Luna wrote that he saw his work subsequent to Vygotsky's premature death as being:
no more than a working out of the psyohological theory which (Vygotsky) constructed."(c\\e6 in Wertsch 1985 p.9)
This chapter aims to add detail to the Vygotskian framework, detail which is provided by a summary of Luria's description of connections between brain physiology and the psychology of mental functioning. This is in order to provide further guidelines to the development of an approach to assessment, and to the interpretation of results.
The Roots Of Development
Like Vygotsky Luna traced development back to two equally important roots, biological and social, which become increasingly more difficult to separate as development progresses. Although development begins with the physiological, in the course of maturation socio-cultural factors increase their influence on the development of the functional systems of the brain (Luria 1973). For example evidence from investigations with animals has shown that environmental factors can have an impact even upon the physiological structure of the brain (Ratner 1991). Experimentation in rats has shown that isolation and lack of stimulation are associated with significantly lighter brains, and less complex dendritic networks, whilst environmental stimulation has the opposite effect (Rosenzweig cited in Ratner 1991).
Development is therefore said to be a combination of a process of physiological maturation, and a product of socio-cultural influences. Luria's unique contribution to the understanding of development lies in his analysis of an important aspect of the physiological social relationship, that is of the relationship between the brain and behaviour (Hynd 1988). Luria described mental activity as a
"complex functional system effected through a combination of concertedly working brain structures, each of which makes its own contribution to the functional system as a whole. " (Luria 1973 p.38)
The understanding of the functional system was expanded through a study of the effects of damage and impairment on subsequent behaviour, for the
"functional system as a whole can be disturbed by a lesion of a very large number of zones, and also (that) it can be disturbed differently in lesions in different localisations".(Luria 1973 p.38)
Equipotentialitv vs. Localisation
Luria's analysis of the brain-behaviour relationship provides a model which is an integration of two opposing theories, Localisation and Equipotentiality (Shallice 1988). The former suggests that functions in the brain are carried out by highly specialised regions, and consequently the effect of brain damage should directly relate to the area of the damage. In support of existence of localisation of function, damage to localised cortical regions are found to produce highly specific cognitive deficits (Luria 1973). For example damage to that part of the brain known as Wernicke's area leads to receptive aphasia, whilst damage to Broca's area leads to expressive aphasia. However damage to other cortical regions do not always result in these types of highly specific deficits (Luria 1973). In direct contrast the equipotential approach suggests that the brain is not so specialised by function, and that therefore damage will result in impairments in relation to the amount of damage, rather than its specific location. In support of equipotentiality is the amount of recovery found possible following brain damage, and the relative importance of the amount of tissue damage in determining the extent and permanence of impairment (Luria 1973). As neither approach explains satisfactorily all outcomes, Luria puts forward a synthesis of the two (Luria 1973). Brain function is described as comprising of highly specialised cortical regions (localisation) connected to other cortical/sub-cortical regions through complex functional systems (equipotentiality).
Specific areas of the brain are therefore not responsible for determining entire behaviours. Rather, specific areas appear to be responsible only for components of behaviour, and need to interact with other specialised areas to produce these behaviours. The relationship between localisation, equipotentiality and damage was expressed in the following way:
"Higher mental functions may be disturbed by lesion of one of the many different links of the functional systems; nevertheless they will be disturbed differentially by lesions of different links. " (Luria 1980 p.71 ).
Indeed the accumulation of evidence relating brain structure and behaviour supports the notion of a network of systems (Shallice 1988). Recovery of function is then explained by a situation where it has been possible for a system to re organise by integrating with another system so that the behaviour in question can continue to be performed, but by a new chain. Where damage persists, the extent of damage has meant that the previously used system has collapsed, and that it has not been possible to find another system with which to re-organise (Luria 1980).
