Implicit and Explicit Routes to Recognize the Own Body: Evidence from Brain Damaged Patients

Much research suggested that recognizing our own body-parts and attributing a body-part to our physical self-likely involve distinct processes. Accordingly, facilitation for self-body-parts was found when an implicit, but not an explicit, self-recognition was required. Here, we assess whether implicit and explicit bodily self-recognition is mediated by different cerebral networks and can be selectively impaired after brain lesion. To this aim, right- (RBD) and left- (LBD) brain damaged patients and age-matched controls were presented with rotated pictures of either self- or other-people hands. In the Implicit task participants were submitted to hand laterality judgments. In the Explicit task they had to judge whether the hand belonged, or not, to them. In the Implicit task, controls and LBD patients, but not RBD patients, showed an advantage for self-body stimuli. In the Explicit task a disadvantage emerged for self-compared to others' body stimuli in controls as well as in patients. Moreover, when we directly compared the performance of patients and controls, we found RBD, but not LBD, patients to be impaired in both the implicit and explicit recognition of self-body-part stimuli. Conversely, no differences were found for others' body-part stimuli. Crucially, 40% RBD patients showed a selective deficit for implicit processing of self-body-part stimuli, whereas 27% of them showed a selective deficit in the explicit recognition of their own body. Additionally, we provide anatomical evidence revealing the neural basis of this dissociation. Based on both behavioral and anatomical data, we suggest that different areas of the right hemisphere underpin implicit and explicit self-body knowledge

fMRI of emotion: some clinical applications at 3 Tesla.

INTRODUCTION It is well known that amygdala is a key point nervous structure in the emotional limbic system. When, for instance, the situation becomes dangerous for the individual, the amygdala comes into play and, by the activation of a series of pathways (conscious and unconscious), may trigger biologic and behavioural responses, which enable the individual to cope with the danger and to survive it (fight or flight). The emotional system output acts through both the classic somatic motor system and its own motor pathways (the emotional motor system), which act in parallel to promote the correct behavioural response. The advent of functional Magnetic Resonance Imaging (fMRI) allowed a better definition of the activity of these limbic structures, not only in the normal population, but also in some clinical applications. At our Neuroscience Department we applied fMRI to two very different pathologies: panic disorder and ulcerative colitis. PANIC DISORDERS. Aim. Panic disorder (PD) is an anxiety disorder characterized by recurring severe panic attacks and chronic hyperarousal. It has been shown that, in normal population, amygdala activates in response to fearful faces even if presented below the threshold of conscious visual perception. Our aim was to establish whether the amygdala was engaged by the two different presentations of fearful faces and whether its responses were different in PD patients and controls. Materials and Methods. 13 PD patients and 15 healthy volunteers underwent two passive viewing tasks during a 3T fMRI scanning: 1) presentation of faces with fearful vs neutral expressions (17 ms, subliminar stimulus) using a backward masking procedure; 2) presentation of the same faces vs neutral expressions (200 ms, consciously perceived stimulus), whose spatial frequency contents had been manipulated by low-pass filtering (low spatial frequencies, LSF). Results. Whereas controls showed a bilateral activation for fearful masked faces and left amygdala activation for the LSF condition, patients failed to show any activation within the amygdala in both conditions. Conclusions. Findings showed that the chronic hyperarousal in PD patients is correlated with a reduced amygdala activation to potentially threatening visual stimuli, thus becoming maladaptive. Therapeutic approaches should consider not only the clearly visible overreaction to harmless stimuli, but also the hyporeaction to real danger that chronic PD patients might have developed over time. ULCERATIVE COLITIS. Aim. The aim of this study was to investigate the emotional system in patients suffering from Ulcerative Colitis (UC). To this aim, we focused on Amygdala, perigenual Anterior Cingulate Cortex (pACC), anterior part of Middle Cingulate Cortex (aMCC) and medial Prefrontal Cortex (mPFC), the main nervous structures crucially involved in the emotional processing. We used fMRI to evaluate the changes in Blood Oxigenation Level Dependent (BOLD) signal induced by single and repeated visual emotional stimulations, within the aforesaid limbic structures, in patients with mild UC in clinical remission, compared to healthy people. Materials and Methods. We tested 10 UC patients having mild disease in clinical remission and 10 healthy Control subjects by 3T fMRI, during a visual emotional stimulation (by using International Affective Picture System (IAPS) images). Two identical visual emotional stimulations were repeated for each subject in the same session, in order to study amygdala, pACC, aMCC and mPFC ROI-based BOLD signal changes in the 1st response (1st Trial) and habituation (2nd Trial). A repeated measures ANOVA was used for the statistical analysis of the results. Results. UC patients showed a different emotional activation pattern with respect to Control subjects. In the 1st Trial, UC patients showed a significantly lower bilateral fMRI BOLD signal in all the limbic structures examined, with respect to the Control group. In the 2nd Trial, the Control..

