Laura Zapparoli

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 anarchic brain in action: the contribution of task-based fMRI studies to the understanding of Gilles de la Tourette syndrome.

PURPOSE OF REVIEW Gilles de la Tourette syndrome (GTS) is a frequent neurological disorder characterized by the production of tics, and frequently associated with obsessive-compulsive disorder or attention-deficit hyperactivity disorder. The aim of this article is to summarize the contribution of imaging activation techniques to the study of the syndrome. RECENT FINDINGS GTS has been studied with a variety of functional MRI (fMRI)/PET activation paradigms to characterize the origin of tics or their suppression, and how they compare physiologically with voluntary actions or response inhibitions. Current studies indicate overactivations of prefrontal and premotor cortices, including the supplementary motor area, and subcortical structures. Resting state functional connectivity studies complement activation studies in showing perturbed connectivity of cortico-subcortical networks. Several such findings correlate with the severity of the disease. SUMMARY fMRI activation techniques are contributing a system-level neurophysiological description of GTS and bridge the gap between animal models and clinical observations. fMRI clarifies brain networks involved in different aspects of GTS phenomenology with some good clinical face validity. A future generation of fMRI studies should have higher ambitions and contribute, for example, to treatment optimization including the identification of ideal targets for deep brain stimulation in drug-resistant cases; however, such goals will be achieved only through controlled large-scale cooperative studies.

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.

When I am (almost) 64: The effect of normal ageing on implicit motor imagery in young elderlies

Motor imagery (M.I.) is a cognitive process in which movements are mentally evoked without overt actions. Behavioral and fMRI studies show a decline of explicit M.I. ability (e.g., the mental rehearsal of finger oppositions) with normal ageing: this decline is accompanied by the recruitment of additional cortical networks. However, none of these studies investigated behavioral and the related fMRI ageing modifications in implicit M.I. tasks, like the hand laterality task (HLT). To address this issue, we performed a behavioral and fMRI study: 27 younger subjects (mean age: 31 years) and 29 older subjects (mean age: 61 years) underwent two event-related design fMRI experiments. In the HLT, participants were asked to decide whether a hand rotated at different angles was a left or right hand. To test the specificity of any age related difference in the HLT, we used a letter rotation task as a control experiment: here subjects had to decide whether rotated letters were presented in a standard or a mirror orientation. We did not find any group difference in either behavioral task; however, we found significant additional neural activation in the elderly group in occipito-temporal regions: these differences were stronger for the HLT rather than for the LRT with group by task interactions effects in right occipital cortices. We interpret these results as evidence of compensatory processes associated with ageing that permit a behavioral performance comparable to that of younger subjects. This process appears to be more marked when the task specifically involves motor representations, even when these are implicitly evoked.

A functional magnetic resonance imaging investigation of motor control in Gilles de la Tourette syndrome during imagined and executed movements

The current study investigated the neural correlates of voluntary motor control in 24 adult Gilles de la Tourette (GTS) patients. We examined whether imagination and the execution of the same voluntary movement – finger oppositions with either hand – were associated with specific patterns of activation. We also explored whether these patterns correlated with the severity of the syndrome, as measured by the Yale Global Tic Severity Scale (YGTSS) for motor tics. The presence of brain morphometric abnormalities was also assessed using voxel‐based morphometry. Crucial to our experiment was the manipulation of the presence of an explicit motor outflow in the tasks. We anticipated a reduction in the ticking manifestation during the explicit motor task and brain activation differences between GTS patients and 24 age/gender‐matched normal controls. The anticipated differences were all evident in the form of hyperactivations in the GTS patients in the premotor and prefrontal areas for both motor tasks for both hands; however, the motor imagery hyperactivations also involved rostral pre‐frontal and temporo‐parietal regions of the right hemisphere. The blood oxygen level‐dependent responses of the premotor cortices during the motor imagery task were significantly correlated with the YGTSS scores. In contrast, no significant brain morphometric differences were found. This study provides evidence of a different neurofunctional organisation of motor control between adult patients with GTS and healthy controls that is independent from the actual execution of motor acts. The presence of an explicit motor outflow in GTS mitigates the manifestation of tics and the need for compensatory brain activity in the brain regions showing task‐dependent hyperactivations.

The what, the when, and the whether of intentional action in the brain: A meta-analytical review

In their attempt to define discrete subcomponents of intentionality, Brass and Haggard (2008) proposed their What, When, and Whether model (www-model) which postulates that the content, the timing and the possibility of generating an action can be partially independent both at the cognitive level and at the level of their neural implementation. The original proposal was based on a limited number of studies, which were reviewed with a discursive approach. To assess whether the model stands in front of the more recently published data, we performed a systematic review of the literature with a meta-analytic method based on a hierarchical clustering (HC) algorithm. We identified 15 PET/fMRI studies well-suited for this quest. HC revealed the existence of a rostro-caudal gradient within the medial prefrontal cortex, with the more anterior regions (the anterior cingulum) involved in more abstract decisions of whether to execute an action and the more posterior ones (the middle cingulum or the SMA) recruited in specifying the content and the timing components of actions. However, in contrast with the original www-model, this dissociation involves also brain regions well outside the median wall of the frontal lobe, in a component specific manner: the supramarginal gyrus for the what component, the pallidum and the thalamus for the when component, the putamen and the insula for the whether component. We then calculated co-activation maps on the three component-specific www clusters of the medial wall of the frontal/limbic lobe: to this end, we used the activation likelihood approach that we applied on the imaging studies on action contained in the BrainMap.org database. This analysis confirmed the main findings of the HC analyses. However, the BrainMap.org data analyses also showed that the aforementioned segregations are generated by paradigms in which subjects act in response to conditional stimuli rather than while driven by their own intentions. We conclude that the available data confirm that the neural underpinnings of intentionality can be fractionated in discrete components that are partially independent. We also suggest that intentionality manifests itself in discrete components through the boosting of general purpose action-related regions specialized for different aspects of action selection and inhibition.

