Stability of mismatch negativities in children.

OBJECTIVES AND METHODS: Mismatch negativities (MMN) to frequency and duration changes in a series of repetitive tones and to two different consonant-vowel syllables (ba and ga, standard da) were recorded in a test and retest session in 15 children aged 7-11 years. Reliability within one session and stability between the sessions of MMN amplitudes and the ERP-components P1 and N1 were determined by correlation coefficients. RESULTS: Mean amplitudes of the grand averages showed a decrease of MMN during the second test session in a late latency window (400-500 ms) for the frequency MMN and of the MMN elicited by speech stimuli. The individual stability reached significance only for the duration deviant and one of the syllables. Compared to results found in adults with similar stimulus conditions the stability of the MMN in children seems to be somewhat lower. The components P1 and N1 to both stimulus types (tone and speech), however, showed a high reliability and individual stability. CONCLUSION: While MMN is a useful tool to study processing deficits in groups of children, as e.g. in language-impaired children, MMN as a individual diagnostic measure should be interpreted very cautiously.     

Right hemisphere dominance of different mismatch negativities

Auditory stimulus blocks were presented to 10 reading subjects. Each block consisted of 2 types of stimulus, standard (P = 90%) and deviant (P = 10%), delivered in a random order with short constant inter-stimulus intervals. The standard stimuli were 600 Hz, 80 dB SPL 50 msec sine wave bursts. In different blocks, the deviant stimuli differed from the standards either in frequency (650 Hz), intensity (70 dB) or duration (20 msec). Left- and right-ear stimulations were used in separate blocks. Event-related brain potentials (ERPs) were recorded with 16 electrodes over both hemispheres. All the different types of deviant stimuli elicited an ERP component called the mismatch negativity (MMN). The MMN was larger over the right hemisphere irrespective of the ear stimulated whereas the N1 component, elicited by both standards, and deviants, was larger over the hemisphere contralateral to the ear stimulated. The results provide further evidence for the view that the MMN reflects a neural mismatch process with a memory trace which automatically codes the physical features of the repetitive stimuli.     

The significance of the negativities in the brainstem auditory evoked potential (BAEP)

This study was designed to investigate the negativities of the brainstem auditory evoked potential (BAEP), especially to determine if they represented a part of a composite waveform together with a given positivity. Subjects (10) and patients (56) provided the data, mainly in the form of correlation coefficients of latency and amplitude values, trace by trace comparisons of multiple responses from the same subject and the specific grouping of abnormal waves from the patient population. The results show that the strongest relationships of latency and amplitude involved completely different pairs of waves, that the negative and positive values often changed in opposite directions, and that no pair of waves of opposite polarity were typically abnormal together. Thus, the negativities are not generally associated with given positivities and likely have their own generators.     

Mediofrontal theta‐band oscillations reflect top‐down influence in the ventriloquist illusion

In the ventriloquist illusion, spatially disparate visual signals can influence the perceived location of simultaneous sounds. Previous studies have shown asymmetrical responses in auditory cortical regions following perceived peripheral sound shifts. Moreover, higher‐order cortical areas perform inferences on the sources of disparate audiovisual signals. Recent studies have also highlighted top‐down influence in the ventriloquist illusion and postulated a governing function of neural oscillations for crossmodal processing. In this EEG study, we analyzed source‐reconstructed neural oscillations to address the question of whether perceived sound shifts affect the laterality of auditory responses. Moreover, we investigated the modulation of neural oscillations related to the occurrence of the illusion more generally. With respect to the first question, we did not find evidence for significant changes in the laterality of auditory responses due to perceived sound shifts. However, we found a sustained reduction of mediofrontal theta‐band power starting prior to stimulus onset when participants perceived the illusion compared to when they did not perceive the illusion. We suggest that this effect reflects a state of diminished cognitive control, leading to reliance on more readily discriminable visual information and increased crossmodal influence. We conclude that mediofrontal theta‐band oscillations serve as a neural mechanism underlying top‐down modulation of crossmodal processing in the ventriloquist illusion.     

The nature of anterior negativities caused by misapplications of morphological rules

This study investigates functional interpretations of left anterior negativities (LANs), a language-related electroencephalogram effect that has been found for syntactic and morphological violations. We focus on three possible interpretations of LANs caused by the replacement of irregular affixes with regular affixes: misapplication of morphological rules, mismatch of the presented form with analogy-based expectations, and mismatch of the presented form with stored representations. Event-related brain potentials were recorded during the visual presentation of existing and novel Dutch compounds. Existing compounds contained correct or replaced interfixes (dame + s + salons > damessalons vs. *dame + n + salons > *damensalons "women's hairdresser salons"), whereas novel Dutch compounds contained interfixes that were either supported or not supported by analogy to similar existing compounds (kruidenkelken vs. ?kruidskelken "herb chalices"); earlier studies had shown that interfixes are selected by analogy instead of rules. All compounds were presented with correct or incorrect regular plural suffixes (damessalons vs. *damessalonnen). Replacing suffixes or interfixes in existing compounds both led to increased (L)ANs between 400 and 700 msec without any evidence for different scalp distributions for interfixes and suffixes. There was no evidence for a negativity when manipulating the analogical support for interfixes in novel compounds. Together with earlier studies, these results suggest that LANs had been caused by the mismatch of the presented forms with stored forms. We discuss these findings with respect to the single/dual-route debate of morphology and LANs found for the misapplication of syntactic rules.     

