerveux, dans les animaux vertbrs. Paris: Crevot; the second edition was published in 1842.

155 Bain, A. (1855). The Senses and the Intellect. London: John W. Parker and Son; Spencer, H. (1855). ThePrinciples of Psychology. London: Longman, Brown, Green, and Longmans. For a superb analysis of theseadvances and of their relationship to the work of Jackson among others, see Young, R.M. (1970). Mind, Brainand Adaptation in the Nineteenth Century. Cerebral Localization and Its Biological Context from Gall to Ferrier.Oxford: Clarendon Press, 1970; for a general discussion of the work of Bain and Spencer, see the essays onthese authors in this volume.

156 Mller, J. (183440). Handbuch der Physiologie fr Vorlesungen. Coblenz: Hlscher.

157 Bain, op. cit., p. 67.

158 18351911. For biographical information on Jackson, see Clarke, E. (1973). John Hughlings Jackson. InC.C. Gillispie (Ed.). Dictionary of Scientific Biography (Vol. 7). New York: Scribners, pp. 4650.

159 Jackson, J.H. (1932). Selected Writings of John Hughlings Jackson (2 Vols.). Edited by J. Taylor. London:Hodder and Stoughton; all page references to quotations from Jackson are keyed to the Selected Writings.

160 Ibid., Vol. 2, p. 3.

161 Ibid., Vol. 2, p. 6.

162 Ibid., Vol. 2, p. 5.

163 Ibid., Vol. 2, p. 6.

164 Ibid., Vol. 2, p. 46.

165 Ibid., Vol. 2, p. 41.

166 Ibid.

167 Ibid.

168 Ibid.

169 Ibid., Vol. 2, p. 6.

170 Ibid., Vol. 2, p. 8.

171 Ibid., Vol. 2, p. 21.

172 Ibid., Vol. 2, p. 13.

173 Ibid., Vol. 2, p. 11.

174 Ibid., Vol. 2, p. 16.

175 James, W. (1890). The Principles of Psychology (2 vols.). New York: Henry Holt, Vol. 2, pp. 1256.

Extracted from Classics in Psychology, 18551914: Historical Essays ISBN 1 85506 703 X Robert H. Wozniak, 1999

Classics in Psychology, 18551914 Historical Essays - Contents