Search PubMed⌕ Search

Biomedical subjects

G Schlaug

Publications and source records attributed to G Schlaug.

At least 19 recordsLinked to original sources
PubMed2006

Antiplatelets, ACE inhibitors, and statins combination reduces stroke severity and tissue at risk.

BACKGROUND: Antiplatelets (APL), angiotensin-converting enzyme (ACE) inhibitors (ACEI), and statins (STAT) are commonly used for stroke prevention. The authors examined whether combination therapy with these agents has additive protective effects in reducing ischemic stroke severity. METHODS: The authors retrospectively analyzed data from 210 consecutive patients presenting within 24 hours of stroke onset. Baseline NIH Stroke Scale (NIHSS) score and diffusion-weighted imaging (DWI), perfusion-weighted imaging (PWI), and PWI-DWI mismatch lesion volumes as clinical and radiologic measures of stroke severity were measured among patients who were not taking APL, ACEI, or STAT before stroke onset vs those who were taking APL alone or in combination with either ACEI, STAT, or both. RESULTS: Sixty-nine patients were not on APL, ACEI, or STAT at stroke onset; 47 were on APL alone, 43 on dual (14 APL + STAT, 29 APL + ACEI), and 20 on triple combination therapy. Patients on triple therapy had lower NIHSS score (p = 0.001) and smaller mean PWI-DWI mismatch lesion volumes (p = 0.03) than those on two agents, APL alone, or no prestroke therapy. Higher percentages of patients on triple therapy had shorter length of hospitalization and better functional status upon discharge. Age, risk factor profile, blood pressure, glucose levels, onset to evaluation time, stroke subtypes, and DWI lesion volumes were comparable among all groups. CONCLUSIONS: Prestroke use of available drugs for stroke prevention, in combination, may result in additive reduction in stroke severity, as measured by NIH Stroke Scale, and the volume of ischemic tissue at risk, as assessed by perfusion-weighted imaging-diffusion-weighted imaging mismatch. These findings require further validation in larger-scale, randomized, prospective studies.

Aged↗
PubMed2005

Sleep-dependent motor memory plasticity in the human brain.

Growing evidence indicates a role for sleep in off-line memory processing, specifically in post-training consolidation. In humans, sleep has been shown to trigger overnight learning on a motor-sequence memory task, while equivalent waking periods produce no such improvement. But while the behavioral characteristics of sleep-dependent motor learning become increasingly well characterized, the underlying neural basis remains unknown. Here we present functional magnetic resonance imaging data demonstrating a change in the representation of a motor memory after a night of sleep. Subjects trained on a motor-skill memory and 12 hours later, after either sleep or wake, were retested during functional magnetic resonance imaging. Following sleep relative to wake, regions of increased activation were expressed in the right primary motor cortex, medial prefrontal lobe, hippocampus and left cerebellum; changes that can support faster motor output and more precise mapping of key-press movements. In contrast, signal decreases were identified in parietal cortices, the left insular cortex, temporal pole and fronto-polar region, reflecting a reduced need for conscious spatial monitoring and a decreased emotional task burden. This evidence of an overnight, systems-level change in the representation of a motor memory holds important implications for acquiring real-life skills and in clinical rehabilitation following brain trauma, such as stroke.

Adult↗
PubMed2005

Examining rhythm and melody processing in young children using FMRI.

While it is often reported that musical experience can have positive effects on cognitive development in young children, the neural basis of such potential effects remains relatively unexplored. Employing functional magnetic resonance imaging (fMRI) for such research presents as many challenges as possibilities, not least of which is the fact that young children can find it difficult to remain still and attentive for long periods of time. Here we describe an fMRI scanning protocol designed specifically for young children using short scanning runs, a sparse temporal sampling data acquisition technique, simple rhythmic and melodic discrimination tasks with a button-press response, and a child-oriented preparation session. Children were recruited as part of a large-scale longitudinal study examining the effects of musical training on cognitive development and the structure and function of the growing brain. Results from an initial analysis of 33 children and from the first five children to be re-scanned after musical training indicate that our scanning protocol is successful and that activation differences can be detected both between conditions and over time.

