Untersuchungen und Überlegungen zur Richtungswahrnehmung bei willkürlichen sakkadischen Augenbewegungen

Zusammenfassung Die vorliegende Arbeit hatte das Ziel, die Umstimmung der retinalen Raumwerte während willkürlicher horizontaler Blicksprünge (Sakkaden) zu untersuchen.Die Methodik bestand darin, während oder nach der Augenbewegung kurzzeitig einen ca. 1° großen Lichtreiz (Elektronenblitz) im Gesichtsfeld der Vp zu exponieren, den diese in bezug auf eine kopffeste Skala zu lokalisieren hatte. Die Auslösung des Lichtreizes erfolgte auf elektrookulographischem Weg durch die Augenbewegung selbst.Bei diesen Versuchen traten in systematischer Abhängigkeit vom retinalen Ort des Reizes und von der zwischen Sakkadenbeginn und Reizexposition verstrichenen Zeit deutliche Verlagerungstäuschungen auf. Sie lassen sich am besten interpretieren, wenn man die Umwertungsprozesse als Wanderung eines lokalisatorischen Bezugssystems über ein zentralnervöses Projektionsfeld der Retina auffaßt. Diese Wanderung wird eingeleitet und angeführt durch ein rasches Einschwingen der Koordinate des Zielpunktes der Blickbewegung in die Fovea; in der zielabgekehrten Netzhauptperipherie vollzieht sich die Umwertung wesentlich langsamer. Dabei kann es vorübergehend zu topologischen Veränderungen des Bezugssystems kommen, deren Genese noch unklar ist.Ausgehend von den bislang vorliegenden Ansätzen zur Erklärung der Richtungskonstanz (insbesondere vom Reafferenzprinzip, den Aufmerksamkeitstheorien und der Theorie MacKays) wird ein eigenes Modell entwickelt, in dessen Rahmen die Versuchsergebnisse diskutiert werden.

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Investigations and considerations of directional perception during voluntary saccadic eye movements

Summary This investigation attempts to examine the change of retinal local signs during voluntary horizontal saccadic eye movements. The method used was to expose the S. to a short light stimulus (electronic flash) of approximately one degree angular width during or after a 16 degree eye movement. The stimulus was released by the eye movement itself via the retino-corneal potential. The S.'s task was to localize the stimulus on a fixed luminous scale.Clear translatory illusions occurred in these experiments. They depended systematically on the spot on the retina stimulated, and on the time elapsed between the onset of the saccade and the release of the stimulus. These illusions are best interpreted as due to the shift of a coordinate system across the retinal field. The shift is initiated by the coordinate of the retinal spot on which the target of the eye movement was projected before the saccade began. This coordinate rapidly swings into the fovea. The processes on the retinal hemisphere opposite to the target occur at a much slower rate. Moreover, temporary changes of the topology of the coordinate system may take place during the saccade. Their origin is still unclear.The results of the experiments are discussed in terms of a special model based on the previous explanations of the phenomenon of directional constancy (especially the reafference principle, the attention theories, and MacKays theory).

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Diese Arbeit wurde mit Unterstützung der Deutschen Forschungsgemeinschaft ausgeführt. Wir danken unseren Versuchspersonen für ihre ausdauernde Mitarbeit sowie Frau Dipl.-Psych. Doris Bischof, Herrn Peter Heinecke und Frau Dr. Maria V. Schaetz für ihre Hilfe bei der Durchführung und Auswertung der Versuche.     

Conditioning,sensations, and the ergotropic-trophotropic balance

Analysis of Pschonik’s work on conditioning and sensation, in the light of Gellhorn’s studies on the tuning of the central nervous system through changes in the ergotropic-trophotropic balance, leads to the following results. Vasomotor and sensory reactions (VSR) induced by stimulation of cutaneous warmth and pain receptors (US), or by the conditional stimulus (CS) reinforced by the US, show parallel changes in a variety of circumstances: 1) anesthesia of the skin abolishes the effect of the US but not that of the CS; 2) various procedures lead to a reversal of VSR in the conditioned state in response to the US; 3) in a near-neurotic state VSR may be abolished while the plethysmogram gives evidence that ergotropic and trophotropic discharges occur at the same time. Changes in the ergotropic-trophotropic balance at the hypothalamic level alter VSR quantitatively and qualitatively. In an ergotropicallytuned state not only ergotropically-acting stimuli, but also trophotropically-acting stimuli lead to vasoconstriction and pain. Thus, stimulation of pain receptors, as well as stimulation of warmth receptors, produces vasoconstriction and pain. Similarly, these stimuli effect vasodilatation and warmth in the trophotropically-tuned state. It is concluded that the ergotropic-trophotropic balance has a profound influence on sensations and perceptions. It is of clinical significance that this balance can be altered through a conditional reflex mechanism,i.e., on the basis of individual experience.     

