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Biomedical subjects

Karl Zilles

Publications and source records attributed to Karl Zilles.

At least 73 records · Page 4Linked to original sources
PubMed2005

Multimodal metabolic imaging of cerebral gliomas: positron emission tomography with [18F]fluoroethyl-L-tyrosine and magnetic resonance spectroscopy.

OBJECT: The purpose of this study was to determine the predictive value of [18F]fluoroethyl-L-tyrosine (FET)-positron emission tomography (PET) and magnetic resonance (MR) spectroscopy for tumor diagnosis in patients with suspected gliomas. METHODS: Both FET-PET and MR spectroscopy analyses were performed in 50 consecutive patients with newly diagnosed intracerebral lesions supposed to be diffuse gliomas on contrast-enhanced MR imaging. Lesion/brain ratios of FET uptake greater than 1.6 were considered positive, that is, indicative of tumor. Results of MR spectroscopy were considered positive when N-acetylaspartate (NAA) was decreased in conjunction with an absolute increase of choline (Cho) and an NAA/Cho ratio of 0.7 or less. An FET lesion/brain ratio, an NAA/Cho ratio, and signal abnormalities on MR images were compared with histological findings in neuronavigated biopsy specimens. The FET lesion/brain ratio and the NAA/Cho ratio were identified as significant independent predictors for the histological identification of tumor tissue. The accuracy in distinguishing neoplastic from nonneoplastic tissue could be increased from 68% with the use of MR imaging alone to 97% with MR imaging in conjunction with FET-PET and MR spectroscopy. Sensitivity and specificity for tumor detection were 100 and 81% for MR spectroscopy and 88 and 88% for FET-PET, respectively. Results of histological studies did not reveal tumor tissue in any of the lesions that were negative on FET-PET and MR spectroscopy. In contrast, a tumor diagnosis was made in 97% of the lesions that were positive with both methods. CONCLUSIONS: In patients with intracerebral lesions supposed to be diffuse gliomas on MR imaging, FET-PET and MR spectroscopy analyses markedly improved the diagnostic efficacy of targeted biopsies.

Adolescent↗
PubMed2005

18F-CPFPX PET identifies changes in cerebral A1 adenosine receptor density caused by glioma invasion.

UNLABELLED: Adenosine plays a critical role in both tumor proliferation and the cerebral response to tumor invasion. We used 8-cyclopentyl-3-(3-18F-fluoropropyl)-1-propylxanthine (18F-CPFPX) PET to investigate A1 adenosine receptor (A1AR) density as a potential indicator of the local cerebral response to glioma invasion. METHODS: A1AR density in F98 glioma-bearing rats was examined by 18F-CPFPX and 3H-CPFPX using PET, quantitative in vitro and ex vivo double-label receptor autoradiography, and immunohistochemical analyses. RESULTS: For all imaging modalities, A1AR signal intensity was increased in a zone surrounding experimental tumors (136%-146% that in control tissue) (P < 0.01). Immunostaining identified activated astrocytes as the main origin of peritumoral A1AR upregulation. The results of a pilot 18F-CPFPX PET study on a patient with recurrent glioblastoma multiforme confirmed increases in A1AR density in the immediate vicinity of the tumor. CONCLUSION: 18F-CPFPX PET is suitable for the detection of peritumoral changes in A1AR density. Molecular imaging with 18F-CPFPX PET may open novel possibilities for gaining experimental and clinical insights into the cerebral response to tumor invasion.

Animals↗
PubMed2004

Quantification of cerebral A1 adenosine receptors in humans using [18F]CPFPX and PET: an equilibrium approach.

The cerebral A(1) adenosine receptor (A(1)AR) has recently become accessible for in vivo imaging using the selective A(1)AR ligand [(18)F]CPFPX and PET. For broad application in neurosciences, imaging at distribution equilibrium is advantageous to quantify stimulus-dependent changes in receptor availability and to avoid arterial blood sampling. Here we propose a bolus/infusion (B/I) protocol to assess the total distribution volume (DV(t)) of [(18)F]CPFPX under equilibrium conditions. Employing a bolus-to-infusion ratio of 0.8 h, (near) equilibrium conditions were attained within 60 min. The regional DV(t)' given by arterial and venous equilibrium analyses agreed well with conventional two-tissue compartment model analyses (r(2) > 0.94 and r(2) > 0.84, respectively) and Logan's graphical analyses (r(2) = 1.0 and r(2) > 0.93, respectively) (n = 4 healthy volunteers). The mean regional DV(t)' values of these equilibrium analyses and of venous equilibrium analyses in additional seven volunteers demonstrated excellent agreement with the results of earlier bolus studies (r(2) > 0.98). Error simulations show that minor deviations from true equilibrium are associated with negligible to small DV(t) errors. In conclusion, [(18)F]CPFPX shows suitable characteristics for A(1)AR quantification by B/I PET scanning. Carefully standardized venous equilibrium analyses may substitute arterial analyses and thus considerably enhance applicability of A(1)AR PET in clinical routine.

