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1Introduction
This paper addresses the
problem of psychological rehabilitation of children with multiple visual
impairments and deaf partially sighted children (visus 1-10%) aged 6-12
years old. Modern approach to the problem in question insists on multidimensional
and multilevel character of mental development where factors of heredity,
biological maturation, education, individual experience, and culture interact.
So we undertook a longitudinal experimental verification (1984-1996) of
complex visual perceptual training based on multidisciplinary assessment
and included medical corrective, psychophysiological, psychological and
pedagogical factors.
Previous studies have shown
the perspectives of further investigation on the problem of visual perception
development (N. Barraga, 1964, 1986; A. Kaplan et al, 1982; P. Apkarian,
1983; J. Bell, 1986; O. Backman, 1988). For many years, the problem of
sensory deprivation has been studied by L. Novikova and her colleagues
(L. Novikova, 1966, 1986; N. Zislina, 1987; L. Grigorieva, 1983, 1990;
J. Kuman, S. Fedorov et al, 1983;etc.). In infants with impaired vision
or hearing, a limitation of sensory experience was demonstrated to impair
the formation of neurophysiological mechanisms of perception. Compensation
for perceptual disorders is a critical point for a number of theoretical
and practical problems of cognitive activity formation, personality and
education of children with special needs. We think it would not be an exaggeration
that the visual perceptual system is the main perceptual system of the
brain providing a child with the greater part of external information.
Visual perception is highly responsible for a child's interaction with
the environment and plays a leading role in his/her mental development.
In this study a child's
perceptual development is considered not as an autonomous, but rather as
a systemic process closely related to maturation of some mental functions
(e.g., memory, thinking, speech, ets.). Therefore, complex visual perceptual
training (VPT) includes not only psychophysiological stimulation which
decreases deprivation effects , but also various methods of cognitive development
(e.g., visual memory, visual thinking, interrelations between sensory and
semantic domains, ets.). Systematic VPT according to curriculum special
programmes was carried out at Moscow School for Blind Children and at the
Sergiev Posad Rehabilitation Centre for Deafblinds.
2Complex Model of Visual
Perceptual Training
Active systemic perception
within the context of the proposed model was formed using realization of
several factors. Medical corrective factors implied medical treatment of
somatic defects combined with optic correction .
Psychophysiological factors
were intended for the specific activation of visual neuronal networks and
reduction of the deprivation effect by means of light stimulation . We
used dosed rhythmical stimulation of the eyes by an extensive set of images
during training lessons. It is possible that this method improves functional
state of visual centres by activating those elements of the neuronal network
which were deprivated as a result of nonuse. Besides, adequate afferent
stimulation forms some specialized cortical neuronal network, representing
neurophysiological basis for recognition processes (N. Bekhtereva et al,
1977; E. Sokolov, 1981, 1989; etc.).
It should be noted that
in organic diseases of the neurovisual system, psychophysiological factors
improve the sensory basis of recognition only partially. Long-lasting and
substantial disruption of the visual channel makes perception possible
only within a limited number of object features. Therefore, maximum mobilization
of psychological factors is required promoting functional maturation of
systemic interaction between different cortical zones of the right and
left hemispheres in ontogenesis (D Farber, 1993; T Beteleva, 1993; etc.).
Psychological factors include the formation of motivated need to see better.
Under conditions of motivated activity, corresponding activational systems
of the brain becom mobilized, this improving a state of the neuronal network
responsible for the formation of visual image.
In severe disorders of sensory
processes, perception is impossible without involvement of cognitive factor
. The development of perceptual cognitive operations includes analysis
by means of synthesis, comparison, generalization, abstraction, concretizing,
and transformation. Intensification of cognitive factor ensures active
mental processing of visual information and reconstruction of the whole
image of an object according to restricted set of perceived features.
Verbal factor seems to be
very important for the formation of speech functions (communication, definition,
generalization, abstraction ) in visual perceptual processing. This factor
ensures the formation of a system visual image incorporating both sensory
and semantic components. It is a basis of the semantic network filled with
sensory content. However, there should be principal differences in models
of perception formation between children only with visual defects and deafblinds.
