Impact of Inaccuracy in fMRI Experimental Stimulation

Práce se zabývá zkoumáním vlivu nepřesností v provedení požadovaného úkolu (nepřesnost reakce na experimentální stimulaci) osobou, která podstupuje fMRI vyšetření. Práce je řešena v několika úrovních. Nejprve byl proveden teoretický rozbor problematiky nepřesností v provedení experimentu a byly realizovány simulace s využitím syntetických dat. Sledovány byly hodnoty proměnných v obecném lineárním modelu a vypočtená hodnota t-statistiky. Bylo zjištěno, že velikost odhadnutého efektu závisí lineárně na kovarianci resp. lineární kombinaci kovariancí, odpovídajících sloupců matic X a D. Dále bylo zjištěno, že při úrovních šumu obvyklých v reálných datech je složka reziduálního rozptylu způsobená nepřesnostmi prakticky zanedbatelná. Závislost t-statistiky na nepřesnosti je pak také lineární. Následně byly zjištěné charakteristiky ověřeny pomocí reálných dat. V zásadě byly potvrzeny všechny skutečnosti zjištěné v předchozí úrovni řešení práce. V poslední úrovni řešení jsem se zaměřil na potenciální uplatnění zjištěných charakteristik. Jsou diskutovány možnosti využití pro optimalizaci experimentu, možnosti korekce nepřesných dat a možnosti ohodnocení věrohodnosti nepřesných výsledků. Mezi možné praktické uplatnění patří zejména tvorba map maximální přípustné nepřesnosti, které vyznačují robustnější nebo naopak k chybě náchylné a nevěrohodné aktivace z reálných experimentů.Aim of this work is to study the impact of inaccuracy in execution of required task (inaccuracy in subject’s behavioral response to experimental stimulation) by person who undergoes fMRI examination. The work is solved in several stages. First, theoretical analysis of inaccuracy in fMRI experiment was performed, and simulations with synthetic data were created. Several variables in general linear model and t-statistics were followed. We found that estimated effect size depends linearly on covariance between the corresponding columns of X and D matrices or their linear combination. The component of residual variance caused by inaccuracy is negligible at real-life noise levels. In such case, moreover, the dependence of t-statistics on inaccuracy becomes linear. Next, our theoretical results (dependencies/characteristics of variables) were verified using real data. All results were confirmed. Last, I focused on possible practical use of the uncovered characteristics and dependencies. Optimization of experimental design with respect to inaccuracy, correction of inaccurate results and reliability of inaccurate results are introduced and discussed. Especially, the calculation of maps of maximal tolerable inaccuracy can be useful to find robust or weak (tending to be not detected or to be significantly different from accurate value) activation in real fMRI experiments.

An evaluation of traffic-awareness campaign videos:Empathy induction is associated with brain function within superior temporal sulcus

Acting appropriately within social contexts requires an ability to appreciate others' mental and emotional states. Indeed, some campaign programs designed to reduce anti-social behaviour seek to elicit empathy for the victims. The effectiveness of these campaigns can be evaluated according to the degree to which they induce such responses, but by applying neuroscientific techniques this can be done at the behavioural and neurophysiological level. Neuroimaging studies aimed at identifying the neural mechanisms behind such socio-cognitive and -emotional processes frequently reveal the role of the superior temporal sulcus (STS). We applied this knowledge to assess the effectiveness of traffic-awareness campaign adverts to induce empathic expression. Functional magnetic resonance imaging (fMRI) data were acquired from 20 healthy male volunteers as they watched these campaign videos consisting of a dramatic sequence of events and catastrophic endings, and control videos without such dramatic endings. Among other structures, a significantly greater neural response was observed within bilateral STS, particularly within the right hemisphere, during the observation of campaign relative to control videos. Furthermore, activation in these brain regions correlated with the subjects' empathic expression. Our results develop our understanding of the role of STS in social cognition. Moreover, our data demonstrate the utility of neuroscientific methods when evaluating the effectiveness of campaign videos in terms of their ability to elicit empathic responses. Our study also demonstrates the utility of these specific stimuli for future neuroscientific research

Functional anatomy of outcome evaluation during Iowa Gambling Task performance in patients with Parkinson's disease: an fMRI study

