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PubMed2006

The effect of visual task difficulty and attentional direction on the detection of acoustic change as indexed by the Mismatch Negativity.

Näätänen's model of auditory processing purports that attention does not affect the MMN. The present study investigates this claim through two different manipulations. First, the effect of visual task difficulty on the passively elicited MMN is assessed. Second, the MMNs elicited by stimuli under attended and ignored conditions are compared. In Experiment 1, subjects were presented with mixed sequences of equiprobable auditory and visual stimuli. The auditory stimuli consisted of standard (80 dB SPL 1000 Hz), frequency deviant (1050 Hz), and intensity deviant (70 dB SPL) tone pips. In a first instance, subjects were instructed to ignore the auditory stimulation and engage in an easy and difficult visual discrimination task (focused condition). Subsequently, they were asked to attend to both modalities and detect visual and auditory deviant stimuli (divided condition). The results indicate that the passively elicited MMN to frequency and intensity deviants did not significantly vary with visual task difficulty, in spite of the fact that the easy and difficult tasks showed a wide variation in performance. The manipulation of the attentional direction (focused vs. divided conditions) did result in a significant effect on the MMN elicited by the intensity, but not frequency, deviant. The intensity MMN was larger at frontal sites when subjects' attention was directed to both modalities as compared to only the visual modality. The attentional effect on the MMN to the intensity deviants only may be due to the specific deviant feature or the poorer perceptual discriminability of this deviant from the standard. Experiment 2 was designed to address this issue. The methods of Experiment 2 were identical to those of Experiment 1 with the exception that the intensity deviant (60 dB SPL) was made to be more perceptible than the frequency deviant (1016 Hz) when compared to the standard stimulus (80 dB SPL 1000 Hz). The results of Experiment 2 also demonstrated that the passively elicited MMN was not affected by large variations in visual task difficulty; this provides convincing evidence that the MMN is independent of visual task demands. Similarly to Experiment 1, the direction of attention again had a significant effect on the MMN. In Experiment 2, however, the frequency MMN (and not the intensity MMN) was larger at frontal sites during divided attention compared to focused visual attention. The most parsimonious explanation of these results is that attention enhances the discriminability of the deviant from the standard background stimulation. As such, small acoustic changes would benefit from attention whereas the discriminability of larger changes may not be significantly enhanced.

Acoustic Stimulation↗
PubMed1993

A longitudinal CNV study of the evolution and treatment of bipolar illness.

In a longitudinal CNV study of bipolar illness we followed the evolution of this illness in six bipolar patients by recording their CNV and mood changes as well as their psychopharmacological treatment for a period of 8 months. The longitudinal CNV recordings of these patients did not show changes corresponding to their mood variations. The most salient result emerging from this study was the consistency in the patterns of the records in different patients in spite of variations in their clinical state and medications. We believe that these electrophysiological parameters cannot be used as markers of the mental state in bipolar patients nor do they reflect specific drug effect. These findings are congruent with available data which do not support a linear relationship between a complex psychological process such as manic depressive illness and a single physical dimension of brain activity. Further studies are warranted for a deeper understanding of this phenomenon.

Adult↗
PubMed2003

Contextual information modulates initial processes of syntactic integration: the role of inter- versus intrasentential predictions.

The authors demonstrate that intersentential context may influence syntactic integration processes during online sentence comprehension, although this influence appears to be restricted to cases in which a contextual requirement must be fulfilled. By applying event-related brain potentials to the processing of clause-medial word order variations in German, the authors show that the local processing difficulty (a negativity from 300 to 450 ms) observed for object-initial sentences in a neutral context is also obtained in a (behaviorally) facilitating context in which the object is contextually given. By contrast, the processing pattern for a focused (questioned) initial object does not differ from that for a focused subject: both elicit a parietal positivity (280-480 ms) post-onset of the focused phrase. The authors interpret this early positivity as a general marker of focus integration, a process that appears to briefly supersede sentence-internal requirements.

Adult↗
PubMed1982

A new method of evaluating the postimperative negative variation (PINV).

The PINV has been widely applied to psychiatric investigations in which the definition of its abnormality depended on the visual evaluation without giving attention to its wave form. We have developed a new method of evaluating the PINV by applying the exponential regression correlation to raw and smoothed PINVs for the amplitude of the 15 points at the intervals of 70 msec. The significant correlation between the PINV wave form and the exponential curve was observed both in the raw and smoothed PINVs. Coefficient A was positively correlated with the PINV duration quantified by a visual measurement. Coefficients A and B had the negative and positive correlation with the CNV magnitude. The findings obtained in 28 healthy subjects suggest that the PINV may correlate to the CNV magnitude.

