Neurophysiological Determinants of Tic Severity in Children with Chronic Motor Tic Disorder

Tics wax and wane in severity. Although the understanding of the natural course of symptoms in tic disorder (TD) is important for planning and assessing therapeutic interventions, neurophysiological mechanisms and predictors of tic exacerbation and remission have not been sufficiently investigated. In each of seven children suffering from TD, contingent negative variation (CNV) was recorded on 10 occasions over a period of 2 months. CNV parameters of children with TD were compared with CNV data of healthy, age-matched children. During the entire time of observation, tic severity was assessed by parents and the investigator using a scale developed from the Yale Global Tic Severity Scale. Moreover, tic severity was also evaluated using video assessments. Patients with TD were characterized by significantly lower amplitude of the total CNV and more pronounced habituation of the early CNV component as compared to healthy children. Correlation analysis between tic severity and CNV parameters demonstrated that the more severe the tics were, the lower the amplitude of the total CNV. Since CNV amplitude represents processes of resource mobilization and control over neuronal excitability, tic severity may result from less ability to control neurophysiological functions in patients with TD.     

Two phases of the contingent negative variation in humans: connection with motor and mental functions

The question of dependence of the contingent negative variation (CNV) on the regulating mechanisms of motor and mental functions is not sufficiently studied. The tasks of the present work were: to investigate the dependence of the CNV early and late phases on the state of motor and mental functions in patients with Parkinson's disease (PD), and to elucidate the levodopa influence on the CNV parameters. 18 healthy subjects and 56 patients with PD were studied. In PD patients, significant reductions of amplitudes and squares of two CNV phases were observed. A negative correlation of the degree of coordinating muscle relationships disturbance with amplitudes of two CNV phases was found (p < 0.01). A positive interdependence between values of the both CNV phases and the state of mental functions was established, memory in particular (p < 0.05). After levodopa administration in PD patients, the early CNV phase did not significantly change, whereas the late CNV phase significantly increased (p < 0.05). Results of the investigation suggest an important role of the structures ensuring both direct motor control and mental functions in two CNV phases formation. A more obvious levodopa influence on the late CNV phase suggest participation of the basal ganglia efferent system in generation of the late CNV phase rather than in organization of the early CNV phase.     

Reliability and Stability of Contingent Negative Variation

Reliability parameters of a test indicate the stability (and quality) of the test itself. Reliability coefficients greater than 0.70 suggest an attribute as being sufficiently stable over time to be characterized as a trait. Reliability parameters of contingent negative variation (CNV) amplitudes in 27 healthy individuals were determined using a test-retest design. CNV was recorded at Cz, with an interstimulus interval of 3 s, on 2 separate occasions: initial session and 10 days later. Correlation coefficients between the 2 recording sessions were 0.675 for the total-CNV (tCNV), 0.855 for the early component (iCNV), 0.631 for the late component (lCNV), and 0.420 for the post-imperative negative variation (PINV). Statistical retest parameters for Spearman Brown were 0.806 for tCNV, 0.922 for iCNV, 0.774 for lCNV, and 0.655 for PINV. The iCNV, more than the other parameters, remained stable over the period of 10 days. It is suggested that the described standardized CNV recording procedure ensures reproducible and stable results in healthy subjects.     

Locus of Psychological Control and Peculiarities of Event-Related EEG Potentials

In a group including 74 adults of both sexes, we examined interrelations between the locus of psychological control (diagnosed using the Rotter questionnaire) and parameters of event-related EEG potentials, ERPs, recorded in the course of performance of two behavioral test acts with a motor component. Task A corresponded to maximally fast pushing on the button after a signal with warning; the time of the sensorimotor reaction was measured. Task B included internal counting of a definite time interval limited by two pushings on the button. Under these conditions, we recorded the contingent negative variation (CNV), the P300 potential, and, in task B, the readiness potential (RP). EEG leads C3 and C4, according to the 10-20 system, were used. Internals (estimates by the questionnaire, 6 stens or higher) were characterized by higher amplitudes of the terminal CNV (CNV-T), integral CNV, and P300 in task A, by greater RP and CNV amplitudes in task B, and also by shorter reaction times and their smaller dispersion. It should be supposed that the corresponding peculiarities of the neurodynamic constitution of an individual are determined, to a considerable extent, by the specificity of organization and functioning of a few neurotransmitter (aminergic in particular) and neurohumoral systems.     

