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Expectation Suppression in Early Visual Cortex Depends on Task Set.

St John-Saaltink E, Utzerath C, Kok P, Lau HC, de Lange FP - PLoS ONE (2015)

Bottom Line: Stimulus expectation can modulate neural responses in early sensory cortical regions, with expected stimuli often leading to a reduced neural response.In the third task, the predictable stimulus was task-relevant, and therefore spatially attended.When the grating was task-relevant and spatially attended, there was no significant effect of expectation in early visual cortex.

View Article: PubMed Central - PubMed

Affiliation: Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, the Netherlands.

ABSTRACT
Stimulus expectation can modulate neural responses in early sensory cortical regions, with expected stimuli often leading to a reduced neural response. However, it is unclear whether this expectation suppression is an automatic phenomenon or is instead dependent on the type of task a subject is engaged in. To investigate this, human subjects were presented with visual grating stimuli in the periphery that were either predictable or non-predictable while they performed three tasks that differently engaged cognitive resources. In two of the tasks, the predictable stimulus was task-irrelevant and spatial attention was engaged at fixation, with a high load on either perceptual or working memory resources. In the third task, the predictable stimulus was task-relevant, and therefore spatially attended. We observed that expectation suppression is dependent on the cognitive resources engaged by a subjects' current task. When the grating was task-irrelevant, expectation suppression for predictable items was visible in retinotopically specific areas of early visual cortex (V1-V3) during the perceptual task, but it was abolished when working memory was loaded. When the grating was task-relevant and spatially attended, there was no significant effect of expectation in early visual cortex. These results suggest that expectation suppression is not an automatic phenomenon, but dependent on attentional state and type of available cognitive resources.

No MeSH data available.


Related in: MedlinePlus

Experimental paradigm.(A) During each of the three tasks, stimuli were presented in predictable and non-predictable blocks, alternating every 12 trials. Each trial started with an auditory tone that either perfectly predicted the orientation of the subsequent grating stimulus (45° or 135°), or carried no orientation information. (B) Participants performed two tasks on the stimuli in the fixation bull’s-eye. During the perceptual task, targets were 1-back letter repetitions (the magenta ‘N’ is a target) that were difficult to perceive due to added noise. During the working memory task, targets were 2-back colour repetitions (the blue ‘H’ is a target) that were easy to perceive (as the whole inner ring has the same colour) but taxed the working memory system more strongly than the 1-back task. During the grating task, participants responded to the spatial-frequency of the grating stimuli. Targets had lower spatial-frequency than non-targets. (C) Pairing between auditory tones and grating orientations. In predictable blocks, tones predicted grating orientation with 100% accuracy. In non-predictable blocks, the tones provided no orientation information. ITI = inter-trial interval.
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pone.0131172.g001: Experimental paradigm.(A) During each of the three tasks, stimuli were presented in predictable and non-predictable blocks, alternating every 12 trials. Each trial started with an auditory tone that either perfectly predicted the orientation of the subsequent grating stimulus (45° or 135°), or carried no orientation information. (B) Participants performed two tasks on the stimuli in the fixation bull’s-eye. During the perceptual task, targets were 1-back letter repetitions (the magenta ‘N’ is a target) that were difficult to perceive due to added noise. During the working memory task, targets were 2-back colour repetitions (the blue ‘H’ is a target) that were easy to perceive (as the whole inner ring has the same colour) but taxed the working memory system more strongly than the 1-back task. During the grating task, participants responded to the spatial-frequency of the grating stimuli. Targets had lower spatial-frequency than non-targets. (C) Pairing between auditory tones and grating orientations. In predictable blocks, tones predicted grating orientation with 100% accuracy. In non-predictable blocks, the tones provided no orientation information. ITI = inter-trial interval.

Mentions: Stimuli were generated using MATLAB (MathWorks, Natick, MA, US) in conjunction with Psychophysics Toolbox [13]. In the behavioural session, stimuli were displayed on a Samsung SynchMaster 940BF monitor (60 Hz refresh rate, 1280 X 1024 resolution). In the fMRI session, stimuli were displayed on a rear projection screen using a luminance-calibrated EIKI projector (60 Hz refresh rate, 1024 X 768 resolution) which participants viewed through a mirror. A fixation “bull’s-eye” (outer ring 0.8° of visual angle) was presented at the centre of a gray background throughout each task. On each trial, a grating annulus (outer diameter: 15° of visual angle; inner diameter: 2°) of luminance-defined sinusoids at 80% contrast was displayed around the fixation bull’s-eye (200 ms; Fig 1A). Gratings were oriented at either 45° or 135°, with a phase randomly selected from 10 possibilities, evenly spaced between pi and 2pi. To mitigate afterimages, the phase of the grating was inverted halfway through stimulus presentation. On each trial, gratings had one of two possible spatial frequencies (mean: 1.5 cpd), with the specific spatial frequency values set for each individual by a staircasing procedure (see below). Simultaneously with the grating presentation, coloured letters were presented in the centre of the fixation bull’s-eye, with noise of the same colour superimposed (Fig 1B). Six letters (A, H, N, R, T, Z) and six colours (red, blue, green, cyan, yellow, magenta) were used. The number of coloured pixels that degraded the letters was similarly set by a staircasing procedure. The titration of these stimulus parameters for each subject ensured that tasks were matched on difficulty. Auditory cues that were played before each stimulus consisted of four pure tones (329, 440, 493 and 659 Hz) that were played for 200 ms.


