The Power of mind: Blocking visual perception by hypnosis.

The present study investigated the effects of suggestion on the processing of visual stimuli. Participants counted rare visual stimuli presented on a screen, once during a hypnosis condition where they were suggested that their vision of the screen is blocked by a virtual wooden board in front of their eyes and once during a control condition without suggestion. In the hypnosis condition, counting performance was about 20% worse than in the control condition. At the same time, the P3b amplitude of the event-related brain potential was about 37% reduced. Smaller P3b amplitudes were significantly associated with deficient counting performance, and this effect was largest in participants who reported the blockade as real. In contrast, earlier brain responses (N1, P2) that reflect basic processing of the visual stimuli were not affected by the suggested blockade. We conclude that the suggestion of the blockade affects later stages of visual perception, leaving early processes intact. This illustrates the impact of suggestions and the power of mind.

Altered activation of the ventral striatum under performance-related observation in social anxiety disorder.

BACKGROUND: Social anxiety disorder (SAD) is characterized by fear of social and performance situations. The consequence of scrutiny by others for the neural processing of performance feedback in SAD is unknown. METHODS: We used event-related functional magnetic resonance imaging to investigate brain activation to positive, negative, and uninformative performance feedback in patients diagnosed with SAD and age-, gender-, and education-matched healthy control subjects who performed a time estimation task during a social observation condition and a non-social control condition: while either being monitored or unmonitored by a body camera, subjects received performance feedback after performing a time estimation that they could not fully evaluate without external feedback. RESULTS: We found that brain activation in ventral striatum (VS) and midcingulate cortex was modulated by an interaction of social context and feedback type. SAD patients showed a lack of social-context-dependent variation of feedback processing, while control participants showed an enhancement of brain responses specifically to positive feedback in VS during observation. CONCLUSIONS: The present findings emphasize the importance of social-context processing in SAD by showing that scrutiny prevents appropriate reward-processing-related signatures in response to positive performances in SAD.

Laser heat hyperalgesia is not a feature of non-specific chronic low back pain.

BACKGROUND: Based upon studies using mechanical pin-prick, pressure, electrical or heat stimuli applied to painful and/or pain-free parts of the body, chronic low back pain (CLBP) has been shown to be associated with generalized and enhanced pain sensitivity and altered brain responses to noxious stimuli. To date, no study examined the processing of noxious laser heat pulses, which are known to selectively excite thermal nociceptors located in the superficial skin layers, in CLBP. METHODS: We studied laser heat pain thresholds (LHPTs) and nociceptive laser-evoked brain electrical potentials (LEPs) following skin stimulation of the pain-affected back and the pain-free abdomen using noxious laser heat stimulation in 16 CLBP patients and 16 age- and gender-matched healthy controls (HCs). RESULTS: We observed no statistically significant differences in LHPTs between CLBP patients and HCs, neither on the back nor on the abdomen. Furthermore, we found no evidence for altered brain responses between CLBP patients and HCs in response to stimulation of the back and abdomen in single-trial latencies and amplitudes of LEP components (N2, P2). CONCLUSION: The results are in contrast to previous studies showing hypersensitivity to different experimental noxious stimuli (e.g., contact heat). We argue that these discrepancies may be due to low spatial and temporal summation within the central nervous system following laser heat stimulation. Our results indicate important methodological differences between laser heat and thermode stimulation that should be taken into account when interpreting results, such as from thermal quantitative sensory testing.

[Emotional impact of facial palsy]. / Emotionale Auswirkungen einer Fazialisparese.

Facial palsy is not only a movement disorder but leads also to an emotional and communicative disorder in chronic stage but also in some patients already during the acute phase of the disease. The present review describes the current knowledge of the neurobiological and psychological fundamentals on the relation of facial movement and its emotional context. So far there is not much knowledge on the impact of a facial palsy on the interaction between facial movement, emotional processing and communicative skills of the patient. The emotional contagion seems to be reduced in patients with facial palsy. The ability to express emotions seems also to be reduced. Moreover, the patients feel to be perceived negatively. In fact, most of the expressions of patients with facial palsy are allocated with a negative affect even when the patients are smiling. Patients with facial palsy react with negative stress, anxiety and depression. The patients avoid social contacts. In turn, this reinforces the communicative disorder. The otorhinolaryngologist can use the Facial Disability Index as a simple questionnaire to detect such dysfunctions. Diagnostics that are necessary to develop a therapy program are presented in this review. Standardized therapy concepts that are not only treat the movement disorder but also the emotional context is missing so far. Finally, the review will give an outlook on potential therapy strategies.

[Pain words activate pain-processing neural structures]. / Schmerzwörter aktivieren schmerzverarbeitende Hirnareale.

