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logically meaningless. We do not increase our knowl- edge a bit when renaming for instance psychosomatics for “psychophysiology” (and that did really happen when the term “psychophysiology” became, due to real experimental contributions gained in this field, respect- ful). That does not mean naturally that v is unrelated to psychosomatics. In contrary it provides powerful means for analyzing the pathogenic mechanisms of psychosomatic diseases. Different applied branches of do exist. Contemporary w, however, does represent a unique and unified science characterized by consider- able knowledge on the topic a common system of concepts, specific set of methods and common method- ology. It is worth mentioning that traditions of our v@ go back to J.E. Purkyne, who belongs to those who started to analyze in an objective way subjective psychic phenomena.

References Radil-Weiss, T. (1973) Psychophysiology - an inter- disciplinary branch (in Czech). Cs. Psychologie 17: 485-491 Radil, T. (1985) Psychophysiology and its methodol- ogy. Activ. Nerv. Super. 27:131-133 Radil, T. (1988) Ontological errors from the point of view of hierarchical organization of human brain. (In Czech). Filosoficky Easopis, (in press) Radil-Weiss, T., Radilova, J. (1975) Psychophysiology its object and methodology (in Czech)&. psychologie 19:230-234

A NEW TYPE OF HUMAN VISUAL MEMORY MECHANISM REFLECTED IN BLOCK IMAGE RECOGNITION HYSTERESIS

Radil, T.*, Nyman, G., Laurinen, P., Haikonen, S. Institute of Psychology, Helsinki University, Helsinki; *Institute of Physiology, Czechoslovak Academy of Sciences, Prague

Block images (Harmon, Julesz 1973, Morrone et al. 1983), portraits and geometrical figures have been generated using two types of computer image process- ing systems.

Hysteresis in image recognition has been described (Radii et al. 1987, 1988) in the following experiments:

The subjects start to look at the image from a near position and then move away (increase spatial frequen- cy of the image) gradually until he/she can recognize its semantic meaning (in the present experiments a face or the ambiguous nature of the impossible triangle). This minimal distance has been recorded and converted into angular measures (B/deg., i.e. number of image blocks per angular degree). Then the subjects stepped slightly more away and started to move toward the display. The distance at which he/she could no longer recognize the portrait has been recorded and expressed again in B/deg. The stimulus was on during the whole experiment (with the exception of special measure- ments - see below), which has been performed in a dark room. The basic finding confirmed in two series of experiments was that the image is still seen at distances equalling approximately to the half of that being necessary for recognition before, when moving toward the display.

It is apparent that much less information is sufficient for maintaining the cognitive-semantic features of the image already recognized before. It seems to be prob- able that a specific visual memory mechanism is involved in the process of hysteresis of image recogni- tion described.

We have tried to analyze some of its features. The phenomenon is present when the subject moves away from the display with only one eye open and then approaches the image looking with the other eye. Thus the mechanism seems to be central. It is probably linked to cognitive processes underlying the semantics of the image. No similar hysteresis was found when using Snellen optotypes or sinusoidal gratings as sti- muli. The memory trace enabling to maintain recogni- tion of the semantic meaning of the image does contribute probably to the actual percept when the external stimulus becomes subthreshold. Experiments on subjects staying with covering image or replacing it by masking stimuli consisting of randomly distributed blocks of equal size proved that the trace does not disappear when not being supported by the specific sensory information represented by the image for 5 min. That also means that the mechanisms involved are different from those of iconic visual memory character- ized by a much shorter time course. Both eyes have been closed in other experiments for a part of trajectory when moving away from or approaching the display, without influencing the hysteresis markedly. It follows

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that continuous change in angular size (zooming) of the image is not a condition of the phenomenon. Approach- ing the image beyond the minimal distance of its recognition erases the specific memory trace effective- ly. It has to be still analyzed, however, whether or not this process is specific with respect to the actual image. Thus the hysteresis phenomenon can be repeated many times with the same image gaining very stable values of both distances (i.e. spatial frequencies) for the subjective onset and disappearance of the semantics of the stimulus. In pilot experiments two images (a face and the impossible triangle pattern) have been presented in succession. Hysteresis to both of them simultaneous- ly could be proved. That suggests that the storing capacity of the memory involved is considerable. In a few subjects hysteresis of block phase photographs of familiar faces (including the own face of the subject) has been tested. The results point to the possibility that they are being recognized at shorter distances (lower spatial frequencies), the hysteresis phenomenon still being present. That might mean that the hysteresis memory mechanisms are somehow linked to those of longterm visual information storage.

It might be concluded that the above experiments strongly suggest the existence of a still unknown visual memory mechanism (which might be called hysteresis memory.

References Harmon, I. D., Julesz, B. (1973) Science 180: 1194- 1197 Morrone, M. C., Burr, D. C., Ross, J. R. (1983) Nature 305: 226-228 Radii, T., Laurinen, P., Nyman, G. (1987) Activ. Nerv. Super. 29: 137-138 Radil, T., Nyman, G, Laurinen, P., Haikonen, S. (1988) Physiol. Bohemoslov. (in press)

P300 AND EMOTIONAL STATES STUDIED BY PSYCHOPHYSIOLOGICAL METHODS

J. Radilova Laboratory of Evolutionary Biology, Czechoslovak Academy of Sciences, Prague, Czechoslovakia

Psychophysiological approaches are a valuable tool in

trying to understand perceptive and cognitive processes in human brain. Among them event-related brain potentials (ERPs) - the electrical responses to external stimuli, when amplified and averaged scalprecorded EEG, provide a non-invasive method. One of the most interesting ERPs component is P3OO wave discovered by S. Sutton in 1964 (Sutton et al., 1965).

When recorded from the human scalp, it is large- amplitude, positive, late, evoked potential component which appears with the latency of about 280 ms till about 750 ms. The P300 has been studied extensively over the past 20 years mainly in experiments concem- ing human cognitive processes (Sutton et al. 1965, 1967, Donchin et al. 1974, Radilova 1982, Radilova, Radil 1982, Radilova 1988).

Forty one healthy subjects participated in the experi- ment (ranging in age from 18-45 years). A special technique was developed, based upon the DEC LAB 8/E computer, and on an electronic programming device which enabled to classify single evoked poten- tials induced by geometrical stimuli into two groups according to a binary psychological criterion and to average them separately. Using this method, adopting a modification of Miller’s “7+2” paradigm, we have found previously that when the number of simultan- eously presented items, light squares, was recognized correctly, the late positive component, the P300, was in the majority of cases of higher amplitude. In this experiment an important factor determining the differ- ence in P300 could be the subject’s certainty or uncertainty in the correctness of his judgement.

Each subject was in the present experiments seated in an armchair in a darkened, electrically and partially acoustically shielded chamber. He or she were commu- nicating with the experimenter by an Intercom device. The subjects were pretrained and instructed to remain relaxed, but watching carefully the center of the screen which was placed in front of them in the distance of 90 cm. Randomly placed white light squares (3x3 cm), numbering from 6 to 9, were projected on the screen by a Kodak-Carousel Tachistoscope. The subjects had to tell the experimenter the number of projected squares and whether they were certain or uncertain about their judgement. The experiments run usually between 9 a.m. - 1 p.m. and took about forty min. Every trial started with a warning 200 ms beep followed after 1200 ms by opening of the tachistoscope shutter for 200 ms. The total number of projected slides was 200 for each