Mental steps: Differential activation of internal pacemakers in motor imagery and in mental imitation of gait

Gait imagery and gait observation can boost the recovery of locomotion dysfunctions; yet, a neurologically justified rationale for their clinical application is lacking as much as a direct comparison of their neural correlates. Using functional magnetic resonance imaging, we measured the neural correlates of explicit motor imagery of gait during observation of in‐motion videos shot in a park with a steady cam (Virtual Walking task). In a 2 × 2 factorial design, we assessed the modulatory effect of gait observation and of foot movement execution on the neural correlates of the Virtual Walking task: in half of the trials, the participants were asked to mentally imitate a human model shown while walking along the same route (mental imitation condition); moreover, for half of all the trials, the participants also performed rhythmic ankle dorsiflexion as a proxy for stepping movements. We found that, beyond the areas associated with the execution of lower limb movements (the paracentral lobule, the supplementary motor area, and the cerebellum), gait imagery also recruited dorsal premotor and posterior parietal areas known to contribute to the adaptation of walking patterns to environmental cues. When compared with mental imitation, motor imagery recruited a more extensive network, including a brainstem area compatible with the human mesencephalic locomotor region (MLR). Reduced activation of the MLR in mental imitation indicates that this more visually guided task poses less demand on subcortical structures crucial for internally generated gait patterns. This finding may explain why patients with subcortical degeneration benefit from rehabilitation protocols based on gait observation. Hum Brain Mapp 38:5195–5216, 2017.

Functional brain effects of hand disuse in patients with trapeziometacarpal joint osteoarthritis: executed and imagined movements

The human trapeziometacarpal (TMC) joint has a crucial evolutionary importance as it permits rotation and opposition of the thumb to the other fingers. In chronic TMC joint osteoarthritis (i.e., rhizarthrosis), this motor ability, essential for pinching, grasping, and manipulating objects, may become difficult or impossible due to intolerable pain. Here, we assess whether patients with rhizarthrosis show signs of abnormal brain representation of hand movements. To this end, we studied 35 patients with rhizarthrosis, affecting predominantly one of the two hands, and 35 healthy subjects who underwent both behavioural and fMRI measures of brain activity during overtly executed or imagined thumb-to-finger-opposition movements. The patients with rhizarthrosis were slower than controls both in motor execution and imagination. In the patients, correlation between the motor execution and imagination times was preserved, even though such correlation was less strong than in normal controls. The fMRI measures showed reduced activation in the hand primary motor and dorsal premotor cortex for the patients only during explicit movements. This was true for both hands, yet more so for the most affected hand. No significant differences were seen for the motor imagery task. These results show that an orthopaedic disorder that reduces patients’ motoric repertoire in the absence of any neurological impairment is sufficient to induce neurofunctional changes in the cortical representation of hand movements. The substantial preservation of motor imagery with its neural counterparts distinguishes the neurological patterns of rhizarthrosis from those of complete immobilization or amputation suggesting that motor imagery may be used to boost motor recovery in rhizarthrosis after surgical treatment.

Dissecting the neurofunctional bases of intentional action

Significance We provide evidence that our intentions can be fragmented in various components subserved by partially dissociable neural circuits. We found that the decision of what to do, when to do it, and whether to do it depends on separable systems that go beyond the mesial prefrontal wall of previous proposals, involving cortical and subcortical brain regions in a component-specific manner. In addition, we found that deciding whether to act or not requires strong interhemispheric interactions of the frontal lobes. This explicit evidence of dissociable neural foundations of intentional actions will guide the exploration of brain disorders of specific components of intentionality. Here we challenge and present evidence that expands the what, when, and whether anatomical model of intentional action, which states that internally driven decisions about the content and timing of our actions and about whether to act at all depend on separable neural systems, anatomically segregated along the medial wall of the frontal lobe. In our fMRI event-related paradigm, subjects acted following conditional cues or following their intentions. The content of the actions, their timing, or their very occurrence were the variables investigated, together with the modulating factor of intentionality. Besides a shared activation of the pre-supplementary motor area (pre-SMA) and anterior cingulate cortex (ACC) for all components and the SMA proper for the when component, we found specific activations beyond the mesial prefrontal wall involving the parietal cortex for the what component or subcortical gray structures for the when component. Moreover, we found behavioral, functional, anatomical, and brain connectivity evidence that the self-driven decisions on whether to act require a higher interhemispheric cooperation: This was indexed by a specific activation of the corpus callosum whereby the less the callosal activation, the greater was the decision cost at the time of the action in the whether trials. Furthermore, tractography confirmed that the fibers passing through the callosal focus of activation connect the two sides of the frontal lobes involved in intentional trials. This is evidence of non-unitary neural foundations for the processes involved in intentional actions with the pre-SMA/ACC operating as an intentional hub. These findings may guide the exploration of specific instances of disturbed intentionality.