Previous studies suggested that areas of the neural"pain matrix" are activated by the processing of pain-related environmental cues such as pain-related pictures or descriptors of pain. However, it is still sketchy whether these activations are specific to the pain-relevant content of the stimuli or simply reflect a general effect of negative emotional valence or increased arousal. The present study addressed this question by investigating the neural mechanisms underlying the processing of pain-related, negative (non-pain-related), positive and neutral words. When subjects were instructed to image a situation associated with the word presented (imagination task), we found increased activation within the dorsolateral prefrontal cortex (DLPFC) and inferior parietal cortex (IPC) when processing pain-related words compared to other words. When attention was focused on a distracting task (distraction task), we found a decrease in activation within the dorsal anterior cingulum (dACC) and a relative increase in activation within the subgenual anterior cingulum (sACC) when processing pain-related words compared to other words. These results indicate that the differences in processing pain-related words compared to non-pain-related words are specific to the content of the words and cannot simply be explained by emotional valence or arousal. Additionally, we showed that the specific activations to pain-related words are substantially modulated by the attention demands of the task.

Connectivity analysis of somatosensory evoked potentials in patients with major depression. Analysis of connectivity.

OBJECTIVES: Connectivity analysis was used to investigate the processing of intracutaneous stimuli and directed interactions within the pain matrix in patients with major depression (MD) and healthy controls (HCs), by means of frequency selective generalized partial directed coherence (gPDC). METHODS: Eighteen patients with MD and 18 HCs underwent stimulations consisting of moderately painful intracutaneous electrical stimuli to the right and left middle fingers. Connectivity analysis was based on nine selected EEG electrodes. RESULTS: Stimulus-induced changes of the gPDC in a pre/post stimulus comparison and changes in the connectivity pattern in the post-stimulus condition were found. We could identify network changes correlating to the side stimulated, as well as differences between HCs and MD patients. CONCLUSIONS: These data support the suggestion that pain processing in response to noxious stimulation in MD patients is different compared to healthy controls, suggesting aberrant functional connectivity. Generalized partial directed coherence is shown to be a promising method to detect changes in connectivity in both within- and between-subject designs.

[Stimulation of tiny skin areas for selective stimulation of C fibres]. / Selektive C-Faser-Stimulation durch Stimulation winziger Hautareale.

BACKGROUND: It has been found difficult to stimulate the primary C-fibre afferents separately from those of Adelta fibres. A necessary and sufficient condition for the investigation of the C-fibre system is the selective stimulation of C fibres without activation of Adelta fibres. The stimulation of tiny skin areas allows such a selective activation of C fibres. METHODS AND RESULTS: The main aspects of the method for stimulation of tiny skin areas as well as some results obtained by this method are reported here. The application of this method is compared with applications of other methods that allow an investigation of central processing of human C-fibre input. CONCLUSION: The stimulation of tiny skin areas represents a simple method for selective stimulation of C fibres.

Laser-evoked potentials to noxious stimulation during hypnotic analgesia and distraction of attention suggest different brain mechanisms of pain control.

Psychological accounts of hypnosis have hypothesized that hypnosis and attention might share similar mechanisms and that hypnosis simply represents an extensive state of reduced attention. This assumption implies that reports of pain and electrocortical brain responses to painful stimulation should be similarly reduced when subjects are exposed to suggestions of hypnotic analgesia (HA) or requested to distract their attention from painful stimuli (distraction of attention: DA) as compared to a control condition (CC). To test this hypothesis, we recorded event-related electrical brain potentials to noxious laser-heat stimuli and pain reports during HA, DA, and CC from subjects highly susceptible to hypnotic suggestions. Pain reports were significantly reduced during HA and DA as compared to CC. The amplitudes of the late laser-evoked brain potential (LEP) components N200 and P320 were also significantly smaller during DA than during CC. However, no significant difference of these late LEP amplitudes was obtained for HA as compared to CC. Results indicate that hypnotic analgesia and distraction of attention represent different mechanisms of pain control and involve different brain mechanisms.

Scalp topography of ultralate (C-fibres) evoked potentials following thulium YAG laser stimuli to tiny skin surface areas in humans.

