Brain Mechanisms in Language Cognition and Consciousness T-144

8/13/2019 Brain Mechanisms in Language Cognition and Consciousness T-144

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\ \ \ {4 2 4 BRAIN MECHANISMS IN LANGUAGE COGNITION, AND CONSCIOUSNESS

g en er at io n o f w hi te m at te r in hypoxia, acidosis an dedema. Journal of Neuropathology and ExperimentalNeurology, 1973, 32, 124-143.

JEu..INGER, K. an d NEUMAYER, E. Progressive subcorticalevasculare Encephalopathie Binswanger. Eine Klinisch-neuropathologische Studie. Archiven ii r Psychiatrie un d Nervenkrankheiten 1964, 2 5 523-554.

IRWIN FEIGIN

BRAIN MECHANISMS IN LANGUAGE,COGNITION, AND CONSCIOUSNESS

IntroductionIn th e recent past, an encyclopedia section onphysiological psychology would have fore :.

sworn any attempt to deal with th e brain mechanisms involved in language, cognition or consciousness. Even today most physiological textsin psychology are so behavioristically orientedthat th e very words language, cognition an despecially consciousness are eschewed. Yet itwa s not alw ay s thus. During th e nineteenthcentury, the initial strides in relating br ai n a ndbehavior came from th e neurological clinic,w he re th e study of disturbances of languagedu e to brain lesions m ad e t he names of Brocaand Wernic ke c elebra te d; where studies ofbrain-caused disturbances of cognitive processes led Freud to coin t he t er m agnosia; wheret he s am e Freud pointed ou t that if consciousness is a function of cortex, t he n t he rest o f t hebrain must be concerned with unconsciousdeterminants of behavior.

During th e classical behaviorist period ofpsychology, studies of language, cognition an dconsciousness were deemed beyond th e scopeof scientific psychology. Euphemisms such assecond signaling system for language),highernervous f un ct io ns f or cognitions), an d complex mental sta te s for consciousness) wereused to keep psychology pure, much as in Victorian times w om en w er e sa id to h av e l im bsrather than legs. Bu t psychology as an aspiringscience became liberated during th e 1960s an donce more is facing t he r aw facts of subjectiveexperience. So once again physiologically oriented psychologists are turning to th e clinic inorder to study th e relationships o f th e humanbrain to subjective experience.

Th e harvest of t hi s n ew direction in physiological psychology is already surprisingly rich.

N ew i ns ig ht s ar e continually being achievedinto th e structure of language, th e types of cognitive processes, a nd t he brain mechanisms operative in various states of consciousness.These i ns ig ht s c om e through th e careful ap plication of th e techniques an d concepts developed in experimental and animal psychology toth e human condition.Language

The specialization o f th e left hemisphere of right-handed)man s brain fo r th e understandin g an d production of language has beenknown for t ho us an ds o f years. Egyptian an dclassical Greek m ed ic in e w er e in for me d by, cases o f h ea d injury that, as a rule, only leftsided injuries would interfere w i th l an gu ag efunctions. The fact that c hi ldr en c an c ar r y ou tcommands an d otherwise signifY,that t he y u nderstand spoken l an gu ag e w he n they as yetcannot express themselves adequately has suggested t hat t he receptive decoding and expressive encoding aspects of language can beseparated. Th e names of Wernicke an d Brocaare associated w i th t he locating ofthe receptivean d expressive portions of t he bra in s involvem en t i n language. However, a good deal of evidence suggests that Broca placed his locus toofa r forward, that what is now known as Broca sarea the thirdfrontal convolution) may in facthave little to do with language, a nd t ha t Broca saphasia results from lesions closer to th e motorrepresentation o f t he vocal apparatus the baseof th e precentral convolution). A more unitaryview of an a ud it or il y b as ed l an gu ag e m ec hanism has resulted: Wernicke s locus beingc ri ti ca l i n primary aphasia) w i th a dd it io na linvolvement of visual mechanisms leading toalexia reading disturbance); of motor handmechanisms leading to agraphia; an d of motorvocal mechanisms leading to Broca s aphasia.But a more profound impact on th e ~ r o l mofthe relationship between br ai n a nd languagehas come from th e successful training of greatapes in th e us e of gestural s ig n l an gu a ge byGardner an d Gardner, and th e communicativemanipulation of visual symbols by David Premack. Well over a hundred signs can be mastered and hierarchies of visual symbolsmanipulated. Communication takes place inth e somatomotor and visual modes r a th e r t h anacoustic-vocally. Th is h as raised th e question