Adult↗
PubMed2004

Evolution of the brainstem orofacial motor system in primates: a comparative study of trigeminal, facial, and hypoglossal nuclei.

The trigeminal motor (Vmo), facial (VII), and hypoglossal (XII) nuclei of the brainstem comprise the final common output for neural control of most orofacial muscles. Hence, these cranial motor nuclei are involved in the production of adaptive behaviors such as feeding, facial expression, and vocalization. We measured the volume and Grey Level Index (GLI) of Vmo, VII, and XII in 47 species of primates and examined these nuclei for scaling patterns and phylogenetic specializations. Allometric regression, using medulla volume as an independent variable, did not reveal a significant difference between strepsirrhines and haplorhines in the scaling of Vmo volume. In addition, correlation analysis using independent contrasts did not find a relationship between Vmo size or GLI and the percent of leaves in the diet. The scaling trajectory of VII volume, in contrast, differed significantly between suborders. Great ape and human VII volumes, furthermore, were significantly larger than predicted by the haplorhine regression. Enlargement of VII in these taxa may reflect increased differentiation of the facial muscles of expression and greater utilization of the visual channel in social communication. The independent contrasts of VII volume and GLI, however, were not correlated with social group size. To examine whether the human hypoglossal motor system is specialized to control the tongue for speech, we tested human XII volume and GLI for departures from nonhuman haplorhine prediction lines. Although human XII volumes were observed above the regression line, they did not exceed prediction intervals. Of note, orang-utan XII volumes had greater residuals than humans. Human XII GLI values also did not differ from allometric prediction. In sum, these findings indicate that the cranial orofacial motor nuclei evince a mosaic of phylogenetic specializations for innervation of the facial muscles of expression in the context of a generally conservative scaling relationship with respect to medulla size.

Animals↗
PubMed2004

Dominance of the right hemisphere and role of area 2 in human kinesthesia.

We have previously shown that motor areas are engaged when subjects experience illusory limb movements elicited by tendon vibration. However, traditionally cytoarchitectonic area 2 is held responsible for kinesthesia. Here we use functional magnetic resonance imaging and cytoarchitectural mapping to examine whether area 2 is engaged in kinesthesia, whether it is engaged bilaterally because area 2 in non-human primates has strong callosal connections, which other areas are active members of the network for kinesthesia, and if there is a dominance for the right hemisphere in kinesthesia as has been suggested. Ten right-handed blindfolded healthy subjects participated. The tendon of the extensor carpi ulnaris muscles of the right or left hand was vibrated at 80 Hz, which elicited illusory palmar flexion in an immobile hand (illusion). As control we applied identical stimuli to the skin over the processus styloideus ulnae, which did not elicit any illusions (vibration). We found robust activations in cortical motor areas [areas 4a, 4p, 6; dorsal premotor cortex (PMD) and bilateral supplementary motor area (SMA)] and ipsilateral cerebellum during kinesthetic illusions (illusion-vibration). The illusions also activated contralateral area 2 and right area 2 was active in common irrespective of illusions of right or left hand. Right areas 44, 45, anterior part of intraparietal region (IP1) and caudo-lateral part of parietal opercular region (OP1), cortex rostral to PMD, anterior insula and superior temporal gyrus were also activated in common during illusions of right or left hand. These right-sided areas were significantly more activated than the corresponding areas in the left hemisphere. The present data, together with our previous results, suggest that human kinesthesia is associated with a network of active brain areas that consists of motor areas, cerebellum, and the right fronto-parietal areas including high-order somatosensory areas. Furthermore, our results provide evidence for a right hemisphere dominance for perception of limb movement.

Adult↗
PubMed2004

Representation of interaural temporal information from left and right auditory space in the human planum temporale and inferior parietal lobe.

