Awareness of the Functioning of One's Own Limbs Mediated by the Insular Cortex?

Abstract

Normally, we are aware of the current functions of our arms and legs. However, this self-evident status may change dramatically after brain damage. Some patients with "anosognosia" typically are convinced that their limbs function normally, although they have obvious motor defects after stroke. Such patients may experience their own paretic limbs as strange or as not belonging to them and may even attribute ownership to another person and try to push their paralyzed limb out of bed. These odd beliefs have been attributed to disturbances somewhere in the right hemisphere. Here, we use lesion mapping in 27 stroke patients to show that the right posterior insula is commonly damaged in patients with anosognosia for hemiplegia/hemiparesis but is significantly less involved in hemiplegic/hemiparetic patients without anosognosia. The function of the posterior insular cortex has been controversially discussed. Recent neuroimaging results in healthy subjects revealed specific involvement of this area in the subject's feeling of being versus not being involved in a movement. Our finding corresponds with this observation and suggests that the insular cortex is integral to self-awareness and to one's beliefs about the functioning of body parts.

Motor versus body awareness: Voxel-based lesion analysis in anosognosia for hemiplegia and somatoparaphrenia following right hemisphere stroke

“…In this 4-point scale, if the disorder is spontaneously reported by the patient following a general question about their complaints the 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 8 score is '0' = no anosognosia; '1' is scored if the disorder is reported only following a specific question about the strength of the patient's limbs; '2' is scored if the disorder is acknowledged only after demonstration; and finally '3' is scored if no acknowledgement of the disorder can be obtained. We considered patients as anosognosic when they scored 2 or 3 (Karnath et al, 2005;Orfei et al, 2007).…”

“…Other cortical areas selectively associated with AHP are the right premotor and the inferior frontal cortex, in particular Broadmann's areas 6, 44/45 and 47 (Berti et al, 2005;Fotopoulou et al, 2010;Kortte et al, 2015), which are involved in motor initiation, preparation and monitoring. However, there are conflicting results between these studies regarding which areas of the frontal operculum are implicated in AHP (Berti et al, 2005;Kortte et al, 2015) and other studies fail to find a selective role for premotor areas and the inferior frontal gyrus in AHP (Karnath et al, 2005). In addition, some but not all studies report that lesions involving subcortical structures such as the thalamus, the basal ganglia and the amygdala-hippocampal complex may relate to certain behavioural facets of AHP Moro et al, 2011;Vocat et al, 2010, see Table 4 for a review of previous studies).…”

“…Cocchini, Beschin, Cameron, Fotopoulou, & Della Sala, 2009 for left hemisphere cases; Jehkonen, Laihosalo, & Kettunen, 2006), recent neuroimaging studies have not identified a consistent pattern of brain lesion or dysfunction selectively associated with AHP. Specifically, some studies have highlighted the potential role of cortical areas such as the right insula in AHP (Berti et al, 2005;Fotopoulou et al, 2010; Baier, & Nägele, 2005;Vocat et al, 2010). The insular cortex has been more generally implicated in body ownership, perceived agency and interoceptive representations of body states (Craig, 2009;Karnath et al, 2005;Tsakiris, Hesse, Boy, Haggard, & Fink, 2007).…”

“…Specifically, some studies have highlighted the potential role of cortical areas such as the right insula in AHP (Berti et al, 2005;Fotopoulou et al, 2010; Baier, & Nägele, 2005;Vocat et al, 2010). The insular cortex has been more generally implicated in body ownership, perceived agency and interoceptive representations of body states (Craig, 2009;Karnath et al, 2005;Tsakiris, Hesse, Boy, Haggard, & Fink, 2007). Other cortical areas selectively associated with AHP are the right premotor and the inferior frontal cortex, in particular Broadmann's areas 6, 44/45 and 47 (Berti et al, 2005;Fotopoulou et al, 2010;Kortte et al, 2015), which are involved in motor initiation, preparation and monitoring.…”

“…In addition to intrinsic limitations of lesion mapping studies (Rorden, Fridriksson, & Karnath, 2009;Rorden & Karnath, 2004), part of the aforementioned differences between studies may be attributed to different sample sizes and selection criteria, including criteria for diagnosis, subtype of anosognosia, age, lesion size, perfusion patterns, white matter involvement, and the time interval since stroke for both diagnosis and neuroimaging examination (Karnath et al, 2005;Kortte et al, 2015;Vocat et al, 2010). Unfortunately, addressing all these limitations in a single study is currently unfeasible for most labs.…”