Habituation of auditory evoked potentials and emotional state

"Fast" and "slow" habituation of N1 and N1-P2 components of auditory evoked potentials was studied in healthy subjects and in depressed patients. In patients, initially more low amplitudes of N1 and N1-P2 were revealed, as well as slowing down of habituation in the beginning of stimuli series and acceleration to its end (in healthy people--the greatest habituation in the initial part of the series and amplitude increase at its end), the absence of power effect in the component N1 at reaching, in the process of habituation, of the same minimum parameters as in healthy subjects. This points to weakening of dishabituation process parallel with well expressed "slow" habituation in patients and allows to suggest at expressed negative emotions a deficit of attention processes as a result of "internal abstraction".     

On the pathophysiology of migraine--links for "empirically based treatment" with neurofeedback

Psychophysiological data support the concept that migraine is the result of cortical hypersensitivity, hyperactivity, and a lack of habituation. There is evidence that this is a brain-stem related information processing dysfunction. This cortical activity reflects a periodicity between 2 migraine attacks and it may be due to endogenous or exogenous factors. In the few days preceding the next attack slow cortical potentials are highest and habituation delay experimentally recorded during contingent negative variation is at a maximum. These striking features of slow cortical potentials are predictors of the next attack. The pronounced negativity can be fed back to the patient. The data support the hypothesis that a change in amplitudes of slow cortical potentials is caused by altered habituation during the recording session. This kind of neurofeedback can be characterized as empirically based because it improves habituation and it proves to be clinically efficient.     

Cortical Reorganisation during a 30-Week Tinnitus Treatment Program

Subjective tinnitus is characterised by the conscious perception of a phantom sound. Previous studies have shown that individuals with chronic tinnitus have disrupted sound-evoked cortical tonotopic maps, time-shifted evoked auditory responses, and altered oscillatory cortical activity. The main objectives of this study were to: (i) compare sound-evoked brain responses and cortical tonotopic maps in individuals with bilateral tinnitus and those without tinnitus; and (ii) investigate whether changes in these sound-evoked responses occur with amelioration of the tinnitus percept during a 30-week tinnitus treatment program. Magnetoencephalography (MEG) recordings of 12 bilateral tinnitus participants and 10 control normal-hearing subjects reporting no tinnitus were recorded at baseline, using 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz tones presented monaurally at 70 dBSPL through insert tube phones. For the tinnitus participants, MEG recordings were obtained at 5-, 10-, 20- and 30- week time points during tinnitus treatment. Results for the 500 Hz and 1000 Hz sources (where hearing thresholds were within normal limits for all participants) showed that the tinnitus participants had a significantly larger and more anteriorly located source strengths when compared to the non-tinnitus participants. During the 30-week tinnitus treatment, the participants’ 500 Hz and 1000 Hz source strengths remained higher than the non-tinnitus participants; however, the source locations shifted towards the direction recorded from the non-tinnitus control group. Further, in the left hemisphere, there was a time-shifted association between the trajectory of change of the individual’s objective (source strength and anterior-posterior source location) and subjective measures (using tinnitus reaction questionnaire, TRQ). The differences in source strength between the two groups suggest that individuals with tinnitus have enhanced central gain which is not significantly influenced by the tinnitus treatment, and may result from the hearing loss per se. On the other hand, the shifts in the tonotopic map towards the non-tinnitus participants’ source location suggests that the tinnitus treatment might reduce the disruptions in the map, presumably produced by the tinnitus percept directly or indirectly. Further, the similarity in the trajectory of change across the objective and subjective parameters after time-shifting the perceptual changes by 5 weeks suggests that during or following treatment, perceptual changes in the tinnitus percept may precede neurophysiological changes. Subgroup analyses conducted by magnitude of hearing loss suggest that there were no differences in the 500 Hz and 1000 Hz source strength amplitudes for the mild-moderate compared with the mild-severe hearing loss subgroup, although the mean source strength was consistently higher for the mild-severe subgroup. Further, the mild-severe subgroup had 500 Hz and 1000 Hz source locations located more anteriorly (i.e., more disrupted compared to the control group) compared to the mild-moderate group, although this was trending towards significance only for the 500Hz left hemisphere source. While the small numbers of participants within the subgroup analyses reduce the statistical power, this study suggests that those with greater magnitudes of hearing loss show greater cortical disruptions with tinnitus and that tinnitus treatment appears to reduce the tonotopic map disruptions but not the source strength (or central gain).     

