The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform
Patrick Cavanagh - One of the best experts on this subject based on the ideXlab platform.
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Within-Hemifield Competition in Early Visual Areas Limits the Ability to Track Multiple Objects with Attention
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2014Co-Authors: Viola Störmer, George A. Alvarez, Patrick CavanaghAbstract:It is much easier to divide attention across the left and right visual hemifields than within the same visual hemifield. Here we investigate whether this benefit of dividing attention across separate visual fields is evident at early cortical processing stages. We measured the steady-state visual evoked potential, an oscillatory response of the visual cortex elicited by flickering stimuli, of moving targets and distractors while human observers performed a tracking task. The amplitude of responses at the target frequencies was larger than that of the distractor frequencies when participants tracked two targets in separate hemifields, indicating that attention can modulate early visual processing when it is divided across hemifields. However, these attentional modulations disappeared when both targets were tracked within the same hemifield. These effects were not due to differences in task performance, because accuracy was matched across the tracking conditions by adjusting target speed (with control conditions ruling out effects due to speed alone). To investigate later processing stages, we examined the P3 component over central-parietal scalp sites that was elicited by the Test Probe at the end of the trial. The P3 amplitude was larger for Probes on targets than on distractors, regardless of whether attention was divided across or within a hemifield, indicating that these higher-level processes were not constrained by visual hemifield. These results suggest that modulating early processing stages enables more efficient target tracking, and that within-hemifield competition limits the ability to modulate multiple target representations within the hemifield maps of the early visual cortex.
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Within-hemifield competition in early visual areas limitsthe ability to track multiple objects with attention
Journal of Neuroscience, 2014Co-Authors: Viola Störmer, George Alvarez, Patrick CavanaghAbstract:It is much easier to divide attention across the left and right visual hemifields than within the same visual hemifield. Here we investigate whether this benefit of dividing attention across separate visual fields is evident at early cortical processing stages. We measured the steady-state visual evoked potential (SSVEP), an oscillatory response of the visual cortex elicited by flickering stimuli, of moving targets and distractors while human observers performed a tracking task. The amplitude of responses at the target frequencies was larger than that of the distractor frequencies when participants tracked two targets in separate hemifields, indicating that attention can modulate early visual processing when it is divided across hemifields. However, these attentional modulations disappeared when both targets were tracked within the same hemifield. These effects were not due to differences in task performance, because accuracy was matched across the tracking conditions by adjusting target speed (with control conditions ruling out effects due to speed alone). To investigate later processing stages, we examined the P3 component over central-parietal scalp sites that was elicited by the Test Probe at the end of the trial. The P3 amplitude was larger for Probes on targets than on distractors, regardless of whether attention was divided across or within a hemifield, indicating that these higher-level processes were not constrained by visual hemifield. These results suggest that modulating early processing stages enables more efficient target tracking, and that within-hemifield competition limits the ability to modulate multiple target representations within the hemifield-maps of the early visual cortex.
Viola Störmer - One of the best experts on this subject based on the ideXlab platform.
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Within-Hemifield Competition in Early Visual Areas Limits the Ability to Track Multiple Objects with Attention
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2014Co-Authors: Viola Störmer, George A. Alvarez, Patrick CavanaghAbstract:It is much easier to divide attention across the left and right visual hemifields than within the same visual hemifield. Here we investigate whether this benefit of dividing attention across separate visual fields is evident at early cortical processing stages. We measured the steady-state visual evoked potential, an oscillatory response of the visual cortex elicited by flickering stimuli, of moving targets and distractors while human observers performed a tracking task. The amplitude of responses at the target frequencies was larger than that of the distractor frequencies when participants tracked two targets in separate hemifields, indicating that attention can modulate early visual processing when it is divided across hemifields. However, these attentional modulations disappeared when both targets were tracked within the same hemifield. These effects were not due to differences in task performance, because accuracy was matched across the tracking conditions by adjusting target speed (with control conditions ruling out effects due to speed alone). To investigate later processing stages, we examined the P3 component over central-parietal scalp sites that was elicited by the Test Probe at the end of the trial. The P3 amplitude was larger for Probes on targets than on distractors, regardless of whether attention was divided across or within a hemifield, indicating that these higher-level processes were not constrained by visual hemifield. These results suggest that modulating early processing stages enables more efficient target tracking, and that within-hemifield competition limits the ability to modulate multiple target representations within the hemifield maps of the early visual cortex.