Adult↗
PubMed1995

The relation between event-related brain potential, heart rate, and blood pressure responses in an S1-S2 paradigm.

Event-related brain potential (ERP), heart rate (HR), and blood pressure (BP) responses were examined during the 6 s foreperiod of a choice-reaction task. Low and high trait-anxious males were required to make same/different judgements based on the similarity of two successively presented visual patterns. The pitch of a warning tone, presented at the beginning of the foreperiod, indicated whether speed or accuracy was to be emphasized on that trial. In different conditions, subjects received either a monetary reward or aversive noise, depending on their performance. Two clusters of parallel variations were observed in the foreperiod: (1) speed/accuracy instructions affected the amplitude of the CNV and, in interaction with anxiety group, the initial decreases in HR and diastolic BP; (2) type of reward, in interaction with speed/accuracy instructions, affected the amplitude of the P300 and PSW, the mid-interval HR acceleration, and subsequent increases in diastolic and systolic BP. A correlational analysis showed a close relationship between changes in HR and BP, whereas no relationship was evident between changes in ERPs and changes in HR and BP.

Adult↗
PubMed2004

Sound perception affected by nonlinear variation of accuracy in memory trace.

The mismatch negativity (MMN) reflects the neural representation of the acoustic environment stored in sensory memory. The short phase of sensory memory corresponds to the temporal window of integration (TWI) which integrates the neighboring sounds into a unitary event. We measured the magnetic MMN (MMNm) and the discriminative reaction time (RT) responding to an omitted segment incorporated into a complex sound. Consequently, for the late omitted segments, the MMNm amplitudes were decreased, and those latencies and the RTs were prolonged. The percentages of the correct responses were also reduced for the late omitted segments. In sum, the discriminative sensitivity nonlinearly declined toward the end of the TWI, suggesting that the time-wise accuracy of the neural trace nonlinearly varies in sensory memory.

Acoustic Stimulation↗
PubMed1995

The temporal selectivity of additive factor effects on the reaction process revealed in ERP component latencies.

An experiment was conducted to relate individual components of the event-related brain potential to specific stages of information processing in a two-choice reaction time (RT) task in a group of undergraduate students. Specifically, the latency of the P300 component and the lateralized readiness potential (LRP) were studied as a function of variations in stimulus degradation and response complexity. It was hypothesized that degrading the stimulus would delay the P300 and LRP to the same extent as RT, and that increasing response complexity would affect RT but not P300 latency. The extant literature did not permit any hypothesis regarding the effect of response complexity on LRP latency. The two task variables were found to have additive effects on RT. As predicted, variations in stimulus degradation influenced the latencies of both components, whereas alterations in response complexity had no effect on P300 latency. A significant new finding was that the onset latency of the LRP remained unchanged across levels of response complexity. The overall pattern of results supports the notion of temporal selectivity of stage manipulations that is derived from discrete stage models of human information processing. Furthermore, these results refine the functional interpretation of the LRP by indicating that within the conceptual framework of a stage model the processes this component indexes succeed the start of response choice but preceded the start of motor programming.

Adult↗
PubMed1982

[Slow brain potentials in writing: the correlation between writing hand and speech dominance in right-handed humans].

1. Slow cerebral potential shifts were recorded from the scalp over both cerebral hemispheres by retrograde summation while 23 right-handers were writing. Averaging included writing errors, but eliminated eye movements and other artifacts. Repeated writing of the same word or sentence was compared to writing different dictated words, to drawings, and to other control experiments. 2. Surface negative readiness potentials (Bereitschaftspotential) appeared about 1 s before writing, which was similar to those preceding other voluntary movements. 3. During writing, the writing potentials in different cortical regions began with a negative increase of the Bereitschaftspotential, usually followed by a plateau or positive waves. One or several biphasic potentials persisted for another 2 s after writing had ceased. 4. The writing potentials had rather constant forms in the same individual, but showed large interindividual variations of form and polarity. The largest initial negativity (with both ear lobes serving as reference) occurred at the vertex and the left motor region contralateral to the writing hand. 5. The left hemispheric preponderance of writing potentials, maximal at the precentral region contralateral to the writing hand, was less marked when writing with the left hand. An interaction of the writing hand and language dominance is assumed. 6. Writing the same word or short sentence repeatedly caused potentials of larger amplitude than the preceding readiness potentials. Writing dictated words or drawing figures after verbal stimuli that require language processing caused larger potentials in the left hemisphere than did repeated word writing. 7. The fact that negative potentials with larger left hemispheric amplitudes appear after verbal stimuli may indicate that language information is processed in the speech-dominant hemisphere before and during writing or drawing. 8. By variously combining bipolar leads, the lateral differences of the potential fields can be more clearly distinguished than by using only unipolar leads with ear reference.