AIM: To investigate (1) the scalp topography of ultralate laser evoked potentials (LEPs) related to C-fibre activation, which can directly be obtained by thulium YAG (Tm YAG) laser stimulation of tiny skin surface areas (about 0.23 mm(2)) and (2) the influence of the performance of a motor task on ultralate LEPs. METHODS: Laser stimuli were applied to the dorsum of the left hand. LEPs were recorded with 58 scalp electrodes from 9 healthy subjects in two different conditions, with and without a reaction time (RT) task (press a button upon detection). RESULTS: On high resolution electroenchephalogram recordings, ultralate LEPs were characterized by a broad positive component (peak latency: 1133+/-91 ms) with maximum amplitude about the vertex. Moreover, the performance of a RT task had no influence on latency, amplitude and topographical patterns of two maps chosen at the positive peak latency in ultralate LEPs. Nevertheless, a negative inflexion (latency 1300 ms) appeared after the positive component in the task condition possibly reflecting movement-related potentials. CONCLUSION: Tm YAG laser stimulation of tiny skin surface areas allows recording the dynamic scalp topography of ultralate (C-fibres) LEPs, with or without the performance of a RT task.

Increased excitability in the primary motor cortex and supplementary motor area in patients with phantom limb pain after upper limb amputation.

Using functional magnetic resonance imaging and single slice FLASH technique, we investigated reorganization of the hand representation of the primary sensorimotor cortex (SMC) in 16 patients with upper extremity amputation. Patients were asked to perform finger tapping with the intact hand, repetitive eye closing and anteflexion of the amputation stump or intact shoulder. Six normal volunteers served as control. In the normal volunteers activations during shoulder anteflexion, finger tapping and eye closure were located within the central sulcus in a medio-lateral fashion. Patients demonstrated invasion of the face or shoulder representation into the hand representation of the amputated limb. Eight phantom limb pain patients showed significantly greater activation in SMC and supplementary motor area (SMA) in contrast to eight patients without phantom limb pain. We conclude, that different parts of the motor system are affected in patients with phantom limb pain--possibly in the sense of an up-regulation of excitability.

Dipole analysis of ultralate (C-fibres) evoked potentials after laser stimulation of tiny cutaneous surface areas in humans.

Ultralate (C-fibres) laser evoked potentials (LEP) can be obtained by stimulation of a tiny skin surface area (0.23 mm(2)). Since their generators are unknown up to now, we performed brain source analyses of ultralate LEPs using high resolution electroencephalography (64 channels) and a realistic head model that was based on individual magnetic resonance images. Ultralate LEPs were characterized by a negative-positive complex with a large positive component maximal at the vertex. Source analysis revealed that ultralate LEPs could be explained by two dipole sources in the upper bank of the contralateral and ipsilateral Sylvian fissure (SII) and one dipole in the median region corresponding to the anterior cingulate gyrus.

Rapid functional plasticity of the somatosensory cortex after finger amputation.

Recent research indicates that areas of the primary somatosensory (SI) and primary motor cortex show massive cortical reorganization after amputation of the upper arm, forearm or fingers. Most of these studies were carried out months or several years after amputation. In the present study, we describe cortical reorganization of areas in the SI of a patient who underwent amputation of the traumatized middle and ring fingers of his right hand 10 days before cortical magnetic source imaging data were obtained. Somatosensory-evoked magnetic fields (SEF) to mechanical stimuli to the finger tips were recorded and single moving dipoles were calculated using a realistic volume conductor model. Results reveal that the dipoles representing the second and fifth fingers of the affected hand were closer together than the comparable dipoles of the unaffected hand. Our findings demonstrate that neural cell assemblies in SI which formerly represented the right middle and ring fingers of this amputee became reorganized and invaded by neighbouring cell assemblies of the index and little finger of the same hand. These results indicate that functional plasticity occurs within a period of 10 days after amputation.

Treatment-induced cortical reorganization after stroke in humans.

BACKGROUND AND PURPOSE: Injury-induced cortical reorganization is a widely recognized phenomenon. In contrast, there is almost no information on treatment-induced plastic changes in the human brain. The aim of the present study was to evaluate reorganization in the motor cortex of stroke patients that was induced with an efficacious rehabilitation treatment. METHODS: We used focal transcranial magnetic stimulation to map the cortical motor output area of a hand muscle on both sides in 13 stroke patients in the chronic stage of their illness before and after a 12-day-period of constraint-induced movement therapy. RESULTS: Before treatment, the cortical representation area of the affected hand muscle was significantly smaller than the contralateral side. After treatment, the muscle output area size in the affected hemisphere was significantly enlarged, corresponding to a greatly improved motor performance of the paretic limb. Shifts of the center of the output map in the affected hemisphere suggested the recruitment of adjacent brain areas. In follow-up examinations up to 6 months after treatment, motor performance remained at a high level, whereas the cortical area sizes in the 2 hemispheres became almost identical, representing a return of the balance of excitability between the 2 hemispheres toward a normal condition. CONCLUSIONS: This is the first demonstration in humans of a long-term alteration in brain function associated with a therapy-induced improvement in the rehabilitation of movement after neurological injury.

