Basal ganglia participation in language pathology

Language disturbances were studied in 40 patients with well-demarcated vascular lesions of the speech-dominant hemisphere. Computerized cranial tomography was used for localization of the lesion. Special emphasis was given to the analysis of automatized speech and repetitive verbal phenomena.Subcortical infarctions with basal ganglia involvement led to transient aphasia although long-lasting abnormalities of language could be detected in these patients. Aphasia was more severe if a cortical lesion was combined with a basal ganglia lesion. Automatisms and recurring utterances occurred only with combined cortical and basal ganglia lesions. A lesion of Wernicke's area alone, without involvement of prerolandic structures or subcortical nuclei, was sufficient to produce long-lasting aphasia, whereas lesions of Broca's area alone produced only transient language disturbances. The results are compatible with a recent theory of multiple cerebral representation of function.     

Direction-specific motion thresholds for abnormal image shifts during saccadic eye movement

Eye movements were monitored and a target circle subtending an angle of 7^o was made to move during and dependent on the eye movements. Thresholds of detection of the resulting abnormal image displacements were obtained. Thresholds were low when both the eyes and the target moved either horizontally or vertically. They were higher by a factor of two or more when the eye movements and the target motions were not in the same plane. In the latter conditions, two processes account for the detection of target motion. One is a compensation process where the extent of that component of the motion of the retinal image of the target which is parallel to the eye movement is compared with the extent of the eye movement. The other process detects an angle between the plane of the target image motion and the plane of the eye movement. Our results indicate that the higher thresholds occurred when detection of this angle was required.     

Two forms of retinal disparity

The retinal disparities in stereograms where the vertical alignment of pairs of homologous points in one eye differs from that in the other eye were found to be more effective than disparities that do not involve that kind of binocular difference. The presence of such “transverse disparities” was found to shorten the time elapsed until perceived depth was reported in four instances, in two simple stereogram pairs and in two different pairs of random dot pattern stereograms. In an experiment where binocular parallax was in conflict with an effect of past experience, the presence of transverse disparities caused binocular parallax to prevail. The presumption that the amount of perceived depth depends only on the amount of disparity (provided distances from the eyes are unchanged) and not on the configuration in which it manifests itself was found not to hold in stereograms containing transverse disparities.     

The constancy of the orientation of the visual field

Evidence is presented that the perceived immobility of the environment during tilting of the head from side to side results from a compensating process. This compensating process operates well only when peripheral vision is present. An objectively stationary environment was, for instance, not perceived as immobile during head tilting when vision was confined to the macular region of the retina. The compensating process could be rapidly altered by exposure to environmental tilting during and dependent on head tilting. Such adaptation had the result that some environmental tilting that normally is perceived led to apparent immobility.     

Nieuwentijt und der teleologische Gottesbeweis

Ohne ZusammenfassungVortrag bei der Gedächtnisfeier am 31. Aug. 1954 in Purmerend     

Extent-of-motion thresholds under subject-relative and object-relative conditions

The experiment was designed to discover the threshold extent of motion at medium speeds amounting to 41, 82, and 164 min./sec., and to compare the perception of motion arising from subject-relative displacement with the perception of motion arising from object-relative displacement. Extent thresholds were found while velocity was kept constant. Different groups of ten Ss were used for each displacement velocity, and for each S the extent threshold was twice obtained by the method of constant stimuli, once under subjectrelative and once under object-relative displacement conditions. Sensitivity to brief displacements of a continuously visible target was high; average thresholds ranged from 1.0 to 4.4 min. under the various conditions employed. The thresholds were higher for subject-relative conditions and the slower displacement velocities and lower for objectrelative conditions and faster displacements.     

FACTOR ANALYSIS OF A NEUROTICISM INVENTORY

The Lidvall neuroticism inventory is comprised of 25 questions referring to symptoms presumed to be connected with manifest neurotic anxiety. It was presented to 377 persons, an unscreened group with respect to neurotic symptoms, and a factor analysis with rotation to simple structure was performed.—Four factors could be identified: (1) manifest neurotic anxiety, (2) neurotic difficulties in interpersonal relations, (3) neurasthenic symptoms and (4) obsessive-compulsive symptoms. The factor scales were correlated with Neuroticism and Extraversion in MPI. Neuroticism was shown to be a heterogeneous factor. The correlation between Factor (2) and Extraversion was high.     

Book reviews

The Chances of Explanation: Causal Explanation in the Social, Medical, and Physical Sciences Paul Humphreys, 1989 Princeton University Press x+170 pp., £12.95 (paperback) ISBN 0 691 020286 8; £25.00 (hardback) ISBN 0 69107353 8

In Search of a Better World: Lectures and Essays from Thirty Years Karl Popper London, Routledge £25.00 (hardback)

Artificial Morality: Virtuous Robots for Virtual Games Peter Danielson, 1992 London, Routledge £35.00 (hardback) ISBN 0 415 034841; £10.99 (paperback) ISBN 0 415 07691 9

A System of Pragmatic Idealism Nicholas Rescher, 1992 Princeton, Princeton University Press 335pp., $37.50 (hardback)