Rare Tones Research Articles

Changes in event-related potentials in a three-stimulus auditory oddball task after mild head injury

Previous research has demonstrated changes in event-related potentials in a variety of cognitive tasks after severe closed head injury. We sought to establish if similar changes were present in patients who had sustained only apparently mild head injury (MHI) by recording event-related potentials in a group of 24 mild head injured and 24 control participants during a three-stimulus auditory target detection task. For this ‘oddball’ task participants were required to press a button every time they heard a rare target tone and to ignore rare novel sounds and frequent non-target tones. Neuropsychological test results indicated that the mild head injured group had mild memory and attention impairments. Analysis of behavioural performance on the three-stimulus ‘oddball’ task showed no difference in reaction times or error rates between the two groups. Target condition N2 deflections appeared to be larger in the mild head injured but peak amplitude measures revealed that this effect was not significant. There were no significant differences in the amplitude or latency of the P3b evoked by target stimuli or the P3a evoked by novel stimuli. However, a putative ‘O-wave’ or ‘reorienting negativity’ following the P3a was more negative in the mild head injured group suggesting increased activation of components of the attention network. These findings lend support to the hypothesis that MHI can cause subtle cognitive impairments that are associated with abnormal allocation of attention resources in the context of normal behavioural performance.

Developmental change in auditory selective attention as reflected by phasic heart rate changes

Heart rate was recorded from five different groups of children (ages 7, 10, 12, 14, and 20 years) while they were performing an auditory selective attention task. The participants were instructed to count rare tone pips embedded in a series of standard tone pips presented at one (attended) ear while ignoring rare and standard stimuli presented at the other (unattended) ear. A pattern of anticipatory heart rate deceleration followed by acceleration was associated with rare tone pips at the attended ear but not with rare tone pips that should be ignored. The absence of differential sensitivity of heart rate responses to rare tone pips presented at the unattended ear was observed for all age groups. These findings were interpreted to suggest that the ability to ignore irrelevant target stimuli has reached mature levels during middle childhood. The depth of anticipatory deceleration increased until age 14, suggesting that the ability to maintain attentional set continues to develop beyond childhood.

VIQ‐PIQ Discrepancies in Partial Epilepsy: On the Relation to Lat‐ eralities of Focal MRI Lesions, P3 Peaks, and Focal Spikes.

Purpose: A number of previous ncurophysiological studies have indicated that the glutamatergic system is important in the induction of epileptiform activity and the dcvelopment of epileptogenesis. Clutamate transport is the primary mechanism of inactivation of syiiaptically released glutamate. GLAST is classified BS an astrocytic transporter and occurs in high concentrations in the ccrebcllum. The pathophysiologic rolc of GLAST in epilepsy is not known in detail. To investigate the role of thc astroglial glutamatc transporter GLAST in epileptogenesis, we compared amygdalu‐kindling and pentylenctetrazolc (PTZ) induced seizures in GLAST‐deficient mice (GLAST(‐/‐)) wild‐type mice (GLAST(+/+)), and maternal C57Black6/J mice (C57). Purpose: Subtest IQ such as verbal IQ (VIQ) and performance IQ (PIQ) in WAIS or WISC are thought to represent neuropsychological functions of the left and right hemispheres, respectively. The P300 (P3) event‐related potential reflects cognitive processes. We do not ye1 know the brain site of P3 origin or how epileptogenic foci (EF) influ‐ ence P3 potentials. To examine neuropsychological influence by partial epilepsy (PE), we studied VIQ‐PIQ discrepancies in PE in relation to lateralities of focal MRI lesions, P3 peaks, and EF. Methods: Thirteen patients showed VIQ‐PIQ discrepancies significant at the p7lt;O.O5 level, represented by a>l2‐point spread for the WAIS in adults, and a 15‐point spread in the WISC in children. We evoked P3 potentials in the individuals with discrepant IQ differences by asking them to keep a mental count of rare tones, including introduction of oddbail tones. EEGs were recorded by the international 10–20 system and P3 peaks were shown in a topographical view by offline analysis. Patients were divided into normal and abnormal groups according to MRI findings, and were examined for the laterali‐ ties of the dominant side in subtest IQ (conventionally, we regarded higher VIQ as left hemisphere dominant and higher PIQ as right hemisphere dominant), P3 peaks, and EF. We did not correlate results with lert or right handedness. Results: Five patients (38.5%) were in the normal group and 8 patients (61.5%) were in the abnormal group. Concordance of the lateralities in P3 peaks and dominant side in subtest IQ was shown in 1 patient (20%) in the normal group and 5 patients (62.5%) in the abnormal group. In the normal group, all patients showed contralateral P3 peak shift to EF, and all except I patient showed contralateral P3 peak shift to the dominant side in subtest IQ. The other 3 patients in the abnormal group showed unilateral focal cortical dysplasias (FCD), ipsilateral P3 shift, and contralateral dominant side in subtest IQ to the focal MRI lesions. Conclusion: In our partial epilepsy series with VIQ‐PIQ discrepancies, concordance of the lateralities in P3 peaks and dominant side in subtest IQ was shown in < half of the patients. Epileptogenic foci seem to have 3 different grades of influence on P3 peak shift and dominant side in subtest IQ according to the severities of accompanying focal MRI lesions: 1. Without MRI lesions, EF can make P3 peak shift contralaterally, but the dominant side in the subtest IQ shift ipsilaterally; 2. With less severe focal MRI lesions such as hippocampal atrophy etc., EF can make not only P3 peaks but also the dominant side in the subtest IQ shift contralaterally; 3. With severe focal MRI lesions such as FCD, EF can make the dominant side in the subtest IQ shift contralaterally, but the P3 peak may shift ipsilaterally. Epileptogenic foci without MRI lesions seem to control ipsilateral P3 potentials. MRI lesions render a hemisphere unlikely to become dominant, but epileptogenic foci can coexist with apparently normal neuropsychological function.

