Paola Invernizzi

An anatomical account of somatoparaphrenia

Somatoparaphrenia is a delusional belief whereby a patient feels that a paralyzed limb does not belong to his body; the symptom is typically associated with unilateral neglect and most frequently with anosognosia for hemiplegia. This association of symptoms makes anatomical inference based on single case studies not sufficiently specific. On the other hand, the only three anatomical group studies on somatoparaphrenia are contradictory: the right posterior insula, the supramarginal gyrus and the posterior corona radiata, or the right medial or orbito-frontal regions were all proposed as specific lesional correlates. We compared 11 patients with and 11 without somatoparaphrenia matched for the presence and severity of other associated symptoms (neglect, motor deficits and anosognosia). To take into account the frequent association of SP and neglect and hemiplegia, patients with and without somatoparaphrenia were also compared with a group of fifteen right brain damage patients without neglect and hemiplegia. We found a lesion pattern involving a fronto-temporo-parietal network typically associated with spatial neglect, hemiplegia and anosognosia. Somatoparaphrenic patients showed an additional lesion pattern primarily involving white matter and subcortical grey structures (thalamus, basal ganglia and amygdala). Further cortical damage was present in the middle and inferior frontal gyrus, postcentral gyrus and hippocampus. We propose that somatoparaphrenia occurs providing that a distributed cortical lesion pattern is present together with a subcortical lesion load that prevents most sensory input from being processed in neocortical structures; involvement of deep cortical and subcortical grey structures of the temporal lobe may contribute to reduce the sense of familiarity experienced by somatoparaphrenic patients for their paralyzed limb.

Productive symptoms in right brain damage

Purpose of reviewThe purpose of this review is to summarize the more recent studies on productive symptoms from the neuropsychological, neurophysiological and anatomical points of view. The integration of these aspects may provide some clarifications on the cognitive impairments underpinning the main productive disorders, also contributing to better understand the normal functioning of the brain. Recent findingsProductive symptoms are closely associated to spatial neglect and are distinguished in relation to the part of space they manifest. The investigation of perseveration in extrapersonal space with different manipulations helps to understand the neuropathological mechanisms underlying this symptom. Anosognosia for hemiplegia and somatoparaphrenia may be considered as disorders of body representation (personal space). Recently it has been proposed that these disorders may be ascribed to an impairment of different levels of motor control. The identification of the anatomical correlates of these two disorders contributes to better understanding of their the cognitive nature. SummaryProductive behaviours have diverse clinical manifestations and may be induced by different mechanisms. Lesional studies are beginning to provide evidence for specific anatomical correlates of these disorders. Further investigations are needed to better understand to what extent productive symptoms can be disentagled from spatial neglect. These attempts may contribute to clarifying the role of the right hemisphere in monitoring spatial cognition.

What is Mine? Behavioral and Anatomical Dissociations between Somatoparaphrenia and Anosognosia for Hemiplegia

We describe the clinical manifestations and the lesion patterns of five patients with somatoparaphrenia, the denial of ownership for a paralyzed limb, who showed the rare dissociation from anosognosia for hemiplegia. Similar cases have been only occasionally cited in the literature with scanty descriptions of their symptoms and no detailed anatomical assessment. All patients had extrapersonal and at least mild personal neglect. The lesions pattern was mainly subcortical, with a significant involvement of the right thalamus, the basal ganglia and the internal capsule. A formal comparison between the anatomical pattern previously associated with anosognosia in a study performed in 2005 by Berti and colleagues, and the lesion distribution of each patient clearly shows that our pure somatoparaphrenic patients had a sparing of most of the regions associated with anosognosia for hemiplegia. The behavioral dissociation between SP and anosognosia for hemiplegia, together with this new anatomical evidence, suggests that motor awareness is not sufficient to build up a sense of ownership and therefore these two cognitive abilities are at least in part functionally independent and qualitatively different.

Like the back of the (right) hand? A new fMRI look on the hand laterality task

AbstractThere is a common saying for expressing familiarity with something. It refers to our hands, and strangely enough, in English, one says to know something like the back of the hand, whereas in other cultures, for example, Italy, Spain and France, the same expression is with the palm. Previous behavioural data have suggested that our ability to visually discriminate a right from a left hand is influenced by perspective. This behavioural finding has remained without neurophysiological counterparts. We used an implicit motor imagery task in which 30 right-handed subjects were asked to decide whether a picture portrayed a right rather than a left hand during an fMRI event-related experiment. Both views (back and palm) were used, and the hands were rotated by 45° in 8 possible angles. We replicated previous behavioural evidence by showing faster reaction times for the back-view and view-specific interaction effects with the angle of rotation: for the back view, the longest RTs were with the hand facing down at 180°; for the palm view, the longest RTs were at 90° with the hand pointing away from the midline. In addition, the RTs were particularly faster for back views of the right hand. fMRI measurements revealed a stronger BOLD signal increase in left premotor and parietal cortices for stimuli viewed from the palm, whereas back-view stimuli were associated with stronger occipital activations, suggesting a view-specific cognitive strategy: more visually oriented for the back of the hand; more in need of the support of a motoric imagery process for the palms. Right-hand back views were associated with comparatively smaller BOLD responses, attesting, together with the faster reaction times, to the lesser need for neural labour because of greater familiarity with that view of the hand. These differences suggest the existence of brain-encoded, view-dependent representations of body segments.

The physiology of motor delusions in anosognosia for hemiplegia: implications for current models of motor awareness.

Right brain damaged patients sometimes deny that their left arm is paralysed or even claim to have just moved it. This condition is known as anosognosia for hemiplegia (AHP). Here, we used fMRI to study patients with and without AHP during the execution of a motor task. We found that the delusional belief of having moved was preceded by brain activation of the cortical regions that are implicated in motor control in the left intact hemisphere and in the spared motor regions of the right hemisphere; patients without anosognosia did not present with the same degree of activation. We conclude that the false belief of movement is associated with a combination of strategically placed brain lesions and the preceding residual neural activity of the fronto-parietal motor network. These findings provide evidence that the activity of motor cortices contributes to our beliefs about the state of our motor system.