A rapid technique to assess the resting states of the eyes and other threshold phenomena: The Modified Binary Search (MOBS)

Tyrrell, Richard A.; Owens, D. Alfred

doi:10.3758/bf03203817

Cited by 148 publications

(96 citation statements)

References 8 publications

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“…Subjects indicated whether the time they saw the first circle was longer or shorter than that for which the reference circle was displayed. The duration of the first circle was controlled by a modified binary search (MOBS; Tyrrell & Owens, 1988) procedure that homed in on a single matched estimate (five reversals to terminate, initial presentation random in the range 0.8-1.2 x stimulus duration). Blocks finished when the MOBS had terminated, typically after 6-20 trials.…”

Section: Figure 2 About Herementioning

confidence: 99%

Action, arousal, and subjective time

Yarrow

Haggard

Rothwell

2004

Consciousness and Cognition

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This is the unspecified version of the paper.This version of the publication may differ from the final published version. Permanent repository link: AbstractSaccadic chronostasis refers to the subjective temporal lengthening of the first visual stimulus perceived after an eye movement. It has been quantified using a duration discrimination task. Most models of human duration discrimination hypothesise an internal clock. These models could explain chronostasis as a transient increase in internal clock speed due to arousal following a saccade, leading to temporal overestimation. Two experiments are described which addressed this hypothesis by parametrically varying the duration of the stimuli that are being judged.Changes in internal clock speed predict chronostasis effects proportional to

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Section: Figure 2 About Herementioning

confidence: 99%

Action, arousal, and subjective time

Yarrow

Haggard

Rothwell

2004

Consciousness and Cognition

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“…In control trials, subjects fixated a "0" at equivalent eccentricity that changed to become the judged digit ("1") 500 ms after the subject's key press. The computer controlled the duration of the first digit by a modified binary search (MOBS) 24 procedure that "homed in" on a single matched estimate (low boundary 400 ms, high boundary 1600 ms, initial presentation random 800-1200 ms, 5 reversals to terminate). Four estimates were obtained per condition, then corrected post hoc to match the time the "1" was on screen following target foveation.…”

Section: Methodsmentioning

confidence: 99%

Illusory perceptions of space and time preserve cross-saccadic perceptual continuity

Yarrow

Haggard²,

Heal

et al. 2001

Nature

249

230

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This is the unspecified version of the paper.This version of the publication may differ from the final published version. average 72 and 139 ms respectively) to a numerical counter. The movement of the eyes was used to start the counter incrementing once every second, with the exception that the duration of the first number could be varied between 400 and 1600 ms. Subjects had to say whether the time they had seen the first digit was more or less than that for the subsequent digits (a constant 1 s). suggesting that the illusion of chronostasis is linked to the time taken to move the eyes. In fact, subjects appeared to extend the time that they thought they had seen the first target back in time to approximately 50 ms prior to the start of eye movement. Although subjects reported no awareness of the counter changing during their saccades, it is possible that they were able to use this digit shift as a cue to initiate time judgements. This would invalidate the matched times we calculated (measured from the moment the eyes actually reached the counter). However, a control experiment in which the counter was triggered either very early or very late during a large (55º) saccade showed no difference in the duration of chronostasis, despite modifying the period that the digit was actually on screen by 85 ms. Permanent repository link 3The tight coupling of the duration of chronostasis to the duration of the saccade suggests that the effect may be linked to the perceptual "gap" caused by saccadic suppression and retinal blur that occurs when we move the eyes 3,4 . However, it is possible that the illusion of chronostasis is not tightly coupled to movement of the eyes per se, but occurs because subjects also shift the locus of their visual attention at around the time their eyes move 5 . This attention shift may act as the reference point to which the target is predated. In order to test this, subjects were asked either to make the usual saccade to target or first to shift their attention to the target and then move their eyes. Figure 2a shows that the illusion of chronostasis persisted with a similar magnitude when subjects shifted their attention before moving their eyes. Control trials intermixed with the eye movement trials verified that subjects were successful in shifting the locus of their visual attention 6 . They fixated a central cross and had to saccade to a target appearing on the right or left of the screen. If they had been told to shift their attention to the correct side before the target appeared, their reaction time was faster than if they had been incorrectly cued (Fig 2b).Although chronostasis is linked to voluntary saccades, the coupling is not obligatory:there is at least one condition under which the illusion is not experienced. We designed a third experiment in which the positional stability of the target counter was systematically broken.Subjects made a saccade to target, but in some trials the computer displaced the target by up to 9 degrees during the time the eyes were moving. Under such condi...

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“…To determine phosphene thresholds for each TMS condition the intensity of V1/V2 pulse was varied according to a modified binary search (MOBS, Tyrell and Owens 1988), an adaptive threshold finding algorithm. The TMS intensity was increased or decreased according to the subject's report on the previous trial.…”

Section: Subjectsmentioning

confidence: 99%

The Perceptual and Functional Consequences of Parietal Top-Down Modulation on the Visual Cortex

et al. 2008

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The posterior parietal cortex (PPC) has been proposed to play a critical role in exerting top-down influences on occipital visual areas. By inducing activity in the PPC (angular gyrus) using transcranial magnetic stimulation (TMS), and using the phosphene threshold as a measure of visual cortical excitability, we investigated the functional role of this region in modulating the activity of the visual cortex. When triple-pulses of TMS were applied over the PPC unilaterally, the intensity of stimulation required to elicit a phosphene from the visual cortex (area V1/V2) was reduced, indicating an increase in visual cortical excitability. The increased excitability that was observed with unilateral TMS was abolished when TMS was applied over the PPC bilaterally. Our results provide a demonstration of the top-down modulation exerted by the PPC on the visual cortex and show that these effects are subject to interhemispheric competition.

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A rapid technique to assess the resting states of the eyes and other threshold phenomena: The Modified Binary Search (MOBS)

Cited by 148 publications

References 8 publications

Action, arousal, and subjective time

Action, arousal, and subjective time

Illusory perceptions of space and time preserve cross-saccadic perceptual continuity

The Perceptual and Functional Consequences of Parietal Top-Down Modulation on the Visual Cortex

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