Component-Specific Self-Regulation of Slow Cortical Potentials and its Effect on Behavior: An Exploratory Study

In the present study, the possibility of component-specific self-regulation of the contingent negative variation (CNV) and the functional significance of the iCNV (initial or early CNV component) and tCNV (terminal or late CNV component) were investigated in twenty-four healthy volunteers. The subjects were able to achieve control over a particular CNV component within four sessions. Regulation of the tCNV was more successful than for the iCNV. Specific control over iCNV was associated with strategies mainly related to the pre-stimulus interval or the warning stimulus (S1), while regulation of the tCNV was assigned to activities during the whole interstimulus interval or around the imperative stimulus (S2). It can be concluded that component-specific regulation of the CNV can be used in studies of the psychophysiological meaning of this potential, representing different stages of information processing. The role of cortical pre-activation in the generation of the iCNV and the phasic performance-directed activation of the tCNV can be hypothesized.     

Étude de divers aspects de la prise en charge des acouphènes pour un sourd unilatéral avec le stimulateur électrique implantable extracochléaire Tinnelec RW®

Study of some aspects of the tinnitus treatment for unilateral deaf with an extracochlear electrical stimulation device. In France, there are about 6000 cases of sudden hearing loss, all of them bring with tinnitus. At present, the treatment of chronic tinnitus is based on the natural development or the facilitation of habituation. For the tinnitus, which resist to the habituation, the principle of the treatments consists in facilitating the habituation process. In a sound therapy the use of a sound generator, with a hearing aid if necessary, is proposed in order to facilitate habituation. But, in case of unilateral deafness acoustical habituation is not possible and tinnitus may cause a depression. Electrical stimulation offers a new therapeutic perspective, which overcomes the main problems to habituation. This approach is very promising that's why it seems essential to study some aspects. The project tries to answer to four questions: How do we have to stimulate electrically for a maximal efficiency? how can we fit the electric stimulation for maximal efficiency? When is it necessary to set up the stimulation? Can we intend to apply this technique to subjects having hearing residues? Recent experimental studies have proposed Tinnelec^® stimulator of the MXM Company as a therapeutic solution for the difficult tinnitus treatment in-patient with unilateral deafness. Many points will be examined through a clinical study and an animal study.     

State- and Trait-Related Alterations of Motor Cortex Excitability in Tinnitus Patients

Chronic tinnitus is a brain network disorder with involvement of auditory and non-auditory areas. Repetitive transcranial magnetic stimulation (rTMS) over the temporal cortex has been investigated for the treatment of tinnitus. Several small studies suggest that motor cortex excitability is altered in people with tinnitus. We retrospectively analysed data from 231 patients with chronic tinnitus and 120 healthy controls by pooling data from different studies. Variables of interest were resting motor threshold (RMT), short-interval intra-cortical inhibition (SICI), intra-cortical facilitation (ICF), and cortical silent period (CSP). 118 patients were tested twice - before and after ten rTMS treatment sessions over the left temporal cortex. In tinnitus patients SICI and ICF were increased and CSP was shortened as compared to healthy controls. There was no group difference in RMT. Treatment related amelioration of tinnitus symptoms were correlated with normalisations in SICI. These findings confirm earlier studies of abnormal motor cortex excitability in tinnitus patients. Moreover our longitudinal data suggest that altered SICI may reflect a state parameter, whereas CSP and ICF may rather mirror a trait-like predisposing factor of tinnitus. These findings are new and innovative as they enlarge the knowledge about basic physiologic and neuroplastic processes in tinnitus.     