The localization of low-frequency sounds mainly relies on the processing of microsecond temporal disparities between the ears, since low frequencies produce little or no interaural energy differences. The overall auditory cortical response to low-frequency sounds is largely symmetrical between the two hemispheres, even when the sounds are lateralized. However, the effects of unilateral lesions in the superior temporal cortex suggest that the spatial information mediated by lateralized sounds is distributed asymmetrically across the hemispheres. This paper describes a functional magnetic resonance imaging experiment, which shows that the interaural temporal processing of lateralized sounds produces an enhanced response in the contralateral planum temporale (PT). The response is stronger and extends further into adjacent regions of the inferior parietal lobe (IPL) when the sound is moving than when it is stationary. This suggests that the interaural temporal information mediated by lateralized sounds is projected along a posterior pathway comprising the PT and IPL of the respective contralateral hemisphere. The differential responses to moving sounds further revealed that the left hemisphere responded predominantly to sound movement within the right hemifield, whereas the right hemisphere responded to sound movement in both hemifields. This rightward asymmetry parallels the asymmetry associated with the allocation of visuo-spatial attention and may underlie unilateral auditory neglect phenomena.

Adult↗
PubMed2004

Neural circuits underlying imitation learning of hand actions: an event-related fMRI study.

The neural bases of imitation learning are virtually unknown. In the present study, we addressed this issue using an event-related fMRI paradigm. Musically naive participants were scanned during four events: (1) observation of guitar chords played by a guitarist, (2) a pause following model observation, (3) execution of the observed chords, and (4) rest. The results showed that the basic circuit underlying imitation learning consists of the inferior parietal lobule and the posterior part of the inferior frontal gyrus plus the adjacent premotor cortex (mirror neuron circuit). This circuit, known to be involved in action understanding, starts to be active during the observation of the guitar chords. During pause, the middle frontal gyrus (area 46) plus structures involved in motor preparation (dorsal premotor cortex, superior parietal lobule, rostral mesial areas) also become active. Given the functional properties of area 46, a model of imitation learning is proposed based on interactions between this area and the mirror neuron system.

Adult↗
PubMed2004

Functional diversity of layer IV spiny neurons in rat somatosensory cortex: quantitative morphology of electrophysiologically characterized and biocytin labeled cells.

Previous analyses of the spiny layer IV neurons have almost exclusively focused on spiny stellate cells. Here we provide detailed morphological data characterizing three subpopulations of spiny neurons in slices of adolescent rats: (i) spiny stellate cells (58%), (ii) star pyramidal cells (25%) and (iii) pyramidal cells (17%), which can be distinguished objectively by the preferential orientation of their dendritic stems. Spiny stellate cells lacked an apical dendrite and frequently confined their dendritic and axonal arbors to the respective column. Star pyramidal and pyramidal cells possessed an apical dendrite, which reached the supragranular layers. Their axonal arbors were similar, showing both a columnar component and transcolumnar branches with direct transbarrel projections. However, a small fraction of star pyramidal cells possessed few or even no transcolumnar branches. Electrophysiologically, all three types of neurons were either regular-spiking or intrinsically burst-spiking without a significant relation to the morphological subtypes. The basic synaptic properties of thalamic inputs were also independent of the type of target layer IV spiny neuron. All remained subthreshold and showed paired-pulse depression. In conclusion, the columnar axonal arborization of spiny stellate cells is supplemented by a significant oblique to horizontal projection pattern in pyramidal-like neurons. This offers a structural basis for either segregation or early context-dependent integration of tactile information, in a cell-type specific manner.

Action Potentials↗
PubMed2004

Neural mechanisms underlying reaching for remembered targets cued kinesthetically or visually in left or right hemispace.

Reaching for a target involves integrative coordinate transformation processes between the representation of the target location, the sensorimotor information of limb of reach, and body space. Although right hemisphere dominance for visuospatial information processing is well established, corresponding right hemisphere dominance for kinesthetic spatial information processing remains to be demonstrated. We explored neural mechanisms of encoding target locations using 15O-butanol positron emission tomography (PET) in normal volunteers in a factorial experiment, where modality (visual/kinesthetic) and hemispace of target presentation (left/right of midsagittal plane) were varied systematically. After target presentation, subjects reached to the encoded target location. PET data analysis using SPM99 showed increased neural activity (P < 0.05, corrected) associated with left hemispace target presentation in right hemisphere areas (sensorimotor, anterior cingulate, insular, and temporo-occipital cortex) only. By contrast, right hemispace target presentation activated bilateral temporo-occipital cortex, which extended into the right temporo-parietal cortex and left sensorimotor cortex. A significant interaction of hemispace and modality of target presentation observed in right temporo-parietal cortex resulted from an increase in neural activity with kinesthetic target presentation in right hemispace. The data support an important role for the right temporo-parietal area in visuospatial processing and suggest a specific role of the right hemisphere in kinesthetic spatial processing.

