Peter Erhard

Distraction modulates connectivity of the cingulo-frontal cortex and the midbrain during pain--an fMRI analysis.

&NA; Neuroimaging studies with positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) have delineated a human pain network in vivo. Despite the recognition of cerebral structures engaged in pain transmission, the cerebral mechanisms involved in pain modulation are still not well understood. Here, we investigated healthy volunteers using fMRI during experimental heat pain and distraction induced by a visual incongruent color‐word Stroop task. A factorial design permitted categorical and covariation analysis of four conditions, namely innocuous and noxious heat; with and without distraction. Pain without distraction evoked an activation pattern similar to that observed in previous neuroimaging pain studies. Distraction was associated with a significant reduction of the visual analogue scale (VAS) ratings for pain intensity and unpleasantness and a reduction of pain‐related activation in multiple brain areas, particularly in the so‐called ‘medial pain system’. Distraction significantly increased the activation of the cingulo‐frontal cortex including the orbitofrontal and perigenual anterior cingulate cortex (ACC), as well as the periaquaeductal gray (PAG) and the posterior thalamus. Covariation analysis revealed functional interaction between these structures during pain stimulation and distraction, but not during pain stimulation per se. According to our results, the cingulo‐frontal cortex may exert top–down influences on the PAG and posterior thalamus to gate pain modulation during distraction.

Transmodal Sensorimotor Networks during Action Observation in Professional Pianists

Audiovisual perception and imitation are essential for musical learning and skill acquisition. We compared professional pianists to musically naive controls with fMRI while observing piano playing fingerhand movements and serial fingerthumb opposition movements both with and without synchronous piano sound. Pianists showed stronger activations within a fronto-parieto-temporal network while observing piano playing compared to controls and contrasted to perception of serial fingerthumb opposition movements. Observation of silent piano playing additionally recruited auditory areas in pianists. Perception of piano sounds coupled with serial fingerthumb opposition movements evoked increased activation within the sensorimotor network. This indicates specialization of multimodal auditory sensorimotor systems within a fronto-parieto-temporal network by professional musical training. Musical language, which is acquired by observation and imitation, seems to be tightly coupled to this network in accord with an observation execution system linking visual and auditory perception to motor performance.

A functional magnetic resonance imaging study of the role of left posterior superior temporal gyrus in speech production: Implications for the explanation of conduction aphasia

Conduction aphasia, characterized by good auditory comprehension and fluent but disordered speech production, is classically viewed as a disconnection syndrome. We review recent evidence which suggests that at least one form of conduction aphasia results from damage to cortical fields in the left posterior superior temporal gyrus which participate not only in speech perception, but also in phonemic aspects of speech production. As a test of this hypothesis, we carried out a 4T functional magnetic resonance imaging study in which subjects named visually presented objects sub-vocally. Group-based analyses showed that a majority of participants showed activation in two regions on the dorsal portion of the left posterior superior temporal gyrus.

Left inferior parietal dominance in gesture imitation : an fMRI study

The inability to imitate gestures is an essential feature of apraxia. However, discrepancies exist between clinical studies in apraxic patients and neuroimaging findings on imitation. We therefore aimed to investigate: (1) which areas are recruited during imitation under conditions similar to clinical tests for apraxic deficits; (2) whether there are common lateralized areas subserving imitation irrespective of the acting limb side; and also (3) whether there are differences between hand and finger gestures. We used fMRI in 12 healthy, right handed subjects to investigate the imitation of four types of variable gestures that were presented by video clips (16 different finger and 16 different hand gestures with either the right or the left arm). The respective control conditions consisted of stereotyped gestures (only two gestures presented in pseudorandom order). Subtraction analysis of each type of gesture imitation (variable>stereotyped) revealed a bilateral activation pattern including the inferior parietal cortex Brodmann Area (BA 40), the superior parietal cortex, the inferior frontal cortex (opercular region), the prefrontal motor cortex, the lateral occipito-temporal junction, and the cerebellum. These results were supported by statistical conjunction of all four subtraction analyses and by the common analysis of all four types of gesture imitation. The direct comparison of the right and left hemispheric activation revealed a lateralization to the left only of the inferior parietal cortex. Comparisons between different types of gesture imitation yielded no significant results. In conclusion, gesture imitation recruits bilateral fronto-parietal regions, with significant lateralization of only one area, namely the left inferior parietal cortex. These in vivo data indicate left inferior parietal dominance for gesture imitation in right handers, confirming lesion-based theories of apraxia.