The recovery functions of auditory event-related potentials during split-second discriminations

We examined the recovery cycles of auditory event-related potentials (ERPs) in a high-speed auditory discrimination task and in passive conditions. Each trial contained 3 tones cued by a warning flash. In passive conditions, auditory ERPs consisted mainly of N1 (108 msec) and P2 (213 msec) components superimposed on a small CNV. The N1 and P2 were comparable in amplitude and both had prolonged refractory periods. In discriminative reaction time (DRT) conditions the same tones cued or inhibited press responses and elicited additional endogenous components (principally the Nd and P3). ERPs in DRT conditions were superimposed upon a prominent CNV that began after the warning cue and lasted throughout the signal delivery period.The N1 was larger in active than passive conditions and showed less marked refractory effects, while the P2 was smaller and showed more marked refractoriness. Differences between active and passive conditions could be explained by the presence of an endogenous negative potential (the Nd) with a short refractory period that was superimposed upon the N1 and P2.The P3 was recorded only in active conditions. At short ISIs (0.5 sec), P3 amplitudes were reduced and P3 latencies lengthened in parallel with prolongations in reaction time due to so-called psychological refractory period (PRP) effects. Both P3 recovery and the PRP reflected central mechanisms since they were observed at short ISIs when stimuli cueing different responses succeeded one another.N1 and P3 amplitudes diminished over the course of the experiment in both active and passive conditions. The decrease (amounting to about 30% of initial amplitudes) did not appear due to reductions in vigilance, since it was not accompanied by changes in reaction time or response accuracy, or by changes in other endogenous components (CNV or Nd). Short-term N1 habituation was unaffected by long-term amplitude reductions suggesting that independent mechanisms were responsible for the two phenomena.     

Predisposition for and Prevention of Subjective Tinnitus Development

Dysfunction of the inner ear as caused by presbyacusis, injuries or noise traumata may result in subjective tinnitus, but not everyone suffering from one of these diseases develops a tinnitus percept and vice versa. The reasons for these individual differences are still unclear and may explain why different treatments of the disease are beneficial for some patients but not for others. Here we for the first time compare behavioral and neurophysiological data from hearing impaired Mongolian gerbils with (T) and without (NT) a tinnitus percept that may elucidate why some specimen do develop subjective tinnitus after noise trauma while others do not. Although noise trauma induced a similar permanent hearing loss in all animals, tinnitus did develop only in about three quarters of these animals. NT animals showed higher overall cortical and auditory brainstem activity before noise trauma compared to T animals; that is, animals with low overall neuronal activity in the auditory system seem to be prone to develop tinnitus after noise trauma. Furthermore, T animals showed increased activity of cortical neurons representing the tinnitus frequencies after acoustic trauma, whereas NT animals exhibited an activity decrease at moderate sound intensities by that time. Spontaneous activity was generally increased in T but decreased in NT animals. Plastic changes of tonotopic organization were transient, only seen in T animals and vanished by the time the tinnitus percept became chronic. We propose a model for tinnitus prevention that points to a global inhibitory mechanism in auditory cortex that may prevent tinnitus genesis in animals with high overall activity in the auditory system, whereas this mechanism seems not potent enough for tinnitus prevention in animals with low overall activity.     

