Subjective figure reversal in two- and three-dimensional perceptual space.

A permanently illuminated pattern of Mach's truncated pyramid can be perceived according to the experimental instruction given, either as a three-dimensional reversible figure with spontaneously changing convex and concave interpretation (in one experiment), or as a two-dimensional reversible figure-ground pattern (in another experiment). The reversal rate was about twice as slow, without the subjects being aware of it, if it was perceived as a three-dimensional figure compared to the situation when it was perceived as two-dimensional. It may be hypothetized that in the three-dimensional case, the process of perception requires more sequential steps than in the two-dimensional one.

Alternation of EEG alpha and non-alpha periods does not differ in open and closed eye condition in darkness.

In relaxed subjects sitting in darkness no difference in the duration of EEG alpha and non-alpha (mostly desynchronized) periods were found under conditions of open and closed eyes.

Men in extreme conditions: some medical and psychological aspects of the Auschwitz concentration camp.

The second world war ended many years ago. Most of those who survived the stay at the German concentration camp at Auschwitz have already died of the consequences of their imprisonment; those still alive are already in the last third of their life. Is there any point in returning to the experiences of those days? Consideration of the mental hygiene of former prisoners cautions us that perhaps we should not do it.

Visual stimulus threshold related to EEG alpha and non-alpha epochs.

In humans sitting in darkness with open eyes the presence of EEG alpha and non-alpha epochs was detected automatically and the threshold of detection of a dim visual stimulus was measured under both conditions. No differences in threshold were found. However, the reaction times for stimulus detection during alpha epochs were significantly longer than during non-alpha ones.

Scanning open and closed polygons.

The process of selection of target points during voluntary eye movements when contoured polygonal shapes with open and closed angles are observed was analysed in humans by means of an eye recording technique. It has been found for both types of stimuli that the majority of fixation points where located at angles and that the mean value of distribution was found to be more distant from the vertex for acute angles than for obtuse ones. In this respect a difference was found between open and closed contours.

Mental transformation in a visual recognition task.

Rectangular geometrical patterns with equal number of lines, identical relations between their vertical and horizontal components, identical angles, line crossing knots and free ends of lines were presented tachistoscopically to human subjects with a restricted recognition time caused by backward masking. Symmetrical linear transformation with respect to the Y or X axes and rotations of the patterns were performed and the correctness of their reproduction was measured in psychophysical experiments. A mental pattern transformation was a fast operation (under 100 ms) not directly linked to a graphic or a verbal expression of the results of reproduction.

Pacing of behavioral and electroencephalographic events.

Time characteristics of lateral-hypothalamic self-stimulation were analyzed in rats using point process statistics. Inter-barpressing interval distributions were usually unimodal and asymmetrical and resembled shifted exponential distribution, i.e.

Evoked response correlates of letter recognition.

The positive late wave of the average evoked responses induced by tachistoscopic presentation of single letters had a higher amplitude when the letters were correctly recognized than when they were not. The results suggest that the late positive component of VER is a correlate of complex cognitive processes engaged in object’s identification.

Alpha detection: some comments on Hardt and Kamiya, "Conflicting results in EEG alpha feedback studies".

The problem of defining EEG alpha activity, and of detecting and measuring it, is outlined. Some advantages of a threshold method are presented and compared with an amplitude-integration method. Characteristics of percent-time scoring, based upon observable alpha spindles in the waking EEG, are discussed.