The influence of semantic priming on event-related potentials to painful laser-heat stimuli in humans.

In this study we investigated the effects of different semantic primes on the processing of painful stimuli. For prime stimuli, descriptors of three categories were used: somatosensory pain-related, affective pain-related, and neutral adjectives. While subjects (n=10) processed these primes, a painful laser-heat stimulus was applied. Laser-evoked potentials (LEPs) were recorded and pain intensity ratings were obtained after each single laser stimulus. Painful stimuli applied while subjects processed pain-related primes (affective and somatosensory adjectives) resulted in larger LEP amplitudes at 370 ms post laser stimulus compared to amplitudes of laser-evoked activities while subjects processed neutral primes (F((2,18))=3.90, P=0.05). It is suggested that pain-related semantic primes might preactivate neural networks subserving pain memory and pain processing. The processing of pain-related primes seems to preactivate cortical cell-assemblies involved in the processing of the succeeding painful laser stimuli.

Objective measurement of functional upper-extremity movement using accelerometer recordings transformed with a threshold filter.

BACKGROUND AND PURPOSE: The consensus is that the most important outcome for rehabilitation is functional activity in the life situation. Constraint-Induced Movement Therapy, a new treatment that transfers in-clinic gains to the life situation, demands objective measurement of real-world movement. However, direct, objective, and accurate measures of arm use in the real world are not available. Previous attempts to use accelerometry to measure extremity movement have failed because of unacceptable variability. This problem has been addressed here by use of a threshold filter. METHODS: Nine stroke patients and 1 healthy individual wearing accelerometers were videotaped while they carried out their usual activities at home or in the clinic; the duration of their arm, torso, and ambulatory movements was judged by 2 observation teams. In addition, 11 college students performed 5 standardized activities of daily living for varying durations in the laboratory. The accelerometer data were transformed; the raw value recorded for a given epoch was set to a constant if it exceeded a low threshold. RESULTS: The threshold-filtered recordings measured the duration of movement accurately and with very little variability. Correlations between the threshold-filtered recordings and the observer ratings of the duration of arm, torso, and ambulatory movements were 0.93, 0.93 and 0.99, respectively; the corresponding correlations for the raw values were -0.17, 0.34, and 0.85. CONCLUSIONS: These results present initial evidence for the validity of threshold-filtered accelerometer recordings for objectively measuring the amount of real-world upper-extremity movement as an index of treatment outcome for rehabilitation patients.

Decrease in phantom limb pain associated with prosthesis-induced increased use of an amputation stump in humans.

The experience of phantom limb pain, non-painful phantom limb sensation and telescoping was ascertained by questionnaire in a group of upper extremity amputees wearing a functionally effective Sauerbruch prosthesis which permits extensive use of the affected limb and in a group of patients wearing a cosmetic prosthesis that did little to increase the utilization of the amputation stump. The Sauerbruch prosthesis group exhibited a significant and large decrease in amount of phantom limb pain while the cosmetic prosthesis group showed no change. Neither group experienced a decrease in non-painful phantom limb sensation or telescoping. The amount of phantom limb pain has been found to be highly correlated with the amount of injury-related, afferent-decrease cortical reorganization. It is possible that the increased use of the amputation stump induced by wearing a Sauerbruch prosthesis produced a countervailing use-dependent, afferent-increase type of cortical reorganization that reversed the phantom limb pain. These preliminary results require replication. Their therapeutic implications are discussed.

Effects of constraint-induced movement therapy on patients with chronic motor deficits after stroke: a replication.

BACKGROUND AND PURPOSE: Constraint-induced movement therapy (CI therapy) has previously been shown to produce large improvements in actual amount of use of a more affected upper extremity in the "real-world" environment in patients with chronic stroke (ie, >1 year after the event). This work was carried out in an American laboratory. Our aim was to determine whether these results could be replicated in another laboratory located in Germany, operating within the context of a healthcare system in which administration of conventional types of physical therapy is generally more extensive than in the United States. METHODS: Fifteen chronic stroke patients were given CI therapy, involving restriction of movement of the intact upper extremity by placing it in a sling for 90% of waking hours for 12 days and training (by shaping) of the more affected extremity for 7 hours on the 8 weekdays during that period. RESULTS: Patients showed a significant and very large degree of improvement from before to after treatment on a laboratory motor test and on a test assessing amount of use of the affected extremity in activities of daily living in the life setting (effect sizes, 0.9 and 2.2, respectively), with no decrement in performance at 6-month follow-up. During a pretreatment control test-retest interval, there were no significant changes on these tests. CONCLUSIONS: Results replicate in Germany the findings with CI therapy in an American laboratory, suggesting that the intervention has general applicability.