Assessment and Svndrome Analysis
Luria built up the detail of his theories through an individualised approach to assessment, which emphasises an analysis of errors, with the unit of analysis being functional systems rather than individual mental functions (Luria 1966/1980). The assessment procedures used by Luria were not standard or standardised. They varied across patients, depending upon the types of dysfunction found to be present. A wide battery of tasks was applied to each individual, additional tasks being added, as necessary, to increase the detail of the picture. Functions were tested in a variety of ways thereby determining the links operating at any one point in time. The aim of the assessment being to evaluate functional systems, and to assess the integrity of separate links (Luria 1973). Luria's methodology was therefore that of syndrome analysis. In-depth individual case studies were structured around a process oriented view of intelligent behaviour (Luria 1973). According to this approach the responses
elicited from each individual were understood to be the result of a set or sequence of processes. The pattern of abilities and the nature of the impairments giving a picture of the location and nature of the damage, and the brain's ability to overcome the deficits in functioning subsequently incurred.
Svndrome analysis: a case study
Luria gave the example of the syndrome of deficits following a lesion of local focus in the parieto-occipital region of the left hemisphere. The main consequence was impairment of the spatial organisation of perception and movement. Other deficits found included an inability to read the hands of a clock; a confusion in subtraction requiring carrying over (e.g. 31-7); and understanding complex grammatical structures. The ability to understand simpler grammatical structures and the ability to understand and play musical melodies remained unimpaired. The common factor amongst those tasks which were impaired was spatial processing, not an essential component of those which were unimpaired (Luria 1973).
Models Of Functional Systems And Models Of Development
Working in reverse, from information gleaned on a case-by- case basis, a more generalised picture was then constructed of the systemic organisation of functions. Luria describes this approach as
"an analysis of the internal structure of psychological processes and of that inner connection which unites the various psychological processes. "
(Luria 1973 p.343).
Put another way, it is a form of factor analysis using neuropsychological methods (Luria 1973). What is being determined are those processes common to a variety of tasks (the factors), which help describe the potential combinations of strengths and weaknesses of an individual, and the subsequent pattern of performance which might be observed. Information collected concerning the pattern of performance of brain damaged adults was then used to construct models of the development of mental functions and the factors, or processing strategies.
underlying them. One such example concerns the ontogenetic foundation of the concept of number {Lur\a 1973). Observations were made of the order in which number operations disappeared with brain damage in adults, and the proposal made that the reverse order would be found for the developmental sequence.
In the case of arithmetic acquisition the proposed developmental sequence in processing strategies parallels that described by Piaget (Piaget 1952), and is supported by observational data (Gaddes & Edgell 1994). The progression of stages was said to begin with visual processing, early number operations requiring the manipulation of concrete objects. Spatial processing was said to develop next, such that tasks were carried out through the perception and manipulation of spatial relationships within the material (five dots = five). This was followed by the development of conceptual processing, when reasoning is abstract, using symbolic representations of number, but even at this later stage spatial processing was found to have a dominant role to play in arithmetical operations (Luria 1966). According to Luria's model, therefore, underlying performance on arithmetical tasks is spatial synthesis, or processing.
The Two Forms Of Synthesis Or Processing. Luria postulated that spatial synthesis was one of :
"two basic forms of integrative activity of the cerebral cortex, by which different aspects of the outside world may be reflected" (Luria 1966/1980, p.74).
Different parts of the brain were implicated in these two forms of synthesis, and the specific location of lesions were found to result in different outcomes. Lesions in parieto-occipital regions, for example, were found to lead to gross impairment of simultaneous (spatial) synthesis (Luria 1973). One effect of which is, as has already been stated, poor performance on arithmetical tasks. In addition impairment in this processing capacity was also associated with poor performance in such tasks as art and map reading. In a case study described in Gaddes and Edgell (1994) of a 13 year old boy with a mild left hemiparesis, the
pattern of learning deficits found corresponded to impairment in spatial synthesis. His performance and progress at school in other areas, such as reading and writing and even algebra, were found to be unimpaired.
