Rudolf Groner

Does excessive memory load attenuate activation in the prefrontal cortex? Load-dependent processing in single and dual tasks: functional magnetic resonance imaging study

Functional magnetic resonance imaging was used to investigate the relationship between cortical activation and memory load in dual tasks. An n-back task at four levels of difficulty was used with auditory-verbal and visual-nonverbal material, performed separately as single tasks and simultaneously as dual tasks. With reference to single tasks, activation in the prefrontal cortex (PFC) commonly increases with incremental memory load, whereas for dual tasks it has been hypothesized previously that activity in the PFC decreases in the face of excessive processing demands, i.e., if the capacity of the working memorys central executive system is exceeded. However, our results show that during both single and dual tasks, prefrontal activation increases continuously as a function of memory load. An increase of prefrontal activation was observed in the dual tasks even though processing demands were excessive in the case of the most difficult condition, as indicated by behavioral accuracy measures. The hypothesis concerning the decrease in prefrontal activation could not be supported and was discussed in terms of motivation factors. Similar changes in load-dependent activation were observed in two other regions outside the PFC, namely in the precentral gyrus and the superior parietal lobule. The results suggest that excessive processing demands in dual tasks are not necessarily accompanied by a diminution in cortical activity.

Attention and eye movement control: an overview

SummaryA review of recent experimental and theoretical findings is presented which relates the results of neurophysiological and psychological research on attention and eye movement to cognitive theorizing. With respect to the relation between shifts of attention and saccadic eye movements, several experiments have demonstrated that it is possible to dissociate the line of attention from the gaze direction. On the other hand, there is some indirect (although not yet conclusive) evidence that saccadic eye movements always produce a concomitant shift of attention. Another question is whether there is a moment-to-moment control of each consecutive saccade and latency or whether indirect control models (i.e. planning several saccades in advance) are more appropriate. The function of attentional processes which have to coordinate stimulus driven (bottom-up) and concept driven (top-down) mechanisms are discussed and related to some studies investigating local and global scanpaths.

Task difficulty in mental arithmetic affects microsaccadic rates and magnitudes

Microsaccades are involuntary, small‐magnitude saccadic eye movements that occur during attempted visual fixation. Recent research has found that attention can modulate microsaccade dynamics, but few studies have addressed the effects of task difficulty on microsaccade parameters, and those have obtained contradictory results. Further, no study to date has investigated the influence of task difficulty on microsaccade production during the performance of non‐visual tasks. Thus, the effects of task difficulty on microsaccades, isolated from sensory modality, remain unclear. Here we investigated the effects of task difficulty on microsaccades during the performance of a non‐visual, mental arithmetic task with two levels of complexity. We found that microsaccade rates decreased and microsaccade magnitudes increased with increased task difficulty. We propose that changes in microsaccade rates and magnitudes with task difficulty are mediated by the effects of varying attentional inputs on the rostral superior colliculus activity map.

Language-independent working memory: Evidence from German and French reading span tests

The efficiency of working memory was measured with two versions of reading span tests, written in German and in French, using German/French bilingual subjects. The correlation between German and French versions was found to be highly significant (r = 0.85). Our results indicate that the efficiency of working memory for reading is independent of language, reconfirming the results obtained by Osaka and Osaka (1992).

On the Confounding Effects of Phosphor Persistence in Oscilloscopic Displays

Phosphor persistence has been a source of confounding in studies of temporal integration in vision. We examined the confounding by assessing the effects of the persistence of two commonly-used phosphors (P15 and P31) on performance of a temporal-integration task. In one experiment we eliminated the visibility of phosphor persistence by closing two mechanical shutters upon display termination. In a second experiment we estimated the duration of phosphor persistence by displaying the image behind closed shutters which opened upon display termination. No detectable persistence was every produced by P15 phosphor. By contrast, P31 phosphor produced persistence that lasted several hundred milliseconds even when a veiling light was projected on the screen. We ascribe the earlier instances of confounding to inadequate interpretation of the technical data on phosphor decay.

