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Study of an old Man's Profile - Galleria degli Uffizi - Firenze
VISUAL PERCEPTION AND INFORMATIONAL PROCESSING CAPABILITY IN AGING Torna agli editoriali


Georgiy Korobeynikov

Introduction
The aging changes of psychophysiological functions are very serious and multifactorial. Modern gerontological research shows a decline in the sensory-motor reaction, deterioration of information processing and perception as well as reduction of mental capability with aging (Katzman, Tarry, 1983, Arlinger, 1989; Carella, 1990, Monk, 1990, Arbuckle, Conney, Milne & Melchior, 1994 ). However, the age-related decline of perception and information processing leads to an increased fatigue and deterioration of the cognitive functions, especially memory and thinking (Gallagher T.J., Wagenfeld M.O., Baro F., Haepers K.,1994; Falkenstein, Hohnsbein, Hoorman, 2000).

At the same time, the following physiological adaptation reactions arise which prevent the aging process. The adaptation theory of aging is based on this concept (Frolkis, 1989-1993). According to the terminology for aging development, proposed by Frolkis (1993), the whole period of human development from fertilization to human death can be viewed as the etagenesis, which includes ontogenesis, mezogenesis and geterontogenesis.

One may assume that perception and informational processing capability in the aging people are determined by the balance between aging and vitauct processes (life extension). Unfortunately, studies on the visual perception and informational processing capability in aging are lacking.

Methods
Human subjects (80 males and 90 females) belonging to the three age groups (30-39, 40-49 and 50-60 years) were examined. The visual perception and information processing were studied by a special computer test with three algorithm changes.

First algorithm.
Four digits (from 0 to 9) are presented on the computer's monitor randomly. The subjects were requested to perform a combination digit test, the task was to calculate (in mind) the number of digits transposed on the display. The aim of each presented digits road was to transpose in the increasing order.

For example:

5 2 3 4 -initial order
2 5 3 4 - first transposition
2 3 5 4 -second transposition
2 3 4 5 - final transposition, the result.

Thus, the result of this task consists of "3" transpositions which need four digits on the display in the increasing order. To answer, a person must press the computer's key "3".

Second algorithm.
Four digits (from 0 to 9) are presented on the computer's monitor randomly. The subjects were requested to perform a combination digit test, the task was to calculate (in mind) the number of digits transposed on the display. The aim of each presented digits road was to transpose in the decreasing order.

For example:

0 4 7 8 -initial order
0 4 8 7 - first transposition
0 8 4 7 -second transposition
8 0 4 7 -third transposition
8 0 7 4 -fourth transposition
8 7 0 4 -fifth transposition
8 7 4 0 -final transposition, the result.

Thus, the result of this task consists of "6" transpositions which need four digits on the display in order to calculate (in mind) the number of digits transposed on the display in the decreasing order. To answer, a person must press the computer's key "6".

Third algorithm.
Seven digits (from 0 to 7) are presented on the computer's monitor randomly. In each figure, one digit is absent. The subjects were requested to find a missing digit among the following seven digits.

For example:

0 4 7 6 5 1 2

The result of this task consists of digit "3", which is missing in this row. To answer, a person must press the computer's key "3".
The time and the accuracy of performing each assignment were registered for each person. The duration of a whole informational process was 9 minutes (3 minutes for each test). The used model of visual perception and informational processing was submitted as part of the computer's system of psychophysiological capacity diagnosis (Polyakov, Burov, Korobeinikov, 1993).
Based on the testing results, the following psychophysiological parameters were determined: attention volume (AV) and operational thinking coefficient (OT):

AV = (Nr / N)* 100% (1)

where
Nr - the number of tasks performed successfully,
N - the number of all tasks performed.

OT = (Nr / T)* 100 (2)

where

T - average time of solving a test problem (msec).
100 - coefficient.

For the evaluation of time perception, we used a modified "individual minute" test proposed by Halberg, 1978 (time perception error, T).

