Facilitation of pattern recognition by cuing foveation with the luminance centroid as origin of the frame of reference.

The strategy for visual information processing must vary with the specific situation. We assume that in recognition of pre-learnt letter-like patterns under time-pressure conditions, mechanisms of selective attention are involved. We propose that, with simple stimuli, foveation is to the luminance centroids of such patterns, and if normally the latter has to be computed by the brain, cuing such information should improve performance. This assumption was tested on three subjects with five stimuli. In confirmation of the working hypothesis, we found significant improvements in performance (P = 0.01 or better) for each of the stimuli, with cuing to 'relevant' as compared with 'irrelevant' sites, and also when the point of foveation was nearer to the 'nodal' site. It is concluded that in pattern recognition processes, nodal regions are computed, the luminance centroid for example, for simple pattern stimuli.

Similarity between Fourier transforms of objects predicts their experimental confusions.

Two sets of stimuli were presented tachistoscopically to 4 subjects. On each trial, a single stimulus was presented, and the subject was required to identify the stimulus by verbal response. An exposure duration was chosen such that the subject's identification performance fell within a range from faultless identification to chance guessing. The object-identification data of each subject obtained for all stimulus exposures were pooled to form an object confusion matrix. A model of visual processing based on two-dimensional spatial frequency content (Fourier transforms) was used to predict confusions among stimulus pairs. The model properties that appear to be the most essential are those that allow it (1) to account for the obvious dependence of the Fourier transform on the choice of an origin point; and (2) choose the point of origin for each object separately, irrespective of other objects of the set. The point of origin of the reference frame, in which Fourier transforms are performed, is chosen so as to minimize the low-frequency phase component for each object. A high correlation (up to .96) between confusion matrices and model interobject distances was attained. The results demonstrate that such a distance measure gives a good prediction of object confusability.

[Effect of heparin on oxidative phosphorylation and ultrastructure of rabbit heart mitochondria]. / Vpliv heparinu na okisniuval'ne fosforiliuvannia ta ul'trastruktury mitokhondrii sertsia krolia

The effect of heparin on isolated rabbit heart mitochondria was studied in usual clinical (0.25 u/ml) and higher doses. Hepain concentration 0.25 u/ml stimulated respiration in the state 4, decreased ADP/O ratio and phosphorylation rate and did not affect mitochondria ultrastructure. Higher concentration caused two-phase changes in respiration-short-time stimulation with the following inhibition, oxidative phosphorylation (respiratory control, ADP/O, phosphorylation rate) was progressively depressed and decoupled. The mitochondria ultrastructure is changed under the influence of 1.25 u/ml and of higher doses; the external membrane lost its two-layer character, the crista were converted into a small granular mass. Concentration of 1.25 u/ml transformed many mitochondria into empty vesicles.