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R J Seitz

Publications and source records attributed to R J Seitz.

At least 19 recordsLinked to original sources
PubMed2000

Visual hallucinations in recovery from cortical blindness: imaging correlates.

OBJECTIVE: To investigate the cerebral metabolic and functional patterns during recovery from cortical blindness. DESIGN: Follow-up study with serial clinical, metabolic, and functional imaging and visual evoked potentials. CASE PRESENTATION: A 24-year-old woman suffered from cortical blindness after cardiac arrest and recovered over a 6-month period. During recovery, she experienced complex visual hallucinations that could be initiated by visual imagery. RESULTS: Initially, the regional cerebral metabolic rate of glucose was severely reduced in the visual and parieto-occipital cortex bilaterally but recovered almost completely. Visual hallucinations led to significant increases of the regional cerebral blood flow in the initially severely hypometabolic parieto-occipital and temporo-lateral cortex. CONCLUSIONS: Recovery of vision was related to normalization of the postlesionally dysfunctional cortex. Visual hallucinations appeared as the clinical correlate of the electrophysiological hyperexcitability of the recovering partially damaged visual cortex.

Adult↗
PubMed2000

Temporal lobe epilepsy with sensory aura: interictal glucose hypometabolism.

Patients with mesial temporal lobe epilepsy (mTLE) exhibit marked depressions of the regional cerebral glucose metabolism (rCMRGlu) in the mesiotemporal region. We hypothesised that patients with temporal lobe epilepsy (TLE) who have a bilateral somatosensory or acoustic ( = temporolateral/SII-) aura can be differentiated from mTLE by rCMRGlu depressions primarily involving temporo-perisylvian locations. We therefore used this ictal semiology as a clinical criterion to define a subgroup of such patients and measured the rCMRGlu in 16 patients with TLE as evident from interictal and ictal EEG-video monitoring. Clinically, they presented with medically refractory complex partial seizures and were subjected to presurgical evaluation. The pattern of the interictal rCMRGlu in the TLE patients was different from that observed in patients with mTLE and showed significant depressions ipsilateral to the epileptic focus in mesial temporal and lateral temporal regions but spared the thalamus. The neocortical metabolic depressions were spatially more extended in right than in left TLE patients. Magnetic resonance images (MRI) were either normal (n = 5) or revealed unilateral or bilateral hippocampal atrophy/sclerosis (n = 7), or temporal or extratemporal focal cortical dysplasia (n = 4). The selected TLE patients presented here comprise a heterogeneous group showing most pronounced metabolic depressions in the lateral temporal cortex. Thus, our data suggest that non-invasive metabolic imaging can assist in identifying the neocortical symptomatogenic zone in putative temporo-perisylvian lobe epilepsy.

Abdomen↗
PubMed1999

Mirror agnosia and mirror ataxia constitute different parietal lobe disorders.

We describe two new clinical syndromes, mirror agnosia and mirror ataxia, both characterized by the deficit of reaching for an object through a mirror in association with a lesion of either parietal lobe. Clinical investigation of 13 patients demonstrated that the impairments affected both sides of the body. In mirror agnosia, the patients always reached toward the virtual object in the mirror and they were not capable of changing their behavior even after presentation of the position of the object in real visual space. In mirror ataxia (resembling optic ataxia) although some patients initially tended to reach for the virtual object in the mirror, they soon learned to guide their arms toward the real object, all of them producing many directional errors. Both patient groups performed poorly on mental rotation, but only the patients with mirror agnosia were impaired in line orientation. Only 1 of the patients suffered from neglect and 3 from apraxia. Magnetic resonance imaging showed that in mirror agnosia the common zone of lesion overlap was scattered around the posterior angular gyrus/superior temporal gyrus and in mirror ataxia around the postcentral sulcus. We propose that both these clinical syndromes may represent different types of dissociation of retinotopic space and body scheme, or likewise, of allocentric and egocentric space normally adjusted in the parietal lobe.

Adult↗
PubMed1999

A parieto-premotor network for object manipulation: evidence from neuroimaging.