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BRAIN MECHANISMS IN LANGUAGE, COGNITION,AND CONSCIOUSNESS 425as to how communication through speech differs from that through. gestures. One obviousdifference is the rapidity of sequencing. inspeech and the greater possibility for simultaneous s igna ling by gestures. Is the ape brainlimited in its processing speed and thus cannotuse the acoustic-vocal mode? Can aphasichumans be taught to use gestural sign language,or is the aphasic disturbance a deeper one, pre- .eluding any form o f communication? Perhapssome aphasics can learn the gestural languagewhile others cannot. Which can? And whatthen characterizes th e deeper process? Theseate al l questions initiated by th e animal workand currently are beillg. actively pursued invarious clinics. Ogm itJiOIlll

Our understanding of the relationship between b ra in and cognitive processes has alsobeen enriched by animal studies and by a moresophisticated approach to hemispheric specialization. Some thirty years ago, Pribram initiated a program of research aimed at th e production of animal models of the agnosias.Since, at that time, animals had not ye t beenshown to use signs, aphasias were not considered suitable for modeling-and even now mostlinguists would hold that human language cannot be readily modeled in animal communications . This program was successful in locatingspecific brain systems separately involved in.making visual, auditory, tactile and gustatoryidentifications. When BrendaMilner took theseresults back to th e clinic, she found such nonlinguistic disturbances more likely to be produced by lesions ofthe right hemisphere. Thus,two types of cognitive processes, linguistic andnonlinguistic, were separately served by one ofth e hemispheres of man s brain.The technique of di hoti and di hoptipresentation of stimulus materials combinedwith computer analysis of electroencephalographic patterns gave further evidence of thisseparation of cognitive modes of function. Theleft hemisphere s electrical activity reflectsverba l input , while the righ t hemisphere selectrical activity appears more sensitive to thefigural aspects of sounds. In fact, a great dealof evidence has suggested that the r ight hemisphere s nonverbal speciality lies in the processing of figural information. Face recognition

and musical ability are two well-known figurally dependent processes handled predomi-nantly by the right hemisphere. _

But the yield from the animal models ha sbeen greater than just stimulating reinvestigation of b r i n ~ p r o d u c e d cognitive disturbancesin man. StUdies on th e animal models haveshown that brain organization in cognition, atleast in th e nonhuman primate,is cortical-sub-. cortical rather than cortico-corticaL This finding has raised th e question as to whether th ehuman brain is similarly organized. Up to now,human cognitive brain processes have beenthought to be dependent on cortico-cortical association tracts. If, in fact, the importance ofcortico-cortical organization in man stands thetest of future research, a major difference between functional anatomy of the brains ofmenand beasts will have been established. Hithertono anatomical differences have been acceptedas accounting fo r hemispheric specializationor man s linguistic and other cultural accomplishments.

Finally, work with the animal models of cognitive processes has shown that th e brainmechanisms involved are distributed withinfunctional systems; that one aspect of thesemechanisms (the connecting pathways) operate probabilistically, and tha t the probabilitiesbecome progressively constrained duringlearning; however, that at the same time storage (probably at syn pti and dendriti sites)continues to be distributed and reduplicateswith repetition; tha t the learned connectivitiesact as programs re-membering th e dis-membered, distributed stored elements much as acomputer program assembles s tored itemsfrom a distributed core. In fact, th e use of sequential information processing by computersand parallel processing by distributed (optical,holographic) information systems has servedthe investigator ofbrain mechanisms in cognition much as in vitro analyses have served th ebiochemist.Consciousness

Once again hemispheric specialization hasbeen the takeoff point fo r studies of consciousness. Roger Sperry led th e way with a tour deforce in showing that splitting apart the hemispheres of the human brain (by sectioning th eorpus c llosum produced two minds in one