The factor underlying this second group of tasks, successive or temporal synthesis, is the second of the basic forms of 'integrative activity', identified by Luria as audio-verbal memory (Luria 1973). Lesions of the left temporal region, for example, have given rise to disturbances in the retention of a series of elements, organised in sequence. Associated impairments include disruption of the analysis and synthesis of speech sounds, and thus also commonly difficulties with reading and writing. Another case study presented by Gaddes and Edgell (1994) was of a child with a lesion in the left temporal lobe. The focus of his learning difficulties were poor verbal abilities exemplified by poor spelling and slow reading. He achieved considerable success in spatial tasks, however, such as mechanics and industrial drawing.
Three Principal Functional Units Of The Brain
These two forms of integrative activity were said to be only one component of mental functioning, and two other components were also isolated. Luria postulated that the brain is in fact divided into three blocks, the Principle Functional Units (Luria 1973), each contributing to a different aspect of intelligent behaviour. The blocks, or functional units, are scattered throughout large parts of the brain, and their location is determined by observing complex interactions among the various cortical zones.
1. Unit one is the arousal unit. It is located in the brain stem and the thalamus, and its main function is to regulate tone or waking. It is therefore concerned with motivation, attention and drive, and the control of excitation and inhibition. The behavioural correlates of damage to this unit will be distractibility and hyperactivity, through interference with processes of attention (Luria 1973, Das et al 1979, Gaddes & Edgell 1994).
2. Unit two is the sensory receptive/intearative unit. It is located in the occipital, temporal and parietal cortices. Its main function is information processing. It is therefore concerned with receiving, analysing, interpreting and storing information. The behavioural correlates of damage to this unit are impaired performance in specific mental activities, through interference with information processing systems (Luria 1973, Das et al 1979, Gaddes & Edgell 1994).
3. Unit three is the planning and organisational unit It is located in the frontal lobes, and its main function is to promote efficiency of behaviour. It is therefore concerned with creating intentions, and uses accumulated experience in order to plan and manage behaviour, and to guide problem solving. The behavioural correlates of damage to this unit are the application of inefficient strategies to task completion, through interference with planning behaviour, for example through a random pattern of visual search (Luria 1973, Das et al 1979, Gaddes & Edgell 1994).
The hierarchical structure of functional units
Each unit consists of three cortical zones, which are organised hierarchically, with the lowest layer being modality specific, and the highest layer cross-modal (Luria 1973).
A. The lowest layer, the primary (projection) area, consists of the centres for the reception of incoming neural impulses, and for their transmission to other zones. These are believed to record elements of experience in their raw state, as it were, not in any meaningful pattern. Each sense has its own primary projection area, the reception of visual stimuli being in the occipital lobe, and acoustic stimuli in the parietal etc.(Luria 1973).
B. The secondary cortical zones are the projection association areas, and are concerned with organisation. They contain thousands of neuronal traces built up through experience which organise the incoming messages into recognisable and meaningful perceptions and experiences. Incoming information is processed and meaning is given to the input. They are located adjacent to their corresponding primary projection areas, for example adjacent to the primary visual areas in the occipital lobe.
c.
The highest, or tertiary layers, fzones of overlappina). are concerned with integration of responses. They are located between various sensory association cortical areas, and this permits an integrated multi-sensory experience.The same developmental progression of the three functional units, and the three cortical zones, is seen both phylogenetically and ontogenetically (Luria 1973, Gaddes and Edgell 1994, Spreen et al 1995). Behavioural changes are paralleled by changes in brain structure including increasing brain weight, dendritic development and myelination (Spreen et al 1995).
