Volume loss in the deep gray matter and thalamic subnuclei: a longitudinal study on disability progression in multiple sclerosis

Journal of Neurology - Volume loss in the deep gray matter (DGM) has been reported in patients with multiple sclerosis (MS) already at early stages of the disease and is thought to progress...     

Structural and functional asymmetry of lateral Heschl's gyrus reflects pitch perception preference

The relative pitch of harmonic complex sounds, such as instrumental sounds, may be perceived by decoding either the fundamental pitch (f0) or the spectral pitch (fSP) of the stimuli. We classified a large cohort of 420 subjects including symphony orchestra musicians to be either f0 or fSP listeners, depending on the dominant perceptual mode. In a subgroup of 87 subjects, MRI (magnetic resonance imaging) and magnetoencephalography studies demonstrated a strong neural basis for both types of pitch perception irrespective of musical aptitude. Compared with f0 listeners, fSP listeners possessed a pronounced rightward, rather than leftward, asymmetry of gray matter volume and P50m activity within the pitch-sensitive lateral Heschl's gyrus. Our data link relative hemispheric lateralization with perceptual stimulus properties, whereas the absolute size of the Heschl's gyrus depends on musical aptitude.     

Differentiation of multiple sclerosis plaques,subacute cerebral ischaemic infarcts,focal vasogenic oedema and lesions of subcortical arteriosclerotic encephalopathy using magnetisation transfer measurements

Although multiple sclerosis (MS) plaques, subacute cerebral ischaemic infarcts, focal vasogenic brain oedema, and subcortical arteriosclerotic encephalopathy (SAE) often have typical radiological patterns, they are sometimes difficult to distinguish from each other. Our aim was to determine whether they can be differentiated by magnetisation transfer (MT) measurements. We measured MT ratios (MTR) in ten patients with plaques of MS, 11 with subacute ischaemic infarcts, 12 with focal vasogenic oedema, and ten with lesions of SAE and compared the mean MTRs statistically. The MTR of normal white matter was 47.3%; the lowest MTR was found in plaques of MS (mean 26.4%). With the exception of vasogenic oedema and subacute cerebral ischaemic infarcts the mean MTRs were significantly different between all groups. MT measurements can provide additional information for the differentiation of these conditions, but we could not distinguish vasogenic oedema from subacute cerebral ischaemic infarcts.     

Funktionelle Neuroanatomie: Sensomotorisches System

The sensorimotor flow of information can be divided in three steps: perception, processing and reaction. Environmental impulses are conducted through receptors to the central nervous system (CNS). The impulses arriving in the somatosensory cortex are processed through complex interactions between sensory and motor areas. The motor action in response to the environmental changes is transferred from the motor cortex via the pyramidal tract, spinal tracts and motor neurons to the respective muscles. With functional magnetic resonance imaging (fMRI) it is possible to assess somatosensory and motor activation in the different cortical areas involved. Clinically, this information is used to assess the local relationship between brain tumors and functionally important areas. This is important to ensure an optimal individual therapeutic approach with the aim of an as radical as possible tumor resection with preservation of the motor and somatosensory functions. Furthermore, fMRI enables the evaluation of pathological changes of cerebral activation. This review describes the functional somatosensory and motor systems and gives an insight into the potential of fMRI.     

Interaction of tactile input in the human primary and secondary somatosensory cortex--a magnetoencephalographic study

Interaction of simultaneous tactile input at two finger sites in primary (SI) and secondary somatosensory cortex (SII) was studied by whole-head magnetoencephalography. Short pressure pulses were delivered to fingers of the right and left hand at an interstimulus interval of 1.6 s. The first phalanx of the left digit 1 and four other sites were stimulated either separately or simultaneously. We compared four sites with increasing distance: the second phalanx of left digit 1, left digit 5, and digits 1 and 5 of the right hand. The temporal evolution of source activity in the contralateral SI and bilateral SII was calculated using spatiotemporal source analysis. Interaction was assessed by comparing the source activity during simultaneous stimulation with the sum of the source activities elicited by separate stimulation. Significant suppressive interaction was observed in contralateral SI only for stimuli at the same hand, decreasing with distance. In SII, all digits of the same and the opposite hand interacted significantly with left digit 1. When stimulating bilaterally, SII source waveforms closely resembled the time course of the response to separate stimulation of the opposite hand. Thus, in bilateral simultaneous stimulation, the contralateral input arriving first in SII appeared to inhibit the later ipsilateral input. Similarly, the separate response to input at two unilateral finger sites which arrived slightly earlier in SII dominated the simultaneous response. Our results confirm previous findings of considerable overlap in the cortical hand representation in SII and illustrate hemispheric specialization to contralateral input when simultaneous stimuli occur bilaterally.     

