Intra and inter hemispheric dynamics revealed by reaction time in the Dimond paradigm: a quantitative review of the literature

In stimulus matching tasks requiring discrimination of two unilaterally or bilaterally presented stimuli (Dimond paradigm), a well established intrahemispheric processing bottleneck model predicts that an increase in task difficulty as measured by reaction time should provide an advantage to bilateral stimulations. The purpose of the current investigation was to review the entire relevant literature on the Dimond paradigm and identify the experimental variables which reliably yield such effects. Forty nine experimental effects compatible with the "intrahemispheric processing bottleneck" model and 26 contrary effects were found. Manipulation of the complexity of the stimulus matching criterion significantly produced intrahemispheric bottleneck effects. This effect was also significantly greater when non-target stimuli required heavier processing. These two findings support the intrahemispheric bottleneck model: computationally complex tasks seem to overload a hemisphere׳s processing capacity, an effect seen in the unilateral presentation conditions. However, manipulating the similarity of target stimuli produced contrary effects. Contrary effects were also obtained more readily when two physical matching tasks were compared. These two latter effects may best be explained as low level visual-perceptual limitations of interhemispheric transfer or integration.

Reaction Time of Erroneous Responses in the Go/No-Go Paradigm

Abstract. Reaction time (RT) of erroneous responses in go/no-go tasks tends to be shorter than RT of correct responses. An opposite difference has been reported ( Halperin, Wolf, Greenblatt, & Young, 1991 ) which could be attributed to differences in go trial probability, or to high memory demand. Two experiments aimed here to test these two explanations, a simultaneous matching task with low memory load (Experiment 1), and a sequential matching task with high memory load (Experiment 2). Go trial probability was also manipulated. Short false positive RT was obtained only in the sequential matching task with high go trial probability, while long false positive RT was obtained in the other three conditions. Low go trial probability and high memory load were both found to be sufficient, by themselves, to create long false positives attributable to confusion. Short false positives in the high go trial probability/low memory load condition were attributed to failure of response inhibition.

Affective States During the First Wave of the COVID-19 Pandemic: Progression of Intensity and Relation With Public Health Compliance Behavior

The COVID-19 pandemic was expected to cause intense affective reactions. This situation provided a unique opportunity to examine the characteristics and correlates of emotions in a real-world context with great significance. Our study aimed to describe the progression of positive and negative affective states during the pandemic, and to investigate which affective states predicted compliance with public health measures. We undertook a survey of affective states in the province of Quebec at the beginning, the peak, and the aftermath of the first wave of the COVID-19 pandemic. We recruited 530 responders; 154 responded to all three surveys. We used self-report scales to measure affective states and compliance with public health measures. We then computed separate linear regressions for the three phases of our study, with compliance with health measures as the dependent variable. Affective states were generally most intense at the beginning of the pandemic. Fear-related pandemic-related affective states reliably predicted compliance with public health measures in the three phases of our study. Positively valenced affective states related to the societal response also contributed predictive value, but only at the peak of the first wave.

Inter-hemispheric dynamics revealed by reaction time in the Dimond paradigm

The Dimond paradigm (DP) consists of tachistoscopically presenting two stimuli to be discriminated--either both stimuli in a single visual hemifield or one in each. The DP has recently been implemented using predecessors to index homotopy of the callosal fibre projection with reaction time (RT) as the dependent measure. Using simple perceptual discrimination tasks, it has recently been reported that the advantage of the unilateral stimulation condition significantly decreases with practice. This effect has been interpreted as being due to the plasticity of the callosal network. Two experiments were designed to replicate these two little-known effects, namely callosal homotopy and callosal network plasticity. In addition, new evidence of another type of callosal network plasticity, termed "callosal network dispatching", was sought by introducing double manipulation of orientations of both stimulus-contours and inter-stimulus arrays to the DP. Strong support for the callosal homotopy and callosal network plasticity effects was obtained. In addition, evidence for a "callosal network dispatcher" effect accrued.

Perceptual processing of stimuli related to an analogue traumatic event: An ERP study

Previous research has suggested that exposure to potentially traumatic events can lead to increased perceptual processing specific to trauma-related stimuli. Moreover, conceptual processing strategies during encoding may reduce the effect of trauma exposure on perceptual processing. The current study investigated the effect of a trauma film on perceptual processing with visual evoked potentials. Participants were primed with perceptual or conceptual processing strategies, then viewed a trauma film and a control film. Participants then looked at emotionally negative and neutral images that were related or unrelated to the films. The amplitude of the P1 evoked potential was measured during image presentation. P1 amplitude was more positive specifically for negative film-related stimuli. Moreover, this effect was stronger in participants primed with perceptual processing. These results suggest that potentially traumatic events increase perceptual processing specifically for trauma-related stimuli, and that conceptual encoding strategies attenuate the effect of exposure to potentially traumatic events on perception.