The laws governing cortical maturation
The structure of the cortical zones are said to be governed by three basic laws (Luria 1973). These are:
1. The law of the hierarchical structure of cortical zones
Development is initially 'from below upward' (Vygotsky 1934/ 1986), with the development of the optimal functioning of higher cortical zones being dependent upon the integrity of the earlier zones (Luria 1973). In the course of development the higher zones come to have an increasingly dominant role in behaviour (Luria 1973). In cases of faulty development they seem to be highly vulnerable, and at greatest risk in attaining mature, normal functioning levels (Gaddes and Edgell 1994). The primary areas are not seen as so vulnerable. Following injury the re organisation of the functional systems involved appears to take place automatically and quickly, such that the patient is often not aware of the recovery process. Secondary area lesions are more intractable and require re organisation of the cerebral links. This may require specialist programmes to re train the brain to carry out behaviours in a different way (Luria 1973).
2. The law of diminishing specificity
The maturation of the primary cortical zones, and the first functional unit, takes place largely within the first twelve months of life (Spreen et al 1995). As can be seen in the description supplied above the primary zones posses maximal modal specificity. That is they are each concerned with one sensory input, visual, auditory etcetera. In the secondary unit some integration of information occurs,
and the modal specificity of the neurons reduces. These cortical zones develop more slowly, but dominate mental functions up until about six years of age. This is identified as the beginning of the third stage of brain development (Spreen et al 1995). The tertiary cortical zones are the latest to mature, and are concerned with integration of behaviour. Functioning then comes under the influence of ‘top
down' (Luria 1973). (This structural progression towards more integrated functional systems is paralleled in the changes in performance which were found in the development of concepts (Sakharov 1930/1994), described previously).
3. The law of progressive latéralisation of functions
Also changing in the course of maturation is an increasing tendency towards a latéralisation of functioning in the hemispheres of the brain (Luria 1973). The right hemisphere appears to mature earlier than the left (Goldberg & Costa 1981). In humans it is in the left hemisphere where language functions are predominantly localised, and through the course of development it is the left hemisphere which most commonly becomes the dominant hemisphere (Luria 1973).
Normal and Abnormal Development
A failure to achieve optimal performance on any task might be as a consequence of impairment in any of three functional units, arousal, synthesis or planning (Luria 1973). The details of the possible consequences of specific damage has been discussed earlier. Luria was also interested in the question of the impact of impairment upon later development, and upon the development of children with generalised learning difficulties, labelled oligophrénies {Luna 1963). In the normal pattern of development speech was said to play a central role in transforming practical interaction with the external world. When speech becomes internalised it is said to govern the development of all mental functions (Luria 1963). When impairment occurs, this development is then said to follow a qualitatively different course. Such that;
"The mentally retarded child Is sharply distinguished from the normal by the range of ideas he can comprehend and by the character of his perception of reality." (Luria 1963 p.5)
To illustrate this Luria contrasted the outcome of damage to the occipital areas, the primary mediating centres for visual experiences, incurred in adulthood or childhood. In adults the injury would lead to impairment in visual perception and to the ability to analyse and synthesize visual stimuli. As tactile and auditory analysis and synthesis were preserved, reading, for example, could continue through the substitution of different functional systems to complete these tasks, (e.g. tracing the outline of letters with the finger to read them). Luria suggests a rather negative outcome following the same injury experienced in childhood. Before the brain has matured this injury would lead to impairments additional to the loss of visual perception, as the basis on which more complex behaviours are formed would also be disturbed.
" If the perceptual world of the child remains unorganised, the speech which ordinarily develops on a foundation of clear and continuous visual perceptions cannot develop properly. The speech of the child for whom words acquired in communication do not develop in the firm basis of concrete perception, becomes empty and devoid of the necessary content. The result is that all his thinking and the suitability of his behaviour is under-developed. " (Luria 1963 p. 17)
Generalised difficulties were related to underlying anatomical changes in the brain structure, leading to the underdevelopment of the brain (Luria 1963). It was noted that:
"the brain injuries which subsequently provoke mental retardation remove the healthy foundation for future deveiopment." (Luria 1963 p.16).
Dynamic Development
The effects of injuries such as those described above are not seen as irreversible. Central to Luria's description of intellectual development are three main features: a) the importance of the physiological structure, b) the importance of the social environment, and c) the importance of language (Luria 1973). The