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Target Onset (target + onset)

Distribution by Scientific Domains

Psychology	50%

Selected Abstracts

Activity in the superior colliculus reflects dynamic interactions between voluntary and involuntary influences on orienting behaviour

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2008
Andrew H. Bell
Abstract Performance in a behavioural task can be influenced by both bottom-up and top-down processes such as stimulus modality and prior probability. Here, we exploited differences in behavioural strategy to explore the role of the intermediate and deep layers of the superior colliculus (dSC) in covert orienting. Two monkeys were trained on a predictive cued-saccade task in which the cue predicted the target's upcoming location with 80% validity. When the delay between cue and target onset was 250 ms, both monkeys showed faster responses to the uncued (Invalid) location. This was associated with a reduced target-aligned response in the dSC on Valid trials for both monkeys and is consistent with a bottom-up (i.e. involuntary) bias. When the delay was increased to 650 ms, one monkey continued to show faster responses to the Invalid location whereas the other monkey showed faster responses to the Valid location, consistent with a top-down (i.e. voluntary) bias. This latter behaviour was correlated with an increase in activity in dSC neurons preceding target onset that was absent in the other monkey. Thus, using the information provided by the cue shifted the emphasis towards top-down processing, while ignoring this information allowed bottom-up processing to continue to dominate. Regardless of the selected strategy, however, neurons in the dSC consistently reflected the current bias between the two processes, emphasizing its role in both the bottom-up and top-down control of orienting behaviour. [source]

Electrophysiological correlates of direct selection by color

PSYCHOPHYSIOLOGY, Issue 4 2008
Esther Vierck
Abstract We report an experiment using event-related potentials (ERPs) to study selection by color uncontaminated from selection by location. Participants monitored an RSVP sequence for a given target letter that could appear in upper- or lowercase. Prior to the sequence, a cue indicated the most likely color of the target letter. Replicating E. Vierck and J. Miller (2005), upper-/lowercase discrimination accuracy was higher following valid than invalid color cues. Within the ERPs, the target onset produced a negative component between 150 and 350 ms at occipital sites, with shorter latencies following valid than invalid cues. We also found larger amplitude components for valid than invalid color cues at central and parietal sites between 150 and 325 ms. The results not only demonstrate clear effects of color cuing on both behavior and ERPs but also suggest that the observed ERP differences between valid versus invalid trials mediate the behavioral effects. [source]

Orienting of visual attention among persons with autism spectrum disorders: reading versus responding to symbolic cues

THE JOURNAL OF CHILD PSYCHOLOGY AND PSYCHIATRY AND ALLIED DISCIPLINES, Issue 7 2009
Oriane Landry
Background:, Are persons with autism spectrum disorders (ASD) slower than typically developing individuals to read the meaning of a symbolic cue in a visual orienting paradigm? Methods:, Participants with ASD (n = 18) and performance mental age (PMA) matched typically developing children (n = 16) completed two endogenous orienting conditions in which the cue exposure time and response preparation time were manipulated within a consistent series of cue-target stimulus onset asynchronies (SOAs). Results:, Participants with ASD displayed facilitation effects at all SOAs, whereas typically developing children displayed facilitation effects only at shorter SOAs. The magnitude of the facilitation effect was greater for the group with ASD at 400ms SOA. Both groups showed similar effects of condition, with similar patterns of facilitation in both conditions. Conclusion:, Persons with ASD were not slower to read the symbolic cue, as the effect was elicited by brief cues within longer SOAs before target onset. The participants with ASD were also less efficient in using the predictability of the cues to guide responding. The difficulties of participants with ASD on endogenous orienting occur at the response selection level, not the perceptual level. [source]

Transcranial magnetic stimulation of the human frontal eye field facilitates visual awareness

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2003
Marie-Hélène Grosbras
Abstract What are the brain mechanisms allowing a stimulus to enter our awareness? Some theories suggest that this process engages resources overlapping with those required for action control, but experimental support for these ideas is still required. Here, we investigated whether the human frontal eye field (FEF), an area known to control eye movements, is involved in visual awareness. Volunteers participated in a backward masking task in which they were able to detect a target in a small proportion of trials. We observed that a single pulse of transcranial magnetic stimulation applied over the FEF shortly before the target's onset facilitated visual sensitivity; subjects were able to detect an otherwise subliminal object. These results show that modulating the neuronal activity of the FEF can enhance visual detection, thereby yielding new insights into the neural basis of visual awareness. [source]