82 CHAPTER 4 Imagery-related effects in right extrastriate cortex NA patients had decreased activity in right extrastriate cortex when imagining complex movements with their affected (right) limb. In both healthy participants and NA patients, motor imagery of biomechanically complex movements with the right limb evoked robust activity in the ipsilateral (right) extrastriate cortex, as well as other areas along the right ventral and dorsal visual streams. Similar findings have been observed in other populations. 40 The decreased activity in NA patients in right extrastriate cortex was observed at the junction between occipital, parietal and temporal lobes, with partial overlap with V5 and inferior parietal area PGp, just anterior and superior to the EBA. The EBA is defined by its sensitivity to body parts, 144, 145 particularly when those percepts need to be translated in motor plans, 146-150 as during the hand laterality task. 40, 60, 123 These functional properties extend to other extrastriate areas, including V5 and parietal areas in the dorsal visual stream. 147, 151-153 The receptors fingerprint of area PGp, another element of our extrastriate cluster, is similar to the fingerprint of extrastriate cortex, and it is similarly connected with occipital and parietal areas. 154-156 Accordingly, we found that the right extrastriate cluster was functionally connected to areas in dorsal and ventral visual streams, as well as to posterior parietal and premotor areas. The EBA works together with posterior parietal and premotor cortex to form a sensorimotor representation of the own upper limb through integration of visual and proprioceptive information. 27, 148, 150, 157, 158 More precisely, it has been argued that the EBA is an important interface between visual perception and action, 146 calculating a predicted goal posture during motor planning. 148-150 The decrease in extrastriate imagery-related activity as persistent pain increased thus suggests that persistent pain related to motor dysfunction reduced patients’ reliance on goal posture predictions when solving the motor imagery task. In agreement with our observation, the EBA has been shown to be involved in anticipation and observation of painful movements, and first-person perspective pain observation. 159, 160 These considerations qualify previous reports on the consequences of persistent pain in other peripheral disorders, 117, 118, 161-163suggesting that altered visuomotor processing may underly the effects of persistent pain on patients’ ability to imagine biomechanically complex movements of the affected limb. This interpretation is in line with the wellknown, strong relation between altered biomechanics and persistent pain in NA. 6, 8, 10 Imagery-related effects in bilateral parieto-occipital sulcus NA patients also had decreased activity along the parieto-occipital sulcus, covering parts of the ventral posterior cingulate cortex and the precuneus. This area forms a major hub in various brain circuits. 164-166 In rest and task-unfocused mindsets, it is involved in internal modes of cognition as part of the default mode network. 165-169 In task-focused mindsets, this higher-order visual region contributes to a multisensory representation of the spatial location of the own body through integration of self-relevant information. 157, 164, 165, 169-172 Patients with more behavioural difficulty in performing the task with their affected limb (as indexed by reaction times) had less activity along the parieto-occipital sulcus. Our findings could potentially be interpreted as reflecting deactivation of the default mode network, as it is known to deactivate with increasing task difficulty. 168 However, although the cluster in the parieto-occipital sulcus was functionally connected to other regions that are part of the default mode network, there were no group differences in functional coupling between those regions. Moreover, the parieto-occipital sulcus cluster was also
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