Brain and Behavior

Research in Clinical Neuropsychology

Michael Peter Smith,Arthur L. Benton

• Publisher: Routledge
• Year: 2017
• ISBN:
  9781351530880
• Edition: 1
• Topic: Psicología
• Subtopic: Historia y teoría en psicología

Research in the field of clinical neuropsychology has greatly advanced understanding of the complex relationships between brain functions and human behavior. This edited collection, originally published in the early days of this dynamic field, draws from the findings of clinical study, animal experimentation, and developmental observation to clarify the relationships between brain and behavior. The result is a report on the state of knowledge at that time, and a barometer of how far the field has come.

The book's contributors include some of the leading figures in the field of human and developmental neuropsychology. They present comprehensive reviews of salient topics on which they themselves have done important investigative work. An introduction by Klaus Poeck describes the historical evolution of clinical neuropsychology and discusses the status of the field from both substantive and methodological standpoints. George Ettlinger and Colin Blakemore describe understanding of inter-hemispheric relations as demonstrated by studies in animals and man. Sidney Weinstein discusses the phenomenon of the "phantom" in patients with amputated body parts and its implications for the concept of body image.

Norman Geschwind, who was instrumental in reviving interest in the anatomical approach to aphasia, focuses on some unsolved anatomical problems and suggests needed clinical and experimental study. Arthur L. Benton outlines questions concerning constructional apraxia. Josephine Semmes offers a brilliant reformulation on whether there are discrete basic types of somatosensory function. Luigi Vignolo presents a masterful analysis of the concept of auditory agnosia and describes his own research in this area. Concentrating on a few important problem areas, each of which is intensively probed, this book offers valuable insight into how research advances understanding of the neuroanatomical bases of behavior.

1
Modern Trends in Neuropsychology

Klaus Poeck

Neuropsychology is a relatively young science. Originally, its objective was limited to the study of the psychological disturbances observed after circumscribed or diffuse brain lesions in man. Increasingly, however, the field covers also the examination of comparable behavioral disorders in animals, particularly in primates. This development corresponds to the general trend towards interdisciplinary, problem oriented research.

The most prominent among the neuropsychological syndromes are:

Aphasia, i.e., a particular receptive and expressive impairment in dealing with verbal symbols.

Disturbance of spatial orientation and constructional dyspraxia, i.e., difficulty in putting objects or parts of objects in proper spatial relationship.

Apraxia, i.e., impairment in performing gestures or in handling objects properly.

The group of agnosias, i.e., disturbances of recognition in one or other sensory modality that are not explained by perceptual deficit. Conventionally, visual agnosia, auditory agnosia, and tactile agnosia are distinguished.

These behavioral disturbances were described in detail by Continental authors mostly between 1870 and 1930. For a certain period of time, the clinical description of these symptoms enjoyed general acceptance and their interpretation remained basically undisputed. After World War II, however, the classical symptoms were studied anew, and it was recognized that many of the old observations were open to serious methodical objections.

The classical papers were based on the examination of single cases or of small groups of patients, which were selected because they presented with a striking symptom. Every examiner had his own way of testing, and it was held legitimate to adapt the method of examination to the particular conditions of the individual case.

The tests applied were never standardized. No norms existed for the performances of normal and brain damaged control subjects. The influence of unspecific variables—for instance, of age and education—was not taken into consideration. Performances were evaluated exclusively according to the personal experience and knowledge of the examiner and there was no quantification of data but instead a very crude classification, as pass or fail.

The aim of research had been the description of so-called pure cases, presenting an isolated psychological or sensory defect, not complicated by other behavioral disturbances. As a rule, however, the pure symptoms were nothing else than an artifact brought about by the method of examination; testing was limited to the performance the author was looking for, and further possibilities, particularly the dependance of a given symptom upon other specific and unspecific variables, were not even discussed.

The interpretation of the findings was centered on the recognition of Grundstörungen, that is, of basic disturbances which of necessity cause certain symptoms. The assumption of these Grundstörungen was likewise highly subjective.

It was inevitable that many of the results of this type of research were seriously biased according to the expectation and the subjective opinion of the author. In essence, this methodological approach led to a wealth of scattered data that were not really comparable with each other and that did not establish convincing concepts.

