28 research outputs found
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Stimulus specific cortical activity associated with ignoring distraction during working memory encoding and maintenance
Distraction disrupts Working Memory (WM) performance, but how the brain filters distraction is not known. One possibility is that neural activity associated with distractions is suppressed relative to a baseline/passive task (biased competition). Alternatively, distraction may be denied access to WM, with no suppression. Furthermore, behavioural work indicates separate mechanisms for ignoring distractions which occur (1) while we put information into WM (Encoding Distraction, ED) and (2) while we maintain already encoded information during the WM delay period (Delay Distraction, DD). Here we used fMRI in humans to measure category-sensitive cortical activity and probe the extent to which ED/DD mechanisms involve enhancement/suppression during a WM task. We observed significant enhancement of task-relevant activity, relative to a passive view task, which did not differ according to whether or when distractors appeared. For both ED and DD we found no evidence of suppression, but instead a robust increase in stimulus specific activity in response to additional stimuli presented during the passive view task, which was not seen for the WM task, when those additional stimuli were to be ignored. The results indicate that ED/DD resistance does not necessarily involve suppression of distractor-related activity. Rather, a rise in distractor-associated activity is prevented when distractors are presented, supporting models of input gating, and providing a potential mechanism by which input-gating might be achieved
Universal emission intermittency in quantum dots, nanorods, and nanowires
Virtually all known fluorophores, including semiconductor nanoparticles,
nanorods and nanowires exhibit unexplainable episodes of intermittent emission
blinking. A most remarkable feature of the fluorescence intermittency is a
universal power law distribution of on- and off-times. For nanoparticles the
resulting power law extends over an extraordinarily wide dynamic range: nine
orders of magnitude in probability density and five to six orders of magnitude
in time. The exponents hover about the ubiquitous value of -3/2. Dark states
routinely last for tens of seconds, which are practically forever on quantum
mechanical time scales. Despite such infinite states of darkness, the dots
miraculously recover and start emitting again. Although the underlying
mechanism responsible for this phenomenon remains an enduring mystery and many
questions remain, we argue that substantial theoretical progress has been made.Comment: 9 pages, 2 figures, Accepted versio
Recommended from our members
Stimulus specific cortical activity associated with ignoring distraction during working memory encoding and maintenance.
Distraction disrupts Working Memory (WM) performance, but how the brain filters distraction is not known. One possibility is that neural activity associated with distractions is suppressed relative to a baseline/passive task (biased competition). Alternatively, distraction may be denied access to WM, with no suppression. Furthermore, behavioural work indicates separate mechanisms for ignoring distractions which occur (1) while we put information into WM (Encoding Distraction, ED) and (2) while we maintain already encoded information during the WM delay period (Delay Distraction, DD). Here we used fMRI in humans to measure category-sensitive cortical activity and probe the extent to which ED/DD mechanisms involve enhancement/suppression during a WM task. We observed significant enhancement of task-relevant activity, relative to a passive view task, which did not differ according to whether or when distractors appeared. For both ED and DD we found no evidence of suppression, but instead a robust increase in stimulus specific activity in response to additional stimuli presented during the passive view task, which was not seen for the WM task, when those additional stimuli were to be ignored. The results indicate that ED/DD resistance does not necessarily involve suppression of distractor-related activity. Rather, a rise in distractor-associated activity is prevented when distractors are presented, supporting models of input gating, and providing a potential mechanism by which input-gating might be achieved