Migraine and Meditation: Characteristics of Cortical Activity and Stress Coping in Migraine Patients,Meditators and Healthy Controls—An Exploratory Cross-Sectional Study

The aim of this exploratory cross-sectional study was to investigate the characteristics of cortical activity and stress coping in migraine patients, meditation experienced subjects, and healthy controls. 45 meditation experienced subjects, 46 migraine patients, and 46 healthy controls took part in the study. Cortical activity was measured with the contingent negative variation (CNV), a slow cortical event-related potential. Stress coping was examined with the standardized Stress Coping Questionnaire SVF-78. A one-way analysis of variance was used to investigate possible differences between the groups. CNV-amplitude was significantly higher in migraineurs than in controls. The meditators showed significantly lowest amplitudes. Migraine patients used negative stress-coping strategies significantly more often than meditators and healthy controls. Especially the application of the strategy “rumination” was most frequent in migraine patients and least frequent in meditators. Moreover, frequent rumination was significantly correlated with high CNV-amplitudes. Cortical and stress processing in people with meditation experience was improved compared to migraine patients and healthy controls.     

A Coronary-Prone Type of Personality: Peculiarities of Event-Related EEG Potentials

In a group of 70 adults of both sexes, we examined interrelations between the estimates of expression of a coronary-prone type (type A) of the personality (measured using the Jenkins questionnaire) and the parameters of event-related EEG potentials (ERPs). The latter potentials were recorded in the course of performance of two behavioral test tasks including motor components. Within the framework of the “A” task, the subject is had to maximally rapidly push the button after a signal with warning (with measurement of the latency of the sensorimotor reaction); under these conditions, we recorded the contingent negative variation (CNV) and P300 potential. In the case of the “B” task, a definite time interval was to be measured and limited by two pressings of the button. In this task, the readiness potential (RP) was recorded in addition to the CNV and P300. The C3 and C4 EEG leads (according to the 10–20 system) were used. Within the framework of the “A” task, subjects belonging to the coronary-prone type were characterized by the lowest amplitudes of the CNV and its separate components and also by greater amplitudes and relatively long latencies of the P300 wave. Persons of type B were distinguished by the highest CNV amplitudes in both hemispheres, while values of the P300 amplitude in this group were usually medium. In the “B” task, representatives of type A demonstrated the lowest RP and P300 amplitudes, especially clearly pronounced negative CNVs in the left hemisphere, and relatively long P300 latencies; individuals belonging to type B showed the highest RP and CNV amplitudes in the right hemisphere and medium values of the P300 amplitude. The correlations found are probably due, to a considerable extent, to the fact that both characteristics of the behavioral types A and B and amplitude parameters of ERPs depend significantly on genetically determined neurochemical factors, namely specificities of organization and functioning of a few neurotransmitter (in particular, aminergic) and neurohumoral systems.     

Abnormal cortical responses to somatosensory stimulation in medication-overuse headache

Background

Medication-overuse headache (MOH) is a frequent, disabling disorder. Despite a controversial pathophysiology convincing evidence attributes a pivotal role to central sensitization. Most patients with MOH initially have episodic migraine without aura (MOA) characterized interictally by an absent amplitude decrease in cortical evoked potentials to repetitive stimuli (habituation deficit), despite a normal initial amplitude (lack of sensitization). Whether central sensitization alters this electrophysiological profile is unknown. We therefore sought differences in somatosensory evoked potential (SEP) sensitization and habituation in patients with MOH and episodic MOA.

Methods

We recorded median-nerve SEPs (3 blocks of 100 sweeps) in 29 patients with MOH, 64 with MOA and 42 controls. Episodic migraineurs were studied during and between attacks. We measured N20-P25 amplitudes from 3 blocks of 100 sweeps, and assessed sensitization from block 1 amplitude, and habituation from amplitude changes between the 3 sequential blocks.

Results

In episodic migraineurs, interictal SEP amplitudes were normal in block 1, but thereafter failed to habituate. Ictal SEP amplitudes increased in block 1, then habituated normally. Patients with MOH had larger-amplitude block 1 SEPs than controls, and also lacked SEP habituation. SEP amplitudes were smaller in triptan overusers than in patients overusing nonsteroidal anti-inflammatory drugs (NSAIDs) or both medications combined, lowest in patients with the longest migraine history, and highest in those with the longest-lasting headache chronification.