Comparing reading processes on e-ink displays and print

Abstract E-book reading devices open new possibilities in the field of reading. More activities than just reading a book can be performed with a single electronic device. For a long time, electronic reading devices have not been favored because their active LCD displays used to have a relatively low contrast. The new generation of electronic reading devices differs from earlier ones in the nature of the display: active LCD displays have been replaced with displays based on e-ink technology, which has display properties closer to that of printed paper. Moreover, e-ink technology has higher power efficiency, thereby increasing battery life and reducing weight. At first sight, the display looks similar to paper print, but the question remains whether the reading behavior also is equal to that of reading a printed book. In the present study, we analyzed and compared reading behavior on e-reader displays and on printed paper. The results suggest that the reading behavior on e-readers is indeed very similar to the reading behavior on print. Participants shared similar proportions of regressive saccades while reading on e-readers and print. Significant differences in fixation duration suggest that e-readers, in some situations, may even provide better legibility.

Dubbing or Subtitling

Dubbing and subtitling are the two most common methods of translating television broadcasts or movies. Both dubbing and subtitling may present specific advantages and disadvantages. In this study, the effects of these two methods on presence, transportation, flow, and enjoyment were investigated in an experimental approach. Participants (N = 154) watched a 30-min segment of a movie. Between-subject factors were translation method (dubbing without subtitles, dubbing with subtitles in a foreign language, and original language with subtitles) and genre (drama, comedy, and thriller). Findings indicate that subtitles in a foreign language decrease feelings of spatial presence, transportation, and flow. However, the difference between dubbing and subtitling failed to reach significance. No effect of translation method on enjoyment was found. The pattern of results is equal for all genres. Further analyses showed spatial presence, transportation, and flow to be related. In addition, transportation is more strong...

Influence of diazepam and methylphenidate on identification of rapidly presented letter strings: Diazepam enhances visual masking

The effect of diazepam (0, 5, 10 mg) and methylphenidate (0, 5, 10 mg) on the identification of briefly displayed letter strings composing words was investigated. Each letter was presented for 70 ms. The interstimulus interval (ISI) between two successive letters was 10, 100 or 200 ms. The length of the words (WL) was three, five, seven or nine letters. The dependent variable was the number of correctly identified words. As predicted, strong visual masking effects, the strength of which was dependent on ISI and WL, appeared. In the 10 ms condition, diazepam at both doses, but not methylphenidate, further enhanced masking.It is suggested that the results reflect the effect of GABA on masking, and support certain psychological theories about the inhibitory neuronal pathways that are involved in masking. The human peripheral visual system is a promising model for the experimental assessment and integration of pharmacodynamic, neurophysiological and psychological observations.

Saccadic Programming With Multiple Targets Under Different Task Conditions

This study deals with the influence of higher cognitive processes on the so-called averaging ( Ottes et al., 1984 ) or global effect ( Findlay, 1982 ). Using three types of targets consisting of random dot patterns the influence of (1) various task demands, of (2) target location in the visual field and of (3) more than two simultaneously presented stimuli on the global effect was investigated. The results show that the programming of saccades is based on a hierarchical response system dependent on the complexity of stimulation and the task of the observer.

Kurz-, mittel- und längerfristige Effekte eines Trainings in phonologischer Bewusstheit und in Buchstaben-Laut-Korrespondenz auf die phonologische Bewusstheit und die Lese- und Rechtschreibleistung

Zusammenfassung: Fragestellung: Die vorliegende Studie hatte zum Ziel, die kurz, mittel- und langerfristige Wirksamkeit eines vorschulischen Trainings in phonologischer Bewusstheit und in Buchstaben-Laut-Korrespondenz, durchgefuhrt in Schweizer Mundart an einer Schweizer Stichprobe, an Hand der Outcomevariablen phonologische Bewusstheit und Lese- und Rechtschreibleistungen zu uberprufen. Methodik: Aus insgesamt 109 Kindern mit vollstandigen Datensatzen uber den Erhebungszeitraum wurde fur die statistischen Analysen eine gepaarte Stichprobe aus je 26 Kindern aus Experimental- und Kontrollgruppe extrahiert. Es wurden einerseits Effekte des Trainings auf die kurz, mittel- und langerfristige Entwicklung der phonologischen Bewusstheit untersucht, andererseits die mittleren Lese- und Rechtschreibleistungen von Trainings- und Kontrollgruppe sowie der Anteil an lese- und rechtschreibschwachen Kindern in den jeweiligen Gruppen am Ende des 1. und 2. Schuljahres verglichen. Ergebnisse: Effekte des Trainings auf die ...