Central post-stroke pain is a neuropathic syndrome characterized by intolerable contralesional pain and, in rare cases, somatic delusions. To date, there is limited evidence for the effective ...treatments of this disease. Here we used caloric vestibular stimulation to reduce pain and somatoparaphrenia in a 57-year-old woman suffering from central post-stroke pain. Resting-state functional magnetic resonance imaging was used to assess the neurological effects of this treatment. Following vestibular stimulation we observed impressive improvements in motor skills, pain, and somatic delusions. In the functional connectivity study before the vestibular stimulation, we observed differences in the patient's left thalamus functional connectivity, with respect to the thalamus connectivity of a control group (N = 20), in the bilateral cingulate cortex and left insula. After the caloric stimulation, the left thalamus functional connectivity with these regions, which are known to be involved in the cortical response to pain, disappeared as in the control group. The beneficial use of vestibular stimulation in the reduction of pain and somatic delusion in a CPSP patient is now documented by behavioral and imaging data. This evidence can be applied to theoretical models of pain and body delusions.
Functional magnetic resonance imaging was used to compare the neural correlates of three different types of spatial coding, which are implicated in crucial cognitive functions of our everyday life, ...such as visuomotor coordination and orientation in topographical space. By manipulating the requested spatial reference during a task of relative distance estimation, we directly compared viewer-centered, object-centered, and landmark-centered spatial coding of the same realistic 3-D information. Common activation was found in bilateral parietal, occipital, and right frontal premotor regions.
The retrosplenial and ventromedial occipital–temporal cortex (and parts of the parietal and occipital cortex) were significantly more activated during the landmark-centered condition. The ventrolateral occipital–temporal cortex was particularly involved in object-centered coding. Results strongly demonstrate that viewer-centered (egocentric) coding is restricted to the dorsal stream and connected frontal regions, whereas a coding centered on external references requires both dorsal and ventral regions, depending on the reference being a movable object or a landmark.
Several studies have found in the sense of touch a good sensory modality by which to study body representation. Here, we address the "metric component of body representation", a specific function ...developed to process the discrimination of tactile distances on the body. The literature suggests the involvement of the right angular gyrus (rAG) in processing the tactile metricity on the body. The question of this study is the following: is the rAG also responsible for the visual metric component of body representation? We used tDCS (anodal and sham) in 20 subjects who were administered an on-body distance discrimination task with both tactile and visual stimuli. They were also asked to perform the same task in a near-body condition. The results allow us to confirm the role of rAG in the estimation of tactile distances. Further, we also showed that rAG might be involved in the discrimination of distances on the body not only in tactile but also in visual modality. Finally, based on the significant effects of anodal stimulation even in a near-body visual discrimination task, we proposed a higher-order function of the AG in terms of a supramodal comparator of quantities.
The spatial location of an object can be represented in the brain with respect to different classes of reference frames, either relative to or independent of the subject's position. We used ...functional magnetic resonance imaging to identify regions of the healthy human brain subserving mainly egocentric or allocentric (object-based) coordinates by asking subjects to judge the location of a visual stimulus with respect to either their body or an object. A color-judgement task, matched for stimuli, difficulty, motor and oculomotor responses, was used as a control. We identified a bilateral, though mainly right-hemisphere based, fronto-parietal network involved in egocentric processing. A subset of these regions, including a much less extensive unilateral, right fronto-parietal network, was found to be active during object-based processing. The right-hemisphere lateralization and the partial superposition of the egocentric and the object-based networks is discussed in the light of neuropsychological findings in brain-damaged patients with unilateral spatial neglect and of neurophysiological studies in the monkey.
To assess the specific influence of unilateral spatial neglect (USN) on rehabilitation outcome.
A case-control study in consecutive stroke inpatients.
Rehabilitation hospital.
One hundred ...seventy-eight patients with sequelae of first stroke, enrolled in homogeneous subgroups, matched for age (within 1yr) and onset admission interval (within 3d), and difference because of the presence of USN, evaluated by a specific neuropsychologic battery.