Child↗
PubMed2004

Repetitive TMS of the motor cortex improves ipsilateral sequential simple finger movements.

BACKGROUND: Disruption of cortical function can improve behavior. Motor cortex (M1) transcallosal interactions are mainly inhibitory; after unilateral damage to M1, there is increased excitability of the unaffected M1. Repetitive transcranial magnetic stimulation (rTMS) of M1 produces a temporary reduction in cortical excitability in the same M1 that outlasts the duration of the rTMS train. The authors hypothesize that reducing cortical excitability of M1 by rTMS may improve motor performance in the ipsilateral hand by releasing the contralateral M1 from transcallosal inhibition. METHODS: Sixteen healthy volunteers participated. Using a sequential key-pressing task with the index finger, motor performance was monitored before and after rTMS (1 Hz for 10 minutes with the intensity below motor threshold) applied to the ipsilateral M1, contralateral M1, ipsilateral premotor area, or vertex (Cz). RESULTS: rTMS of M1 shortened execution time of the motor task with the ipsilateral hand without affecting performance with the contralateral hand. This effect outlasted rTMS by at least 10 minutes, was specific for M1 stimulation, and was associated with increased intracortical excitability in the unstimulated M1. CONCLUSIONS: The authors' results support the concept of an interhemispheric "rivalry." They demonstrate the utility of repetitive transcranial magnetic stimulation to explore the functional facilitation of the unstimulated counterpart motor cortex, presumably via suppression of activity in the stimulated motor cortex and transcallosal inhibition.

Adult↗
PubMed2004

A voxel-based approach to gray matter asymmetries.

Voxel-based morphometry (VBM) was used to analyze gray matter (GM) asymmetries in a large sample (n = 60) of male and female professional musicians with and without absolute pitch (AP). We chose to examine these particular groups because previous studies using traditional region-of-interest (ROI) analyses have shown differences in hemispheric asymmetry related to AP and gender. Voxel-based methods may have advantages over traditional ROI-based methods since the analysis can be performed across the whole brain with minimal user bias. After determining that the VBM method was sufficiently sensitive for the detection of differences in GM asymmetries between groups, we found that male AP musicians were more leftward lateralized in the anterior region of the planum temporale (PT) than male non-AP musicians. This confirmed the results of previous studies using ROI-based methods that showed an association between PT asymmetry and the AP phenotype. We further observed that male non-AP musicians revealed an increased leftward GM asymmetry in the postcentral gyrus compared to female non-AP musicians, again corroborating results of a previously published study using ROI-based methods. By analyzing hemispheric GM differences across our entire sample, we were able to partially confirm findings of previous studies using traditional morphometric techniques, as well as more recent, voxel-based analyses. In addition, we found some unusually pronounced GM asymmetries in our musician sample not previously detected in subjects unselected for musical training. Since we were able to validate gender- and AP-related brain asymmetries previously described using traditional ROI-based morphometric techniques, the results of our analyses support the use of VBM for examinations of GM asymmetries.

Brain↗
PubMed2003

Repetitive TMS temporarily alters brain diffusion.

The authors investigated whether repetitive transcranial magnetic stimulation (rTMS) at 1 Hz (12 minutes; 90% of motor threshold) to the primary motor cortex (M1) leads to changes in diffusion-weighted imaging (DWI). After the rTMS train, there was a temporary small restriction in diffusion within the targeted left M1 that disappeared after 5 minutes. These findings provide a physiologic correlate to the reported behavioral consequences of off-line 1-Hz rTMS and reveal the transitory nature of the effects.

Adult↗
PubMed2002

Age-related differences in movement representation.

