Biomedical subjects

Katja Wiech

Publications and source records attributed to Katja Wiech.

16 recordsLinked to original sources

PubMed2006

Neural coding of tactile decisions in the human prefrontal cortex.

The neural processes underlying tactile decisions in the human brain remain elusive. We addressed this question in a functional magnetic resonance imaging study using a somatosensory discrimination task, requiring participants to compare the frequency of two successive tactile stimuli. Tactile stimuli per se engaged somatosensory, parietal, and frontal cortical regions. Using a statistical model that accounted for the relative difference in frequencies (i.e., Weber fraction) and discrimination accuracy (i.e., correct or incorrect), we show that trial-by-trial relative frequency difference is represented linearly by activity changes in the left dorsolateral prefrontal cortex (DLPFC), the dorsal anterior cingulate cortex, and bilateral anterior insular cortices. However, a circumscribed region within the left DLPFC showed a different response pattern expressed as activity changes that were monotonically related to relative stimulation difference only for correct but not for incorrect trials. Our findings suggest that activity in the left DLPFC encodes stimulus representations that underlie veridical tactile decisions in humans.

Adult↗

PubMed2006

Anterolateral prefrontal cortex mediates the analgesic effect of expected and perceived control over pain.

Perceived control attenuates pain and pain-directed anxiety, possibly because it changes the emotional appraisal of pain. We examined whether brain areas associated with voluntary reappraisal of emotional experiences also mediate the analgesic effect of perceived control over pain. Using functional magnetic resonance imaging, we compared self-controlled noxious stimuli with physically identical stimuli that were externally controlled. Self-controlled stimulation was accompanied by less pain and anxiety and higher activation in dorsal anterior cingulate (dACC), right dorsolateral, and bilateral anterolateral prefrontal (alPFC) cortices. Activation in dACC and right alPFC was negatively correlated with pain intensity ratings. For externally controlled pain, activation in right alPFC was inversely correlated with the participants' general belief to have control over their lives. Our results are consistent with a reappraisal view of control and suggest that the analgesic effect of perceived control relies on activation of right alPFC. Failure to activate right alPFC may explain the maladaptive effects of strong general control beliefs during uncontrollable pain.

Adult↗

PubMed2006

Anticipatory brainstem activity predicts neural processing of pain in humans.

Previous neuroimaging studies have shown brain activity during not only the application of noxious stimuli, but also prior to stimulation. The functional significance of the anticipatory response, however, has yet to be explored. Two theoretical responses involve either a decrease or an increase in sensitivity of the nociceptive system. In a functional magnetic resonance imaging (fMRI) study, brainstem responses during anticipation and processing of thermal noxious stimuli were investigated. Twelve healthy subjects were warned prior to and then received noxious stimulation to their left hand. Behavioral data showed a positive correlation between the intensity of anticipation and pain. FMRI data revealed brainstem activation in the PAG during the anticipation period. When correlated with individual anticipation ratings, activation during anticipation included significant clusters within the entorhinal cortex and ventral tegmental area (VTA). During receipt, activation within the brainstem included the PAG, VTA, rostral ventromedial medulla (RVM), and the parabrachial nucleus (PB), all elements of descending pain pathways. Using a backward model approach, we explored the functional significance of the anticipatory neural response for subsequent pain processing. Results of this regression analysis revealed that insula activity during receipt was predicted by activity in both the entorhinal cortex and VTA during anticipation. We suggest that activation in both regions before and during pain may underlie anticipation and subsequent pain modulatory responses, possibly involving the appraisal and control of attention necessary for pain modulation. Together, the results suggest a possible role of brainstem areas in anticipatory mechanisms involved in the maintenance of chronic pain.

Adult↗

PubMed2006

Repetitive transcranial magnetic stimulation-induced changes in sensorimotor coupling parallel improvements of somatosensation in humans.

Repetitive transcranial magnetic stimulation (rTMS) is an established technique for non-invasive stimulation of human cortex. Although studies have shown an influence of rTMS on single cortical regions and on simple behavioral response patterns, its influences on the dynamics of task-related activity in cortical networks have not been characterized. We provide such a characterization by showing that 5 Hz rTMS over primary somatosensory cortex (SI) induces a reconfiguration of activity patterns in a sensorimotor network, comprising the stimulated region and ipsilateral primary motor cortex (MI). These plastic changes endure for up to 120 min and are correlated with behavioral improvement in discrimination. Dynamic causal modeling showed that this reconfiguration could be explained by an rTMS-induced increase in SI excitability (self-connection) and an increase in the effective connectivity from SI to MI. Thus, our data demonstrate that rTMS can temporarily induce behaviorally relevant reorganization within a complex cortical network underlying human somatosensory experience.