All patients received physical rehabilitation: physiotherapy for 60 minutes twice a day (once on Saturday), 6 days a week, within 24 hours of admission. USN-positive (USN(+)) patients received specific treatment of 5, 1-hour sessions per week, for 8 consecutive weeks: (1) visual scanning, (2) reading and copying, (3) copying of line drawings on a dot matrix, and (4) describing a scene. Patients were assessed with neurologic (Canadian Neurological Scale), neuropsychiatric (Hamilton Depression Rating Scale), neuroradiologic, and functional (Barthel Index, Rivermead Mobility Index RMI) examinations.
Length of stay, efficiency (average daily increase in Barthel Index), effectiveness (amount of potential improvement achieved during rehabilitation) of treatment and percentage of low- and high-response patients calculated on the Barthel Index and the RMI, and percentage of urinary incontinence and return home were evaluated. Odds ratios (ORs) of dropouts and of low and high therapeutic response were also quantified.
Compared with USN-negative patients, USN(+) patients had significantly more severe baseline neurologic and functional status at admission, less effectiveness and efficiency on activities of daily living (ADLs) and mobility, a higher percentage of low responders, longer hospitalization, a higher percentage of persistent incontinence at discharge (20.5% vs 4.9%), and a lower percentage of high responders and patients returning home. The presence of USN was incompatible with a high therapeutic response, for both ADLs (OR= 2.94, 95% confidence interval CI= 1.05-8.20; b +/- standard error = 1.08 +/- .52, p< .05), and mobility (OR = 7.16, 95% CI = 2.78-18.44; b = 1.97 +/- .52, p < .001) and was a relevant prognostic factor for institutional discharge (OR = 5.62, 95% CI = 1.63-19.38; b = 1.73 +/-.63, p < .01, accuracy 88.41%).
The results of this study provide further strong evidence of the relationship between USN and disability in right brain-damaged patients and of its unfavorable impact on rehabilitation, despite the cognitive training performed by all USN(+) patients.
The present study aimed at investigating the relationship between Emotional Susceptibility (ES), an aspect of the personality trait Neuroticism, and individual differences in the neural responses in ...anterior insula to primary sensory stimuli colored by affective valence, i.e., distasting or pleasantly tasting oral stimuli. In addition, it was studied whether intrinsic functional connectivity patterns of brain regions characterized by such differential responses could be related to ES. To this purpose 25 female participants underwent functional magnetic resonance imaging scanning, while being involved in a flavor experiment. During the experiment, flavor stimuli were administered consisting of small amounts of liquid with a different affective valence: neutral, pleasant, unpleasant. The results showed that individual differences in ES trait predicted distinct neural activity patterns to the different stimulus conditions in a region of left anterior insula that a previous meta-analysis revealed to be linked with olfacto-gustatory processing. Specifically, low ES was associated with enhanced neural responses to both pleasant and unpleasant stimuli, compared to neutral stimuli. By contrast, high ES participants showed equally strong neural responses to all types of stimuli without differentiating between the neutral and affective stimuli. Finally, during a task-free state, high ES trait appeared also to be related to decreased intrinsic functional connectivity between left anterior insula and left cerebellum. Our findings show that individual differences in ES are associated with differential anterior insula responses to primary sensory (flavor) stimuli as well as to intrinsic functional cortico-cerebellar connectivity, the latter suggesting a basis in the brain intrinsic functional architecture of the regulation of emotional experiences.
Personal neglect (PN) is the hemi-inattention toward the contralesional bodily space that follows a cerebral lesion, usually to the right hemisphere. Objective: To provide a historical, comprehensive ...review of the different theoretical accounts, of the available diagnostic measures, of the relationship with different body representation disorders, and of recovery-related issues. Moreover, to review the anatomo-functional correlates of PN, focusing on group studies that used modern voxel-based lesion-symptoms mapping. Method: PubMed database was searched for all the available studies on PN conducted in the last 30 years. Relevant clinical data for each study were reported in a table, which was used as a reference for developing the discussion on the points of interest. Results: Evaluation tools for PN suffer from limitations and should include both face- and body-related testing as well as require both basic exploration and object use in the same personal space. Dedicated rehabilitative procedures are lacking and advocated, given that recovery of PN and extrapersonal neglect can be dissociated and their degree is not correlated. PN is almost constantly associated with a cohort of body representation disorders that do not reveal themselves unless specifically investigated. PN is significantly correlated to alterations at the level of both the anterior parietal cortex and the underlying fronto-parietal fiber bundles. Conclusions: The discussed data point to the need for a diagnostic and rehabilitative update. Following the topological and hodological lesional pattern, PN might emerge from the combination of a body representation disorder and a spatial inattention for half of the space.