The memory function was determined by using a method for measuring short-term memory volume (MV), which consists in estimating the correctly memorised digits among twelve two-digit figures presented for a subject on a display within 30 s.
The use of traditional statistical methods analysis for study of the visual perception and informational processing capability in aging was insufficient. The application of informative mathematical methods to the study of these processes was more correct. The information processing was studied by informative mathematical methods. According to entropy of systems by C.Shannon, (1948) and Glushkov V. (1974), Glushkov has proposed the self-organisation theory. One of the major parameters of the system organisation (as a reflection of the information processing) is the following organisation measure:

(3)

where

R - measure of system organisation (by Glushkov, 1963);
H - current entropy;
Hm - maximum entropy.
The current entropy was determined by Shannon C.:

(4)

where

Pi - probability of i-state system;
n - number of system states.
Probability of i-state system in informational processing was determined:

(5)

where

Nc - number of correct information processing;
N - number of total information processing.
Maximum entropy was determined:

Hm = log n, (6)

The number of system states for visual information processing was determined as maximum number of one information processing stimulus (according to first and second algorithm n = 6N, for third algorithm n = N).

Results
The results of the study are presented in Table 1. It is seen from the table that average data on the attention volume (AV), short-term memory volume (MV), and operational thinking (OT) are higher in men than in women. The time perception error ( T) is greater in women vs. men. These data indicate the better cognitive functioning in terms of perception, attention, memory and thinking in men compared to women. The values for aging differences between study parameters (AV, MV and OT) are lower in male subjects aged 50-60 in comparison with their 30-39-year old counterparts (p<0,05). The statistically significant differences are seen in OT values between 40-49- and 50-60-year old male groups (Table 1).
This circumstance points to the age-related decline in visual perception and informational processing capability in men.

The dynamics in women differs from that of men. The statistically significant differences between 30-49- and 50-60-year old female groups are observed for the OP and T values (p<0,05). The AV is decreased at age range 50-60 compared to 40-49 (Table 1).
No differences concerning the OT are seen between women in groups aged 30-39 and 40-49 years (Table 1).

Table 1
Psychophysiological parameters in different age and sex groups

* - p < 0,05 compared to the men;
x - p < 0,05 compared to the previous age group.

Thus, aging is associated with the reduction of psychophysiological functioning, visual perception and informational processing capability in women, but these changes have not appeared to be statistically significant in men, especially between age groups 30-39 and 40-49.
The information processing has the probability of change in the input parameters, if we understand the organisation as an entropy system from chaos to higher determinism (Shannon, 1948). To study these class systems, we used the mathematical methods from the informational theory (Antomonov, 1969; Glushkov, 1963).
The organisation measure of information processing in different age and sex groups is presented in Table 2 (men) and Table 3 (women).

Table 2
The organisation measure of information processing in men of different age groups

*-p < 0.05 compared to the first algorithm;
x - p < 0.05 compared to the previous age group.

The data presented in the above tables show a tendency to the increase of organisation measure with changing of the algorithm. This indicates a greater determinism of psychophysiological organisation during adaptation to visual information processing. A more simplified information processing structure, which includes the third algorithm, was defined as the automatically type. Statistically significant reduction of the organisation measure in the second algorithm, compared to the first one (p < 0,05), observable in the male group aged 40-49 years was the exclusion (Table 2).
At the same time, the organisation measure of information processing decreased with increasing age as the algorithm changed. This points to a decrease of the determinism and an increase of the stochastic organisation of the information processing system.
The information processing stochastic organisation provides a search for links, which are needed for the formation of an optimal level of functional system (Korobeynikov, 1998, 1999). Thus, the stochastic organisation of information processing system shows one of the forms of adaptation mechanisms, which prevents aging reduction of mental capability. This conclusion confirms the adaptation theory of aging proposed by Frolkis (1993).

Table 3
The organisation measure of information processing in women of different age groups

*-p < 0.05 compared to the first algorithm;
x - p < 0.05 compared to the previous age group.

However, the organisation measure evaluates the probability of different psychophysiological states, but it does not evaluate the operational structure of information processing.
Several authors (Sternberg, 1969, Rotenberg, 1987, Leonova, 1984, Chaichenko, Tomilina, 1994) have established the linear mathematical relation between time reaction and the number of correct information processing. The results of this investigation are opposite to their findings, but they are consistent with the data of Wickelgren (1977), presenting the speed accuracy tradeoff as a negative accelerating exponential curve. The following exponential model reflects the dependence of the latent time of solution of a test problem on the correct sequence of tasks to be performed:

Lg Y = a - bX, (7)
or
Y = exp(a - bX), (8)

where

Y - time of solving a test problem (msec)
X - number of tasks performed successfully.