Attivazione corticale

Fin dalle sue origini, negli anni Novanta, la tecnica dell'attivazione funzionale cerebrale (functional Magnetic Resonance lmaging, fMRI) \ue8 stata molto usata non solo per la definizione incruenta di molte funzioni fisiologiche cerebrali, ma anche per le ampie possibilit\ue0 d'impiego nella pratica clinica. In questo capitolo saranno presi in considerazione i meccanismi neurofisiologici alla base dell'attivazione corticale, partendo dalla genesi del contrasto BOLD e dall'accoppiamento neurovascolare, fino ad arrivare alla risposta emodinamica. Saranno, quindi, descritte le motivazioni relative all'uso dei paradigmi, saranno illustrati alcuni paradigmi usati nella pratica clinica e verr\ue0 spiegato come viene acquisito ed elaborato un esame di attivazione funzionale corticale. Si esamineranno, poi, vantaggi e limiti della tecnica e le principali applicazioni cliniche. Infine, sar\ue0 brevemente esaminato un nuovo approccio funzionale della fMRI: lo studio del cosiddetto Default Mode Network (DMN)

Use of fMRI activation paradigms: A presurgical tool for mapping brain function

In this paper, we focus our attention on the phenomena at the root of eloquent brain maps, the description of some activation paradigms, their main presurgical application and some new approaches to fMRI

Functional MRI at 3.0 tesla

The localization of the BOLD signal becomes reliable at high MR fields. This allows not only to confirm and deepen many known functional phenomena but also to throw new light in many aspects of the physiology and pathology of the brai

Functional MRI (fMRI) Evaluation of Hyperbaric Oxygen Therapy (HBOT) Efficacy in Chronic Cerebral Stroke: A Small Retrospective Consecutive Case Series

Topics: Functional Magnetic Resonance Imaging (fMRI) evaluation of HyberBaric Oxygen Therapy (HBOT) effects on chronic cerebral stroke Patients (Pts). Introduction: Our aim was to evaluate with fMRI, in a 3 Tesla system, the functional effects of HBOT on the Central Nervous System (CNS) in four Pts with established ischaemic and haemorrhagic cerebral strokes (2 Pts each). To our knowledge, no author used fMRI technique for this purpose, till now. Methods: All four Pts underwent a fMRI study before and after 40 HBOT sessions, with a time window of a few days. They carried out two language (text listening, silent word-verb generation) and two motor (hand and foot movements) tasks (30 s On-Off block paradigms). Results: After HBOT, all Pts reported a clinical improvement, mostly concerning language fluency and motor paresis. fMRI analysis demonstrated an increase in both the extent and the statistical significance of most of the examined eloquent areas. Conclusions: These changes were consistent with the clinical improvement in all Pts, suggesting a possible role of fMRI in revealing neuronal functional correlates of neuronal plasticity and HBOT-related neoangiogenesis. Although only four Pts were examined, fMRI proved to be a sensitive, non-invasive and reliable modality for monitoring neuronal functional changes before and after HBOT

Amygdala responses to masked and low spatial frequency fearful faces. A preliminary fMRI study in panic disorder