With regard to the anatomical basis of psychological deficit, two extremely opposed positions were held. Some authors, e.g., Kleist (1934) and the Vienna school, maintained that it was possible to localize precisely the small lesion producing almost any given symptom. They did so even in the presence of diffuse overall brain disease or large space-occupying lesions with damage to a great area of brain tissue. Others, for the most part members of the Gestalt school, defended a holistic view and some of them went so far as to deny any circumscribed localization of centers at all. Classical examples of these contrasting positions are statements such as the following: “We speak with the left hemisphere” (Broca, 1865) vs. “We do not speak with the left hemisphere, we speak with the whole brain” (Hoff, 1964).

It is apparent from the foregoing critical considerations “that the complexity of the psychological effects of brain lesions has been grossly underestimated by most clinically oriented investigators. A majority of investigations has been inadequate with regard to definition of the independent variables, the range and diversity of dependent variables and the theoretical framework in which psychological deficits resulting from brain lesions are presumed to be subject to identification” (Reitan, 1966, p. 128).

New progress in this field of research began when experimental psychologists, mostly in the Anglo-American countries, introduced their precise methods of experimental work and evaluation of data to the study of behavioral disorders in braindamaged patients. The nature of these symptoms was no longer explained on the basis of single or selected cases. Although single cases can call attention to new phenomena, the significance of these phenomena can be demonstrated only by the examination of great series of unselected brain-damaged patients.

The classical “handmade” methods of testing were abandoned because their validity was not evaluated. Instead, the patients were examined by standardized and valid methods. At the present time, clinicoanatomical inferences are drawn with extreme caution.

This approach is not as new as it seems to be. In the second half of the last century, Hughlings Jackson had already demanded that the researcher “try to classify the facts in order to show their true relations to one another and consider them on the psychical side as defects of mind and on the physical side as defects of the nervous system.” Jackson insisted on the necessity of studying and classifying the phenomena before any attempt was made to correlate them with morphological changes. What he was aiming at was the patient’s performance and not so much some theoretical concept: “Put down what the patient does get at and avoid all such terms as amnesia” (cf. Head, 1926).

In this introductory chapter, I intend to indicate several lines of research that appear representative of present day neuropsychological work. Particular emphasis is laid on those fields discussed in detail in this volume.

Disconnection Syndromes: A New Anatomical Aspect

A very important step toward a precise anatomical basis for certain neuropsychological symptoms is the concept of disconnection syndromes, developed by Geschwind (1965a). This concept is based on “split-brain” experiments in cats and monkeys as well as an investigation of patients with cerebral lesions. The background of these studies is illustrated by the following anatomical data.

In mammals, the cerebral cortex of each hemisphere sends out efferent—i.e., centrifugal—projection fibers to structures in the brain stem and spinal cord that subserve the coordination and execution of movements. Likewise, the cerebral cortex is reached by afferent—i.e., centripetal—projections, originating in the various somatosensory receptors. The great majority of these efferent projections cross the midline at the level of the brain stem. Consequently, each hemisphere sends out motor commands almost exclusively to the contralateral limbs and receives somatosensory informations mainly from the contralateral half of the body.

The visual pathways coming from both eyes cross at the base of the brain in the optic chiasma. From here, they travel upward and reach the primary visual projection area in the occipital lobe. The arrangement of fibers in the chiasma is not such as to connect the right eye with the visual cortex of the left hemisphere and vice versa. Rather, each of the hemispheres receives signals from the contralateral visual half-field of both eyes.

The motor and sensory signals carried along these crossed pathways, however, do not remain restricted to the contralateral hemisphere. It has been demonstrated, in particular by the method of conditioned reflexes, that the signals are also transmitted to the other hemisphere. For example, if an animal has learned to perform a conditioned task with his right forelimb (in other words, with the motor area of his left hemisphere), subsequent testing discloses some degree of learning also in the motor area of the right hemisphere. The pathways subserving this inter-hemispheric transfer are called the commissures. The neocortical commissures connect corresponding points on the cortical surface of both cerebral hemispheres. The most important of these is the corpus callosum.

