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Biomedical subjects

Martin Lotze

Publications and source records attributed to Martin Lotze.

15 recordsLinked to original sources
PubMed2006

The role of multiple contralesional motor areas for complex hand movements after internal capsular lesion.

Imaging techniques document enhanced activity in multiple motor areas of the damaged and contralesional (intact) hemisphere (CON-H) after stroke. In the subacute stage, increased activity within motor areas in the CON-H during simple movements of the affected hand has been shown to correlate with poorer motor outcome. For those patients in the chronic stage who recovered well, the functional relevance of an increased activation within the CON-H is unclear. Using trains of repetitive transcranial magnetic stimulation (TMS) during performance of complex finger movements, we tested the behavioral relevance of regional functional magnetic resonance imaging (fMRI) activation within the CON-H for sequential finger movement performance of the recovered hand in seven patients who had experienced a subcortical stroke. TMS was navigated over fMRI activation maxima within anatomically preselected regions of the CON-H, and effects were compared with those of healthy controls. Stimulation over the dorsal premotor cortex (dPMC), the primary motor cortex (M1), and the superior parietal lobe (SPL) resulted in significant interference with recovered performance in patients. Interference with the dPMC and M1 induced timing errors only, SPL stimulation caused both timing and accuracy deficits. The present results argue for a persistent beneficial role of the dPMC, M1, and SPL of the CON-H on some aspects of effectively recovered complex motor behavior after subcortical stroke.

Aged↗
PubMed2006

Motor imagery.

We describe general concepts about motor imagery and differences to motor execution. The problem of controlling what the subject actually does during imagery is emphasized. A major part of the chapter is dealing with mental training by imagery and the usage of motor imagination in athletes, musicians and during rehabilitation. Data of altered representations of the body after loss of afferent information and motor representation due to limb amputation or complete spinal cord injury are demonstrated and discussed. Finally we provide an outlook on additional work about motor imagery important for further understanding of the topic.

Amputation, Surgical↗
PubMed2006

The role of prefrontal cortex in visuo-spatial planning: A repetitive TMS study.

The visuo-spatial planning process is based on an "opportunistic" combination of heuristics and strategies, carried out in small units during the execution of plans. In order to investigate the functional role of the prefrontal cortex in heuristic switching, 42 healthy controls performed a labyrinth crossing task (the Maps Test). During this computerized version of the Travelling Salesperson Problem, subjects had to decide which order of locations optimizes total travel time and distance. This task was performed with and without 1 Hz repetitive transcranial magnetic stimulation (rTMS), which exerts an inhibitory action on the targeted area, applied during the task over bilateral frontal sites (active stimulation) and parieto-occipital site (sham stimulation). Only repetitive bilateral rTMS over F3 and F4 significantly decreased the number of strategies with changes of heuristics, and increased the number of movements required to solve the task. This behaviour contrasts with the performance of healthy subjects in the planning task, but is consistent with the performance of frontal traumatic brain injury patients. The results indicate that, in a visuo-spatial problem-solving task, the prefrontal cortex is involved in the switching between heuristics during the execution of a plan.

Adult↗
PubMed2006

Segregation of visceral and somatosensory afferents: an fMRI and cytoarchitectonic mapping study.

Ano-rectal stimulation provides an important model for the processing of somatosensory and visceral sensations in the human nervous system. In spite of their anatomical proximity, the anal canal is innervated by somatosensory afferents whereas the rectum is innervated by the visceral nervous system. In a functional magnetic resonance (fMRI) experiment, we examined the cerebral responses to pneumatic balloon distension of these two structures to test whether somatosensory and visceral stimulation elicited distinct brain activations in spite of their spinal convergence. The specificity of the identified activations was analyzed by Bayesian mixed effects modeling. Activations in the parietal operculum were also compared to the location of cytoarchitectonically defined areas OP 1-4, which are part of the secondary somatosensory cortex (SII), to analyze whether the SII region was activated by anal and/or rectal stimulation. The lowest segregation between visceral and somatosensory stimuli was in the insular cortex, which supports the interpretation of the insula as an integrative region, receiving input from different sensory modalities. The most distinct segregation was found in the fronto-parietal operculum. Here the activations following anal and rectal stimulation were not only functionally but also anatomically distinct. Anal sensations were processed similar to other somatosensory stimuli in the SII cortex (area OP 4). Rectal afferents on the other hand were not processed in SII. Rather, they evoked activation at a more anterior location on the precentral operculum. These results demonstrate a functionally and anatomically distinct processing of somatosensory and visceral afferents in the human cerebral cortex.

Adult↗
PubMed2006

Volition and imagery in neurorehabilitation.

New interventional approaches have been proposed in the last few years to treat the motor deficits resulting from brain lesions. Training protocols represent the gold-standard of these approaches. However, the degree of motor recovery experienced by most patients remains incomplete. It would be important to improve our understanding of the mechanisms underlying functional recovery. This chapter examines the role of two possible mechanisms that could operate to improve motor function in this setting: volition and motor imagery. It is argued that both represent possible strategies to enhance training effects.