Abstract The aim of this study was to investigate the functional anatomy of decision-making during the Iowa Gambling Task in patients with Parkinson's disease. We used event-related functional magnetic resonance imaging (fMRI) during a computerized version of IGT to compare 18 PD patients on dopaminergic medication in the ON state and 18 healthy control subjects. Our analyses focused on outcome evaluation following card selection, because we expected this aspect of decision-making to be impaired in PD patients. The PD patients exhibited lower activation of the left putamen than the control group as a reaction to penalty. Using psychophysiological interaction analysis, we identified decreased functional connectivity between the right globus pallidus internus and the left anterior cingulate gyrus in the PD group. In contrast, increased connectivity between these structures was observed after penalty in the control group. Our results suggest altered functioning of the basal ganglia and their connections with the cortical structures involved in the limbic loop (e.g., the limbic fronto-striatal circuit of the basal ganglia) during decision-making in PD patients. Differences in the response to loss could be associated with insufficient negative reinforcement after a loss in PD patients in the ON state in comparison to a healthy population

Cortico-cerebellar functional connectivity and sequencing of movements in schizophrenia

<p>Abstract</p> <p>Background</p> <p>Abnormal execution of several movements in a sequence is a frequent finding in schizophrenia. Successful performance of such motor acts requires correct integration of cortico-subcortical processes, particularly those related to cerebellar functions. Abnormal connectivity between cortical and cerebellar regions with resulting cognitive dysmetria has been proposed as the core dysfunction behind many signs and symptoms of schizophrenia. The aim of the present study was to assess if these proposed abnormalities in connectivity are a unifying feature of schizophrenia, or, rather, reflect a specific symptom domain of a heterogeneous disease. We predicted that abnormal functional connectivity between the motor cortex and cerebellum would be linked with abnormal performance of movement sequencing.</p> <p>Methods</p> <p>We examined 24 schizophrenia patients (SCH) and 24 age-, sex-, and handedness-matched healthy controls (HC) using fMRI during a modified finger-tapping task. The ability to perform movement sequencing was tested using the Neurological Evaluation Scale (NES). The subjects were categorized into two groups, with (SQ+) and without (SQ-) movement sequencing abnormalities, according to the NES-SQ score. The effects of diagnosis and movement sequencing abnormalities on the functional connectivity parameters between the motor cortex and cerebellum (MC-CRBL) and the supplementary motor cortex and cerebellum (SMA-CRBL) activated during the motor task were analyzed.</p> <p>Results</p> <p>We found no effect of diagnosis on the functional connectivity measures. There was, however, a significant effect on the SQ group: SQ + patients showed a lower level of MC-CRBL connectivity than SQ- patients and healthy controls. Moreover, the level of MC-CRBL and SMA-CRBL negatively correlated with the magnitude of NES-SQ abnormalities, but with no other NES domain.</p> <p>Conclusions</p> <p>Abnormal cortico-cerebellar functional connectivity during the execution of a motor task is linked with movement sequencing abnormalities in schizophrenia, but not with the diagnosis of schizophrenia per se. It seems that specific patterns of inter-regional connectivity are linked with corresponding signs and symptoms of clinically heterogeneous conditions such as schizophrenia.</p

Modification of Brain Functional Connectivity in Adolescent Thoracic Idiopathic Scoliosis by Lower Extremities Position

The involvement of the brain motor system in idiopathic scoliosis remains unclear. In this paper, we question whether the functional connectivity (FC) of the central motor circuitry is abnormal in adolescent idiopathic scoliosis (AIS) and whether it can be modified by flexion of the lower extremities. Functional magnetic resonance imaging (fMRI) in 18 patients with a right thoracic idiopathic curve greater than 30&deg; (mean angle 49.4&deg;, mean age 15.3 years, 4 males) and 22 healthy controls (mean age 18.2 years, 4 males) was explored using a 3T MR scanner. We measured their resting-state fMRI: (a) with extended lower extremities; (b) with semiflexion of the left lower extremity and extended right lower extremity, with hip abduction. Decreased FC between the secondary motor area (SMA) and postcentral cortex, pallidum and cuneus, postcentral gyrus and cerebellum, putamen and temporal lateral neocortex was observed in AIS. This pathological connectivity was reversed by lower extremity semiflexion. The FC between cortical and subcortical motor structures is significantly decreased in AIS. The decreased FC of the SMA, basal ganglia, cuneus (a hub structure), and cerebellum indicates the functional impairment of structures involved in regulating muscular tone. FC impairment in patients with AIS appears to be a reaction to the pathological condition. This pathological pattern flexibly reacts to changes in the positioning of the lower extremities, showing that the functional impairment of brain motor circuitry in AIS is reversible. We suggest that the reactivity of cerebral activity leading to brain activity normalization could be used for a rehabilitation program for patients with AIS

Modification of Brain Functional Connectivity in Adolescent Thoracic Idiopathic Scoliosis by Lower Extremities Position