Adult↗
PubMed2004

Effects of 1alpha,25 dihydroxyvitamin D3 on the expression of HO-1 and GFAP in glial cells of the photothrombotically lesioned cerebral cortex.

In ischemic cerebral injuries a cascade of degenerative mechanisms, all participating in the development of oxidative stress, influence the condition of the tissue. The survival of viable tissue affected by secondary injury largely depends on the balance between endogenous protective mechanisms and the ongoing degenerative processes. The inducible enzyme, heme oxygenase-1 metabolizes and thus detoxifies free heme to the powerful endogenous antioxidants biliverdin and bilirubin therefore enhancing neuroprotection. The secosteroid 1alpha,25-dihydroxyvitamin D3 (1,25-D3) is a modulator of the immune system and also exhibits a strong potential for neuroprotection as recently shown in the MCAO model of cerebral ischemia. We studied the effects of 1,25-D3 treatment on heme oxygenase-1 expression following focal cortical ischemia elicited by photothrombosis. Postlesional treatment with 1,25-D3 (4 microg/kg body weight) resulted in a transient, but significant upregulation of glial heme oxygenase-1 immunoreactivity concomitant with a reduction in glial fibrillary acidic protein immunoreactivity in remote cortical regions affected by a secondary spread of injury, whereas the size of the lesion's core remained unaffected. 1,25-D3 did not produce a temporal shift or extension of injury-related heme oxygenase-1 responses, indicating that 1,25-D3 did not prolong ischemia-related heme oxygenase-1 expression. In contrast to glial heme oxygenase-1 upregulation, glial fibrillary acidic protein, a sensitive marker for reactive gliosis, was significantly reduced. These findings support an additional protective action of 1,25-D3 at the cellular level in regions affected by secondary injury-related responses.

Animals↗
PubMed2004

A combined treatment with 1alpha,25-dihydroxy-vitamin D3 and 17beta-estradiol reduces the expression of heat shock protein-32 (HSP-32) following cerebral cortical ischemia.

1alpha,25-(OH)(2)-vitamin D(3) (1,25-D(3)) and 17beta-estradiol are both known to act neuroprotectively in certain experimental in vitro and in vivo settings and it has been noted that both steroids lead to an upregulation of certain neurotrophic factors. Here, we studied the effects of 1alpha,25-(OH)(2)-vitamin D(3) or 17beta-estradiol or their combined application on heat shock protein-32 (HSP-32) distribution after focal cortical ischemia using the well established photothrombosis model. Heat shock protein-32 is a well-established marker of the cerebral oxidative stress response and contributes to neuroprotection by metabolising cytotoxic free heme to carbon monoxide, iron and biliverdin. Photothrombotically lesioned rats were injected i.p. 1h after injury with either 1 microg 1alpha,25-(OH)(2)-vitamin D(3)/kg or 7 microg 17beta-estradiol/kg or a combination of both steroids. Groups of non-lesioned steroid-treated rats and lesioned, solvent-treated rats served as controls. In contrast to non-lesioned rats, in lesioned animals a significant increase in heat shock protein-32 expression occurred which was slightly, but non-significantly altered in the groups treated either with 1alpha,25-(OH)(2)-vitamin D(3) or 17beta-estradiol alone when compared to the solvent-treated control group. Only the combined treatment with 1alpha,25-(OH)(2)-vitamin D(3) and 17beta-estradiol resulted in a significant reduction of glial heat shock protein-32 immunoreactivity within the lesion-remote cortical areas supplied by the affected middle cerebral artery (MCA), indicating that both steroids act synergistically in a protective manner.

Animals↗
PubMed2004

Cerebral expression of the alpha2-subunit of soluble guanylyl cyclase is linked to cerebral maturation and sensory pathway refinement during postnatal development.