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Within-hemifield competition in early visual areas limitsthe ability to track multiple objects with attention
Journal of Neuroscience, 2014Co-Authors: Viola Störmer, George Alvarez, Patrick CavanaghAbstract:It is much easier to divide attention across the left and right visual hemifields than within the same visual hemifield. Here we investigate whether this benefit of dividing attention across separate visual fields is evident at early cortical processing stages. We measured the steady-state visual evoked potential (SSVEP), an oscillatory response of the visual cortex elicited by flickering stimuli, of moving targets and distractors while human observers performed a tracking task. The amplitude of responses at the target frequencies was larger than that of the distractor frequencies when participants tracked two targets in separate hemifields, indicating that attention can modulate early visual processing when it is divided across hemifields. However, these attentional modulations disappeared when both targets were tracked within the same hemifield. These effects were not due to differences in task performance, because accuracy was matched across the tracking conditions by adjusting target speed (with control conditions ruling out effects due to speed alone). To investigate later processing stages, we examined the P3 component over central-parietal scalp sites that was elicited by the Test Probe at the end of the trial. The P3 amplitude was larger for Probes on targets than on distractors, regardless of whether attention was divided across or within a hemifield, indicating that these higher-level processes were not constrained by visual hemifield. These results suggest that modulating early processing stages enables more efficient target tracking, and that within-hemifield competition limits the ability to modulate multiple target representations within the hemifield-maps of the early visual cortex.
George Alvarez - One of the best experts on this subject based on the ideXlab platform.
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Within-hemifield competition in early visual areas limitsthe ability to track multiple objects with attention
Journal of Neuroscience, 2014Co-Authors: Viola Störmer, George Alvarez, Patrick CavanaghAbstract:It is much easier to divide attention across the left and right visual hemifields than within the same visual hemifield. Here we investigate whether this benefit of dividing attention across separate visual fields is evident at early cortical processing stages. We measured the steady-state visual evoked potential (SSVEP), an oscillatory response of the visual cortex elicited by flickering stimuli, of moving targets and distractors while human observers performed a tracking task. The amplitude of responses at the target frequencies was larger than that of the distractor frequencies when participants tracked two targets in separate hemifields, indicating that attention can modulate early visual processing when it is divided across hemifields. However, these attentional modulations disappeared when both targets were tracked within the same hemifield. These effects were not due to differences in task performance, because accuracy was matched across the tracking conditions by adjusting target speed (with control conditions ruling out effects due to speed alone). To investigate later processing stages, we examined the P3 component over central-parietal scalp sites that was elicited by the Test Probe at the end of the trial. The P3 amplitude was larger for Probes on targets than on distractors, regardless of whether attention was divided across or within a hemifield, indicating that these higher-level processes were not constrained by visual hemifield. These results suggest that modulating early processing stages enables more efficient target tracking, and that within-hemifield competition limits the ability to modulate multiple target representations within the hemifield-maps of the early visual cortex.
Robert M Nosofsky - One of the best experts on this subject based on the ideXlab platform.
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Item frequency in Probe-recognition memory search: Converging evidence for a role of item-response learning
Memory & Cognition, 2018Co-Authors: Richard M Shiffrin, Robert M NosofskyAbstract:In short-term Probe-recognition tasks, observers make speeded old–new recognition judgments for items that are members of short lists. However, long-term memory (LTM) for items from previous lists influences current-list performance. The current experiment pursued the nature of these long-term influences—in particular, whether they emerged from item-familiarity or item-response-learning mechanisms. Subjects engaged in varied-mapping (VM) and consistent-mapping (CM) short-term Probe-recognition tasks (e.g., Schneider & Shiffrin, Psychological Review, 84 , 1–66, 1977 ). The key manipulation was to vary the frequency with which individual items were presented across trials. We observed a striking dissociation: Whereas increased presentation frequency led to benefits in performance for both old and new Test Probes in CM search, it resulted in interference effects for both old and new Test Probes in VM search. Formal modeling suggested that a form of item-response learning took place in both conditions: Each presentation of a Test Probe led to the storage of that Test Probe—along with its associated “old” or “new” response—as an exemplar in LTM. These item-response pairs were retrieved along with current-list items in driving observers’ old-– recognition judgments. We conclude that item-response learning is a core component of the LTM mechanisms that influence CM and VM memory search.
Peter Dobeš - One of the best experts on this subject based on the ideXlab platform.
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Calibration of TDR Test Probe for Measuring Moisture in the Body of the Railway Substructure and its Subgrade
Civil and Environmental Engineering, 2015Co-Authors: Peter DobešAbstract:Abstract In the introduction of the paper there is characterized a way of monitoring the moisture in the railway substructure in the experimental stand, which is a part of the experimental workplace of the Department of Railway Engineering and Track Management. A substantial part of the paper is devoted to the calibration of TDR Test Probe for selected rock materials as a basic prerequisite for the determination of the actual moisture in the body of the railway substructure and subgrade.