Functional magnetic resonance imaging (fMRI) was used to assess cerebral activation during manipulation of various complex meaningless objects as compared to manipulation of a single simple object (a sphere). Significant activation was found bilaterally in the ventral premotor cortex (Brodmann's area 44), in the cortex lining the anterior part of the intraparietal sulcus (most probably corresponding to monkey anterior intraparietal area, AIP), in the superior parietal lobule and in the opercular parietal cortex including the secondary somatosensory area (SII). We suggest that the cortex lining the anterior part of the intraparietal sulcus and area 44 are functionally connected and mediate object manipulation in humans.

Adult↗
PubMed1999

Cerebral midline structures in bimanual coordination.

In six healthy right-handed volunteers, we compared the cerebral activation pattern related to unimanual right- and left-hand movements and to bimanual in-phase and anti-phase movements using functional magnetic resonance imaging (fMRI). Internally paced unimanual finger-to-thumb opposition movements led to a strong contralateral activation of primary sensorimotor areas in all six subjects. Midline activity was lateralized to the left side during right-hand movements, but to both sides during left-hand movements. Activity patterns of bimanual in-phase movements resembled the combined activity patterns of the two unimanual conditions: right and left hemispheric activations of the primary sensorimotor cortices and predominantly left-sided medial frontal activity. In contrast, during anti-phase movements, we observed a clear increase in activity, in both right and left frontal midline areas and in right hemispheric, mainly dorsolateral premotor areas compared to in-phase movements. These results indicate that frontal midline activity is not specific for bimanual movements per se. It can already be involved during simple unimanual movements but becomes progressively more involved during more complex aspects of movement control.

Adult↗
PubMed1999

Bilateral reductions of hippocampal volume, glucose metabolism, and wada hemispheric memory performance are related to the duration of mesial temporal lobe epilepsy.

In refractory temporal lobe epilepsy (TLE) temporal lobe structures and functions are continuously or intermittently affected by abnormal brain electrical events, noxious neurochemical agents, and metabolic disturbances. There is conflicting evidence regarding the relationship between the duration of refractory mesial TLE and quantitative measures of temporal lobe functions and volumes of the hippocampi. Twenty patients (aged 28 +/- 7 years, 14 males) with an initial precipitating injury before the age of 5 years were subjected to high-resolution magnetic resonance imaging, fluoro-2-deoxy-d-glucose positron-emission tomography (PET), and the Wada test. We investigated whether the duration of unilateral refractory TLE (12 left, 8 right) affects hippocampal volume, glucose metabolism, or Wada hemispheric memory performance. Ipsilateral to the epileptogenic zone the hippocampal volume, metabolism, and Wada hemispheric memory performance were reduced compared to the corresponding contralateral measures. The duration of epilepsy controlled for age at investigation, side of seizure origin, underlying cause, and sex were negatively correlated with ipsi- and contralateral hippocampal volume, hippocampal metabolism, and Wada hemispheric memory performance. Moreover, ipsilateral Wada hemispheric memory performance and contralateral hippocampal glucose metabolism were correlated with the frequency of habitual seizures. Refractory TLE seems to be associated with a slow but ongoing bilateral temporal lobe damage. These cross-sectional results require verification by longitudinal studies carried out over a period of more than two decades.

Adolescent↗
PubMed1999

Reorganized cerebral metabolic interactions in temporal lobe epilepsy.

Patients with left temporal lobe epilepsy demonstrate language impairments that are not well understood. To explore abnormal patterns of brain functional connections with respect to language processing, we applied a principal component analysis to resting regional cerebral metabolic data obtained with positron emission tomography in patients with right- and left-sided temporal lobe epilepsy and controls. Two principal components were expressed differentially among the groups. One principal component comprised a pattern of metabolic interactions involving left inferior frontal and left superior temporal regions-corresponding to Broca's and Wernicke's areas, respectively-and right mesial temporal cortex and right thalamus. Functional couplings between these brain regions were abnormally enhanced in the left-sided epilepsy patients. The right thalamic left superior temporal coupling was also abnormally enhanced in the right-sided epilepsy patients, but differentially from that in the left-sided patients. The other principal component was characterized by a pattern of metabolic interactions involving right and left mid prefrontal and right superior temporal cortex. Although both the right- and left-sided epilepsy patients showed decreased functional couplings between left mid prefrontal and the other brain regions, a weaker right-left mid prefrontal coupling in the left-sided epilepsy patients best distinguished them from the right-sided patients. The two mutually independent, abnormal metabolic patterns each predicted verbal intelligence deficits in the patients. The findings suggest a site-dependent reorganization of two independent, language-subserving pathways in temporal lobe epilepsy.