If a child's hearing is normal, compensative role of the speech consists
in the control of perception, and in the formation of conceptual components
of systemic visual image. Partially formed semantic network is being filled
with concrete sensory content during VPT. Systemic development of visual
perception in deafblinds occurs in close relation with the formation of
speech and verbal thought. The word is associated with visual image being
formed to prevent formalism in thought and speech.
Experimental Verification
of Complex Model of VPT
It was assumed that in children
with multiple disabilities, visual perception has to be trained as an active,
reseaching, and forecasting ability based on special object activity.Systematical
VPT of children with multiple disabilities was conducted in accordance
with curriculum program for 3-4 years (L Grigorieva, S Stashevsky, 1990).
Diagnostic assessment procedure was carried out before and after VPT course
and during intermediate stages - at the begining and at the end of each
school-year.
Diagnostic Assessment Procedure.
Ophthalmological examination:
lowered vision was due to the damage to the retino- geniculo-striatal pathway
(postoperative aphakia of complicated congenital cataract, glaucoma, high
myopia, tapetoretinal dystrophy, partial optic atrophy, etc.). Feature
discrimination was assessed during visual on-off rhythmical stimulation
(f = 1Hz) with objects varying in colour, shape, and size.
Object recognition and short-term
visual memory (STVM) span were assessed by the method of the visual forward
(5s) and backward (400ms) masking; the duration of exposure of achromatic
stimuli was 80-240 ms.
Gollin's incomplete figures
test: a flexible, computerized version (N Foreman, R Hemmings, 1987).
Computerized method for
measuring visual perception span. A set of stimuli consisted of 10 matrices
varying in the number and disposition of target squares. Visual perception
span is characterized by a number of successfully percepted target squares
during the fixed trime span - 300ms.
We used:
a set of black- and-white
and chromatic objects for the controle evaluation of perception constancy,
Lego mosaic for visuo-operational thinking,
Raven's test for visuo-imaginative
thinking.
Training Methods.
Psychophysiological methods
are based on repetitive on-off rhythmical stimulation with flashes, gratings,
geometrical figures, and images from natural environment varying in colour,
contrast, size, orientation, shape, and location in the visual field. The
methods included: formation of visual attention; development of visuo-motor
function; correction of brightness and contrast sensitivity and reactivity;
correction of chromatic sensitivity and colour contrast; correction of
spatial and temporal resolution of black- and-white and chromatic subsystems
of the visual system; and compensation for the disorders of image recognition.
Psychological methods included
visuo-motor and visuo-imaginative tasks indispensable for the formation
of objectness; integration, detailing, apperception, constancy, anticipation,
and generalization of perception. All methods were performed by means of
special equipment (a photostimulator, a motion picture projector, PC, etc.)
and special didactic material (L Grigorieva, S Stashevsky, 1990).
Results and Discussion.
An examination of children
with multiple visual impairments before VPT revealed a substantially decreased
probability of recognition of undoubtedly suprathreshold images with strengthened
characteristics as compared to the norm. A number of recognition errors
regularly increased with a decrease of stimulus exposure. An increase in
the information load of the perceptual field (three images instead of two)
further decreased the probability of image recognition.
After the VPT course, the
probability of correct recognition of sensory features substantially increased.
This was especially evident for colour (p<0,01) and shape (p<0,05)
of images of different size. It is known that detection of sensory features
is related to the mechanisms of the visual projection system. An increase
in the probability of correct recognition of sensory features after VPT
may reflect functional improvement of the projection system. This substantiates
V. Glezer's concept that "sensory model of the world occurs due to training"
(V. Glezer, 1985, p.5).
During VPT, there occured
not only an improvement of the state of the sensory mechanisms, but also
the development of cognitive components of visual perception. Among such
components there are analysis-synthesis of the object features and decision
making. Formation of the reference image may be considered as a visual
generalization, since it contains the description of the real object invariant
for all its transformations. Perception of the novel object induces cognitive
operation, i.e., its comparison with the reference from memory.