N400-like negativities in action perception reflect the activation of two components of an action representation

Abstract

The understanding of actions of tool use depends on the motor act that is performed and on the function of the objects involved in the action. We used event-related potentials (ERPs) to investigate the processes that derive both kinds of information in a task in which inserting actions had to be judged. The actions were presented as two consecutive frames, one showing an effector/instrument and the other showing a potential target object of the action. Two mismatches were possible. An orientation mismatch occurred when the spatial object properties were not consistent with a motor act of insertion being performed (i.e., different orientations of insert and slot). A functional mismatch happened when the instrument (e.g., screwdriver) would usually not be applied to the target object (e.g., keyhole). The order in which instrument and target object were presented was also varied. The two kinds of mismatch gave rise to similar but not identical negativities in the latency range of the N400 followed by a positive modulation. The results indicate that the motor act and the function of the objects are derived by two at least partially different subprocesses and become integrated into a common representation of the observed action.     

Cinromide in the treatment of absence seizures

Summary: Cinromide (BW-122U) was evaluated in an open pilot study of absence seizures in three naive (previously untreated for absence seizures) patients (one male and two females, 7 to 8 years of age). In these naive patients, cinromide was found to be well tolerated but ineffective in reducing generalized spike-and-wave discharges on the telemetered EEG during the 1week duration of the study.     

Deinstitutionalization in the absence of consensus.

The process of deinstitutionalization began almost unnoticed in 1955 as state hospital populations started to decline, and it proceeded without adequate planning and without development of a social consensus. The inevitable result was strong criticism, severe personal dislocations, and, with rare exceptions, programmatic chaos. The authors trace and describe the reasons for the growing polarization about deinstitutionalization among such groups as mental health professionals, public officials, families, advocacy groups, citizens, and unions. They also note that between 1950 and 1970 the total institutionalized population in the U.S. was not reduced but simply shifted. Deinstitutionalization should focus not on the location of care but on the broader problem of improving the lot of persons with chronic illness, regardless of its cause or time of onset, the authors suggest. They outline the basic elements of a service and financing system to meet both the daily-living and the specifically medical needs of the chronically ill.     

Language in the absence of inner speech

A 54-yr-old man abruptly became mute with mild right hemiparesis. Written expression, comprehension of speech and print, calculating ability, and verbal short-term recall, although slow, were largely preserved. Extensive studies demonstrated complete loss of inner speech. He was unable to speak to himself and unable to appreciate the phonological structure of words. Instead, his preserved language skills were based on a highly developed visual imagery. This case greatly extends the range of language skills previously thought possible in individuals who suffer the loss of inner speech.     

Brain reward in the absence of alpha-synuclein

Alpha-synuclein has been implicated in the pathophysiology of Parkinson's disease. Recent studies revealed its role as a negative regulator of dopamine release in the nigrostriatal dopaminergic system. Alpha-synuclein may, however, play a more universal role in dopaminergic neurotransmission. It may represent an endogenous modulator in the mesolimbic dopaminergic system, and be involved in brain reward. We show here that the absence of alpha-synuclein resulting from spontaneous mutation in a subline of C57BL/6J mice greatly increased the rate of operant behavior during intracranial self-stimulation. The present work demonstrates that a lack of alpha-synuclein sensitized the brain reward system, implying that the levels of alpha-synuclein expression may predispose an individual to drug abuse or to a number of psychiatric diseases.     

Statistical parametric mapping of LORETA using high density EEG and individual MRI: application to mismatch negativities in schizophrenia

We describe a method for the statistical parametric mapping of low resolution electromagnetic tomography (LORETA) using high-density electroencephalography (EEG) and individual magnetic resonance images (MRI) to investigate the characteristics of the mismatch negativity (MMN) generators in schizophrenia. LORETA, using a realistic head model of the boundary element method derived from the individual anatomy, estimated the current density maps from the scalp topography of the 128-channel EEG. From the current density maps that covered the whole cortical gray matter (up to 20,000 points), volumetric current density images were reconstructed. Intensity normalization of the smoothed current density images was used to reduce the confounding effect of subject specific global activity. After transforming each image into a standard stereotaxic space, we carried out statistical parametric mapping of the normalized current density images. We applied this method to the source localization of MMN in schizophrenia. The MMN generators, produced by a deviant tone of 1,200 Hz (5% of 1,600 trials) under the standard tone of 1,000 Hz, 80 dB binaural stimuli with 300 msec of inter-stimulus interval, were measured in 14 right-handed schizophrenic subjects and 14 age-, gender-, and handedness-matched controls. We found that the schizophrenic group exhibited significant current density reductions of MMN in the left superior temporal gyrus and the left inferior parietal gyrus (P < 0. 0005). This study is the first voxel-by-voxel statistical mapping of current density using individual MRI and high-density EEG.     