Repetitive movements have been used as motor activation tasks in the investigation of various neurological disorders. To determine the importance of an age-matched control group in such studies we investigated whether there are significant age-related changes in the pattern of cortical activation seen during simple repetitive movements. Sixteen right-handed healthy subjects were studied-8 young and 8 old. Functional magnetic resonance images were acquired while subjects performed a motor task or a nonmovement rest condition. Two continuous motor tasks, index finger abduction/adduction and wrist extension/flexion, were performed by each hand, paced using a metronome. The fMRI data were processed and analyzed with SPM '99. For the between-group comparisons, for each motor task, contralateral primary sensorimotor cortex and premotor cortex had significantly greater activation in the Young group and caudal supplementary motor area had significantly greater activation in the Old group. Ipsilateral sensorimotor cortex was more significantly activated in the Old group for index finger motor tasks of both hands. All noted differences in the Old group were more prominent for the index finger movement and most prominent when using the nondominant hand. In conclusion, there are significant age-related differences in the activation pattern associated with repetitive movements. This may represent compensatory recruitment of motor cortical units in the older subjects as larger differences are noted in the older group during the more difficult motor tasks, those of isolated finger movement and nondominant hand use. This study has important implications for functional imaging experiments of neurological disorders in older subjects.

Adult↗
PubMed2001

Diffusion-weighted imaging and National Institutes of Health Stroke Scale in the acute phase of posterior-circulation stroke.

BACKGROUND: Occlusive disease of the posterior circulation represents a heterogeneous group of strokes that differ in etiology, clinical presentation, and prognosis. Computed tomography provides suboptimal visualization of posterior-circulation infarcts. Anatomic definition of traditional magnetic resonance imaging sequences has been used for clinicoradiologic correlation in patients with posterior-circulation disease. These studies focused on the subacute rather than the acute phase of ischemia. Lesion volumes on diffusion-weighted imaging (DWI) and perfusion imaging were found to have a good correlation with 24-hour National Institutes of Health stroke scale (NIHSS) score in ischemia of the anterior circulation. Correlation between NIHSS score and lesion volume in posterior-circulation infarcts is unknown. OBJECTIVES: To investigate whether DWI is useful for clinicoradiologic correlation of posterior-circulation ischemia within 24 hours after symptom onset and whether NIHSS score correlates with lesion volumes in patients with posterior-circulation stroke. PATIENTS AND METHODS: In a database analysis of 631 patients with stroke from June 26, 1996, to July 30, 1999, 115 patients (18%) had symptoms of posterior-circulation ischemia by imaging and clinical criteria. Among these 115, we included all patients (n = 40) who underwent DWI within 24 hours from symptom onset (mean, 9.7 +/- 7.1 hours). All 40 patients also underwent magnetic resonance angiography and T2-weighted imaging. Seventy-five did not meet inclusion criteria: in 45, magnetic resonance imaging was performed more than 24 hours after symptom onset; 12 did not have DWI; in 11 patients, symptoms resolved within 24 hours; 6 had hemorrhages; and 1 had a border zone infarct. RESULTS: An acute lesion on DWI corresponding to the patient's symptoms was detected in all 40 patients, 16 (40%) of whom had detectable acute lesions on T2-weighted images. The lesions on DWI were larger in 11 of the 16 patients with positive T2-weighted images. Acute lesion volume did not correlate with NIHSS score (n = 40; rho = 0.30; P =.06, Spearman rank) also when DWI lesion volumes were divided by cause and territory. CONCLUSIONS: Diffusion-weighted imaging is more effective than T2-weighted imaging in patients with acute posterior-circulation strokes. The DWI lesion volume did not significantly correlate with NIHSS score, suggesting that NIHSS is more weighted toward anterior-circulation stroke symptoms.

Acute Disease↗
PubMed2001

Absolute pitch and planum temporale.

An increased leftward asymmetry of the planum temporale (PT) in absolute-pitch (AP) musicians has been previously reported, with speculation that early exposure to music influences the degree of PT asymmetry. To test this hypothesis and to determine whether a larger left PT or a smaller right PT actually accounts for the increased overall PT asymmetry in AP musicians, anatomical magnetic resonance images were taken from a right-handed group of 27 AP musicians, 27 nonmusicians, and 22 non-AP musicians. A significantly greater leftward PT asymmetry and a significantly smaller right absolute PT size for the AP musicians compared to the two control groups was found, while the left PT was only marginally larger in the AP group. The absolute size of the right PT and not the left PT was a better predictor of music group membership, possibly indicating "pruning" of the right PT rather than expansion of the left underlying the increased PT asymmetry in AP musicians. Although early exposure to music may be a prerequisite for acquiring AP, the increased PT asymmetry in AP musicians may be determined in utero, implicating possible genetic influences on PT asymmetry. This may explain why the increased PT asymmetry of AP musicians was not seen in the group of early beginning non-AP musicians.