The auditory event-related potential is a stable and reliable measure in elderly subjects over a 3 year period

Objectives: Valid markers of psychobiological processes, including changes over the lifespan, must be reliable. This study investigated the reliability of the auditory event-related potential (ERP) over a 3 year period.Methods: Predictable and unpredictable rare tones were embedded in common-to-rare sequences at 3 different ratios (2:3, 2:5 and 2:8). Forty-six older (mean age 72.3 years) volunteers pressed a key to the rare tones, and ERPs (Fz, Cz and Pz) and reaction time (RT) were measured. Reliability across years was assessed using 3 methods: (1) determination of the stability of waveform components (P1, N1, P2, N2 and P3); (2) cross-correlation of successive 15 ms epochs of within-subject ERPs; and (3) cross-correlation of 15 ms epochs of between-subject ERPs.Results: With all analyses, the ERP was stable. Analysis of the scored components indicated that P3 was especially stable in the unpredictable rare (2:8) condition. Earlier components were equally stable across all conditions. Analysis of 15 ms ERP epochs indicated significant ERP stability 60 ms after stimulation, lasting over 640 ms.Conclusions: Robust within-subject reliability of the ERP strengthens its potential use for detecting preclinical changes in at-risk elderly populations.

Abstracts of the 26th Annual Scientific Meeting of the British Psychophysiology Society, December 16-18, 1998, in London, UK

Abstract Previous research has demonstrated changes in event-related potentials in a variety of cognitive tasks after severe closed head injury. We sought to establish if similar changes were present in patients who had sustained only apparently mild head injury (MHI) by recording event-related potentials in a group of 24 mild head injured and 24 control participants during a three-stimulus auditory target detection task. For this ‘oddball’ task participants were required to press a button every time they heard a rare target tone and to ignore rare novel sounds and frequent non-target tones. Neuropsychological test results indicated that the mild head injured group had mild memory and attention impairments. Analysis of behavioural performance on the three-stimulus ‘oddball’ task showed no difference in reaction times or error rates between the two groups. Target condition N2 deflections appeared to be larger in the mild head injured but peak amplitude measures revealed that this effect was not significant. There were no significant differences in the amplitude or latency of the P3b evoked by target stimuli or the P3a evoked by novel stimuli. However, a putative ‘O-wave’ or ‘reorienting negativity’ following the P3a was more negative in the mild head injured group suggesting increased activation of components of the attention network. These findings lend support to the hypothesis that MHI can cause subtle cognitive impairments that are associated with abnormal allocation of attention resources in the context of normal behavioural performance.

