Reduced functional connectivity in a right-hemisphere network for volitional ocular motor control in schizophrenia

Institute of Neuroscience, School of Life Sciences, National Yang-Ming University, Taipei 112, Taiwan.
Brain (Impact Factor: 9.2). 02/2010; 133(Pt 2):625-37. DOI: 10.1093/brain/awp317
Source: PubMed


Patients with schizophrenia consistently show deficient performance on tasks requiring volitional saccades. We previously reported reduced fractional anisotropy in the white matter underlying right dorsal anterior cingulate cortex in schizophrenia, which, along with lower fractional anisotropy in the right frontal eye field and posterior parietal cortex, predicted longer latencies of volitional saccades. This suggests that reduced microstructural integrity of dorsal anterior cingulate cortex white matter disrupts connectivity in the right hemisphere-dominant network for spatial attention and volitional ocular motor control. To test this hypothesis, we examined functional connectivity of the cingulate eye field component of this network, which is located in dorsal anterior cingulate cortex, during a task comprising volitional prosaccades and antisaccades. In patients with schizophrenia, we expected to find reduced functional connectivity, specifically in the right hemisphere, which predicted prolonged saccadic latency. Twenty-seven medicated schizophrenia outpatients and 21 demographically matched healthy controls performed volitional saccades during functional magnetic resonance imaging. Based on task-related activation, seed regions in the right and left cingulate eye field were defined. In both groups, the right and left cingulate eye field showed positive correlations with the ocular motor network and negative correlations with the default network. Patients showed reduced positive functional connectivity of the cingulate eye field, specifically in the right hemisphere. Negative functional connectivity of the right cingulate eye field predicted faster saccades, but these relations differed by group, and were only present in controls. This pattern of relations suggests that the coordination of activity between ocular motor and default networks is important for efficient task performance and is disrupted in schizophrenia. Along with prior observations of reduced white matter microstructural integrity (fractional anisotropy) in schizophrenia, the present finding of reduced functional connectivity suggests that functional and structural abnormalities of the right cingulate eye field disrupt connectivity in the network for spatial attention and volitional ocular motor control. These abnormalities may contribute to deficits in overcoming prepotency in the service of directing eye gaze and attention to the parts of the environment that are the most behaviourally relevant.

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Available from: Dara S Manoach, Jan 12, 2015
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    • "In addition, we examined whether learning during training affected resting state functional connectivity by correlating it with motor network connectivity changes in the post-pre MST rest scans and with connectivity in the post-MST rest scan alone. To determine whether functional connectivity with the seed during the MST scan correlated with next-day improvement, we performed the same fcMRI analysis on the MST scan as for the rest scans, as we have done in prior studies examining connectivity during task performance (Agam et al., 2010, 2011; Tu et al., 2010). In this analysis the correlations derive from a combination of task-evoked and spontaneous activity. "
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    ABSTRACT: There is ongoing debate concerning the functions of resting-state brain activity. Prior work demonstrates that memory encoding enhances subsequent resting-state functional connectivity within task-relevant networks and that these changes predict better recognition. Here, we used functional connectivity MRI (fcMRI) to examine whether task-induced changes in resting-state connectivity correlate with performance improvement after sleep. In two separate sessions, resting-state scans were acquired before and after participants performed a motor task. In one session participants trained on the motor sequence task (MST), a well-established probe of sleep-dependent memory consolidation, and were tested the next day, after a night of sleep. In the other session they performed a motor control task (MCT) that minimized learning. In an accompanying behavioral control study, participants trained on the MST and were tested after either a night of sleep or an equivalent interval of daytime wake. Both the fcMRI and the sleep control groups showed significant improvement of MST performance, while the wake control group did not. In the fcMRI group, increased connectivity in bilateral motor cortex following MST training correlated with this next-day improvement. This increased connectivity did not appear to reflect initial learning since it did not correlate with learning during training and was not greater after MST training than MCT performance. Instead, we hypothesize that this increased connectivity processed the new memories for sleep-dependent consolidation. Our findings demonstrate that physiological processes immediately after learning correlate with sleep-dependent performance improvement and suggest that the wakeful resting brain prepares memories of recent experiences for later consolidation during sleep.
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    • "This cyclical pattern of network activation and deactivation around error trials is likely to be reflected in behavior. This is consistent with findings that the relative connectivity [17] and activation [18] of the default and dorsal attention networks correlate with RT. Building on this literature, we hypothesized that reciprocal changes in resource allocation between the default and dorsal attention networks around errors underlie SATOs in RT and are mediated by the PCC. "
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    ABSTRACT: The ability to dynamically and rapidly adjust task performance based on its outcome is fundamental to adaptive, flexible behavior. Over trials of a task, responses speed up until an error is committed and after the error responses slow down. These dynamic adjustments serve to optimize performance and are well-described by the speed-accuracy trade-off (SATO) function. We hypothesized that SATOs based on outcomes reflect reciprocal changes in the allocation of attention between the internal milieu and the task-at-hand, as indexed by reciprocal changes in activity between the default and dorsal attention brain networks. We tested this hypothesis using functional MRI to examine the pattern of network activation over a series of trials surrounding and including an error. We further hypothesized that these reciprocal changes in network activity are coordinated by the posterior cingulate cortex (PCC) and would rely on the structural integrity of its white matter connections. Using diffusion tensor imaging, we examined whether fractional anisotropy of the posterior cingulum bundle correlated with the magnitude of reciprocal changes in network activation around errors. As expected, reaction time (RT) in trials surrounding errors was consistent with predictions from the SATO function. Activation in the default network was: (i) inversely correlated with RT, (ii) greater on trials before than after an error and (iii) maximal at the error. In contrast, activation in the right intraparietal sulcus of the dorsal attention network was (i) positively correlated with RT and showed the opposite pattern: (ii) less activation before than after an error and (iii) the least activation on the error. Greater integrity of the posterior cingulum bundle was associated with greater reciprocity in network activation around errors. These findings suggest that dynamic changes in attention to the internal versus external milieu in response to errors underlie SATOs in RT and are mediated by the PCC.
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    • "Structurally, these regions are amongst the most consistently observed sites of gray-matter reduction in the disorder (Ellison-Wright et al., 2008), and focal alterations in SN volume are observed to be associated with the severity of reality distortion in schizophrenia (Palaniyappan et al., 2011). Reduced functional connectivity has also been observed within the SN in schizophrenia compared to controls during volitional eye saccades (Tu et al., 2010) and at rest (Tu et al., 2012). However, within-SN dysconnectivity is not unequivocally apparent in schizophrenia. "
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