Reduced recruitment of motor association areas during bimanual coordination in concert pianists.

Bimanual motor coordination is essential for piano playing. The functional neuronal substrate for high‐level bimanual performance achieved by professional pianists is unclear. We compared professional pianists to musically naïve controls while carrying out in‐phase (mirror) and anti‐phase (parallel) bimanual sequential finger movements during functional magnetic resonance imaging (fMRI). This task corresponds to bimanually playing scales practiced daily by pianists from the beginning of piano playing. Musicians and controls showed significantly different functional activation patterns. When comparing performance of parallel movements to rest, musically naïve controls showed stronger activations than did pianists within a network including anterior cingulate cortex, right dorsal premotor cortex, both cerebellar hemispheres, and right basal ganglia. The direct comparison of bimanual parallel to mirror movements between both groups revealed stronger signal increases in controls within mesial premotor cortex (SMA), bilateral cerebellar hemispheres and vermis, bilateral prefrontal cortex, left ventral premotor cortex, right anterior insula, and right basal ganglia. These findings suggest increased efficiency of cortical and subcortical systems for bimanual movement control in musicians. This may be fundamental to achieve high‐level motor skills allowing the musician to focus on artistic aspects of musical performance. Hum. Brain Mapping 22:206–215, 2004.

The role of lateral premotor-cerebellar-parietal circuits in motor sequence control: a parametric fMRI study.

Functional characterisation of higher order motor systems can be obtained by modulating the processing demands imposed onto relevant motor circuitries. Here we performed whole-brain functional magnetic resonance imaging (fMRI) and parametric statistical analyses in eight healthy volunteers to study task-related recruitment of motor circuits associated with unilateral finger movement sequences of increasing length and complexity, but with equal basic motor parameters. Statistical parametric mapping software was applied for analysis. Categorical analysis of the main effect of motor action showed cerebral activation in the established cortical and subcortical motor network. Parametric analyses of the blood-oxygen-level-dependent (BOLD) contrast revealed significant signal increases correlating to sequence length and complexity in a subset of activated areas, notably contralateral ventral and dorsal premotor cortex, bilateral superior parietal cortex, left inferior frontal gyrus/Brocas area, right dentate nucleus, and left visual association cortex. These data underscore the importance of ventral premotor-cerebellar-parietal circuits in processing length and complexity of sequential finger movements.

“Silent event-related” fMRI reveals reduced sensorimotor activation in laryngeal dystonia

Objective: To study with fMRI the pattern of sensorimotor activation in patients with spasmodic dysphonia (laryngeal dystonia) compared to healthy controls. Methods: The authors performed fMRI measurements during vocal motor tasks in 12 patients with laryngeal dystonia and compared them with those of 12 healthy volunteers. Patients were scanned before (pre) and after (post) treatment with local injections of botulinum toxin (BTX). They examined two different motor tasks: simple vocalization inducing dystonia and whispering without appearance of dystonic symptoms. To avoid movement artifacts with oral motor tasks, the authors used a silent event-related fMRI approach involving noncontinuous sampling with no data acquisition during task performance. Results: They found reduced activation of primary sensorimotor as well as of premotor and sensory association cortices during vocalization in patients with laryngeal dystonia pre-BTX. This was partly observed also during the asymptomatic whispering task. BTX treatment did not result in reversal of reduced cortical activation. Conclusion: fMRI signal is reduced in sensorimotor cortices associated with movement of the affected body part in laryngeal dystonia, supporting a dystonic basis for this voice disorder.

