HC and patients were comparable on age and sex distribution, but patients had significantly fewer years of education and lower IQ ().
Years in education was not associated with performance when examined separately in HC and patients or across the entire sample (P’s > .15). IQ showed modestly positive correlations with percentage of correct answers during the other-distorted condition (r20 = 0.530, P = .016) but not during the other 3 conditions (self-undistorted r = 0.360, self-distorted r = 0.129, other-undistorted r = 0.10; P’s > .10) in controls and during the self-undistorted (r62 = 0.474, P = .016) and other-distorted (r = 0.503, P = .001) but not (P’s > .10) during the self-undistorted (r = 0.205) or other-undistorted (r = 0.197) conditions in patients.
HC showed more accurate performance than patients (F1,81 = 19.52, P = .001, η2 = 0.194). Both groups had more accurate performance during the undistorted than the distorted conditions (F1,81 = 76.33; P < .001, η2 = 0.485). A group × source × distortion interaction was present (F1,81 = 4.33, P = .04, η2 = 0.051), with HC performing significantly better than patients during the self-undistorted, self-distorted, and other-undistorted conditions but not during the other-distorted condition, possibly due to a much reduced accuracy in this condition in HC ().
Verbal Monitoring Performance in Patients and Healthy Participants and the Results of the Analysis of Simple Main Effects for Variables Showing Significant Main or Interactive Effects Involving the Group Factor
Complementing the results for percentage of correct answers, patients made more misattributions than HC (F1,81 = 14.26, P < .001, η2 = 0.150). This effect was significantly present only for the self-distorted and other-undistorted conditions (), although the group × source × distortion interaction fell short of formal significance (F1,81 = 3.78, P = .06, η2 = 0.045). Both groups made more errors during the distorted than the undistorted conditions (F1,81 = 46.21, P < .001, η2 = 0.363), especially during the other-distorted condition (source × distortion: F1,81 = 6.72, P = .01, η2 = 0.08).
The patients and HC were not significantly different for the percentage of unsure responses (F < 2.40 for group and group × source × distortion). Both groups made more unsure responses during the distorted, relative to undistorted (F1,81 = 14.40, P < .001, η2 = 0.15), and during the other, relative to self, conditions (F1,81 = 9.60, P = .003, η2 = 0.11).
No significant effects involving the group were detected for the percentage of nonresponses (F < 2.15 for group and group × source × distortion).
Across the entire patient sample, no significant or consistent relationships were found between PANSS total or subscale scores and performance accuracy (r range: −0.20 to +0.28) or error rate (r range: −0.22 to +0.17).
Good and Poor Performance Patients
Twenty-seven patients met the criterion for good and 36 for poor performance. Of 27 patients classified as good performers, 4 patients were excluded due to an odd performance pattern: 3 patients did not make any correct responses during the self-distorted condition and 1 patient made no correct response during the other-distorted condition despite excellent performance during the remaining 3 conditions.
As expected, patients classified as good performers had better performance than poorly performing patients (P’s < .05), but no clinical or demographic characteristics differentiated the 2 groups (P’s > .05) ().
Performance and Demographic and Clinical Characteristics of Good and Poor Performance Patient Groups
Functional Magnetic Resonance Imaging
Task-Related Activation Patterns Across All Participants. Individual Conditions.
A network of regions involving (bilaterally) the thalamus (medial geniculate nucleus, MGN), superior-middle TL, inferior frontal gyrus (IFG), insula, and putamen were activated in all conditions, across all participants (, ). The lingual gyrus (mainly right-sided) was activated during the self conditions.
Brain Areas Showing Significant Activation Increases and Decrease in Association With Individual Task Conditions (Voxel Threshold P = .005)
Fig. 1. Task-Related Changes in Brain Activity Across All Participants (Maps Thresholded at P = .005, uncorrected). The top row shows activity increases, and the middle row shows activity decreases associated with individual task conditions in sagittal, axial, (more ...)