Emotional responding in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal disease, leaving the patient in a partially or completely deafferented state. In an explorative study, we investigated responses to visual socio–emotional stimuli in ALS patients. Pictures from the International Affective Picture System (IAPS) were verbally judged by 12 moderately affected ALS patients with a spinal onset and a slow progression and 18 age–matched controls, and data were compared with psychophysiological responses. Verbal emotional judgments of patients were more positive than ratings of controls. Regarding arousal, patients neutralized extreme pictures, in that they rated calm pictures as more exciting than controls and exciting pictures as more calm. These changes of emotional processing were unrelated to depression or frontal lobe dysfunction. There were no major differences between patients and controls concerning physiological responses to emotional stimuli. We conclude that emotional responses of ALS patients tend to be altered towards positive valence and towards a more balanced arousal state in early stages of the disease. These findings contradict assumptions of a generally negative impact of the disease on the emotional disposition and may indicate compensatory cognitive or neuroplastic changes.     

Defective neuronogenesis in the absence of Dlx5

Dlx genes play an important role in the control of the development of the central nervous system (CNS). Single or compound inactivation of Dlx1, Dlx2, or Dlx5 in the mouse causes defects of neuronal migration and differentiation. Dlx5, in particular, is essential for the correct development of the olfactory system. Targeted inactivation of Dlx1 and Dlx2 in the mouse results in abnormal neuronal differentiation in the embryonic subcortical forebrain and is associated to the loss of Dlx5 and Dlx6 expression. So far, however, it has been impossible to investigate the role of Dlx genes on late neurogenesis, as their inactivation leads to perinatal death. We have now generated cultures of neural stem cells (NSCs) derived from embryonic and newborn Dlx5-null mice, and we have compared their capacity to differentiate in vitro to that of equivalent cells derived from normal littermates. We show here that in the absence of Dlx5, NSCs derived from newborn animals have a severely reduced capacity to generate neurons. This is not the case for cells derived from E12.5 embryos. Forced expression of Dlx5 in cultures of newborn mutant NSCs fully restores their neuronogenic potential. Our data suggest that Dlx5 is essential for secondary (postnatal) neuronogenesis.     

Once-daily ethosuximide in the treatment of absence epilepsy

Once-daily ethosuximide was used to treat 10 consecutive children with typical absence seizures. Three patients had gastrointestinal side effects which resolved when the same total daily dose was divided into 2 doses. Two other patients continued to have seizures on ethosuximide, whether given once or twice daily. Five patients had complete seizure control without adverse effects on once-daily ethosuximide.     

Visual discrimination in the absence of visual cortex

Normal rats and rats with devascularization lesions ranging from subtotal removals of striate cortex (Area 17) to complete removal of neocortex were trained in a horizontal/vertical stripe discrimination for a liquid reinforcer. Subgroups of animals were identified on the basis of size and location of lesion (with particular reference to striate cortex) as Subtotal, Striate, Posterior and Decorticate. Some animals in all of the lesion groups were able to acquire the discrimination, but there was a direct relationship between lesion size and number of training trials. Those animals which reached criterion on the original discrimination were trained on a second horizontal/vertical discrimination under either transfer or reversal conditions using 'rotated obliques' stimuli. Performance on this second discrimination indicated that animals from all lesion groups had been using visual stimuli based on stripe orientation in the original problem. Members of all lesion groups solved the rotated obliques problem under the transfer condition, though the speed and completeness with which they did so was again inversely related to lesion size. These data show high levels of visual competence in the absence of visual cortex even when stimuli thought to detect form discrimination are used and thus reinforce the view that superior colliculus may be a more significant visual area for the rat than was previously assumed. They also support other observations that animals do not use residual visual capacities without extensive experience and appropriate motivation.     

Terminal CNV in the absence of motor response

We addressed the question of whether the terminal CNV, or E-wave, can be obtained in the absence of a motor response. In our design, the stimuli served only to reduce uncertainty with respect to a prior prediction, so that no response to S2 was required. In one experiment, the location of uncertainty reducing information was manipulated: in S1 alone or in S2 alone. When S2 reduced uncertainty, the pre-S2 E-wave was larger than when S2 did not reduce uncertainty. Similarly, when S1 reduced uncertainty, a pre-S1 negativity (whose topography did not differ from that of the pre-S2 E-wave) was larger than when S1 did not reduce uncertainty. The pre-S1 results also indicated that a prior experimenter-generated warning signal is not necessary for a non-motoric negativity to be obtained. In another experiment, the S1-S2 interval was manipulated (1 sec versus 3 sec). For the pre-S2 E-wave, onset was later and duration was longer for the longer S1-S2 interval. Peak amplitude and time of termination after S2 did not differ for short and long duration E-waves. Apparently, the timing of the E-wave is related to when in time the process it reflects is 'needed.' The dependence of the amplitude and timing of the pre-stimulus negativity on the temporal location of information, in conjunction with its independence of motor response requirement, suggests that the pre-stimulus negativity reflects some operation in the domain of expectancy, anticipation or 'mental preparation' for the informational stimulus.