Expectation Suppression in Early Visual Cortex Depends on Task Set.

St John-Saaltink E, Utzerath C, Kok P, Lau HC, de Lange FP - PLoS ONE (2015)

Experimental paradigm.(A) During each of the three tasks, stimuli were presented in predictable and non-predictable blocks, alternating every 12 trials. Each trial started with an auditory tone that either perfectly predicted the orientation of the subsequent grating stimulus (45° or 135°), or carried no orientation information. (B) Participants performed two tasks on the stimuli in the fixation bull’s-eye. During the perceptual task, targets were 1-back letter repetitions (the magenta ‘N’ is a target) that were difficult to perceive due to added noise. During the working memory task, targets were 2-back colour repetitions (the blue ‘H’ is a target) that were easy to perceive (as the whole inner ring has the same colour) but taxed the working memory system more strongly than the 1-back task. During the grating task, participants responded to the spatial-frequency of the grating stimuli. Targets had lower spatial-frequency than non-targets. (C) Pairing between auditory tones and grating orientations. In predictable blocks, tones predicted grating orientation with 100% accuracy. In non-predictable blocks, the tones provided no orientation information. ITI = inter-trial interval.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4476778&req=5

pone.0131172.g001: Experimental paradigm.(A) During each of the three tasks, stimuli were presented in predictable and non-predictable blocks, alternating every 12 trials. Each trial started with an auditory tone that either perfectly predicted the orientation of the subsequent grating stimulus (45° or 135°), or carried no orientation information. (B) Participants performed two tasks on the stimuli in the fixation bull’s-eye. During the perceptual task, targets were 1-back letter repetitions (the magenta ‘N’ is a target) that were difficult to perceive due to added noise. During the working memory task, targets were 2-back colour repetitions (the blue ‘H’ is a target) that were easy to perceive (as the whole inner ring has the same colour) but taxed the working memory system more strongly than the 1-back task. During the grating task, participants responded to the spatial-frequency of the grating stimuli. Targets had lower spatial-frequency than non-targets. (C) Pairing between auditory tones and grating orientations. In predictable blocks, tones predicted grating orientation with 100% accuracy. In non-predictable blocks, the tones provided no orientation information. ITI = inter-trial interval.
Mentions: Stimuli were generated using MATLAB (MathWorks, Natick, MA, US) in conjunction with Psychophysics Toolbox [13]. In the behavioural session, stimuli were displayed on a Samsung SynchMaster 940BF monitor (60 Hz refresh rate, 1280 X 1024 resolution). In the fMRI session, stimuli were displayed on a rear projection screen using a luminance-calibrated EIKI projector (60 Hz refresh rate, 1024 X 768 resolution) which participants viewed through a mirror. A fixation “bull’s-eye” (outer ring 0.8° of visual angle) was presented at the centre of a gray background throughout each task. On each trial, a grating annulus (outer diameter: 15° of visual angle; inner diameter: 2°) of luminance-defined sinusoids at 80% contrast was displayed around the fixation bull’s-eye (200 ms; Fig 1A). Gratings were oriented at either 45° or 135°, with a phase randomly selected from 10 possibilities, evenly spaced between pi and 2pi. To mitigate afterimages, the phase of the grating was inverted halfway through stimulus presentation. On each trial, gratings had one of two possible spatial frequencies (mean: 1.5 cpd), with the specific spatial frequency values set for each individual by a staircasing procedure (see below). Simultaneously with the grating presentation, coloured letters were presented in the centre of the fixation bull’s-eye, with noise of the same colour superimposed (Fig 1B). Six letters (A, H, N, R, T, Z) and six colours (red, blue, green, cyan, yellow, magenta) were used. The number of coloured pixels that degraded the letters was similarly set by a staircasing procedure. The titration of these stimulus parameters for each subject ensured that tasks were matched on difficulty. Auditory cues that were played before each stimulus consisted of four pure tones (329, 440, 493 and 659 Hz) that were played for 200 ms.

Bottom Line: Stimulus expectation can modulate neural responses in early sensory cortical regions, with expected stimuli often leading to a reduced neural response.In the third task, the predictable stimulus was task-relevant, and therefore spatially attended.When the grating was task-relevant and spatially attended, there was no significant effect of expectation in early visual cortex.

View Article: PubMed Central - PubMed

Affiliation: Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, the Netherlands.

ABSTRACT
Stimulus expectation can modulate neural responses in early sensory cortical regions, with expected stimuli often leading to a reduced neural response. However, it is unclear whether this expectation suppression is an automatic phenomenon or is instead dependent on the type of task a subject is engaged in. To investigate this, human subjects were presented with visual grating stimuli in the periphery that were either predictable or non-predictable while they performed three tasks that differently engaged cognitive resources. In two of the tasks, the predictable stimulus was task-irrelevant and spatial attention was engaged at fixation, with a high load on either perceptual or working memory resources. In the third task, the predictable stimulus was task-relevant, and therefore spatially attended. We observed that expectation suppression is dependent on the cognitive resources engaged by a subjects' current task. When the grating was task-irrelevant, expectation suppression for predictable items was visible in retinotopically specific areas of early visual cortex (V1-V3) during the perceptual task, but it was abolished when working memory was loaded. When the grating was task-relevant and spatially attended, there was no significant effect of expectation in early visual cortex. These results suggest that expectation suppression is not an automatic phenomenon, but dependent on attentional state and type of available cognitive resources.

No MeSH data available.


Related in: MedlinePlus