The parahippocampal gyrus, posterior cingulate (PC), and medial frontal gyrus (MFG)/AC were deactivated during all conditions. The caudate nucleus was deactivated during the 2 self conditions and the angular gyrus during the 2 other conditions.
Source and Distortion.
The angular gyrus, extending to the PC, showed differential activity in the other < self-contrast; this effect was due to stronger deactivation of these areas during the other, compared with self, conditions regardless of distortion (, ). The caudate activity also differentiated the self and other conditions (regardless of distortion) (see further, diagnosis and symptom effects in this area). A cluster located in the right transverse temporal gyrus, extending to the right IFG, showed greater activity during the undistorted, compared with distorted, feedback conditions (see further, diagnosis and performance effects). A small cluster in the AC showed greater activity during the distorted, relative to undistorted, conditions, but this effect failed to reach corrected significance.
Brain Areas Showing Activation Changes for Source and Distortion Effects Across All Participants (Voxel Threshold P = .005)
Good Performers Vs Poor Performers
Good performers showed greater activity bilaterally in the superior-middle TL during all conditions than poor performers (, ). They also showed greater thalamic and putamen activity during all, except other-undistorted, conditions, and in the IFG and middle occipital gyrus during the self-undistorted condition.
Neural Activity Differentiating Groups of Good (Regardless of Diagnosis) and Poor Performers
Fig. 2. Brain Activity Differentiating Good Performers (Healthy Participants and Well-Performing Patients) and Poor Performers. The top and the middle rows show group differences in activations and deactivations found in individual task condition comparisons (more ...)
Poor performers showed more activity than good performers in the medial prefrontal and posterior temporal parietal cortices during all conditions (failed to reach corrected significance in the self-distorted condition, thus not presented in table or figure). These differences occurred due to stronger deactivation of these areas () in good, relative to poor, performers.
Poor and good performers were also differentiated by right IFG activity. Good, but not poor, performers showed more activity in these regions during the self, compared with other, conditions (regardless of distortion).
Patients Vs Healthy Participants
Patients, regardless of performance, showed less activity than HC in the thalamus (pulvinar) during the self-undistorted condition. They showed more activity bilaterally in the STG during the self-undistorted condition and in the left STG during the other-distorted condition. Subject-specific activation values in these regions did not correlate with age, age at illness onset, illness duration, PANSS scores, IQ, or performance in patients.
Patients showed more activity than HC in the ventral striatum, hypothalamus, and part of the thalamus in the other > self-contrast (, , source × group). This effect occurred due to greater deactivation of these regions to own voice (note that the caudate showed deactivation during the self-conditions across the whole sample due to this effect mainly in patients, ), combined with nonsignificant activation of the same regions to someone else's voice (not shown) and associated positively with negative symptoms. Within the patient group, greater ventral striatal-hypothamic activity during other > self-contrast (, source × group) correlated with higher negative symptoms score (r = 0.293, P = .05). At the individual symptom level, blunted affect (ρ = 0.369, P = .01), emotional withdrawal (ρ = 0.332, P = .026), poor rapport (ρ = 0.359, P = .015), and passive social avoidance (ρ = 0.335, P = .025) contributed to this relationship; poor abstract thinking, lack of spontaneity, and stereotyped thinking items were uncorrelated (P > .15).
Neural Activity Differentiating Groups of Healthy Participants and Patients With Schizophrenia Regardless of Performance
Fig. 3. Brain Activity Differentiating Patients From Healthy Participants. The top row shows group differences with individual task conditions (maps thresholded at P = .005 uncorrected), and the middle and bottom rows show group × source and group × (more ...)
Patients also showed greater activity in the right TL extending to the right IFG and parietal regions during conditions with undistorted, relative to distorted, feedback (regardless of source); HC showed the opposite pattern although to a lesser degree. This activity change in patients did not correlate with IQ (r = −0.134) but correlated negatively with performance (percentage of total correct r = −0.364, P = .014) and positively with positive symptoms (r = 0.349, P = .019), specifically with hallucinations (ρ = 0.437, P = .003), persecution (ρ = 0.320, P = .032), and disorganization (ρ = 0.320, P = .032).