The involvement of the brain motor system in idiopathic scoliosis remains unclear. In this paper, we question whether the functional connectivity (FC) of the central motor circuitry is abnormal in adolescent idiopathic scoliosis (AIS) and whether it can be modified by flexion of the lower extremities. Functional magnetic resonance imaging (fMRI) in 18 patients with a right thoracic idiopathic curve greater than 30° (mean angle 49.4°, mean age 15.3 years, 4 males) and 22 healthy controls (mean age 18.2 years, 4 males) was explored using a 3T MR scanner. We measured their resting-state fMRI: (a) with extended lower extremities; (b) with semiflexion of the left lower extremity and extended right lower extremity, with hip abduction. Decreased FC between the secondary motor area (SMA) and postcentral cortex, pallidum and cuneus, postcentral gyrus and cerebellum, putamen and temporal lateral neocortex was observed in AIS. This pathological connectivity was reversed by lower extremity semiflexion. The FC between cortical and subcortical motor structures is significantly decreased in AIS. The decreased FC of the SMA, basal ganglia, cuneus (a hub structure), and cerebellum indicates the functional impairment of structures involved in regulating muscular tone. FC impairment in patients with AIS appears to be a reaction to the pathological condition. This pathological pattern flexibly reacts to changes in the positioning of the lower extremities, showing that the functional impairment of brain motor circuitry in AIS is reversible. We suggest that the reactivity of cerebral activity leading to brain activity normalization could be used for a rehabilitation program for patients with AIS

Social support modulates subjective and neural responses to sad mental imagery

Mental imagery related to the recent death of a loved one is associated with intense sadness and distress. Social relations, such as with one's significant other, can regulate negative emotions and provide comfort, but the neural correlates of social comfort are largely unknown. In this functional magnetic resonance imaging study, we examined brain responses to sad mental imagery and how these are modulated by holding hands with one's romantic partner. We found that mental imagery of a recently deceased loved one was associated with increased reactivity in the dorsal striatum, medial prefrontal cortex, anterior and posterior cingulate cortex, thalamus and cerebellum. Holding hands with one's partner as compared to being alone or holding hands with a stranger provided subjective comfort and reduced neural reactivity in the dorsal striatum without affecting the vividness of the imagery. Our findings indicate an important role for the dorsal striatum in sad mental imagery and social comfort and suggest that tactile social support by one's romantic partner regulates subjective distress through other processes than mere distraction from the mental imagery

Magnetic resonance spectroscopy of the thalamus in patients with typical absence epilepsy

SummaryPurposeTo investigate possible neuronal dysfunction of the thalamus in patients suffering from typical absence epilepsy, using magnetic resonance spectroscopy (MRS). Special attention was paid to levels of N-acetylaspartate (NAA) and creatine (Cr), and to the NAA/Cr ratio.MethodsMRS was performed over the right and left thalamus in nine patients suffering from typical absence epilepsy, and in nine sex- and age-matched healthy controls. All patients and controls were examined using a standard MRS-CSI (chemical shift imaging) technique.ResultsStatistical analysis of the obtained data demonstrated a significantly lower thalamic NAA/Cr ratio in patients with typical absence epilepsy when compared to the healthy controls. Our MRS data showed symmetrical distribution of NAA/Cr ratio in the right and left thalamus within both the patient group and the group of healthy controls. No significant correlation between the patients’ thalamic NAA/Cr values and the duration of the epilepsy or seizure frequency was revealed.ConclusionsThe present MRS data clearly indicate neuronal dysfunction in the thalami of patients with typical absence epilepsy. In agreement with other recent MRS findings in different idiopathic generalized epilepsy syndromes, our results confirm the role of the thalamus as an important structure in the pathogenesis of typical absence epilepsy

Soothing the emotional brain : modulation of neural activity to personal emotional stimulation by social touch

Social touch may modulate emotions, but the neurobehavioral correlates are poorly understood. Here, we investigated neural responses to a picture of a deceased close person and if neural activity and connectivity are modulated by social touch from one's romantic partner. Using functional magnetic resonance imaging (fMRI) we found altered reactivity in several brain areas including the anterior cingulate cortex (ACC) and the anterior insula in response to the personal picture compared to a picture of an unfamiliar person. Hand holding with the romantic partner, compared to being alone, reduced reactivity in the ACC and cerebellum and provided subjective comfort. To separate physical touch from the emotional effect of partner presence, we evaluated hand holding with the partner relative to a stranger, and found reduced reactivity in the anterior insula. Connectivity between the anterior insula and the ACC was reduced during partner touch, and the connectivity strength were negatively related to attachment security, with higher reported partner security associated with weaker connectivity. Overall, holding hands with one's partner attenuates reactivity in emotional brain areas and reduces between-region connectivity