In the split-brain experiments referred to above, all neocortical commissures as well as the optic chiasma were sectioned so that the transfer of signals from one hemisphere to the other was interrupted. Somatosensory afferences were practically limited to the contralateral hemisphere, and the visual input of the right or left eye, respectively, was projected only to the ipsilateral hemisphere. Consequently, each of the hemispheres “knew” everything it had learned before the operation by the direct crossed route as well as by the indirect transcallosal route via the other half of the brain. However, the ipsilateral hemisphere no longer participated in learning processes when the contralateral hemisphere was trained after the operation (cf. Ettlinger, 1965).

The application of these experimental results to human neuropsychology was studied first by Gazzaniga, Bogen, and Sperry (1962, 1963, 1965) and Gazzaniga and Sperry (1967) in four patients who underwent split-brain surgery for the treatment of intractable epilepsy. In man, the situation for examining the functions of the two independent hemispheres is particularly favorable because of a distinct functional asymmetry between the two halves of the brain. The best known (but not the only) example of this asymmetry is the lateralization of a circumscribed area for the organization of language performances.

The importance of interhemispheric transfer across the neocortical commissures was demonstrated in a series of tasks requiring the subjects to match sensory information with the appropriate verbal concept. The patients were able to identify objects verbally only when the stimulus was given to the right hand or to the left eye. In both instances, the signals were projected to the left hemisphere, where the language area is situated. When the signals were projected to the right hemisphere, the patients were not able to name an object they had palpated or seen or to select its name by way of multiple choice. Some patients were not even able to say whether they had perceived a stimulus.

In contrast to this impairment in the sensory-verbal association, the subjects could carry out rather complex tasks with their left hand, that is, with their right hemisphere, provided these tasks did not call for language performances.

These findings and many further consistent observations not reviewed here in detail were explained convincingly on an anatomical basis. It was obvious that a sensory stimulus arriving in the sensory area of the right hemisphere could reach the ipsilateral motor area over association pathways within the same half of the brain and thus elicit appropriate motor behavior. It was equally obvious that because of the split-brain operation the same stimulus could no longer travel across the neocortical commissures and reach the language area of the left hemisphere.

The split-brain experiments gave a new impetus to the study of subcortical connections and their functional significance. It was recognized that many neuropsychological symptoms do not indicate dysfunction or loss of function in a circumscribed, specialized area of cerebral cortex but do indicate the interruption of association fibers connecting two cortical areas of different functions within the same hemisphere and the interruption of commissural pathways connecting corresponding areas of the two hemispheres.

It is true that a similar hypothesis had been advanced earlier by some authors under the heading of the so-called Leitungsstörungen. The classical example is Liepmann’s (1900, 1908a) theory that the neural basis of apraxia consists in the interruption of subcortical fibers linking the language area with the motor area. Another case is that particular impairment in the repetition of spoken language termed “conduction aphasia.” By this is meant that the disturbance is due to the interruption of fibers associating the auditory receiving area with the language area (Isserlin, 1936).

Apart from these two instances, however, the concept of Leitungsstörungen had not gained broad acceptance. This was partly due to the impact of the holistic view of Gestalt psychology and partly to the difficulty in assessing reliable anatomical data in human disease processes that all too often bring about widespread damage to the brain.

It meant a renaissance of anatomical reasoning in neuropsychology when Geschwind, after an extensive review of the literature and the description of pertinent personal cases, postulated a disconnection mechanism to be the basis of various types of aphasia, of the apraxias, and of the agnosias (Geschwind, 1965a) • His ideas are most convincing where he assumes disconnection between sensory or motor areas and the language area. As a consequence of these lesions, afferent signals cannot be associated with verbal concepts and verbal concepts cannot be transformed into motor performances.

This view appears very promising for the understanding of the agnosias and apraxias. In the classical papers, testing for the presence of agnosia required the patient to match the perceived object with the proper name. If, in the absence of severe primary sensory deficit and of gross aphasia, the subject did not succeed, he was considered agnostic. Remarkably enough, the patients with visual agnosia described by Stauffenberg (1914) asked for permission to palpate the object, instead of looking at it, in order to be able to give the correct name. It is very likely that many cases of visual agnosia or tactile agnosia did in fact present with a modality-specific aphasia, that is, a disturbance in sensory-verbal association limited, by anatomical reasons, to a given sensory modality.