Adult↗
PubMed1989

Human fetal dopamine neurons grafted into the striatum in two patients with severe Parkinson's disease. A detailed account of methodology and a 6-month follow-up.

By using stereotaxic surgical techniques, ventral mesencephalic tissues from aborted human fetuses of 8 to 10 weeks' gestational age were implanted unilaterally into the striata in two patients with advanced Parkinson's disease. The patients were treated with a cyclosporine, azathioprine, and steroid regimen to minimize the risk for graft rejection. They were examined for 6 months preoperatively and 6 months postoperatively and continued to receive the same doses of antiparkinsonian medication. There were no significant postoperative complications. No major therapeutic effect from the operation was observed. However, in the clinical tests, both patients showed small but significant increases of movement speed for repeated pronation-supination, fist clenching, and foot lifting. The rate of walking also increased in the one patient tested. For both patients, there was an initial worsening postoperatively, followed by improvement vs preoperative performance at 1 to 3 months. Both patients also showed significant improvement in the magnitude of response to a single dose of levodopa (L-dopa), but there was no increase in the duration of drug action. The motor readiness potential increased in both patients postoperatively, primarily over the operated hemisphere. Neurophysiological measurements also showed a more rapid performance of simple and complex arm and hand movements on the side contralateral to transplantation in one patient at 5 months postoperatively. Positron emission tomography demonstrated no increased uptake of 6-L-(18F)-fluorodopa in the transplanted striatum at 5 and 6 months. Taken together, these results suggest that the fetal nigral implants may have provided a modest improvement in motor function, consistent with the presence of small surviving grafts. Although our results support further scientific experimentation with transplantation in Parkinson's disease, widespread clinical trials with this procedure are probably not warranted at this time.

Contingent Negative Variation↗
PubMed2002

Impaired visual object recognition and dorsal/ventral stream interaction in schizophrenia.

BACKGROUND: Schizophrenia is associated with well-documented deficits in high-order cognitive processes such as attention and executive functioning. The integrity of sensory-level processing, however, has been evaluated only to a limited degree. Our study evaluated the ability of patients with schizophrenia to recognize complete objects based on fragmentary information, a process termed perceptual closure. Perceptual closure processes are indexed by closure negativity (N(cl)), a recently defined event-related potential (ERP) component that is generated within the visual association cortex. This study assessed the neural integrity of perceptual closure processes in schizophrenia by examining N(cl) generation. Generation of the preceding positive (P1) and negative (N1) ERP components was also examined. METHODS: We evaluated 16 patients with chronic schizophrenia and 16 healthy comparison subjects. Successively less fragmented images were presented during high-density ERP recording, which permitted the monitoring of brain activity during perceptual closure processes prior to object recognition. Analyses were performed at parieto-occipital and occipitotemporal sites consistent with dorsal and ventral stream generators of P1, N1, and N(cl). RESULTS: Patients with schizophrenia showed significant impairment in the ability to recognize fragmented objects, along with impaired generation of N(cl). The amplitude of visual P1 was significantly reduced, particularly over dorsal stream sites. In contrast, the generation of visual N1 was intact. CONCLUSIONS: Patients with schizophrenia are profoundly impaired in perceptual closure as indicated by both impaired performance and impaired N(cl) generation. The selective impairment in dorsal stream P1 is consistent with prior reports of impaired magnocellular processing in schizophrenia. By contrast, intact ventral N1 generation suggests that the initial stages of ventral stream processing are relatively preserved and that impaired magnocellular dorsal stream functioning in schizophrenia may lead to secondary dysregulation of ventral stream object recognition processing.

Adult↗
PubMed2000

ERPs and PET analysis of time perception: spatial and temporal brain mapping during visual discrimination tasks.