Adult↗

PubMed2006

Levels of appraisal: a medial prefrontal role in high-level appraisal of emotional material.

Appraisal refers to the evaluation of the meaning of emotional stimuli and is considered causal in the generation of an emotional response. Cognitive neuroscience has paid little attention to a theoretical distinction between low-level appraisal, considered to be automatic and preattentive, and high-level appraisal that requires attentional and working memory resources. To disentangle low-level from high-level appraisal, we varied cognitive load in a concurrent, unrelated working memory task, while anxiety was induced through anticipation of impending pain. Confirming theoretical predictions, we show that anxiety-related activity in dorsal medial prefrontal/rostral anterior cingulate cortex (dorsal MPFC/ACC) is attenuated under high, relative to low, cognitive load. Lateral prefrontal regions previously implicated in reappraisal and cognitive emotion regulation show a similar interaction between anxiety and cognitive load. Critically, there were no changes in physiological and subjective measures of low-level appraisal outcome and emotional response generation as a function of load, allowing us to conclude that MPFC/ACC and lateral PFC activity during anticipatory anxiety reflects high-level appraisal. Our data provide neurobiological evidence for a distinction between low-level and high-level appraisal mechanisms.

Adolescent↗

PubMed2006

Neural correlates of self-distraction from anxiety and a process model of cognitive emotion regulation.

Cognitive strategies used in volitional emotion regulation include self-distraction and reappraisal (reinterpretation). There is debate as to what the psychological and neurobiological mechanisms underlying these strategies are. For example, it is unclear whether self-distraction and reappraisal, although distinct at a phenomenological level, are also mediated by distinct neural processes. This is partly because imaging studies on reappraisal and self-distraction have been performed in different emotional contexts and are difficult to compare. We have therefore investigated the neural correlates of self-distraction, as indexed by a thought suppression task, in an anticipatory anxiety paradigm previously employed by us to study reappraisal. Brain activity was measured by functional magnetic resonance imaging. We show that self-distraction recruits the left lateral prefrontal cortex. Based on a review of the existing data, we develop a process model of cognitive emotion regulation. The model posits that both self-distraction and reappraisal attenuate emotional reactions through replacement of emotional by neutral mental contents but achieve replacement in different ways. This is associated with a dependence of self-distraction on a left prefrontal production function, whereas reappraisal depends on a right prefrontal higher order monitoring process.

Acoustic Stimulation↗

PubMed2005

Do cortical maps depend on the timing of sensory input? Experimental evidence and computational model.

Fast adaptations in the functional organization of primary sensory cortex are generally assumed to result from changes of network connectivity. However, the effects of intrinsic neuronal excitability alterations due to the activation of neighboring cortical representational zones, which might as well account for the changes of cortical representative maps, have been paid little attention to. In a recent experiment (Braun et al. 2000b) we showed by neuromagnetic source imaging that random or fixed sequence stimulation of three digits of both hands led to stimulation-timing-induced changes in primary somatosensory (SI) cortical maps. The distance between the cortical representation of thumb and middle finger became significantly shorter during the fixed sequence stimulation. The analysis on the time course of the cortical map changes revealed that these reorganizations occurred within minutes and were fully reversible. The previously reported results were interpreted as the involvement of a superordinate center responsible for detecting and activating the appropriate maps. Here we present an alternative parsimonious explanation that is supported by a computational model. Based on the experimental evidence, we developed a simple model that took intrinsic neuronal excitability together with subthreshold activation into account and assumed partial cortical overlap of the representational zones of neighboring digits. Furthermore, in the model the neuronal excitability decayed slowly with respect to the stimulation frequency. The observed cortical map changes in the experiment could be reproduced by the two-layer feed-forward computational network. Our model thus suggests that the dynamic shifts of cortical maps can be explained by the state and time course of intrinsic neuronal excitability and subthreshold activation, without involving changes in network connectivity.

Adult↗

PubMed2005

Brain processes associated with target finding.

The response execution stage of cognitive skill consists of several substages, including finding the proper response location among available alternatives and moving the effector to the target location. In order to unravel the brain dynamics associated with the finding process, the present experiments used two experimental conditions. In the number condition, which requires both finding and moving, subjects are presented on each trial with a digit, 0-9, are required to find that digit on a circular clock face, and then to move a cursor to that target's location. In the arrow condition, an arrow pointing to the location of the target on the clock face circumference appears simultaneously with the target digit; no target finding is required because subjects need only to move the cursor along the path marked by the arrow. A pilot and the main experiment revealed that response initiation times but not movement times were affected by these experimental manipulations. Analysis of magnetoencephalographic (MEG) activity revealed an early occipital activity which was not affected by experimental manipulations. Later activity with central-parietal and parieto-temporal loci presumably reflected changes in the dorsal and ventral pathways, respectively, and these were affected by experimental conditions. Finally, finding processes seem to be associated with a second late activation of the ventral pathway presumably reflecting ongoing recognition processes.

