Limits...
Unreliable evidence: 2 sources of uncertainty during perceptual choice.

Michael E, de Gardelle V, Nevado-Holgado A, Summerfield C - Cereb. Cortex (2013)

Bottom Line: Here, we asked whether these 2 sources of uncertainty have independent behavioral and neural effects during choice.These findings present a challenge for models that emphasize the role of the dmPFC in detecting conflict, errors, or surprise.We suggest an alternative explanation, whereby evidence is processed with increased gain near the category boundary.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Psychology, University of Oxford, Oxford OX1 3UD, UK.

Show MeSH
Additional imaging results (a) voxels where there was a significant negative correlation between the response to UMr and the response to UVr shown on a sagittal (left panel) and axial (right panel) slice at a threshold of P < 0.001 uncorrected. (b) Results of an analysis in which reaction time (RT) was included in the design matrix. Bar graphs show parameter estimates for response to the mean and variance of task-irrelevant (UMi and UVi) and task-relevant values (UMi and UVi) and reaction time (RT), for a dmPFC region of interest defined by its significant response to UMr (left panel) and UMv (right panel). Stars indicate significance: *P < 0.05, **P < 0.01, ***P < 0.001. Note positive correlation with RT in each region, and that all effects described persist even once RT is included. (c) Voxels showing a negative correlation with D, indexing the absolute distance to bound of all of the elements in the array, rendered on a sagittal slice at a threshold of P < 0.001 uncorrected.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4379999&req=5

BHT287F4: Additional imaging results (a) voxels where there was a significant negative correlation between the response to UMr and the response to UVr shown on a sagittal (left panel) and axial (right panel) slice at a threshold of P < 0.001 uncorrected. (b) Results of an analysis in which reaction time (RT) was included in the design matrix. Bar graphs show parameter estimates for response to the mean and variance of task-irrelevant (UMi and UVi) and task-relevant values (UMi and UVi) and reaction time (RT), for a dmPFC region of interest defined by its significant response to UMr (left panel) and UMv (right panel). Stars indicate significance: *P < 0.05, **P < 0.01, ***P < 0.001. Note positive correlation with RT in each region, and that all effects described persist even once RT is included. (c) Voxels showing a negative correlation with D, indexing the absolute distance to bound of all of the elements in the array, rendered on a sagittal slice at a threshold of P < 0.001 uncorrected.

Mentions: Our statistical approach involved identifying voxels that responded to evidence mean and testing their sensitivity to evidence variability, and vice versa. One limitation of this approach is that 2 adjacent but nonoverlapping clusters might become smeared into one by spatial smoothing, potentially giving rise to the spurious impression that a single region responds to both variables. We thus conducted a further analysis in which we correlated the response to UMr and UVr in a voxelwise fashion using the unsmoothed data, and converted the correlation coefficients at each voxel to a Fisher's z-score, permitting parametric statistics at the group level. The resulting group statistical maps, which were only smoothed after correlations were calculated, indicated voxels where there were significant correlations between the response to UMr and UVr. The results are shown in Figure 4a,b. We observed a cluster of negative correlation between response to these 2 variables in the vicinity of the dmPFC/ACC, with peaks at −2, 28, 30 (z = 3.17, P < 0.001, uncorrected) and −6, 36, 30 (z = −3.34, P < 0.0005, uncorrected; Fig. 4a, left). Additional clusters were observed at the left (−38, 20, −6, z = −3.43, P < 0.0003, uncorrected) and right (42, 24, −2, z = −3.32, P < 0.0005, uncorrected) AINS (Fig. 4a, right). Within the ROI defining, the dmPFC by its sensitivity to UMr, the average Fisher's z-score was also significant (z = −2.39, P < 0.009). In other words, those voxels that responded positively to UMr (higher signal as the mean LPR approached zero) tended to respond negatively to UVr (higher signal as evidence became more homogenous) and vice versa. No positive or negative correlations between response to UMr and response to UVr were observed in other regions sensitive to UMr, such as the parietal cortex.Figure 4.