According to the data of Sternberg (1969), Leonova (1984), Rotenberg (1987), Chaichenko, Tomilina (1994), coefficient a corresponds to the protraction of information processing (perception, processing and motor reaction). Table 4 depicts a coefficient a of a mathematical model information processing. The changes of task algorithm result in the decline of coefficient a. This dynamics corresponds to the increase of determinism of information processing organisation.

Thus the reduction of perception and visual information processing protraction is connected with strength of psychophysiological organisation determinism.

The increase of visual information processing protraction reflects the weakening of psychophysiological organisation determinism with age.

According to the concept of short-term memory activity (Sternberg, 1969, Leonova, 1984, Rotenberg, 1987, Chaichenko, Tomilina, 1994), the information processing has two strategies of response organisation.

The first strategy - successive comparison of positive elements in short-term memory and test information by exhaustive quest. When it is necessary, long-term memory for comparison of information can be used.

Table 4
Coefficient a of mathematical model information processing with change of the algorithm in different age and sex groups

The second strategy - processing by self-finishing quest with a comparison between positive elements of short-term memory, in accordance with the element in test information.
The first strategy of response organisation is more efficacious than the second one, but it has higher protraction of one information processing stimulus. Due to the increase in the number of erroneous responses and the repetition of information processing stimuli, the second strategy will have a longer protraction of the information processing.
number of tasks

Table 5
Average time of solving a test problem and number of tasks performed successfully in different age and sex groups

*-p < 0.05 compared to the first algorithm;
x - p < 0.05 compared to the previous age group.

Thus our data confirm the conception of short-term memory processing (Sternberg, 1969; Band Guido, Kok, 2000). Table 5 depicts the average parameters of efficacy of visual perception and information processing capability of different age and sex groups. As it is seen in Table 5, the visual perception and information processing capability depends on the strategy of response organisation.

The strengthening of determinism of information processing organisation under the influence of algorithm changes was observed in age group 30-39 (Table 2, 3). The information processing by exhaustive quest is present in this age group (Table 4). The increase of visual perception and information processing capability results in such response organisation (Table 5).

The acceleration of involution process in age group 40-49 results in decline of the perception and information processing. At the same time, the decrease of determinism of information processing organisation is shown with the first algorithm performed in women and with second and third algorithms performed in men. There are changes of response organisation strategy by self-finishing quest along with reduction of protraction of one information processing stimulus in women group 40-49 (Table 4).

The result of this response organisation shows the stabilisation of visual perception and information processing capability (Table 5). Besides, there are no statistically significant differences between women age groups 30-39 and 40-49 for parameters: attention volume, short-term memory volume and operational thinking coefficient.

The increase of stochastic organisation of visual information processing has been seen in age group 50-60 (Table 2 and 3). This finding corresponds to the strategy of self-finishing quest response in short-term memory, in accordance with the elements of test information. However, the number of correct processing stimuli decline with not reliable changes of the average time of solving a test problem in age group 50-60 (Table 5). At the same time, no changes in the operational thinking coefficient between female age groups 40-49 and 50-60 have been found (Table 1).

Discussion
In our previous studies the concept of psychophysiological stochastic organisation in the mental activity was substantiated (Korobeynikov, 1998,1999,2001). According to this concept, the psychophysiological stochastic organisation is a mechanism for the quest of optimal mental activity. In the process of aging involution, the adaptative-compensatory mechanisms of decline of visual perception and information processing capability protection get activated. One of these mechanisms is linked with the psychophysiological stochastic organisation.

With age-related decline of perception and information processing intensifies tension of the informational environment on older people. As a result of the negative influence of aging, the efficiency of the mental activity reduces. Decrease of the visual perception and information processing capability with age triggers a compensation of the psychophysiological adaptive mechanisms with the change of an algorithm. The key mechanism consists in the increase of the stochastic organisation of information processing and change of the information processing structure into a self-finishing quest response.
Strengthening of the determinism organisation of information processing reflects an aging advancement and a decline of cognitive functions, particularly the operational thinking.

The study has revealed a tendency to the increase of determinism organisation along with the simplification of information processing structure. The reduction of information processing protraction is related with the high determinism of psychophysiological organisation.

Increase of the determinism of information processing organisation and change of the information processing strategy reflect the psychophysiological mechanisms of life extension in the aging involution of cognitive functions.

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