Gollin's test repeated with
an interval of a school year showed that children of three age groups mastered
object recognition on the basis of incomplete information. Mean percent
age of contour tracing necessary for correct figure identification significantly
decreased (p<0,05). This probably shows the development of anticipation
as a compensatory mechanism for visual object recognition under a sensory
deficit. More perfect anticipation is related to the development of memory
and thinking components of visual perception.
After the completion of
VPT, the span perception substantially increased in experimental situations
which affected the opponent neuronal networks: on-and off-neurons of achromatic
subsystem and color-opponent neurons. These mechanisms play an important
part in neuronal training at higher levels of the visual system.
Constancy of the black-white
and color image perception was very low before VPT. After of three-year
training period, the constancy indices markedly increased. Current literature
evidences that higher analyses of visual stimuli, responsible for their
constant recognition, occurs in the parieto-temporo-occipital and frontal
cortical areas. Perception constancy is due to neuronal mechanisms in the
inferior temporal cortex (ITC) and ensures invariant description of the
object image (V Glezer, 1985). Deprivation retards the formation of this
mechanism, and VPT facilitates its development as evidenced by an improvement
in the perception constancy.
The STVM span substantially
increased after VPT (P<0,01). This could be due to the maturation of
ITC neuronal mechanisms responsible for the formation and memorizing of
visual images V Glezer, 1985; Miyashita Yasushi; 1993).
Substantial development
of visuo-operational thinking studied in three experimental situations
was revealed. In order to construct an intricate heterochrome image following
the sample in the visual field, a child had to analyze its spatial structure
and to reproduce it exactly. In this situation, occipito-temporal mechanisms
dealing with spatial relations between the structural elements and image
identification have to be activated (V Glezer, 1985; etc.). The lower indices
of visuo-operational thinking were obtained during picture constructing
according to the mneumonic image.This is related to weak imprinting of
complex images and poor retrieval of visual information due to structural-functional
immaturity of the temporo-parieto-occipital area (D Farber, T Beteleva,
1995; etc.). Speech control over a child's activity by the psychologist
facilitated image construction.
Indices of visuo-imaginative
thinking gradually improved after each year of VPT. In the experimental
situation, a child, first of all, had to discriminate textures via receptive
fields mechanisms of the visual projection cortex. Moreover, a child had
to compare textures and make a decision over their identity, this being
related to the activity of the occipito-temporal cortical area.
Thus, VPT promoted improvement
of the sensory processes and formation of cognitive components of visual
perception in children with multiple visual impairments.
Diagnostic assessment before
VPT revealed a lack of any basic sensory standard in memory storage of
all deaf-partially sighted children. They had very poor mental imagery
characterized by a weak development of objectness and integration and almost
did not contain the elements of labelling and abstraction.The imaginative
memory was imperceptible. Cognitive operations required for object recognition
in the case of a gross damage of sensory processes were not formed in children.
Control examinations during
the VPT showed efficient formation of sensory standards and also the development
of image recognition according to one or two features. Ready sensory standard
and mental image of the whole object and its parts provides possibility
of the formation of visual images of contour, silhouette,, and of complex
heterochromatic objects. A storage of visual standards in memory promotes
formation of the ability of object recognition on the basis of incomplete
information. The capability of an image reproduction into drawings has
been developed. The operative recollection of one or several images was
facilitated. Moreover, the ability to make up a topic picture according
to verbal description has been formed. During VPT children have been looked
for similarities and differencies of complex images showing the same objects
in different sizes, colors, displacement, etc. Such methods resulted in
development of the constancy of perception and the capability to search
of the conceptual features are general for the same class of objects. Visuo-operational
and visuo-imagenative thinking were being developed. Complex VPT partly
compensates for the communicative impairment and promotes the formation
of the relationship between imaginative and word-thought systems of psychic
of deafblind children.
Summary
An experimental verification
of the VPT complex system revealed considerable potentialities of visual
deficiency compensation through the development of neuronal plasticity
mechanisms underlying learning. An improvement in the visual perception
system as the result of long-term VPT my be caused by plasticity modification
of interneuronal connections in the networks of the visual cortex and higher
associative centres. We believe that phychophysiological and psychological
methods of this VPT complex system promote the formation of compensative
interaction between cortical areas. It may be assumed that an age from
6 to 12 years old is a relatively sensitive period in the ontogenetic development
of visual perception system involvement in cognitive activity. Thus, it
is reasonable to propose the VPT complex system as a means of reducing
deprivation and of improving functional interaction between the projection
and association cortical areas. It could be of great importance for overcoming
deviations in ontogenetic development of visual perception and other cognitive
functions in children with multiple disabilities.