Unreliable evidence: 2 sources of uncertainty during perceptual choice.

Michael E, de Gardelle V, Nevado-Holgado A, Summerfield C - Cereb. Cortex (2013)

Additional imaging results (a) voxels where there was a significant negative correlation between the response to UMr and the response to UVr shown on a sagittal (left panel) and axial (right panel) slice at a threshold of P < 0.001 uncorrected. (b) Results of an analysis in which reaction time (RT) was included in the design matrix. Bar graphs show parameter estimates for response to the mean and variance of task-irrelevant (UMi and UVi) and task-relevant values (UMi and UVi) and reaction time (RT), for a dmPFC region of interest defined by its significant response to UMr (left panel) and UMv (right panel). Stars indicate significance: *P < 0.05, **P < 0.01, ***P < 0.001. Note positive correlation with RT in each region, and that all effects described persist even once RT is included. (c) Voxels showing a negative correlation with D, indexing the absolute distance to bound of all of the elements in the array, rendered on a sagittal slice at a threshold of P < 0.001 uncorrected.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4379999&req=5

BHT287F4: Additional imaging results (a) voxels where there was a significant negative correlation between the response to UMr and the response to UVr shown on a sagittal (left panel) and axial (right panel) slice at a threshold of P < 0.001 uncorrected. (b) Results of an analysis in which reaction time (RT) was included in the design matrix. Bar graphs show parameter estimates for response to the mean and variance of task-irrelevant (UMi and UVi) and task-relevant values (UMi and UVi) and reaction time (RT), for a dmPFC region of interest defined by its significant response to UMr (left panel) and UMv (right panel). Stars indicate significance: *P < 0.05, **P < 0.01, ***P < 0.001. Note positive correlation with RT in each region, and that all effects described persist even once RT is included. (c) Voxels showing a negative correlation with D, indexing the absolute distance to bound of all of the elements in the array, rendered on a sagittal slice at a threshold of P < 0.001 uncorrected.
Mentions: Our statistical approach involved identifying voxels that responded to evidence mean and testing their sensitivity to evidence variability, and vice versa. One limitation of this approach is that 2 adjacent but nonoverlapping clusters might become smeared into one by spatial smoothing, potentially giving rise to the spurious impression that a single region responds to both variables. We thus conducted a further analysis in which we correlated the response to UMr and UVr in a voxelwise fashion using the unsmoothed data, and converted the correlation coefficients at each voxel to a Fisher's z-score, permitting parametric statistics at the group level. The resulting group statistical maps, which were only smoothed after correlations were calculated, indicated voxels where there were significant correlations between the response to UMr and UVr. The results are shown in Figure 4a,b. We observed a cluster of negative correlation between response to these 2 variables in the vicinity of the dmPFC/ACC, with peaks at −2, 28, 30 (z = 3.17, P < 0.001, uncorrected) and −6, 36, 30 (z = −3.34, P < 0.0005, uncorrected; Fig. 4a, left). Additional clusters were observed at the left (−38, 20, −6, z = −3.43, P < 0.0003, uncorrected) and right (42, 24, −2, z = −3.32, P < 0.0005, uncorrected) AINS (Fig. 4a, right). Within the ROI defining, the dmPFC by its sensitivity to UMr, the average Fisher's z-score was also significant (z = −2.39, P < 0.009). In other words, those voxels that responded positively to UMr (higher signal as the mean LPR approached zero) tended to respond negatively to UVr (higher signal as evidence became more homogenous) and vice versa. No positive or negative correlations between response to UMr and response to UVr were observed in other regions sensitive to UMr, such as the parietal cortex.Figure 4.

Bottom Line: Here, we asked whether these 2 sources of uncertainty have independent behavioral and neural effects during choice.These findings present a challenge for models that emphasize the role of the dmPFC in detecting conflict, errors, or surprise.We suggest an alternative explanation, whereby evidence is processed with increased gain near the category boundary.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Psychology, University of Oxford, Oxford OX1 3UD, UK.

Show MeSH