**Àííîòàöèÿ:**
* Objectives:* The experimental work was designed
to find the integrated differences in EEG synchrony between normal people
and patients with disorders of schizophrenic spectrum. EEG recording have
been performed in a state of quiet wakefulness with eyes closed for three
groups of 8–15 years old adolescents: normal group (n=36) and two groups
of mental disorders in nosological categories F20 (n=23) and F21 (n=41)
according to ICD–10.** Methods: In this study we have used the
alternative method for EEG synchrony estimating based on correlation between
envelopes of EEG signals. This method was previously proven as a highly
sensitive tool of differentiation of psychopathological and functional
states.**

**INTRODUCTION**

**MATERIALS AND METHODS**

**RESULTS**
**1. Analysis of records on consistency**

a) |
b) |

** Since our analysis is carried out in 5 frequency
domains, so in order to perform the abovementioned selection, the estimates
should be used that averaged over 5 domains. In the variational series
for F20 and F21 groups (Fig. 1a) we can see the presence of outliers and
of several subgroups of different degree of consistency. Fig. 1b presents
variational series of highly consistency subgroups of F20, F21 and N subjects.
The fact draws the attention that N subgroup is characterized by less averaged
consistency (0.50) compared with F20 and F21 subgroups (0.52 and 0.55).
This confirms the conclusion [14] that a sample from a less representative
general population related to a particular type of pathology turns out
to be more consistent than a sample from a much larger population related
to psychological norm, or in other words according to winged expression:
every “healthy” man is "healthy" in its own way but every "sick" one is
sick alike.**
** It is necessary to emphasize, that in this
study not only the usual problem of differentiation of norm and pathology
was considered, but at the same time also the non–depicted earlier in literature
more complex task of detection of subtle differences between the two close
nosology. Such a formulation of the task proves advisability and necessity
for the following analysis of use of the highly consistent EEG records
(Fig. 1b): 1) F20 subgroup included 23 patients in age of 11.2±2.1;
2) F21 subgroup included 41 patients, in age of 12.2±2.0.
As anyone can see, the selected subgroups reproduce the age ratio of initial
groups in a well–balanced way, and on this basis they are also quite suitable
for the further analysis.**
** In a case of larger volume of experimental
data the second stage could be completed of the source material purification,
which consists in removal of records, synchrony profiles of which contain
two or more values exceeding three standard deviations. A simple statistical
calculation shows that probability of occurrence of such a "complex" outlier
among 36 variables of synchrony profile is 0.054.**

**2. Discriminant classification**

**3. Local relations of synchrony**

** At the topograms (Fig. 2, 3), first of all,
our attention is drawn to the crosswise area of sharp decrease in synchrony
of pathology groups ("downfall") in comparison with the norm, including
sagital?interhemispheric and axial?central segments. It’s possible that
this indicates significant violations of interhemispheric and frontal–occipital
relationships at disorders of schizophrenic spectrum. At comparison of
two pathology groups (F20–F21) in many frequency domains we also observe
distinctive regional and interhemispheric areas of increase–decrease of
synchrony.**
** Due to observed regional structure of intergroup
synchrony relations with a purpose of identification of statistically significant
patterns it is more appropriate now to consider separately interhemispheric
and averaged regional intrahemispheric ratios.**

**4. Interhemispheric synchrony**

** From comparison of the charts and
the statistical distinctions, first of all, it should be noted:**
** 1. In most cases, there can be observed a reduction
of synchrony in center–vertex–occiput direction. Jonckhreere test, which
takes an orientation of factor effect into account, reveals the existence
of such trends at ð=0.03*10^{-7} for all groups and domains
(except for F20 group in b2
domain). The reduction of synchrony in front–center direction is observed
for all groups in a domain
(ð=0.0002*10^{-7}) and for pathology groups also in q
domain (p=0.016–0.0012). This conclusion coincides with the results
of [4].**

**5. Regional intrahemispheric
differences**

**Fig. 4. Differences in interhemispheric synchrony for 5 frequency
domains ( ð=0.04–0.0004). The values averaged for each group synchrony
(vertical axes) are shown for derivation pairs: F3–F4, C3–C4, P3–P4, O1–O2
(horizontal axes). Group markers: circles – F20, squares – F21, triangles
– N. Below graphics, the designation of reliable intergroup differences
is shown in number notation: 1 – F20–F21, 2 – F20–N, 3 – F21–N.**

** From comparison of the charts and shown
statistical differences, first of all, it should be noted:**
** 1. In N group there is observed: a) approximate equality
of synchrony in frontal–central FL, FR, CL, CR region (except its decrease
in a domain, p=0.02–0.0007);
b) reduction of synchrony in the occipital OL, OR area (ð=0.048**–

**6. Regional asymmetry**

** On the one hand, these asymmetries are not
that numerous so to indicate a general pattern, on the other hand, no case
of asymmetry is revealed in N group.**

**7. Age and sex differences**

**8. Comparison with psychometric
measures**

** The proximity of estimates of EEG synchrony
to psychometric indices was assessed by Pearson correlation coefficient
r, critical value of which for those samples is r_{cr}<0.31
at p=0.05. Fig. 6 shows the identified significant correlations
with local estimates of EEG synchrony between derivation pairs in the range
of average and above average correlation values (r=0.45–0.75, p=0.03–0.008).
In addition, it is interesting to calculate correlations with the average
estimates of regional intrahemispheric synchronities as well as of differences
between them that characterize the magnitude of decrease of EEG synchrony
in CL, CR regions in relation to neighboring FL, FR, OR, OL regions**

**9. Reproducibility of results**

**Fig. 7. Differences between synchrony for N and F20 group records
discussed in [4], asterisks denote cases of significant group differences
( p=0.47–10^{-5}) : a – interhemispheric synchrony; b – regional
intrahemispheric synchrony. The remaining notation is similar to Fig. 4,
5.**

**DISCUSSION**

**REFERENCES**