Previous studies have demonstrated amygdala activation in response to fearful faces even if presented below the threshold of conscious visual perception. It has also been proposed that subcortical regions are selectively sensitive to low spatial frequency (LSF) information. However, chronic hyperarousal may reduce amygdala activation in panic disorder (PD). Our aim was to establish whether the amygdala is engaged by masked and LSF fearful faces in PD as compared to healthy subjects. Neutral faces were used as the mask stimulus. Thirteen PD patients (seven females, six males; mean age=29.1 (S.D: 5.9)) and 15 healthy volunteers (seven females, eight males; mean age=27.9 (S.D. 4.5)) underwent two passive viewing tasks during a 3T functional magnetic resonance imaging (fMRI) as follows: 1) presentation of faces with fearful versus neutral expressions (17ms) using a backward masking procedure and 2) presentation of the same faces whose spatial frequency contents had been manipulated by low-pass filtering. Level of awareness was confirmed by a forced choice fear-detection task. Whereas controls showed bilateral activation to fearful masked faces versus neutral faces, patients failed to show activation within the amygdala. LSF stimuli did not elicit amygdala response in either group, contrary to the view that LSF information plays a crucial role in the processing of facial expressions in the amygdala. Findings suggest maladaptive amygdala responses to potentially threatening visual stimuli in PD patients

Neuroradiological diagnostic tools: new MRI perspectives.

MR angiography(5,17) is traditionally divided into "non-contrast enhanced" (NCE MRA) and "contrast-enhanced" (CE MRA) techniques. Contrast-enhanced techniques were initially developed to solve some of the problems encountered with non-contrast-enhanced methods, namely the long examination times, pulsatile flow artefacts, saturation when the mean blood flow is slow or when the imaging slice is parallel to the vessel, the characteristic problems of time of flight (TOF) acquisitions, and the need to define a priori beforehand the velocity sensitivity for phase contrast (PC) acquisitions. Currently used contrast-enhanced techniques(7.8.15.18) are based on the acquisition of 3D gradient-echo sequences synchronized at the first passage of contrast medium by different strategies (detection of a test bolus injection, automated triggering, fluoroscopic imaging). Basically, contrast medium is administered to counteract saturation induced by slow blood flow or flow directed parallel to the imaging slice. Contrast medium serves to obtain a "static" image of vascular structures with acquisitions times ranging from a few seconds to 1-2 minutes. To avoid venous contamination, different methods have been used to collect data (centric-approach, elliptical-centric phase encoding order, etc.) in an attempt to record first the information relating to low spatial frequencies (contrast data) with respect to high spatial frequencies (detail and contour data)

Cerebral areas involved in music perception: studying musicogenic epilepsy.

Functional cerebral areas involved in listening to emotionally charged music are wider than those activated by neutral music. Based on the pathophysiology of musicogenic epilepsy, a rare form of complex reflex epilepsy in which seizures are triggered by music, we can infer the functional organization of the brain's processing of music. We studied a 36-year-old, right-handed male amateur musician, who has had weekly epileptic partial seizures every time he listened to or played music with a strong emotional charge since the age of 24 years. The patient underwent prolonged video-polygraphic recording which documented three right temporal seizures preceded for several seconds by an increase in heart rate and blood pressure, all triggered by listening to music with an emotional content. During functional neuroimaging (fMRI) he listened to both "neutral" and "emotionally charged" music. The “neutral music” activated only a small eloquent area in the right temporal lobe (acoustic area), whereas an “emotionally charged melody" activated diffuse eloquent areas on the fronto-temporo-occipital lobes of the right hemisphere before seizure onset. Numerous studies have demonstrated the predominant involvement of right hemisphere structures in networks involved in processing musical information. Most cases of musicogenic epilepsy showed the dominant role of the right temporal lobe disclosed by functional neuroimaging and neurophysiological techniques. The triggering stimulus in our patient seems to be a strong emotional feeling induced by specific melodies, as his seizures were preceded by an increase in heart rate and blood pressure. Our results emphasize the role of the right temporal lobe in musicogenic epilepsy and show that the cerebral areas activated during the emotional status leading to seizures encompass the auditory cortex activated by neutral music