Testing for apraxia included observation of spontaneous motor behavior, execution of verbal commands, and imitation of movements. On the basis of the split-brain experiences and related observations in human pathology, it could well be that deficient performance in one or some of these situations does not correspond to a major or minor degree of apraxia but rather to a different locus of lesion and that at least certain types of apraxia must be considered as language dependent. Geschwind’s views on apraxia have recently found an interesting confirmation in the case report of Smith (1966). This right-handed man had been subjected to a left hemispherectomy. On postoperative examination, he exhibited no sympathetic dyspraxia of the left hand when he was to carry out purposeful movements on oral command.

Sympathetic dyspraxia is frequently observed after a left-sided cerebral lesion involving the anterior part of the speech area. It is explained by the interruption of a pathway connecting the motor region of the right hemisphere with the left frontal region, where Broca’s area is located. The fact that this patient was able to carry out verbal instructions at all proves that he was understanding them with his right hemisphere. In order to perform purposeful movements on oral command, he had to establish verbal-motor associations-within one hemisphere, i.e., the remaining right half of the brain. Since the pathway needed for this association was intact, it is fully explained on an anatomical basis why this patient had no “sympathetic dyspraxia.”

A New Formulation of Old Concepts

The main stream of recent neuropsychological research has been the re-examination of the classical syndromes. The necessity to test the old data once more was the logical consequence of the growing methodological dissatisfaction mentioned above. The aim of this work was to penetrate more deeply into the description and analysis of the aphasias, of constructional dyspraxia, and of finger agnosia, to name but a few.

Moreover, evidence is accumulating that would suggest that certain of these symptoms are not unitary in nature, so that their existence must be questioned and their dependence on other basic disturbances should be evaluated experimentally.

Research in the field of aphasia had long been centered on three problems: (i) the relationship between handedness and hemispheric dominance for language; (2) the description of various aphasic syndromes; and (3) the precise localization of lesions within one hemisphere producing these types of language disorder. Only recently has a very important aspect been studied, the linguistic structure of aphasic language.

In this brief review of recent progress in this field, we exclude the problem of cerebral dominance for language and its relation to handedness since it is dealt with in another context below.

The description of aphasic syndromes depends, of course, upon the classification of various types of language disturbances that are observed clinically. Unfortunately, until now no classification has been accepted by the majority of researchers and every school has developed its own particular diagnostic scheme, which makes a comparison of the findings of different groups somewhat difficult. The spectrum extends from the Pavlovian concept, based on the assumption of specialized cortical organizations termed “analyzers” and “signalling systems,” to the holistic view that there is only one “true aphasia” accompanied to a varying degree by additional symptoms that do not intrinsically belong to aphasia proper. For a discussion of relevant theories, old and current, see Brain (1965) and Tissot (1966).

In clinical practice, the behavioral distinction between motor, or expressive, and sensory, or receptive, aphasia, suggested by Weisenburg and McBride (1935) and others before them has proven useful, especially with the mental reservation that these are not “pure” and clearly distinguished forms but rather two variants of one basic disorder having certain characteristic properties of their own and other features in common.

Recently, however, even this gross distinction has been sharply criticized (Bay, 1967), and it has been suggested that for the time being any classification be abandoned and replaced by the detailed description of deficits present in a given patient. This standpoint reflects the above mentioned uncertainty with regard to an appropriate or “natural” order of subtypes of aphasia. On the other hand, agnosticism of this type can apply only to problems of research in the field of aphasia. Clinical practice requires some pragmatic subdivision of aphasic syndromes.

Comprehensive description of aphasic speech demands broad testing of the patient’s performances, and real progress could be expected only if there existed a battery of tests agreed upon by most researchers in the field. The performance of a patient on this battery, covering most aspects of language behavior and related functions, could then be charted on a profile sheet. The similarity of performance curves in certain groups of...