General Scientific Summary
Personal neglect is the lack of attention toward the contralesional side of the body, which is frequently observed after right cerebral lesions. It is often associated with the hemi-inattention for the external visual space as well as different deficits of the body representation. Available diagnostic procedures suffer from limitations, and dedicated rehabilitative procedures are still lacking. By reviewing anatomo-clinical correlates and theoretical perspectives, we suggest that personal neglect might be the combination of a body representation disorder and spatial hemi-inattention.
Previous studies have shown that individuals with heroin and cocaine addiction prefer to use these drugs in distinct settings: mostly at home in the case of heroin and mostly outside the home in the ...case of cocaine. Here we investigated whether the context would modulate the affective and neural responses to these drugs in a similar way. First, we used a novel emotional task to assess the affective state produced by heroin or cocaine in different settings, based on the recollections of male and female drug users. Then we used fMRI to monitor neural activity during drug imagery (re-creating the setting of drug use) in male drug users. Consistent with our working hypothesis, the majority of participants reported a shift in the affective valence of heroin from mostly pleasant at home to mostly unpleasant outside the home (
< 0.0001). The opposite shift was observed for cocaine; that is, most participants who found cocaine pleasant outside the home found it unpleasant when taken at home (
< 0.0014). Furthermore, we found a double dissociation, as a function of drug and setting imagery, in BOLD signal changes in the left PFC and caudate, and bilaterally in the cerebellum (all
values <0.01), suggesting that the fronto-striatal-cerebellar network is implicated in the contextualization of drug-induced affect. In summary, we report that the same setting can influence in opposite directions the affective and neural response to psychostimulants versus opiates in humans, adding to growing evidence of distinct substrates for the rewarding effects of these two drug classes.
The rewarding effects of addictive drugs are often thought to depend on shared substrates. Yet, environmental influences can unmask striking differences between psychostimulants and opiates. Here we used emotional tasks and fMRI to explore the influence of setting on the response to heroin versus cocaine in individuals with addiction. Simply moving from one setting to another significantly decreased heroin pleasure but increased cocaine pleasure, and vice versa. Similar double dissociation was observed in the activity of the fronto-striatal-cerebellar network. These findings suggest that the effects of opiates and psychostimulants depend on dissociable psychological and neural substrates and that therapeutic approaches to addiction should take into account the peculiarities of different drug classes and the settings of drug use.
Spatial orientation is based on coordinates referring to the subject's body. A fundamental principle is the mid-sagittal plane, which divides the body and space into the left and right sides. Its ...neural bases were investigated by functional magnetic resonance imaging (fMRI). Seven normal subjects pressed a button when a vertical bar, moving horizontally, crossed the subjective mid-sagittal plane. In the control condition, the subjects' task was to press a button when the direction of the bar movement changed, at the end of each leftward or rightward movement. The task involving the computation of the mid-sagittal plane yielded increased signal in posterior parietal and lateral frontal premotor regions, with a more extensive activation in the right cerebral hemisphere. This direct evidence in normal human subjects that a bilateral, mainly right hemisphere-based, cortical network is active during the computation of the egocentric reference is consistent with neuropsychological studies in patients with unilateral cerebral lesions. Damage to the right hemisphere, more frequently to the posterior-inferior parietal region, may bring about a neglect syndrome of the contralesional, left side of space, including a major rightward displacement of the subjective mid-sagittal plane. The existence of a posterior parietal-lateral premotor frontal network concerned with egocentric spatial reference frames is also in line with neurophysiological studies in the monkey.
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