ERPs were recorded from 12 subjects performing duration and intensity visual discrimination tasks which have been previously used in a PET study. PET data showed that the same network was activated in both tasks [P. Maquet et al., NeuroImage 3:119-126, 1996]. Different ERP waveforms were observed for the late latency components depending on the dimension of the stimulus to be processed: frontal negativity (CNV) for the duration task and parieto-occipital positivity (P300) for the intensity task. Using BESA software, the sources were first modelled with a "PET dipolar model" (right prefrontal, right parietal, anterior cingulate, left and right fusiforms). To obtain a better fit for ERPs recorded in each task, two sources (cuneus, left prefrontal area) had to be added. Consistently with PET findings, dipole modelling indicates that duration and intensity dimensions of a visual stimulus are processed in the same areas. However, ERPs also reveal prominent differences between the time course of the dipole activations for each task, particularly for sources contributing to the late latency ERP components. In the intensity task, dipoles located in the cuneus, the anterior cingulate, and the left prefrontal area yield largest activity within the P300 interval, then activity diminishes rapidly as the stimulus ends, whereas in the duration task, the cuneus and anterior cingulate are still active several hundred milliseconds following stimulus offset. Moreover, in the duration task, the activity of the right frontal dipole parallels the CNV waveform, whereas in the intensity task, this dipole is largely inactive. We assume that the right frontal area plays a specific role in the formation of temporal judgments.

Adult↗
PubMed1999

Movement-related potentials in Parkinson's disease: external cues and attentional strategies.

Hypokinetic movement can be greatly improved in Parkinson's disease patients by the provision of external cues to guide movement. It has recently been reported, however, that movement performance in parkinsonian patients can be similarly improved in the absence of external cues by using attentional strategies, whereby patients are instructed to consciously attend to particular aspects of the movement which would normally be controlled automatically. To study the neurophysiological basis of such improvements in performance associated with the use of attentional strategies, movement-related cortical potentials were examined in Parkinson's disease and control subjects using a reaction time paradigm. One group of subjects were explicitly instructed to concentrate on internally timed responses to anticipate the presentation of a predictably timed go signal. Other subjects were given no such instruction regarding attentional strategies. Early-stage premovement activity of movement-related potentials was significantly increased in amplitude and reaction times were significantly faster for Parkinson's disease subjects when instructed to direct their attention toward internally generating responses rather than relying on external cues. It is therefore suggested that the use of attentional strategies may allow movement to be mediated by less automatic and more conscious attentional motor control processes which may be less impaired by basal ganglia dysfunction, and thereby improve movement performance in Parkinson's disease.

Aged↗
PubMed2003

Mismatch negativity is not correlated with neuroendocrine indicators of catecholaminergic activity in healthy subjects.

The identification of the brain structures and neurotransmitters responsible for the generation and/or modulation of the mismatch negativity (MMN) may contribute to a clearer understanding of its functional significance, and may have clinical implications. In this context, some findings suggest that the scalp-recorded MMN reflects activity from multiple neuronal ensembles within or in the immediate vicinity of the primary auditory cortex and with possible contribution from the frontal cortex. However, few data are available concerning the influence of neurotransmitter systems on the MMN. In this study, the relationship between both noradrenergic and dopaminergic systems and the MMN were investigated in 34 healthy volunteers. Noradrenergic and dopaminergic activities were assessed with the apomorphine and clonidine challenge tests. The results showed no significant relationship between either growth hormone (GH) responses to apomorphine or clonidine and the MMN amplitude or latency. Therefore, this study does not demonstrate the implication of dopaminergic and noradrenergic activities as assessed by GH response to apomorphine and clonidine for the generation and/or the modulation of the MMN. However, given the complexity of the central neurotransmitter systems, these results cannot be considered as definitive evidence against a relationship between dopaminergic and noradrenergic activity and the MMN.

Acoustic Stimulation↗
PubMed2003

Reversible reorganisation of the motor cortical representation of the hand in cervical dystonia.

Previous work has suggested that there may be a widespread disturbance of motor control mechanisms in patients with cervical dystonia. In the present study, we used transcranial magnetic stimulation to investigate the topography of the corticomotor projection to the abductor pollicis brevis (APB) muscle in 10 subjects with idiopathic torticollis. Threshold-adjusted stimuli were delivered at multiple scalp sites during a low-level voluntary contraction of the APB, and maps were generated of motor evoked potential amplitude versus scalp site. The cortical maps for the APB on the side opposite to the direction of head rotation were displaced laterally or posteriorly in all subjects and reverted to a more normal position after botulinum toxin injection of the cervical muscles in 5 subjects. The findings point to a reversible reorganisation of the corticomotor representation of the hand on the same side as the sternocleidomastoid (SCM) muscle that is involved in producing the dystonia. These results provide further evidence for the involvement of cortical centres and for a more widespread abnormality of motor control mechanisms in focal dystonia. The findings also support the notion that head turning is chiefly mediated by the hemisphere ipsilateral to the direction of the head rotation by means of a corticomotor projection to the contralateral SCM.