Adolescent↗

PubMed2005

Opponent appetitive-aversive neural processes underlie predictive learning of pain relief.

Termination of a painful or unpleasant event can be rewarding. However, whether the brain treats relief in a similar way as it treats natural reward is unclear, and the neural processes that underlie its representation as a motivational goal remain poorly understood. We used fMRI (functional magnetic resonance imaging) to investigate how humans learn to generate expectations of pain relief. Using a pavlovian conditioning procedure, we show that subjects experiencing prolonged experimentally induced pain can be conditioned to predict pain relief. This proceeds in a manner consistent with contemporary reward-learning theory (average reward/loss reinforcement learning), reflected by neural activity in the amygdala and midbrain. Furthermore, these reward-like learning signals are mirrored by opposite aversion-like signals in lateral orbitofrontal cortex and anterior cingulate cortex. This dual coding has parallels to 'opponent process' theories in psychology and promotes a formal account of prediction and expectation during pain.

Avoidance Learning↗

PubMed2005

Modulation of pain processing in hyperalgesia by cognitive demand.

The relationship between pain and cognitive function is of theoretical and clinical interest, exemplified by observations that attention-demanding activities reduce pain in chronically afflicted patients. Previous studies have concentrated on phasic pain, which bears little correspondence to clinical pain conditions. Indeed, phasic pain is often associated with differential or opposing effects to tonic pain in behavioral, lesion, and pharmacological studies. To address how cognitive engagement interacts with tonic pain, we assessed the influence of an attention-demanding cognitive task on pain-evoked neural responses in an experimental model of chronic pain, the capsaicin-induced heat hyperalgesia model. Using functional magnetic resonance imaging (fMRI), we show that activity in the orbitofrontal and medial prefrontal cortices, insula, and cerebellum correlates with the intensity of tonic pain. This pain-related activity in medial prefrontal cortex and cerebellum was modulated by the demand level of the cognitive task. Our findings highlight a role for these structures in the integration of motivational and cognitive functions associated with a physiological state of injury. Within the limitations of an experimental model of pain, we suggest that the findings are relevant to understanding both the neurobiology and pathophysiology of chronic pain and its amelioration by cognitive strategies.

Adult↗

PubMed2005

Objective measurement of tactile mislocalization.

Stimulating the skin with intensities close to the sensory threshold causes erroneous localization of the site of stimulation. Previous studies using manual methods for applying faint tactile stimuli have shown that localization errors obey a somatotopic principle in which tactile stimuli are preferentially mislocalized to sites adjacent to the stimulated skin region. However, manual testing of mislocalization is time consuming and only partially objective because results depend on the skills of the tester. To improve the testing procedure, an automated apparatus was developed. The procedure adjusted stimulus intensity adaptively during testing to remain near the individual subject's sensory threshold, so that mislocalizations occurred often enough to assess somatotopic organization. The new method was applied to 12 healthy subjects. In each subject, the five digits of the right hand were stimulated singly in random order. Localization errors were distributed preferentially to fingers close to the stimulated finger rather than to distant fingers. The profile of mislocalization differed significantly from that expected on the basis of response bias or guessing behavior. The present results replicate previous findings obtained for manual testing with improved sensitivity and indicate that the new technique is a useful tool for the study of somatosensory processing on a perceptual level.

Adult↗

PubMed2005

Anxiety reduction through detachment: subjective, physiological, and neural effects.

The ability to volitionally regulate emotions helps to adapt behavior to changing environmental demands and can alleviate subjective distress. We show that a cognitive strategy of detachment attenuates subjective and physiological measures of anticipatory anxiety for pain and reduces reactivity to receipt of pain itself. Using functional magnetic resonance imaging, we locate the potential site and source of this modulation of anticipatory anxiety in the medial prefrontal/anterior cingulate and anterolateral prefrontal cortex, respectively.

Adaptation, Psychological↗

PubMed2004

A placebo-controlled randomized crossover trial of the N-methyl-D-aspartic acid receptor antagonist, memantine, in patients with chronic phantom limb pain.