Stimulus novelty differentially affects attentional allocation in PTSD

Background: This study investigated attentional allocation in 39 Vietnam combat veterans, 25 with and 14 without posttraumatic stress disorder, assessing P300 amplitudes and latencies during both three-tone and novelty “oddball” tasks. Methods: The three-tone oddball task consisted of three stimuli: frequent tones (85%), rare target tones (7.5%), and rare distractor tones (7.5%). The novelty oddball task was identical to the three-tone task except that the rare distractor tones were replaced with nonrepeating novel sounds (7.5%). Results: Combat veterans with posttraumatic stress disorder showed significant P300 amplitude enhancements at frontal sites in response to distracting stimuli during the novelty but not during the three-tone oddball tasks. There were no amplitude differences in target tones during either task. Conclusions: The data suggest that combat veterans with posttraumatic stress disorder demonstrate P300 responses consistent with a heightened orientation response to novel, distracting stimuli. This finding is consistent both with the clinical presentation of the disorder and with theoretical notions that individuals with posttraumatic stress disorder demonstrate information-processing biases towards vague or potentially threatening stimuli.

Dysfunction of the auditory cortex persists in infants with certain cleft types

Language and learning disabilities occur in almost half of individuals with oral clefts. The characteristics of these cognitive dysfunctions vary according to the cleft type, and the mechanisms underlying the relation between cleft type, cognitive dysfunction, and cleft‐caused middle‐ear disease are unknown. This study investigates preattentive auditory discrimination, which plays a significant role in language acquisition and usage, in infants with different cleft types. A mismatch negativity (MMN) component of brain evoked potentials, which indexes preconscious sound discrimination, and brain responses to rare sine‐wave tones were recorded in 12 healthy infants and 32 infants with oral clefts at the ages of 0 and 6 months. Infants with clefts were subdivided into two categories: those with cleft lip and palate (CLP) (n=11 at birth, n=6 at the age of 6 months) and those with cleft palate only (CPO) (n=17 at birth, n=8 at the age of 6 months). At both ages, brain responses to rare sounds tended to be smaller in both cleft subgroups than in healthy peers. However, in the latency range of 300 to 500 ms, the MMN was significantly smaller in infants with CPO. In infants with CLP, the MMN was comparable to that of healthy infants. Differences in auditory discrimination between infants with CLP and CPO, as reflected by MMN, were detectable at birth and persisted into later infancy. This pattern parallels known behavioural differences between children with these cleft types. Brain responses to rare sounds, in contrast, had no differentiative power with respect to the cleft type.

Dysfunction of the auditory cortex persists in infants with certain cleft types.

Language and learning disabilities occur in almost half of individuals with oral clefts. The characteristics of these cognitive dysfunctions vary according to the cleft type, and the mechanisms underlying the relation between cleft type, cognitive dysfunction, and cleft-caused middle-ear disease are unknown. This study investigates preattentive auditory discrimination, which plays a significant role in language acquisition and usage, in infants with different cleft types. A mismatch negativity (MMN) component of brain evoked potentials, which indexes preconscious sound discrimination, and brain responses to rare sine-wave tones were recorded in 12 healthy infants and 32 infants with oral clefts at the ages of 0 and 6 months. Infants with clefts were subdivided into two categories: those with cleft lip and palate (CLP) (n=11 at birth, n=6 at the age of 6 months) and those with cleft palate only (CPO) (n=17 at birth, n=8 at the age of 6 months). At both ages, brain responses to rare sounds tended to be smaller in both cleft subgroups than in healthy peers. However, in the latency range of 300 to 500 ms, the MMN was significantly smaller in infants with CPO. In infants with CLP, the MMN was comparable to that of healthy infants. Differences in auditory discrimination between infants with CLP and CPO, as reflected by MMN, were detectable at birth and persisted into later infancy. This pattern parallels known behavioural differences between children with these cleft types. Brain responses to rare sounds, in contrast, had no differentiative power with respect to the cleft type.