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42 6 BRAIN AND PSYCHOANALYSIShead. Neither hemisphere appears to knowwhat the other is about. As noted above, the lefthemisphere talks, the right cognizes configurally. An embarrassing picture projected intothe right hemisphere will make the patientblush and ask with hi s left what migh t be thematter. Choices given to the right hemisphereto make can be indicated instrumentally bymatching from sample or pointing, and occasionally by simple verbal indicators. The lefthemisphere makes its choices known verballyand has some difficulties with complex configura l problems.The question has been debated as to whether

the r ight hemisphere of these split brains displays conscious properties. Sperry llnequiv.Q-._cal ly says yes ( it can blush ) while Sir JohnEccles cautiously suggests that only from verbal report can we truly determinewhether consciousness exists. The argument may be resolved through a more precise definition ofconsciousness: ordinary perception is obviouslyshared by both hemispheres, but that specialawareness called intentionality by philosophers that distinguishes between the observerand the observed may be a peculiarly human(or at least anthropoid and possibly cetacian)character is tic tha t, concomitant with language, is primarily a left-hemisphere function.The evidence is against this left-sided viewof consciousness, however. Weiskrantz andWarrington have portrayed cases of blindsight due to resections of primary visual projection cortex. Their best subject is a patientwith a removal limited to the right occipitalcortex. This subject, as do the others, performsvisual location (by pointing) and visual choiceproblems (by verbally or instrumentally indicating his choices) at 85 to 90 proficiencywhen the visual cues are presented to hisblind field. Despite being told that he is performing well, he reports that he has absolutelyno awareness of the cues, and that he is guessing to the best of h is knowledge.Somewhat similar observations have beenmade on pat ients with medial temporal loberesections. Pribram reported a patientwho, following amygdalectomy ate voraciously, putting on wel l over 100 pounds without ever experiencing hunger or appetite. Another suchpatient is Brenda Milner s famous H. M whohad both amygdala and hippocampus resectedbilaterally with a resultant severe memory

loss. After twenty years of testing, t h ~ p t i e n tdoes not recognize Milner. Nor can he reportany familiarities with events since his'surgery.Yet H. M has been trained to perform discriminations and other tasks instrumentally, and heretains what he has learned despite protestations to the effect that he has no recollection ofever having been shown such tasks. Even withproblems testing verbal memory byrecognitionof items from repeated lists, Warrington andWeiskrantz have shown in similar patients thatint rusion errors occur, indicating that theitems did get into memory. Further, whensome context is provided, such as the first twoor three letters of a word to be recognized orrecalled, the patients perform as well as theirnormal controls.

What this relationship between context,familiarity and consciousness might be remains to be researched. Currently biofeedbackprocedures are proving effective in gaining insights into just such problems. Some visiblereadout is provided of an otherwise obscure internal process in order to obtain control overthat process. Often limited and occasionallysome considerable awareness of the process isattained. Perhaps providing feedback is theequivalent of furnishing the context withinwhich this form of consciousness can occur.

BIBLIOGRAPHYECCLES j. C Facing reality New York: Springer-Verlag1970.GLOBUS G.; MAxWELL G.; an d SAVODNIK I (Eds.). Consciousness and brain New York: Plenum, 1976.JOHN E. R Mechanisms memory New York: AcademicPress, 1967.PRmRAM K. H Languages o f the brain: Experimentaparadoxes and principles in neuropsychology Englewood Cliffs, N.j.: Prentice-Hall, 1971, Chaps. 6, 11, 1617, 18 19 and 20.PRmRAM K H. Self-consciousness and intentionality. In

G E. Schwartz and D. Shapiro (Eds.), Consciousnesand self regulation: Advances in research New YorkPlenum, 1976.

KARL H. PRmRAMBlR lIN ANj[ PYClHIO N lLYlI

Despite the gulf which separa tes the modernpractitioners of psychoanalysis from theirneurologic colleagues, the interests aild professional concerns of these two branches of medi-

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Brain Mechanisms in Language Cognition and Consciousness T-144