Adolescent↗
PubMed1999

A fronto-parietal circuit for object manipulation in man: evidence from an fMRI-study.

Functional magnetic resonance imaging (fMRI) was used to localize brain areas active during manipulation of complex objects. In one experiment subjects were required to manipulate complex objects for exploring their macrogeometric features as compared to manipulation of a simple smooth object (a sphere). In a second experiment subjects were asked to manipulate complex objects and to silently name them upon recognition as compared to manipulation of complex not recognizable objects without covert naming. Manipulation of complex objects resulted in an activation of ventral premotor cortex [Brodmann's area (BA) 44], of a region in the intraparietal sulcus (most probably corresponding to the anterior intraparietal area in the monkey), of area SII and of a sector of the superior parietal lobule. When the objects were covertly named additional activations were found in the opercular part of BA 44 and in the pars triangularis of the inferior frontal gyrus (BA 45). We suggest that a fronto-parietal circuit for manipulation of objects exists in humans and involves basically the same areas as in the monkey. It is proposed that area SII analyses the intrinsic object characteristics whilst the superior parietal lobule is related to kinaesthesia.

Adult↗
PubMed1999

The role of ventral medial wall motor areas in bimanual co-ordination. A combined lesion and activation study.

Two patients with midline tumours and disturbances of bimanual co-ordination as the presenting symptoms were examined. Both reported difficulties whenever the two hands had to act together simultaneously, whereas they had no problems with unimanual dexterity or the use of both hands sequentially. In the first patient the lesion was confined to the cingulate gyrus; in the second it also invaded the corpus callosum and the supplementary motor area. Kinematic analysis of bimanual in-phase and anti-phase movements revealed an impairment of both the temporal adjustment between the hands and the independence of movements between the two hands. A functional imaging study in six volunteers, who performed the same bimanual in-phase and anti-phase tasks, showed strong activations of midline areas including the cingulate and ventral supplementary motor area. The prominent activation of the ventral medial wall motor areas in the volunteers in conjunction with the bimanual co-ordination disorder in the two patients with lesions compromising their function is evidence for their pivotal role in bimanual co-ordination.

Adult↗
PubMed1999

Diffusion- and perfusion-weighted MRI. The DWI/PWI mismatch region in acute stroke.

BACKGROUND AND PURPOSE: Diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) are relatively new MR techniques increasingly used in acute stroke. During the first hours of stroke evolution, the regions with abnormal perfusion are typically larger than the DWI lesions, and this mismatch region has been suggested to be "tissue at risk." The aim of this study was to evaluate the PWI/DWI mismatch region in acute stroke patients and find parameters indicative of both infarct progression and functional impairment. METHODS: Twenty patients with nonlacunar ischemic stroke were imaged with DWI, PWI, and conventional MRI within 24 hours of symptom onset and after 1 week; in addition, the European Stroke Scale (ESS) score was recorded. With PWI, the volumes of regions with "time-to-peak" (TTP) delays of >/=2, 4, 6, 8, and 10 seconds were measured; these volumes were compared with the acute DWI lesion volumes, final infarct size, and ESS score. RESULTS: In 80% of patients the acute DWI lesion was surrounded by regions with abnormal TTP delays (PWI>DWI lesion). A TTP delay of >/=6 s in the mismatch region was found to be associated with lesion enlargement between the initial and follow-up MRI scans. Lesions increased in 9 of 12 patients (75%) in whom the area with TTP delay >/=6 s was larger than the DWI lesion, but they increased in only 1 of 8 (12.5%) of the remaining patients, in whom the area with a TTP delay >/=6 s was smaller than the DWI lesion. The volume of the regions with TTP delays of >/=4 s correlated better with ESS (r=-0.88, P<0.001) than other PWI (or DWI) volumes, which indicated that a TTP delay of approximately 4 s might be the threshold for functional impairment of brain tissue. CONCLUSIONS: Only patients with severe perfusion deficits in the PWI/DWI mismatch (TTP delays of >/=6 s) are at high risk of lesion enlargement. Functionally, more moderate perfusion deficits (TTP delays >/=4 and <6 s) appear to also contribute to the acute clinical deficit.

