Bisecting RT with lateralized readiness potentials: Precue effects after LRP onset

Recent work has sought to use the time at which the Lateralized Readiness Potential (LRP) first develops (LRP onset) as a temporal landmark to bisect experimental effects on reaction time (RT). Many studies have found experimental effects on the time between the signal and LRP onset, but few have found effects on the time between LRP onset and RT (LRP-RT interval). The primary goal of this study was to produce an effect on the LRP-RT interval. We employed precuing, a manipulation likely to influence motor-programming processes at the end of the RT interval. Subjects performed a 4-alternative choice-RT task in which a signal prompted a button-press with the index or middle finger on the left or right hand. Precues preceded the signals and were either informative, reducing the set of response alternatives from four to two, or uninformative. Besides RT and LRP, we also measured electromyographic (EMG) activity and the P300 ERP component. RT, P300 latency, and the interval between the signal and LRP onset were all shorter with informative than uninformative precues, but the timing of EMG activity relative to RT remained the same. Most importantly, precuing affected the LRP-RT interval. Implications for bisecting RT with LRPs and the identity of processes affected by precuing are discussed.     

Lateralization of hand-movements in patients with affective psychoses during an interview situation: An attempt at a physiological interpretation

Summary The results of video analysis of non-verbal interview behavior of patients with affective psychoses were discussed. Characteristic differences were shown for the left-right distribution of certain hand movement types in studies of normal subjects by Kimura (1973) with an essentially comparable technique. A neurodynamic interpretation of such findings was attempted. First we discussed the shortcomings of current neuropsychological interpretations and concluded that they present a challenge to establish a conceptual framework, which would permit the resolution of both neurodynamic and developmental points of view. Finally, we examined the heuristic value of such a conceptual framework. We noted that it is marked by the concept of inter-hemispheric coordination, and applied this concept to our findings as well as to hypotheses in depression research obtained by other methods.     

Models for within-proposition representation tested by cued recall

A model is presented to account for the data from incremental cuing experiments that have been carried out to identify the representation of propositions in memory. In such experiments subjects first learn a list of sentences and are afterward cued for recall with words from the learned sentences. The model proposed distinguishes between a memory structure and stimulus and response processes. The all-or-none tendency in the data is captured by a Gestalt-like memory code. The model is compared with the stochastic theory of Anderson and Bower and the fragmentation hypothesis of Jones.     

Ursachen der gegenseitigen Verdeckung von taktil dargebotenen Buchstaben: Unterbrechung,Summation oder Verzögerung?

Zusammenfassung Für die Erklärung der Verdeckung von Reizen in verschiedenen Sinnesmodalitäten mit einfacher Struktur wurden in der Literature bisher im wesentlichen zwei verschiedene Erklärungskonzepte diskutiert: Die Summationshypotheses behauptet, daß die Eindrücke von schnell aufeinanderfolgenden Reizen sich zu einer Gesamtrepräsentation überlagern, aus der die Einzelreize erschwert herauszuanalysieren sind, die Unterbrechungshypothese dagegen nimmt an, daß die Verdeckung auf eine Störung der Verarbeitung des einen Reizes durch die kurzzeitig folgende Darbietung eines weiteren Reizes zurückgeht. Zur Erklärung der gegenseitigen Verdeckung von taktil dargebotenen Buchstaben sind beide Hypothesen ungeeignet, weil sie die unterschiedliche Beeinträchtigung von Form- und Positionserkennung der Buchstaben nicht erfassen können. Deshalb wurde eine neue Hypothese aufgestellt: Die Repräsentation eines Reizes im sensorischen Register wird durch die Merkmalsanalyse des vorangegangenen Reizes kaum behindert, aber dessen Übertragung aus dem analysierenden System in das Kurzzeitgedächtnis eine bestimmte Zeit verzögert. Diese Verzögerungshypothese wurde mit einem Experiment überprüft, in dem 3 Vpn je etwa 12 Versuchsstunden lang die Erkennung von Buchstabenpaaren übten. Da die Diskrimination zwischen den Buchstaben bei taktiler Darbietung sehr viel schwieriger als bei visueller ist, wurden nur 5 Buchstaben im Experiment verwendet. Die Ergebnisse des Experiments werden durch ein mathematisches Modell beschrieben. Bezüglich der numerischen Werte der freien Parameter machen die 3 Hypothesen unterschiedliche Vorhersagen. Die Parameterschätzung ergab eine gute Übereinstimmung des Modells mit den Daten und zeigte eine Überlegenheit des Konzeptes Verzögerung für die Erklärung der gegenseitigen Verdeckung taktil dargebotener Buchstaben.

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Sources of mutual masking of tactile presented letters: Interruption, summation or delay?

Summary Two different explanations of the masking phenomenon with simple structured stimuli have been discussed in the literature: The summation hypothesis and the interruption hypothesis. The summation hypothesis maintains that the images of quickly succeeding stimuli superimpose and build up one unified representation from which the single stimuli are difficult to analyse. In contrast the interruption hypothesis assumes that masking is caused by the successive stimulus disturbing the processing of its predecessor. Both hypotheses are unacceptable for an explanation of the mutual masking of tactile presented letters where a different impairment of form and position recognition is observed. Therefore a third hypothesis was tried: The processing of a preceding stimulus hardly affects the representation of the successive one in the sensory register. Rather the transfer from the analysing system to short-term memory is delayed by a certain time. This delay hypothesis was tested by an experiment in which three subjects practiced to recognize pairs of letters for a total of 12 sessions. Since discrimination between letters is much more difficult with tactile compared to visual presentation only five letters were used as stimuli. The results are described by a mathematical model. The three hypotheses predict discrepant numerical values for the free parameters. Parameter estimation revealed a close fit between the general model and the data and showed a superiority of the delay hypothesis as an explanation of mutual masking of tactile presented stimuli.

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Für die wertvolle Beratung bei der Erstellung des endgültigen Textes danken wir besonders Herrn Professor Dr. K. F. Wender und Herr Dr. K. Nippert.