Postoperative Befunde an der Wirbels?ule

Postoperative imaging after spinal surgery is usually performed to document the correct positioning of implants or to rule out complications if patients still suffer from pain after surgery. Depending on the question various imaging modalities can be used all of which have benefits and limitations. Conventional X-ray is used for the documentation of the correct positioning of spinal implants, stability (olisthesis) and during follow-up to rule out fractures or instability of the implants, whereas soft tissue changes cannot be completely assessed. Besides these indications, imaging is usually performed because of ongoing symptoms (pain for the most part) of the patients. Soft tissue changes including persistent or recurrent herniated disc tissue, hematoma or infection can best be depicted using magnetic resonance imaging (MRI) which should be performed within the immediate postoperative period to be able to distinguish physiological development of scar tissue from inflammatory changes in the area of the surgical approach. Often imaging alone cannot differentiate between these and imaging can therefore only be considered as an adjunct. Computed tomography is the modality of choice for the evaluation of bony structures and an adjunct of new therapies such as image-guided application of cement for kyphoplasty or vertebroplasty.     

Prächirurgische funktionelle Magnetresonanztomographie

Functional magnetic resonance imaging (fMRI) is an important and novel neuroimaging modality for patients with brain tumors. By non-invasive measurement, localization and lateralization of brain activiation, most importantly of motor and speech function, fMRI facilitates the selection of the most appropriate and sparing treatment and function-preserving surgery. Prerequisites for the diagnostic use of fMRI are the application of dedicated clinical imaging protocols and standardization of the respective imaging procedures. The combination with diffusion tensor imaging (DTI) also enables tracking and visualization of important fiber bundles such as the pyramidal tract and the arcuate fascicle. These multimodal MR data can be implemented in computer systems for functional neuronavigation or radiation treatment. The practicability, accuracy and reliability of presurgical fMRI have been validated by large numbers of published data. However, fMRI cannot be considered as a fully established modality of diagnostic neuroimaging due to the lack of guidelines of the responsible medical associations as well as the lack of medical certification of important hardware and software components. This article reviews the current research in the field and provides practical information relevant for presurgical fMRI.     

Neural reward processing is modulated by approach- and avoidance-related personality traits

The neural processing of reward can be differentiated into two sub-components with different functions, “wanting” (i.e., the expectation of a reward which includes appetitive and motivational components) and “liking” (i.e., the hedonic impact experienced during the receipt of a reward), involving distinct neural systems. We hypothesize that variability in neural reward processing previously observed in healthy subjects could reflect inter-individual differences in personality. Therefore, the aim of this study was to investigate how the neural processing during expectation and reception of a reward depends on interpersonal differences in reward sensitivity, more specifically the tendency to approach vs. avoid reward-related situations. We employed event-related functional magnetic resonance imaging during a monetary incentive delay task. Subjects with a high approach motivation showed more activation of the Ventral Striatum (VS) during the receipt of a reward, and more medial orbitofrontal activity during both the receipt and omission of a reward. Subjects with a high behavioral inhibition showed less activation in the VS during the receipt of a reward. These findings indicate that the tendency to approach or avoid reward-related situations exhibits a distinct relation with neural reward processing. Specifically, subjects with high behavioral approach appear to be sensitive mainly to positive outcomes and to a lesser extent to the omissions of rewards, whereas subjects with low behavioral approach as well as those with a high inhibition tendency display a blunted response to rewards.