The role of analogy in transfer between similar problem states

The study investigated the effect of transfer between two problems having similar (homomorphic) problem states. The results of three experiments revealed that although transfer occurred between repetition of the same problems, transfer occurred between the Jealous Husbands problem and the Missionary—Cannibal problem only when (a) Ss were told the relationship between the two problems and (b) the Jealous Husbands problem was given first. The results are related to the formal structure of the problem space and to alternative explanations of the use of analogy in problem solving. These include memory for individual moves, memory for general strategies, and practice in applying operators.     

Functional neuroimaging of autistic disorders

Functional neuroimaging methods hold promise for elucidating the neurobiology of autistic disorders, yet they present difficult practical and scientific challenges when applied to these complex and heterogeneous syndromes. Single-state studies of brain metabolism and blood flow thus far have failed to yield consistent findings, but suggest considerable variability in regional patterns of cerebral synaptic activity. Patients with idiopathic autism are less likely to show abnormalities than are patients with comorbid illness or epilepsy. Activation studies have begun to suggest alterations in brain organization for language and cognition. Neurotransmitter studies using positron emission tomography (PET) suggest abnormalities of serotonergic and dopaminergic function. Studies using magnetic resonance spectroscopy (MRS) have begun to document metabolic deficits in the frontal cortex and cerebellum. A single study using magnetoencephalography suggests a high incidence of epileptiform activity in children with autistic regression. Research needs include well-controlled developmental studies, particularly of young subjects and relatively homogeneous subgroups, which balance scientific rigor with ethical constraints. Investigations of the serotonergic and dopaminergic systems, limbic-based memory and emotional systems, and the role of epileptiform activity in autism represent priorities for future research.     

Tonic Activity Level in the Right Prefrontal Cortex Predicts Individuals' Risk Taking

ABSTRACT— Human risk taking is characterized by a large amount of individual heterogeneity. In this study, we applied resting-state electroencephalography, which captures stable individual differences in neural activity, before subjects performed a risk-taking task. Using a source-localization technique, we found that the baseline cortical activity in the right prefrontal cortex predicts individual risk-taking behavior. Individuals with higher baseline cortical activity in this brain area display more risk aversion than do other individuals. This finding demonstrates that neural characteristics that are stable over time can predict a highly complex behavior such as risk-taking behavior and furthermore suggests that hypoactivity in the right prefrontal cortex might serve as a dispositional indicator of lower regulatory abilities, which is expressed in greater risk-taking behavior.     

What Fitness Can’t Be

Recently advocates of the propensity interpretation of fitness have turned critics. To accommodate examples from the population genetics literature they conclude that fitness is better defined broadly as a family of propensities rather than the propensity to contribute descendants to some future generation. We argue that the propensity theorists have misunderstood the deeper ramifications of the examples they cite. These examples demonstrate why there are factors outside of propensities that determine fitness. We go on to argue for the more general thesis that no account of fitness can satisfy the desiderata that have motivated the propensity account.     

Does contingency awareness mediate the influence of emotional learning on the cueing of visual attention?

Previous research has indicated that conditioning depends on contingency awareness (CA). However, we argue that these studies have examined this issue under methodological conditions that might be insensitive to associative learning without CA. In the present study we examined the effect of an experimental manipulation of CA on attentive processing of classically conditioned stimuli, which is sensitive to associative learning with and without CA. We found that aversive conditioning with additional contingency instructions modulated visual attention, in the sense that the conditioned cues captured and held attention more strongly than the non-conditioned cues. Surprisingly, conditioning under conditions of restricted CA yielded a response pattern that was different from that under full CA. These findings suggest that conditioning with full and restricted CA can lead to qualitatively different effects on attention.