Soluble guanylyl cylase (sGC) has been identified for being a receptor for the gaseous transmitters nitric oxide and carbon monoxide. Currently four subunits alpha1, alpha2, beta1, and beta2 have been characterized. Heterodimers of alpha and beta-subunits as well as homodimers of the beta2-subunit are known to constitute functional sGC which use GTP to form cGMP a potent signal molecule in a multitude of second messenger cascades. Since NO-cGMP signaling plays a pivotal role in neuronal development we analyzed the maturational expression pattern of the newly characterized alpha2-subunit of sGC within the brain of Wistar rats by means of RNase protection assay and immunohistochemistry. alpha2-subunit mRNA as well as immunoreactive alpha2-protein increased during postnatal cerebral development. Topographical analysis revealed a selective high expression of the alpha2-subunit in the choroid plexus and within developing sensory systems involving the olfactory and somatosensory system of the forebrain as well as parts of the auditory and visual system within the hindbrain. In cultured cortical neurons the alpha2-subunit was localized to the cell membrane, especially along neuronal processes. During the first 11 days of postnatal development several cerebral regions showed a distinct expression of the alpha2-subunit which was not paralleled by the alpha1/beta1-subunits especially within the developing thalamo-cortical circuitries of the somatosensory system. However, at later developmental stages all three subunits became more homogenously distributed among most cerebral regions, indicating that functional alpha1/beta1 and alpha2/beta1 heterodimers of sGC could be formed. Our findings indicate that the alpha2-subunit is an essential developmentally regulated constituent of cerebral sensory systems during maturation. In addition the alpha2-subunit may serve other functions than forming a functional heterodimer of sGC during the early phases of sensory pathway refinement.

Aging↗
PubMed2004

Cerebral correlates of alerting, orienting and reorienting of visuospatial attention: an event-related fMRI study.

The identification of brain systems contributing to different aspects of visuospatial attention is of both clinical and theoretical interest. Cued target detection tasks provide a simple means to dissociate attentional subcomponents, such as alerting, orienting or reorienting of attention. Event-related functional magnetic resonance imaging (fMRI) was used to study neural correlates of these distinct attentional processes. Volunteers were scanned while performing a centrally cued target detection task. Four different types of trials (no cue, neutral cue, valid cue and invalid cue trials) with targets appearing either in the right or left hemifield were randomly intermixed. Behaviourally, the data provided evidence for alerting, spatial orienting and reorienting of attention. Neurally, the alerting effect was seen in bilaterally increased extrastriatal blood oxygenation level-dependent (BOLD) activity in neutral as compared to no cue trials. Neural correlates of spatial orienting were seen in anterior cingulate cortex, which was more active during valid as compared to neutral cue trials. Neural correlates of reorienting of attention, that is, higher BOLD activity to invalid as compared to validly cued trials were evident in several brain regions including left and right intraparietal sulcus, right temporo-parietal junction and middle frontal gyrus bilaterally. The data suggest that frontal and parietal regions are specifically involved in reorienting rather than orienting attention to a spatial position. Alerting effects were seen in extrastriate regions which suggest that increased phasic alertness results in a top-down modulation of neural activity in visual processing areas.

Adult↗
PubMed2004

Neural basis of pantomiming the use of visually presented objects.

UNLABELLED: Neuropsychological studies of patients suffering from apraxia strongly imply a left hemisphere basis for skillful object use, the neural mechanisms of which, however, remain to be elucidated. We therefore carried out a PET study in 14 healthy human volunteers with the aim to isolate the neural mechanisms underlying the sensorimotor transformation of object-triggers into skilled actions. We employed a factorial design with two factors ( RESPONSE: naming, pantomiming; and TRIGGER: actions, objects) and four conditions (IA: imitating the observed pantomime; IO: pantomiming the use of the object shown; NA: naming the observed pantomime; NO: naming the object shown). The design thus mainly aims at investigating the interaction [i.e. (IO-IA)-(NO-NA)] which allows the assessment of increased neural activity specific to the sensorimotor transformation of object-triggers into skilled actions. The results (P < 0.05, corrected) showed that producing a wide range of skilled actions triggered by objects (controlled for perceptual, motor, semantic, and lexical effects) activated left inferior parietal cortex. The data provide an explanation for why patients with lesions including left parietal cortex suffer from ideational apraxia as assessed by impaired object use and pantomining to visually presented objects.

Adult↗
PubMed2004

Analysis of neural mechanisms underlying verbal fluency in cytoarchitectonically defined stereotaxic space--the roles of Brodmann areas 44 and 45.