Conclusions

In patients with MOH, especially those overusing NSAIDs, the somatosensory cortex becomes increasingly sensitized. Sensory sensitization might add to the behavioral sensitization that favors compulsive drug intake, and may reflect drug-induced changes in central serotoninergic transmission.

     

Tinnitus: A Large VBM-EEG Correlational Study

A surprising fact in voxel-based morphometry (VBM) studies performed in tinnitus is that not one single region is replicated in studies of different centers. The question then rises whether this is related to the low sample size of these studies, the selection of non-representative patient subgroups, or the absence of stratification according to clinical characteristics. Another possibility is that VBM is not a good tool to study functional pathologies such as tinnitus, in contrast to pathologies like Alzheimer’s disease where it is known the pathology is related to cell loss. In a large sample of 154 tinnitus patients VBM and QEEG (Quantitative Electroencephalography) was performed and evaluated by a regression analysis. Correlation analyses are performed between VBM and QEEG data. Uncorrected data demonstrated structural differences in grey matter in hippocampal and cerebellar areas related to tinnitus related distress and tinnitus duration. After control for multiple comparisons, only cerebellar VBM changes remain significantly altered. Electrophysiological differences are related to distress, tinnitus intensity, and tinnitus duration in the subgenual anterior cingulate cortex, dorsal anterior cingulate cortex, hippocampus, and parahippocampus, which confirms previous results. The absence of QEEG-VBM correlations suggest functional changes are not reflected by co-occurring structural changes in tinnitus, and the absence of VBM changes (except for the cerebellum) that survive correct statistical analysis in a large study population suggests that VBM might not be very sensitive for studying tinnitus.     

Correlations of the Peculiarities of the Motivational Sphere and Characteristics of Event-Related EEG Potentials in Humans

We studied the relations between generalized characteristics of the state of the motivational sphere, the levels of need for achievements (N-Ach) and achievement motivation (AchM) typical of an individual, and the parameters of cerebral event-related potentials (ERPs). The examined group included 70 adults of both sexes. The ERPs were recorded in the course of realization of two behavioral test acts with motor components. In task А, the subject should press a button with the minimum delay with respect to an imperative signal preceded by a warning signal (with the measurement of the time of sensorimotor reaction); in this case, the contingent negative variation (CNV) and Р300 potential were recorded. Under conditions of task B, the subject should measure a definite time interval limiting the latter by two pushings of the button; in this case, the readiness potential (RP) was recorded in addition to CNV and Р300. The ERPs were recorded in the С3 and С4 leads (according to the 10-20 system). The peculiarities of the motivational sphere were diagnosed using Orlov’s and Mechrabian’s questionnaires. We found that a relatively high amplitude of the early CNV component (СNV-O) and low amplitudes of the integral CNV and Р300 in task A and a low amplitude of the RP can serve as task B-related EEG markers of a high NA level. In task A, high levels of the AchM correlated with higher amplitudes of the CNV and Р300, and amplitudes of these potentials were higher in the left hemisphere. The observed interrelations were probably determined by a considerable dependence of the N-Ach and AchM characteristics, on the one hand, and CNV amplitude parameters, on the other hand, on the hereditary factors, in particular neurochemical ones. It is obvious that such peculiarities of the neurodynamic constitution of an individual are, to a considerable extent, determined by the specificity of organization and functioning of a few neurotransmitter (in particular aminergic) and neurohumoral systems.     

Correlation between the parameters of contingent negative variation and characteristics of variational pulsometry in Parkinsonian patients