UNLABELLED: In the present study we investigated the effect of the N-methyl-D-aspartic acid (NMDA) receptor antagonist memantine (30 mg/d) on the intensity of chronic phantom limb pain (PLP) and cortical reorganization. In 8 patients with chronic PLP, memantine was tested in a placebo-controlled double-blinded crossover trial of 4 wk duration per trial. The intensity of PLP was rated hourly by the patients on a visual analog scale during baseline and both treatment periods. At the same time points, the functional organization of the primary somatosensory cortex (SI) was determined by neuromagnetic source imaging. In comparison to baseline and placebo, the NMDA receptor antagonist had no effect on the intensity of chronic PLP. In none of the periods were significant changes in the functional organization of SI observed. Although the conclusions regarding the clinical effect are limited because of the small sample size, the data indicate that in the studied dosage the NMDA receptor antagonist memantine is ineffective in the treatment of chronic PLP and is also ineffective for the reduction of associated neural plasticity in the primary SI. IMPLICATIONS: NMDA receptors play a substantial role in central nervous system changes underlying neuropathic pain. In a placebo-controlled double-blinded study we tested the effect of 30 mg memantine on chronic phantom limb pain and pain-associated cortical reorganization.

Adult↗

PubMed2003

Task-specific plasticity of somatosensory cortex in patients with writer's cramp.

Focal dystonias such as writer's cramp are characterized by muscular cramps that accompany the execution of specific motor tasks. Until now, the pathophysiology of focal dystonia remains incompletely understood. Recent studies suggest that the development of writer's cramp is related to abnormal organization of primary somatosensory cortex (SI), which in turn leads to impaired motor function. To explore contributions of SI on mechanisms of task specificity in focal dystonia, we investigated dynamic alterations in the functional organization of SI as well as sensory-motor gating for rest, left- and right-handed writing and brushing in writer's cramp patients and healthy controls. The functional organization of somatosensory cortex was assessed by neuromagnetic source imaging (151 channel whole-head MEG). In accordance with previous reports, distances between cortical representations of thumb and little finger of the affected hand were smaller in patients compared to healthy subjects. However, similar to healthy controls, patients showed normal modulation of the functional organization of SI as induced by the execution of different motor tasks. Both in the control subjects and patients, cortical distances between representations of thumb and little finger increased when writing and brushing compared to the resting condition. Although, cramps only occured during writing, no differences in the organization of SI were seen among motor tasks. Our data suggest that despite alterations in the organization of primary somatosensory cortex in writer's cramp, the capability of SI to adapt dynamically to different tasks is not impaired.

Adult↗

PubMed2002

Functional organization of primary somatosensory cortex depends on the focus of attention.

We used magnetic source imaging in human subjects to reveal within-subject variations of the homuncular hand representation within the primary somatosensory cortex modulated by attention. In one condition subjects were trained to detect sequential leftward or rightward stimulus motion across the fingers of the left hand ("hand" condition) and in a different condition to detect stimulus motion at a specific finger on this hand ("finger" condition). Afferent input was controlled by applying exactly the same stimulus pattern to the digits in the two tasks. Segregation of the somatotopic hand representation (an increase in the distance between the representations of digits 2 and 5) was observed, commencing with the onset of practice, in the finger relative to the hand condition. Subsequent training in the hand and finger conditions with feedback for correctness did not modify segregation, indicating that segregation was a task effect and not a training effect. These findings indicate that the hand representation within the primary somatosensory cortex is not statically fixed but is dynamically modulated by top-down mechanisms to support task requirements. A greater capacity for modulation of the functional cortical organization was positively correlated with superior learning and task performance.

Adult↗

PubMed2002

Continuous brachial plexus analgesia and NMDA-receptor blockade in early phantom limb pain: a report of two cases.

OBJECTIVE: To provide a mechanism-based acute pain management strategy for early phantom limb pain following traumatic amputations and to collect first evidence of its acute and potentially preventative effects on the formation and maintenance of phantom limb pain. The combination of continuous brachial plexus analgesia and prolonged block of N-methyl-D-aspartate (NMDA) receptors over 4 weeks aimed to attenuate peripheral and central sensitization, currently thought to be substantially involved in establishing and maintaining phantom limb pain. CASE REPORT: Two patients, after traumatic upper limb amputations and early phantom limb pain, were treated on the second and fifth day following amputation by continuous brachial plexus analgesia with ropivacaine 0.375% (30 ml for the initial block, continuous infusion rate = 5 ml/h) for 5 (Patient 1) and 9 days (Patient 2). Both patients received oral memantine (a noncompetitive NMDA-receptor antagonist) in increasing doses from 10 to 30 mg/d over a 4-week period. Ropivacaine only produced minor motor block, with almost unimpaired motor function. Memantine was well tolerated and no relevant side effects were observed. In both patients the treatment prevented the establishment of phantom limb pain, which did not reappear during follow-up of 1 year. CONCLUSIONS: The combination of long-term regional analgesia with prolonged block of NMDA receptors might be effective for treatment and prevention of phantom limb pain following traumatic amputations. The absence of clinically relevant side effects, together with maintained motor function suggests this treatment to be a promising preventive strategy for phantom limb pain following traumatic amputations.

Journal Article↗