Stimulus-response compatibility between stimulated eye and response location: implications for attentional accounts of the Simon effect

[Abstract] One influential theory of the Simon effect, the attention-shift hypothesis, states that attention movements are the origin of spatial stimulus codes. According to this hypothesis, stimulus-response compatibility effects should be absent when attention shifts are prevented. To test this prediction, we used monocular patches of color that required left or right key-press responses. About half of the subjects could discriminate which eye was stimulated (in a subsequent task), and showed strong spatial compatibility effects between the stimulated eye and the response location. The other half of the subjects could not make a utrocular discrimination (i.e., they could not judge which eye had received monocular stimulation), but the pattern of results was the same: the fastest reaction times were observed when the stimulated eye corresponded spatially to the required response (i.e., a Simon effect). Since the subjects presumably did not move their attention (from the subject's point of view, the stimuli were presented centrally), our results indicate that spatial codes can be produced in the absence of attention shifts. These results also show that utrocular discrimination can be assessed via indirect measures that are much more sensitive than explicit measures.Ministerio de Cultura (España); PR2002–007

Vestigial auriculomotor activity indicates the direction of auditory attention in humans

Unlike dogs and cats, people do not point their ears as they focus attention on novel, salient, or task-relevant stimuli. Our species may nevertheless have retained a vestigial pinna-orienting system that has persisted as a 'neural fossil’ within in the brain for about 25 million years. Consistent with this hypothesis, we demonstrate that the direction of auditory attention is reflected in sustained electrical activity of muscles within the vestigial auriculomotor system. Surface electromyograms (EMGs) were taken from muscles that either move the pinna or alter its shape. To assess reflexive, stimulus-driven attention we presented novel sounds from speakers at four different lateral locations while the participants silently read a boring text in front of them. To test voluntary, goal-directed attention we instructed participants to listen to a short story coming from one of these speakers, while ignoring a competing story from the corresponding speaker on the opposite side. In both experiments, EMG recordings showed larger activity at the ear on the side of the attended stimulus, but with slightly different patterns. Upward movement (perking) differed according to the lateral focus of attention only during voluntary orienting; rearward folding of the pinna’s upper-lateral edge exhibited such differences only during reflexive orienting. The existence of a pinna-orienting system in humans, one that is experimentally accessible, offers opportunities for basic as well as applied science

Effects of preliminary information in a go versus no-go task

A series of studies using a GO versus No-go task examined the question of whether preliminary information available early in the recognition of a stimulus is made available to later processes before stimulus recognition is finished, a question relevant to the controversy between discrete and continuous models. Experiment 1 showed that a go resporise is faster following a cue indicating that the response probably would be required than following a cue indicating it probably would not be required. Experiments 2-7 were conducted to find out whether analogous preparation occurred when probability of the Go response was signalied by easily discriminable features of a single stimulus rather than a separate cue. The effect was observed when the easily disenminable features uniquely determined the name of the stimulus letter, but not when they merely indicated that the stirnulus name was one of two visually similar letters. These results are consistent with the Asynchronous Discrete Coding model, in which the perceptual system makes available to later processes only preliminary information corresponding to discretely activated stimulus attributes

Localization of temporal preparation effects via trisected reaction time

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Stimulus-preceding negativity is modulated by action-outcome contingency. Neuroreport 2010;21:277–81

We investigated the relationship between action-outcome contingency and stimulus-preceding negativity (SPN), a motivationally sensitive event-related potential. Neuroimaging studies have shown that insular cortex (a known source of the SPN) is more activated prior to rewards that are contingent on prior correct action than rewards that are given gratuitously. We compared two gambling tasks, one in which the participant attempted to guess the profitable key-press option (choice) and one in which rewards were simply given at random (no-choice). The SPN that developed in anticipation of feedback was larger in the choice condition, especially at right anterolateral sites. These findings suggest that the SPN specifically reflects the expectation of response reinforcement, rather than anticipatory attention toward emotionally salient stimuli

The effect of sense of agency on activity of anterior insular cortex

“Sense of agency” is a subjective sense of responsibility for an action and its outcome. Several previous studies showed that the sense of agency affects the stimulus-preceding negativity (SPN), which is thought to be generated in part by the anterior insular (AI) cortex. Although the emergence of the sense of agency appears to be closely linked to the AI, its neural correlates are still unclear. In the current study, we clarified the relationship between the sense of agency and the insular cortex by conducting two independent experiments, one with event-related potential (ERP) and one with functional magnetic resonance imaging (fMRI). In both experiments, we used the same gambling task where participants (27 for the ERP experiment and 26 for the 1.5 T fMRI experiment) were required to make a choice between two alternatives. There were different participants in the two experiments. The ERP experiment showed that the sense of agency increased the SPN amplitudes over the right prefrontal regions, suggesting the involvement of AI. Consistent with this result, the fMRI experiment revealed enhanced activities of the right anterior insular cortex due to the sense of agency. Although parallel observations in the two experiments cannot warrant causal inference, our findings support the assumption that anterior insular cortex may contribute to the effect of agency on the SPN.2021 SPR Virtual Annual Meetin