CHAPTER LIV 



The intrinsic systems of the forebrain 



KARL H. PRIBRAM I Slari/uivl C'niversily, Palo Alio, California 



C: H A P T E R CONTENTS 



Introduction 



Definition of Intrinsic Systems of tlie Forebrain 

 Neurobehavioral Analysis of Posterior Intrinsic System 



An Experiment 



Review of Other Data 



Analysis of Results 

 Model of Posterior Intrinsic Mechanism 



Deficiencies of Transcortical ReHex 



Partitioninf? of Sets 

 Neurobehavioral Analysis of Frontal Intrinsic System 



Some Definitions 



Some Experiments 



Analysis of Results 



Revievi' of Other Data 

 Model of Frontal Intrinsic Mechanism 



Mediobasal Forebrain and Disposition 



Mechanism of Expectation 

 Summary and Conclusion 



There remains yet another type of integration which claims 

 consideration, although to saddle it upon nerve may perhaps 

 encounter protest. Integration has been traced at work in 

 two great, and in some respects counterpart, systems of the 

 organism. The physico-chemical (or for short physical) pro- 

 duced a unihcd machine from what without it would be merely 

 a collocation of commensal organs. The psychical, creates 

 from psychical data a percipient, thinking and endeavouring 

 mental individual. Though our exposition kept these two 

 systems and their integrations apart, they are largely com- 

 plemental and life brings them co-operatively together at 

 innumerable points. . . . For our purpose the two schematic 

 members of the puppet pair which our method segregated 

 require to be integrated together. Not until that is done can 

 we have before us an approximately complete creature of the 

 type we are considering. This integration can be thought of 

 as the last and hnal integration. 



But theoretically it has to overcome a difficulty of no ordinary 

 kind. It has to combine two incommensurables; it has to unite 

 two disparate entities. To take an example: I see the sim; 



the eyes trained in a certain direction entrap a tiny packet of 

 solar radiation co\'ering certain wave-lengths emitted from 

 the sun rather less than lo minutes earlier. This radiation is 

 condensed to a circular patch on the retina and generates a 

 photo-chemical reaction, which in turn excites nerve-threads 

 which relay their excitation to certain parts of the brain, 

 eventually to areas in the brain-cortex. From the retina on- 

 ward to the brain the medium of propagation is wholly nervous; 

 that is to say, the reaction can be subsumed as electrical. Some 

 of this electrical reaction generated in the eye does not reach 

 the brain-cortex but diverges by a side-path into nerve- 

 threads which relay it to a small muscle, which by contracting 

 prevents excess of light attaining the retina. The electric 

 current propagated to the muscle activates the muscle. The 

 chain of events stretching from the sun's radiation entering 

 the eye to, on the one hand, the contraction of the pupillary 

 muscle, and on the other to the electrical disturbances in the 

 brain-cortex are all straightforward steps in a sequence of 

 physical 'causation', such as, thanks to science, are intelli- 

 gible. But in the second serial chain there follows on, or at- 

 tends, the stage of brain-cortex reaction an event or set of 

 events quite inexplicable to us, which both as to themselves 

 and as to the causal tie between them and what preceded 

 them science does not help us; a set of events seemingly in- 

 commensurable with any of the events leading up to it. The 

 self 'sees' the sun; it senses a two-dimensional disk of bright- 

 ness, located in the 'sky", this last a field of lesser brightness, 

 and overhead shaped as a rather flattened dome, coping the 

 self, and a himdred other visual things as well. Of hint that 

 this scene is within the head there is none. Vision is saturated 

 with this strange property called 'projection', the unargued 

 inference that what it sees is at a 'distance' from the seeing 

 'self. Enough has been said to stress that in the sequence of 

 events a step is reached where a physical situation in the brain 

 leads to a psychical, which however contains no hint of the 

 brain or any other bodily part. We cannot of course suppose 

 that in the instance taken, the 'seeing the sun' breaks into a 

 visual vacuum; in the waking day 'seeing' of some sort is 

 always going on: on the physical side similarly electrical 

 waves in the brain from one source or another must be prac- 

 tically unremitting during the waking day. The supposition 

 has to be, it would seem, two continuous series of events, one 

 physico-chemical, the other psychical, and at times interaction 

 between them. 



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