Brain Injuries↗
PubMed2005

Deficient fear conditioning in psychopathy: a functional magnetic resonance imaging study.

CONTEXT: Psychopaths belong to a larger group of persons with antisocial personality disorder and are characterized by an inability to have emotional involvement and by the repeated violation of the rights of others. It was hypothesized that this behavior might be the consequence of deficient fear conditioning. OBJECTIVE: To study the cerebral, peripheral, and subjective correlates of fear conditioning in criminal psychopaths and healthy control subjects. DESIGN: An aversive differential pavlovian delay conditioning paradigm with slides of neutral faces serving as conditioned and painful pressure as unconditioned stimuli. SETTING: The Department of Medical Psychology at the University of Tübingen, Tübingen, Germany. PARTICIPANTS: Ten male psychopaths as defined by the Hare Psychopathy Checklist-Revised and 10 age- and education-matched healthy male controls. The psychopaths were criminal offenders on bail and waiting for their trial or were on parole. The healthy controls were recruited from the community. MAIN OUTCOME MEASURES: Brain activation based on functional magnetic resonance imaging, electrodermal responses, emotional valence, arousal, and contingency ratings. RESULTS: The healthy controls showed enhanced differential activation in the limbic-prefrontal circuit (amygdala, orbitofrontal cortex, insula, and anterior cingulate) during the acquisition of fear and successful verbal and autonomic conditioning. The psychopaths displayed no significant activity in this circuit and failed to show conditioned skin conductance and emotional valence ratings, although contingency and arousal ratings were normal. CONCLUSION: This dissociation of emotional and cognitive processing may be the neural basis of the lack of anticipation of aversive events in criminal psychopaths.

Adult↗
PubMed2004

Processing of a simple aversive conditioned stimulus in a divided visual field paradigm: an fMRI study.

A left visual hemifield advantage for the processing of negative facial expressions has been demonstrated in a variety of studies. We tested whether the same effect is found for a neutral facial expression that had acquired a negative meaning through pairing with an aversive event. Startle reflex amplitudes, skin-conductance responses (SCR), and two verbal measures of affect (negative valence and arousal) were significantly increased after pairing, but no stimulation side by pairing interaction was observed. Functional magnetic resonance imaging (fMRI) revealed a significant increase of BOLD (blood oxygen level dependent) activity in the medial prefrontal cortex (MPFC), and the right frontal opercular region (RFOP). MPFC activity was correlated with psychophysiological and verbal emotional responses across subjects and, like these responses, was independent of the stimulation side. In contrast, RFOP activity was significantly stronger during left than during right hemifield stimulation but did not correlate with psychophysiological or verbal measures of negative affect. These results suggest that emotional responses to an aversive conditioned expressively neutral face are similar in both visual hemifields. MPFC activity seems to be closely linked to the strength of these responses.

Adult↗
PubMed2004

Parietal somatosensory association cortex mediates affective blindsight.

To investigate the neural substrates underlying emotional feelings in the absence of a conscious stimulus percept, we presented a visual stimulus in the blind field of partially cortically blind patients and measured cortical activity (by functional magnetic resonance imaging, fMRI) before and after the stimulus had been paired with an aversive event. After pairing, self-reported negative emotional valence and blood oxygen level-dependent (BOLD) responses in somatosensory association areas were enhanced, whereby somatosensory activity predicted highly corresponding reported feelings and startle reflex amplitudes across subjects. Our data provide direct evidence that cortical activity representing physical emotional states governs emotional feelings.

Affective Symptoms↗
PubMed2004

Brain activity underlying emotional valence and arousal: a response-related fMRI study.

Emotional behavior is organized along two psychophysiologic dimensions: (1) valence, varying from negative to positive, and (2) arousal, varying from low to high. Behavioral responses along these dimensions are assumed to be mediated by different brain circuits. We recorded startle reflex modulation and skin conductance responses in healthy volunteers during functional magnetic resonance imaging (fMRI) while they viewed a set of emotional pictures and took verbal ratings of the emotional valence and arousal of each picture after scanning. Response-related multiple correlation analysis revealed differential brain activity in five brain regions. Startle reflex changes, associated with the valence of a stimulus, correlated with activity in the amygdala, while verbal reports of negative emotional valence varied with insular activity. Peripheral physiologic and verbal responses along the arousal dimension varied with thalamic and frontomedial activity. Peripheral physiologic responses along both dimensions correlated with activity in somatosensory association areas in the anterior parietal cortex. In the valence dimension, activity in the left anterior parietal cortex was associated with highly correlating peripheral physiologic and verbal responses, suggesting that verbal reports of emotional valence might depend partly on brain circuits representing peripheral physiologic changes. Our data provide direct evidence for a functional segregation of brain structures underlying peripheral physiologic responses and verbal ratings along the emotional dimensions of valence and arousal.