Acute Disease↗
PubMed1999

The role of diaschisis in stroke recovery.

BACKGROUND AND PURPOSE: Recovery from hemiparesis after stroke has been shown to involve reorganization in motor and premotor cortical areas. However, whether poststroke recovery also depends on changes in remote brain structures, ie, diaschisis, is as yet unresolved. To address this question, we studied regional cerebral blood flow in 7 patients (mean+/-SD age, 54+/-8 years) after their first hemiparetic stroke. METHODS: We analyzed imaging data voxel by voxel using a principal component analysis by which coherent changes in functional networks could be disclosed. Performance was assessed by a motor score and by the finger movement rate during the regional cerebral blood flow measurements. RESULTS: The patients had recovered (P<0. 001) from severe hemiparesis after on average 6 months and were able to perform sequential finger movements with the recovered hand. Regional cerebral blood flow at rest differentiated patients and controls (P<0.05) by a network that was affected by the stroke lesion. During blindfolded performance of sequential finger movements, patients were differentiated from controls (P<0.05) by a recovery-related network and a movement-control network. These networks were spatially incongruent, involving motor, sensory, and visual cortex of both cerebral hemispheres, the basal ganglia, thalamus, and cerebellum. The lesion-affected and recovery-related networks overlapped in the contralesional thalamus and extrastriate occipital cortex. CONCLUSIONS: Motor recovery after hemiparetic brain infarction is subserved by brain structures in locations remote from the stroke lesion. The topographic overlap of the lesion-affected and recovery-related networks suggests that diaschisis may play a critical role in stroke recovery.

Adult↗
PubMed1999

The neural circuitry involved in the reading of German words and pseudowords: A PET study.

Silent reading and reading aloud of German words and pseudowords were used in a PET study using (15O)butanol to examine the neural correlates of reading and of the phonological conversion of legal letter strings, with or without meaning. The results of 11 healthy, right-handed volunteers in the age range of 25 to 30 years showed activation of the lingual gyri during silent reading in comparison with viewing a fixation cross. Comparisons between the reading of words and pseudowords suggest the involvement of the middle temporal gyri in retrieving both the phonological and semantic code for words. The reading of pseudowords activates the left inferior frontal gyrus, including the ventral part of Broca's area, to a larger extent than the reading of words. This suggests that this area might be involved in the sublexical conversion of orthographic input strings into phonological output codes. (Pre)motor areas were found to be activated during both silent reading and reading aloud. On the basis of the obtained activation patterns, it is hypothesized that the articulation of high-frequency syllables requires the retrieval of their concomitant articulatory gestures from the SMA and that the articulation of low-frequency syllables recruits the left medial premotor cortex.

Adult↗
PubMed1999

On two methods of statistical image analysis.

The computerized brain atlas (CBA) and statistical parametric mapping (SPM) are two procedures for voxel-based statistical evaluation of PET activation studies. Each includes spatial standardization of image volumes, computation of a statistic, and evaluation of its significance. In addition, smoothing and correcting for differences of global means are commonly performed in SPM before statistical analysis. We report a comparison of methods in an analysis of regional cerebral blood flow (rCBF) in 10 human volunteers and 10 simulated activations. For the human studies, CBA or linear SPM standarization methods were followed by smoothing and computation of a statistic with the paired t-test of CBA or general linear model of SPM. No standardization, linear, and nonlinear SPM standardization were applied to the simulations. Significance of the statistic was evaluated using the cluster-size method common to SPM and CBA. SPM employs the theory of Gaussian random fields to estimate the cluster size distributions; simulations described in the Appendix provided empirical distributions derived from t-maps. The quantities evaluated were number and size of functional regions (FRs), maximum statistic, average resting rCBF, and percentage change. For the simulations, the efficiency of signal detection and rate of false positives could be evaluated as well as the distributions of statistics and cluster size in the absence of signal. The similarity of the results yielded by similar methods of analysis for the human studies and the simulated activations substantiates the robustness of the methods for selecting functional regions. However, the analysis of simulated activations demonstrated that quantitative evaluation of significance of a functional region encounters important obstacles at every stage of the analysis.