We investigated neural activations underlying a verbal fluency task and cytoarchitectonic probabilistic maps of Broca's speech region (Brodmann's areas 44 and 45). To do so, we reanalyzed data from a previous functional magnetic resonance imaging (fMRI) [Brain 125 (2002) 1024] and from a cytoarchitectonic study [J. Comp. Neurol. 412 (1999) 319] and developed a method to combine both data sets. In the fMRI experiment, verbal fluency was investigated in 11 healthy volunteers, who covertly produced words from predefined categories. A factorial design was used with factors verbal class (semantic vs. overlearned fluency) and switching between categories (no vs. yes). fMRI data analysis employed SPM99 (Statistical Parametric Mapping). Cytoarchitectonic maps of areas 44 and 45 were derived from histologic sections of 10 postmortem brains. Both the in vivo fMRI and postmortem MR data were warped to a common reference brain using a new elastic warping tool. Cytoarchitectonic probability maps with stereotaxic information about intersubject variability were calculated for both areas and superimposed on the functional data, which showed the involvement of left hemisphere areas with verbal fluency relative to the baseline. Semantic relative to overlearned fluency showed greater involvement of left area 45 than of 44. Thus, although both areas participate in verbal fluency, they do so differentially. Left area 45 is more involved in semantic aspects of language processing, while area 44 is probably involved in high-level aspects of programming speech production per se. The combination of functional data analysis with a new elastic warping tool and cytoarchitectonic maps opens new perspectives for analyzing the cortical networks involved in language.

Adult↗
PubMed2004

Neural mechanism underlying impaired visual judgement in the dysmetabolic brain: an fMRI study.

An altered brain metabolism in the parietal and prefrontal regions of the cerebral cortex as well as cognitive alterations have been found in patients suffering from hepatic encephalopathy. The neural mechanisms underlying these metabolically induced cognitive alterations, however, are not known. Since patients with liver cirrhosis without clinically overt encephalopathy already show an impaired performance in a flicker light test, the aim of this study was to analyze the normal and pathologically impaired neural mechanisms of these patients using functional magnetic resonance imaging (fMRI). Nine subjects at the early stage of encephalopathy [nonmanifest hepatic encephalopathy (nmHE)] and ten controls underwent scanning, while they indicated the apparent transition from a steady light to the onset of a flicker light, that is, the critical flicker frequency (CFF). Judgement-related blood oxygenation level-dependent (BOLD) activation was decreased in nmHE compared to controls in the right inferior parietal cortex (IPL). Furthermore, the analysis of psychophysiologic interaction suggests impaired neural interaction in patients with nmHE, especially between the IPL and the parietooccipital cortex (Poc), the intraparietal sulcus, the anterior cingulate cortex (ACC), the right prefrontal cortex (PFC), the medial temporal lobe, and the extrastriate cortex V5. In contrast, nonmanifest patients revealed an enhanced coupling between IPL and the postcentral cortex. Our findings provide evidence of an early-impaired and compensatory neural mechanism during visual judgement already in the earliest stages of hepatic encephalopathy and suggest an aberrant coupling between cerebral regions in the dysmetabolic brain.

Brain↗
PubMed2004

Human medial intraparietal cortex subserves visuomotor coordinate transformation.

In the macaque, the posterior parietal cortex (PPC) integrates multimodal sensory information for planning and coordinating complex movements. In particular, the areas around the intraparietal sulcus (IPS) serve as an interface between the sensory and motor systems to allow for coordinated movements in space. Because recent imaging studies suggest a comparable functional and anatomical organization of human and monkey IPS, we hypothesized that in humans, as in macaques, the medial intraparietal cortex (area MIP) subserves visuomotor transformations. To test this hypothesis, changes of neural activity were measured using functional magnetic resonance imaging (fMRI) while healthy subjects performed a joystick paradigm similar to the ones previously employed in macaques for studying area MIP. As hypothesized, visuomotor coordinate transformation subserving goal-directed hand movements activated superior parietal cortex with the local maximum of increased neural activity lying in the medial wall of IPS. Compared to the respective visuomotor control conditions, goal-directed hand movements under predominantly proprioceptive control activated a more anterior part of medial IPS, whereas posterior medial IPS was more responsive to visually guided hand movements. Contrasting the two coordinate transformation conditions, changing the modality of movement guidance (visual/proprioceptive) did not significantly alter the BOLD signal within IPS but demonstrated differential recruitment of modality specific areas such as V5/MT and sensorimotor cortex/area 5, respectively. The data suggest that the human medial intraparietal cortex subserves visuomotor transformation processes to control goal-directed hand movements independently from the modality-specific processing of visual or proprioceptive information.

Adult↗