Adult↗
PubMed2001

Bereitschaftspotential in depressed and non-depressed patients with Parkinson's disease.

Impaired initiation and slowed execution of movements are two of the principal characteristics of Parkinson's disease (PD). A similar pattern of movement impairments (psychomotor retardation) can be seen frequently in patients with idiopathic depression. In addition, affective disorders have been frequently reported in patients with different basal ganglia disorders. The aim of this study was to determine whether there are some particularities in the cerebral electrical activity during the preparation and execution of voluntary internally paced movements (i.e., Bereitschaftspotential, BP) in depressed PD patients, which can distinguish them from non-depressed PD patients, as well as from healthy controls. The BPs were recorded in 16 patients with idiopathic PD, eight of whom were depressed (PD-D), and eight of whom were not (PD-ND). Additional recordings were taken from a group of eight age- and sex-matched healthy subjects. Depression was classified using the Research Diagnostic Criteria and the two PD groups were matched for age, disease severity, and disease duration. The amplitudes and slopes of the BPs from PD patients were generally smaller than in controls, but there was no specific pattern of BP changes that distinguished depressed from non-depressed PD patients. In addition, there was no particular association between measures of depression severity and BP parameters. The data suggest that presence of depression in PD might not have any additional deteriorating influence on already impaired preparation for self-paced spontaneous movements.

Adult↗
PubMed2003

Premonitory sensory phenomenon in Tourette's syndrome.

We administered a questionnaire designed to probe for premonitory sensations associated with motor tics to 50 patients with Tourette's syndrome (TS). Premonitory sensations were reported by 46 (92%) patients, and the most common sensation was an urge to move and an impulse to tic ("had to do it"). Intensification of premonitory sensations, if prevented from performing a motor tic, was reported also in 37 patients (74%), 36 patients (72%) reported relief of premonitory sensations after performing the tic, and 27 of 40 (68%) described a motor tic as a voluntary motor response to an involuntary sensation, rather than a completely involuntary movement. The "just right" sensation correlated with the presence of co-morbid obsessive-compulsive disorder. We conclude that premonitory sensations are an important aspect of motor tics and some patients perceive motor tics as a voluntary movement in response to an involuntary sensation.

Adult↗
PubMed2001

Intracerebral recording of readiness potential induced by a complex motor task.

While exploring 11 epileptic patients with intracerebral electrodes, we recorded readiness potential (RP) preceding a complex motor task. Multilead depth electrodes were positioned stereotactically into the cortex. In three patients, it was also possible to record RP from the putamen. The movement triggering the recording was the turning of a page in an architectural book. The movement was performed under two conditions: in the first condition, without looking at the pictures on the page (typical self-pacing); and in the second condition, following the inspection of the pictures. There were no significant differences in the appearance of RP under these two conditions, neither in duration nor in amplitude. That could be explained by the fact that "self-paced" does not mean "spontaneous," but covers the internal non-conscious program related to a given task. RP were present in the contralateral primary sensorimotor cortex and the bilateral supplementary motor area (SMA), and in the anterior caudal cingulate cortex. No difference between the cortical topography of RP preceding a simple motor task and the topography of RP occurring in connection with complex movement was observed.

Adult↗
PubMed2006

Coherence analysis differentiates between cortical myoclonic tremor and essential tremor.

Familial cortical myoclonic tremor with epilepsy (FCMTE) is characterized by a distal kinetic tremor, infrequent epileptic attacks, and autosomal dominant inheritance. The tremor is thought to originate from the motor cortex. In our patient group, a premovement cortical spike could not be established on electroencephalogram (EEG) back-averaging. Corticomuscular and intermuscular coherence analysis can demonstrate a cortical common drive to muscles. We carried out coherence analysis of electromyography (EMG) of forearm muscles and EEG of contralateral motor cortex in 7 FCMTE patients, 8 essential tremor (ET) patients, and 7 healthy controls. Results showed strong cortico- and intermuscular coherence in the 8- to 30-Hz range in the FCMTE patients, with EEG preceding EMG. Healthy controls and ET patients showed normal weak coherence around 20 Hz. The ET patients showed some additional coherence at tremor frequency (6 Hz), probably the result of sensory information flowing back to the sensorimotor cortex. These findings point to a pathological cortical drive in FCMTE patients leading to tremulous movements. Coherence analysis is an easy and useful method to differentiate FCMTE from ET. Coherence analysis is helpful when investigating a cortical common drive in cortical tremor and other movement disorders.

Adult↗