Adult↗
PubMed1998

Multimodal output mapping of human central motor representation on different spatial scales.

1. Non-invasive mapping by focal transcranial magnetic stimulation (TMS) is frequently used to investigate cortical motor function in the intact and injured human brain. We examined how TMS-derived maps relate to the underlying cortical anatomy and to cortical maps generated by functional imaging studies. 2. The centres of gravity (COGs) of TMS maps of the first dorsal intersosseus muscle (FDI) were integrated into 3-D magnetic resonance imaging (MRI) data sets in eleven subjects. In seven of these subjects the TMS-derived COGs were compared with the COG of regional cerebral blood flow increases using positron emission tomography (PET) in an index finger flexion protocol. 3. Mean TMS-derived COG projections were located on the posterior lip of the precentral gyrus and TMS-derived COG projections were in close proximity to the mean PET-derived COG, suggesting that the two methods reflect activity of similar cortical elements. 4. Criteria for a reliable assessment of the COG and the number of positions with a minimum amplitude of two-thirds of the maximum motor-evoked potential (T3Ps) were determined as a function of the number of stimuli and extension of the stimulation field. COGs and T3Ps were compared with an estimate of the size of the human motor cortex targeting alpha-motoneurons of forearm muscles. This comparison suggests that TMS can retrieve spatial information on cortical organization below the macroanatomic scale of cortical regions. 5. Finally, we studied the cortical representation of hand muscles in relation to facial and foot muscle representations and investigated hemispherical asymmetries. We did not find any evidence for a different ipsi- or contralateral representation of the mentalis muscle. Also, no difference was found between FDI representations on the dominant versus the non-dominant hemisphere.

Adult↗
PubMed1998

Role of the premotor cortex in recovery from middle cerebral artery infarction.

OBJECTIVE: To study the mechanisms underlying recovery from middle cerebral artery infarction in 7 patients with an average age of 53 years who showed marked recovery of hand function after acute severe hemiparesis caused by their first-ever stroke. INTERVENTIONS: Assessment of motor functions, transcranial magnetic stimulation, somatosensory evoked potentials, magnetic resonance imaging, and positron emission tomographic measurements of regional cerebral blood flow during finger movement activity. RESULTS: The infarctions involved the cerebral convexity along the central sulcus from the Sylvian fissure up to the hand area but spared the caudate nucleus, thalamus, middle and posterior portions of the internal capsule, and the dorsal part of the precentral gyrus in each patient. After recovery (and increase in motor function score of 57%, P<.001), the motor evoked potentials in the hand and leg muscles contralateral to the infarctions were normal, whereas the somatosensory evoked potentials from the contralateral median nerve were reduced. During fractionated finger movements of the recovered hand, regional cerebral blood flow increases occurred bilaterally in the dorsolateral and medial premotor areas but not in the sensorimotor cortex of either hemisphere. CONCLUSIONS: Motor recovery after cortical infarction in the middle cerebral artery territory appears to rely on activation of premotor cortical areas of both cerebral hemispheres. Thereby, short-term output from motor cortex is likely to be initiated.

Adult↗
PubMed1998

Somatic and limbic cortex activation in esophageal distention: a functional magnetic resonance imaging study.

Little is known about the cerebral representations of visceral sensations in humans. Using functional magnetic resonance imaging (fMRI), we mapped the cortical areas of the human brain that were activated by mechanical stimulation of the esophagus in 5 healthy volunteers. Stimulation probes were placed into the distal part of the esophagus and inflated to produce a local distention. The cerebral activation pattern was related to the strength and quality of the stimulus. The weakest stimulus accompanied by a well-localized albeit weak retrosternal sensation activated only the parietal opercular cortices, probably including the secondary somatosensory cortex (SII). Additional activation of the primary sensorimotor cortex (SI) at the level of the face and mouth representation as well as of the right premotor cortex was found during repetitive distention of the esophagus at 0.5 Hz. Repetitive stimulation at 1 Hz additionally activated the insula bilaterally. The strongest distention stimulus, which caused a painful retrosternal sensation, resulted in an activation of the anterior cingulate cortex. Our findings demonstrate that SII is the primary cortical target of visceral afferents originating in the esophagus. Limbic structures become engaged when the visceral sensation is unpleasant or painful.

Adult↗