Adult↗
PubMed2001

The brain of musicians. A model for functional and structural adaptation.

Musicians form an ideal subject pool in which one can investigate possible cerebral adaptations to unique requirements of skilled performance as well as cerebral correlates of unique musical abilities such as absolute pitch and others. There are several reasons for this. First, the commencement of musical training usually occurs when the brain and its components may still be able to adapt. Second, musicians undergo long-term motor training and continued practice of complicated bimanual motor activity. Third, imaging studies from our group as well as other groups have shown that motor learning and the acquisition of skills can lead to changes in the representation of motor maps and possibly also to microstructural changes. Whether the unique musical abilities and structural differences that musicians' brains show are due to learning, perhaps during critical periods of brain development and maturation, or whether they reflect innate abilities and capacities that might be fostered by early exposure to music is largely unknown. We will report studies that indicate that certain regions in the brain (corpus callosum, motor cortex, cerebellum) may show some form of adaptation to extraordinary challenges and requirements of performance. These challenges may eventually lead to functional and structural cerebral changes to accommodate the requirements for musical performance. Furthermore, we will also show the neural correlates of one unique musical ability, absolute pitch. This ability may be linked to one structure in the human brain (planum temporale), which is preferentially activated in musicians who have absolute pitch during tone tasks. This structure may undergo some form of functional plasticity that is possible only during a critical period of brain development.

Brain↗
PubMed2000

Multiple acute stroke syndrome: marker of embolic disease?

OBJECTIVE: To determine the frequency and etiologic significance of multiple acute ischemic lesions in stroke. BACKGROUND: Although patients may have more than one stroke during the course of their lives, acute ischemic stroke is usually thought of as a single event. Using diffusion-weighted imaging (DWI), an MRI technique that detects ischemic injury within minutes after onset, we have often observed multiple acute ischemic lesions. METHODS: The MRI scans of 59 consecutively studied patients were reviewed to determine the frequency and etiologic significance of multiple acute ischemic lesions on DWI. RESULTS: Multiple acute ischemic lesions were present in 10 (17%) of 59 patients. The lesions usually occurred within one major circulation (anterior or posterior), but in two patients (3%), lesions occurred in both cerebral hemispheres or in the anterior and the posterior circulations. The lesions often were small and resulted from presumed multiple emboli or the break-up of an embolus. Two patients had internal carotid artery occlusive disease and four had a cardiac or aortic source. In the other four patients the source was not determined. Lesions larger than 1 cm in diameter progressed to infarction, but some smaller lesions were not seen on follow-up T2-weighted imaging. CONCLUSIONS: Multiple acute stroke lesions on DWI are common and could be caused by multiple emboli or the breakup of an embolus. In some cases it might become possible to make early inferences concerning the stroke mechanism that could be of use for immediately directing the clinical work-up and treatment of the patient.

Acute Disease↗
PubMed2000

Diffusion- and perfusion-weighted MRI patterns in borderzone infarcts.

BACKGROUND AND PURPOSE: The pathophysiology of borderzone infarcts is not well understood. We investigated whether combined diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) could identify pathophysiologically meaningful categories of borderzone infarcts. METHODS: Seventeen patients with borderzone infarcts were identified from the Beth Israel Deaconess Medical Center Stroke Database. All patients had DWI and PWI, the majority of them within the first 24 hours of symptom onset. RESULTS: Three patterns of perfusion abnormalities were associated with the diffusion lesions: 1, normal perfusion (5 patients); 2, localized perfusion deficits matching the area of restricted diffusion (5 patients); and 3, extensive perfusion deficits involving 1 or more vascular territories (7 patients). All but 1 patient with pattern 1 had transient peri-infarct hypotension as the presumed stroke mechanism. Two patients with pattern 2 had cardiac or aortic embolic sources; none had large-artery disease or arterial hypotension. Reperfusion was detected in all patients with this pattern who submitted to a follow-up study. All patients with pattern 3 had severe stenosis or occlusion of a large artery: the internal carotid, anterior cerebral, or middle cerebral. CONCLUSIONS: We postulate that the perfusion abnormality varies according to the mechanism of the borderzone infarction. Transient perfusion deficits occurring with hypotension in the absence of significant large-artery disease may not be revealed by PWI. Embolism may cause some cases of small borderzone perfusion deficits. Critical large-artery disease may cause large territorial perfusion deficits and predispose to borderzone infarction.