Acknowledgments
We are grateful to teachers
O G Solntseva (Moscow School for Blind Children) and S V Lazarevskaya (Sergiev
Posad Rehabilitation Centre for Deafblinds) for systematical training lessons
at the primary school.
References
Apkarian P A [1983] Visual
training after long term deprivation: a case report // Intern. J.Neuroscience,
Vol.19, 65-84
Backmann O [1988] Development
of methods and training programes for different groups of visually impaired
persons: Low vision training. //Int. J.Rehab. Research, Vol. 11, N 1.
Barraga N C [1964] Increased
visual behavior in low vision children. N.Y.: Amer.Foundation for the Blind.
Barraga N C [1986] Sensory
perceptual development. // Y. Scholl (Ed). Foundations of education for
blind and visually handicapped children and youth. N.Y.: American foundation
for the Blind.
Bekhtereva NP, Bundzen PV,
Gogolitsyn UL[1977] Brain codes of psychic activity. Leningrad: Nauka,
Russ.
Bell J [1986] An approach
to the stimulation of vision in the profoundly handicapped, visually handicapped
child // The British J. of Visual Impairment, Summer, (IY:2), 46-48
Beteleva T G [1993] Functional
maturation of the perceptual system in ontogenesis. // D Farber and C Njiokiktjien
(eds) Developing Brain and Cognition. Vol. 4. Suyi Publication, Amsterdam,
60-97.
Farber D A [1993] Principles
of structural and functional brain organization in ontogenesis. Main stages
of its formation. // D Faber and C Njiokikjien (eds) Developing Brain and
Cognition. Vol 4. Suyo Pablications Amsterdam, 156-168.
Farber D A, Beteleva T G,
[1995] Visual perception development in early childhood // Fiziol. Chel.,
Vol.21, N5, p.162.
Foreman N, Hemmings R [1987]
The Gollin incomplete figures test: a flexible, computerized version //
Perception, Vol.16, 543-548.
Glezer V D [1985] Vision
and Thinking. Leningrad: Nauka, Russ.
Grigorieva L P, [1983] Psychophysiological
investigations of visual functions in normal-sighted and weak-sighted school
children Moscow: Pedagogika, Russ.
Grigorieva L P, [1990] Visual
memory under sensory-perceptual deficit //Studies of Memory. Moscow: Nauka,
171-193, Russ.
Grigorieva L P, Stashevsky
S V [1990] The main methods of visual perception development under vision
disturbances. Moscow: Acad Ped Nauk, Russ.
Kaplan A I, Egorova O G,
Molotok N A, Solntseva O G, [1982] First results of lessons on visual perception
development in children with residual vision // Defectology, N 3: 41-48.,
Russ.
Kuman J G, Fedorov S N,
and Novikova L A [1983] Study of the sensitive period in the development
of human visual system // Zh. Vyssh. Nervn. Deyat. im. I.P. Pavlova, Vol.33,
N 3, p.434.
Miyashita Yasushi [1993]
Inferior temporal cortex: where visual perception meets memory //Annu.
Rev. Neurosci., Vol 16, p.245.
Novikova L A [1966] Impact
of visual and auditory impairment on the brain function. Moscow: Prosveshenie.
Novikova L A [1986] Neurophysiological
mechanisms of visual and hearing deprivation, // Fisiol Cheloveka, Vol
12; N5, p.844, Russ.
Sokolov E N [1981] Neuron
mechanisms of memory and learning. Moscow: Nauka, Russ.
Sokolov E N, Vaitkyavichus
G G [1989] Neurointelligence: from neuron - towards neuro-computer. Moscow:
Nauka, Russ.
Zislina N N, [1987] Neurophysiological
mechanisms of visual perception disturbance in children and adolescents
Moscow: Pedagogika, Russ.