In patients suffering from Parkinson's disease (PD), we analyzed correlations between the parameters of contingent negative variation (CNV) and data of variational pulsometry (according to the measurements of R-R ECG intervals). Studies were carried out on 35 patients (group PD), 49 to 74 years old, with the stage of disease of 1.5 to 3.0 according to the Hoehn-Yahr international classification. In the course of CNV recording (i.e., in the state of a certain functional loading), we observed significant negative correlations between the integral magnitude (area) of this potential and indices of variational pulsometry (RMSSD, SDNN, C. var, and HF) that characterize the intensity of parasympathetic (respiratory) influences on the cardiovascular system. In the control group, such correlations were absent. We found significant correlations between the autonomic balance, CNV magnitude, and stage of PD reflecting the level of generalization of the pathological process. In the subgroup of patients with the PD stage 1.5 to 2.0, significant changes in the mean values of indices of parasympathetic influences during recording of the CNV were not observed, while in another subgroup (the PD stage 2.5 to 3.0), these values increased significantly (P < 0.05 and P < 0.01). If the estimates of the PD stage were low, the CNV area demonstrated greater values (P < 0.01). The disturbance of coordination of muscle-to-muscle interactions in the PD group is, probably, an important factor responsible for parasympathetic dysregulation and suppression of the CNV generation. We found positive correlation between the intensity of parasympathetic influences in the course of CNV recording and the level of postural disorders (r = 0.37, P < 0.05). On the contrary, the CNV magnitude demonstrated a negative correlation with the intensity of these disorders (r = −0.36, P < 0.05), as well as with the level of postural instability (r = −0.55, P < 0.001). We hypothesize that alterations of the autonomic balance and the activity of those cerebral structures, which are responsible for the motor readiness, result, to a significant extent, from weakening of the activity of the noradrenergic system due to degenerative processes developing in cells of the locus coeruleus. The impairment of the latter structure, together with degeneration of neurons of the substantia nigra and a decrease in the level of nigro-striatal dopamine, underlies the pathomorphological pattern of PD. Neirofiziologiya/Neurophysiology, Vol. 40, No. 3, pp. 242–253, May–June, 2008.     

Dysfunctional Noise Cancelling of the Rostral Anterior Cingulate Cortex in Tinnitus Patients

Background

Peripheral auditory deafferentation and central compensation have been regarded as the main culprits of tinnitus generation. However, patient-to-patient discrepancy in the range of the percentage of daytime in which tinnitus is perceived (tinnitus awareness percentage, 0 – 100%), is not fully explicable only by peripheral deafferentation, considering that the deafferentation is a stable persisting phenomenon but tinnitus is intermittently perceived in most patients. Consequently, the involvement of a dysfunctional noise cancellation mechanism has recently been suggested with regard to the individual differences in reported tinnitus awareness. By correlating the tinnitus awareness percentage with resting-state source-localized electroencephalography findings, we may be able to retrieve the cortical area that is negatively correlated with tinnitus awareness percentage, and then the area may be regarded as the core of the noise cancelling system that is defective in patients with tinnitus.

Methods and Findings

Using resting-state cortical oscillation, we investigated 80 tinnitus patients by correlating the tinnitus awareness percentage with their source-localized cortical oscillatory activity and functional connectivity. The activity of bilateral rostral anterior cingulate cortices (ACCs), left dorsal- and pregenual ACCs for the delta band, bilateral rostral/pregenual/subgenual ACCs for the theta band, and left rostral/pregenual ACC for the beta 1 band displayed significantly negative correlations with tinnitus awareness percentage. Also, the connectivity between the left primary auditory cortex (A1) and the rostral ACC, as well as between the left A1 and the subgenual ACC for the beta 1 band, were negatively correlated with tinnitus awareness percentage.

Conclusions

These results may designate the role of the rostral ACC as the core of the descending noise cancellation system, and thus dysfunction of the rostral ACC may result in perception of tinnitus. The present study also opens a possibility of tinnitus modulation by neuromodulatory approaches targeting the rostral ACC.     

Activation of the human cortex during visual attention and selection

Cortical activation in visual discrimination tasks was estimated by measurement of the CNV (contingent negative variation) and N1-P3 components of visual ERPs in frontal, parietal, occipital and temporal leads recorded in 18 young healthy adults. In all investigated tasks, the maximal values of CNV and ERPa were observed in parietal regions. The estimation of cortical readiness state (CNV) is quite a useful procedure in the attention tasks because amplitude and stability of ERPs depend on preceding cortical excitability. The prevalence of parietal activation in visual attention tasks may be considered as the dominance of occipito-parietal way (stream) in human visual attention system.