Individualized and Clinically Derived Stimuli Activate Limbic Structures in Depression: An fMRI Study

Objectives In the search for neurobiological correlates of depression, a major finding is hyperactivity in limbic-paralimbic regions. However, results so far have been inconsistent, and the stimuli used are often unspecific to depression. This study explored hemodynamic responses of the brain in patients with depression while processing individualized and clinically derived stimuli. Methods Eighteen unmedicated patients with recurrent major depressive disorder and 17 never-depressed control subjects took part in standardized clinical interviews from which individualized formulations of core interpersonal dysfunction were derived. In the patient group such formulations reflected core themes relating to the onset and maintenance of depression. In controls, formulations reflected a major source of distress. This material was thereafter presented to subjects during functional magnetic resonance imaging (fMRI) assessment. Results Increased hemodynamic responses in the anterior cingulate cortex, medial frontal gyrus, fusiform gyrus and occipital lobe were observed in both patients and controls when viewing individualized stimuli. Relative to control subjects, patients with depression showed increased hemodynamic responses in limbic-paralimbic and subcortical regions (e.g. amygdala and basal ganglia) but no signal decrease in prefrontal regions. Conclusions This study provides the first evidence that individualized stimuli derived from standardized clinical interviewing can lead to hemodynamic responses in regions associated with self-referential and emotional processing in both groups and limbic-paralimbic and subcortical structures in individuals with depression. Although the regions with increased responses in patients have been previously reported, this study enhances the ecological value of fMRI findings by applying stimuli that are of personal relevance to each individuals depression.

Hypothalamic activation in trigeminal autonomic cephalgia: functional imaging of an atypical case.

We report headache induced BOLD changes in an atypical case of trigeminal autonomic cephalgia (TAC). A 68-year-old patient was imaged using fMRi during three attacks of a periorbital head-pain with a average duration of 3 min. During the attacks, left sided conjunctival injection, rhinorrhea, lacrimation, facial sweating and hypersalivation were apparent. These attacks were usually partly responsive to oxygen administration but otherwise refractory to any drug. The patient described either attacks with a duration of one minute or less or longer attacks persisting for maximum of 20 min with headaches occurring up to 100 times a day. When considering the symptoms, frequency, duration and therapeutic response of the patients headache, no clear-cut classification to one of the subtypes of trigeminal autonomic cephalgias (cluster headache, paroxysmal hemicrania, SUNCT) or trigeminal neuralgia was possible. The cerebral activation pattern was similar but not identical to those previously observed in cluster headache and SUNCT with a prominent activation in the hypothalamic grey matter. This case study underlines the conceptual value of the term TAC for the group of headaches focusing around the trigeminal-autonomic reflex. Our results emphasize the importance of the hypothalamus as key region in the pathophysiology of this entity.

Functional Neuroanatomy of Perceiving Surprised Faces

Surprise is one of six emotions having a specific and universally recognized facial expression. Functional imaging and neuropsychologic studies have uncovered partly separable neural substrates for perceiving different facial expressions; however, the functional neuroanatomy of perceiving surprised faces has not yet been investigated. Using functional magnetic resonance imaging (fMRI), we aimed to identify the neural substrate of surprise perception from facial expressions. Based on the assumption of unexpectedness and novelty as elicitors of facial surprise reactions, we hypothesized recruitment of medial temporal lobe structures implicated in novelty detection during the perception of surprise in others. Healthy subjects were scanned while they were presented with surprised faces. As a control, they viewed faces depicting neutral or disgust expressions. Activations during the emotional conditions were contrasted with each other and with the neutral face condition. Compared to both control conditions, perception of surprised facial expressions yielded consistently increased signals in the parahippocampal region, an area associated previously with novelty detection. Our findings therefore suggest a close relation between perceiving surprise in others and the response to novel events. Additionally, we confirmed activation of the insula during perception of disgust expressions. Hum. Brain Mapping 23:181–187, 2004.