Aged↗
PubMed1999

The ischemic penumbra: operationally defined by diffusion and perfusion MRI.

BACKGROUND: Identifying tissue at risk for infarction is important in deciding which patients would benefit most from potentially harmful therapies and provides a way to evaluate newer therapies with regard to the amount of ischemic tissue salvaged. OBJECTIVE: To operationally define and characterize cerebral tissue at risk for stroke progression. METHODS: We retrospectively selected 25 patients with an acute onset of a hemispheric stroke from our database who had undergone a combination of two diffusion-weighted MRI studies and a perfusion-weighted MRI study. We applied a logistic regression model using maps of the relative mean transit time and relative cerebral blood flow (rCBF) as well as three different maps of the relative cerebral blood volume (rCBV) to predict an operationally defined penumbra (region of mismatch between the diffusion lesion on day 1 and its extension 24 to 72 hours later). RESULTS: Maps of the rCBF and initial rCBV were significant predictors for identifying penumbral tissue. Our operationally defined penumbral region was characterized by a reduction in the initial rCBV (47% of contralateral control region [CCR]), an increase (163% of CCR) in the total rCBV, and a reduction (37% of CCR) in the rCBF, whereas the operationally defined ischemic core showed a more severe reduction in the rCBF (12% of CCR) and in the initial rCBV (19% of CCR). CONCLUSION: These MR indexes may allow the identification and quantification of viable but ischemically threatened cerebral tissue amenable to therapeutic interventions in the hyperacute care of stroke patients.

Aged↗
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

Functional burst imaging.

A quiet magnetic resonance (MR) imaging technique for detecting changes in cerebral activity functions is presented. This single-shot method, functional Burst imaging (FBI), combines elements of Burst imaging with an offset technique known as asymmetric spin echo (ASE). The FBI sequence has the unique feature of being nearly silent, because of the low number of gradient switching steps involved. Furthermore, this approach has the key advantage that it can be implemented on conventional MR systems. Established auditory and visual paradigms were used to evaluate whether FBI can detect changes in cerebral activity using a 1.5 Tesla MR system. In a second set of experiments, the FBI technique was used to evaluate cerebral activity changes during different sleep stages in humans. The results obtained demonstrate that the FBI sequence provides an alternative approach for functional imaging of brain activity in primary and secondary sensory areas of the human brain. Furthermore, in using this quiet MR technique, it was possible to scan continuously during different stages of human sleep without acoustic noise perturbation.

Acoustic Stimulation↗
PubMed1998

Unsolved problems in comparing brain sizes in Homo sapiens.

When brain size is compared across taxonomic levels, there is a clear relation between body parameters and brain size. It is generally stated that the correlation between brain size and body parameters becomes very small at the species level (Aboitiz, 1996), but this is not the case for Homo sapiens where there is a strong correlation between brain size and body size across racial groups that differ in body size. The control for body size across racial groups (and sexes) is rendered difficult because bodies do not just differ only in height and weight. Within groups different studies show weak and inconsistent brain size/body height correlations. A better understanding of brain size/body height relations must await better quality data and a better understanding of how exactly body parameters should be scaled between groups and sexes. We attribute the clear between-group and weak within-group correlations to the large variety of body sizes and body types in our species, a variety which is only equalled in selectively bred species of animals. At present, there is no meaningful basis for the comparison of brain sizes within and between racial groups and sexes.

Adult↗