Adult↗
PubMed2003

Disinhibition of the contralateral motor cortex by low-frequency rTMS.

Low-frequency repetitive transcranial magnetic stimulation (rTMS) of the primary motor cortex (M1) results in a lasting decrease of motor evoked potentials (MEPs). Here we investigated the effects of supra-threshold rTMS (15 min, 1 Hz) to the left M1 on the excitability of the stimulated and homologous (unstimulated) M1 in healthy subjects by using single and double pulse TMS before and after rTMS. We found reduction of MEP amplitudes on the stimulated side and, most importantly, disinhibition of intracortical excitability of the homologous M1. This crossed effect of rTMS supports the concept of a physiological balance of reciprocal inhibitory projections and emphasizes that rTMS can induce remote effects that are relevant for the physiological interpretation of such interventions.

Adult↗
PubMed2003

Motor learning elicited by voluntary drive.

Motor training consisting of voluntary movements leads to performance improvements and results in characteristic reorganizational changes in the motor cortex. It has been proposed that repetition of passively elicited movements could also lead to improvements in motor performance. In this study, we compared behavioural gains, changes in functional MRI (fMRI) activation in the contralateral primary motor cortex (cM1) and in motor cortex excitability measured with transcranial magnetic stimulation (TMS) after a 30 min training period of either voluntarily (active) or passively (passive) induced wrist movements, when alertness and kinematic aspects of training were controlled. During active training, subjects were instructed to perform voluntary wrist flexion-extension movements of a specified duration (target window 174-186 ms) in an articulated splint. Passive training consisted of wrist flexion- extension movements elicited by a torque motor, of the same amplitude and duration range as in the active task. fMRI activation and TMS parameters of motor cortex excitability were measured before and after each training type. Motor performance, measured as the number of movements that hit the target window duration, was significantly better after active than after passive training. Both active and passive movements performed during fMRI measurements activated cM1. Active training led to more prominent increases in (i) fMRI activation of cM1; (ii) recruitment curves (TMS); and (iii) intracortical facilitation (TMS) than passive training. Therefore, a short period of active motor training is more effective than passive motor training in eliciting performance improvements and cortical reorganization. This result is consistent with the concept of a pivotal role for voluntary drive in motor learning and neurorehabilitation.

Adult↗
PubMed2002

Brain circuits involved in emotional learning in antisocial behavior and social phobia in humans.

While psychopaths (PP) lack anticipatory fear, social phobics (SP) are characterized by excessive fear. Criminal PP, SP and healthy controls (HC) participated in differential aversive delay conditioning with neutral faces as conditioned (CS) and painful pressure as unconditioned stimuli. Functional magnetic resonance imaging revealed differential activation in the limbic-prefrontal circuit (orbitofrontal cortex, insula, anterior cingulate, amygdala) in the HC. By contrast, the PP displayed brief amygdala, but no further brain activation. The SP showed increased activity to the faces in the amygdala and orbitofrontal cortex already during habituation. Thus, a hypoactive frontolimbic circuit may represent the neural correlate of psychopathic behavior, whereas an overactive frontolimbic system may underly social fear.

Adult↗
PubMed2002

Modulation of slow cortical potentials by transcranial magnetic stimulation in humans.

We studied the effects of transcranial magnetic stimulation (TMS) on slow cortical potentials (SCPs) of the brain elicited during performance of a feedback and reward task. Ten healthy participants were trained to self-regulate their SCP amplitude using visual feedback and reward for increased or decreased amplitudes. Subjects participated in 27 runs (each comprising 70 trials) under three different conditions: single-pulse TMS delivered with the coil centered over Cz (vertex), over a lateral scalp position (LSP), which increased task difficulty, and in the absence of stimulation. Cz stimulation led to a non-significant enhancement of negative SCPs, while LSP stimulation led to a significant increase of positive SCPs. These results are consistent with the idea that enhanced task difficulty, as in LSP stimulation, enhances cognitive processing load leading to an increase of positive SCPs. Additionally, the data raise the hypothesis that TMS delivered to bilateral midcentral regions could modulate the amplitude of negative SCPs.

Adult↗
PubMed1999

Reorganization in the primary motor cortex after spinal cord injury - A functional Magnetic Resonance (fMRI) study.

Activation maps in the primary motor cortex (M1) were investigated in three patients with complete spinal cord injury (SCI) at level TH3, TH7 and TH9 and in one patient with an incomplete spinal cord injury at level L1 during right elbow (4 patients), right thumb (4 patients), bilateral lip (2 patients) and right foot (3 patients during imagined, 1 patient during executed) movements using functional Magnetic Resonance Imaging (fMRI). Compared to controls fMRI activation maps of patients with complete paraplegia showed a cranial displacement of the activation maxima in the contralateral primary motor cortex during elbow movement of 13.3mm, whereas the maxima of thumb and lip movements were not altered. The patient with an incomplete spinal cord injury revealed no displacement of elbow activation maxima. The reorganization is likely to occur on the cortical and not on the spinal level.

Journal Article↗