Electromagnetic responses of the human auditory cortex generated by sensory-memory based processing of tone-frequency changes

Event-related brain potentials (ERPs) and magnetoencephalographic (MEG) responses to infrequent (‘deviant’) tones occurring among frequent (‘standard’) tones of different pitch were compared with responses to rare tones presented alone. The subjects were to ignore the tones. Deviant tones elicited the mismatch negativity (MMN) and its MEG counterpart (MMNm), while the rare tones delivered alone elicited a larger N1 and its MEG counterpart (N1m) than did standard tones. Source modeling of MEG responses indicated a difference in auditory-cortex source locations between the MMNm to deviant tones and the enhanced N1m to the rare tones presented alone. Thus, the MMN/MMNm is elicited by infrequent sounds only when they occur among frequent sounds. This supports the idea that a sensory-memory trace formed in the auditory cortex by preceding repetitive sounds is a necessary precondition for MMN/MMNm elicitation.

Two cognitive systems simultaneously prepared for opposite events

Event-related potentials (ERPs) were recorded during a go/no-go reaction time (RT) task in which subjects responded to rare target tones and withheld response to frequent tones. In a predictable condition, a rare visual stimulus signalled the impending occurrence of a rare tone, whereas a frequent visual stimulus signalled that a frequent tone would be presented. The rare visual stimuli elicited P3, associated with violations of expectations, whereas the rare tones, being predictable, did not. The rare tones elicited the mismatch negativity (MMN), a component associated with preattentive deviance detection, despite the fact that they were expected. RT was faster in the predictable condition than in another condition in which the tones were not predictable. The P3 and RT data indicate, respectively, that subjects anticipated and were ready to respond to the target tones. The MMN result indicates that immediately before target tones, the preattentive system underlying the MMN was set for frequent tones, being unaffected by the information available to the higher order system. Thus, the higher order cognitive system associated with P3 and the lower order cognitive system associated with the MMN were prepared simultaneously for opposite events.

Two cognitive systems simultaneously prepared for opposite events

Event-related potentials (ERPs) were recorded during a go/no-go reaction time (RT) task in which subjects responded to rare target tones and withheld response to frequent tones. In a predictable condition, a rare visual stimulus signalled the impending occurrence of a rare tone, whereas a frequent visual stimulus signalled that a frequent tone would be presented. The rare visual stimuli elicited P3, associated with violations of expectations, whereas the rare tones, being predictable, did not. The rare tones elicited the mismatch negativity (MMN), a component associated with preattentive deviance detection, despite the fact that they were expected. RT was faster in the predictable condition than in another condition in which the tones were not predictable. The P3 and RT data indicate, respectively, that subjects anticipated and were ready to respond to the target tones. The MMN result indicates that immediately before target tones, the preattentive system underlying the MMN was set for frequent tones, being unaffected by the information available to the higher order system. Thus, the higher order cognitive system associated with P3 and the lower order cognitive system associated with the MMN were prepared simultaneously for opposite events.

Benzodiazepine temazepam suppresses the transient auditory 40-Hz response amplitude in humans

To discern the role of the GABA A receptors in the generation and attentive modulation of the transient auditory 40-Hz response, the effects of the benzodiazepine temazepam (10 mg) were studied in 10 healthy social drinkers, using a double-blind placebo-controlled design. Three hundred Hertz standard and 330 Hz rare deviant tones were presented to the left, and 1000 Hz standards and 1100 Hz deviants to the right ear of the subjects. Subjects attended to a designated ear and were to detect deviants therein while ignoring tones to the other. Temazepam significantly suppressed the amplitude of the 40-Hz response, the effect being equal for attended and non-attended tone responses. This suggests involvement of GABA A receptors in transient auditory 40-Hz response generation, however, not in the attentive modulation of the 40-Hz response.

Auditory event-related potentials and clinical scores in unmedicated schizophrenic patients

Event-related potentials (ERPs) have been widely examined in schizophrenic patients. However, although neuroleptic medication could be a potentially confounding variable, studies with unmedicated patients are relatively scarce. The present work was undertaken to determine whether ERP abnormalities persist in stabilized schizophrenic patients after drug withdrawal. In addition, ERP amplitudes and latencies were compared with clinical ratings (the Positive and Negative Syndrome Scale, PANSS) by means of Spearman rank order correlation coefficients. The P300 and N200 responses to rare tones and the P200 and N100 responses to frequent tones were recorded in 20 clinically stabilized drug-free schizophrenic patients and 19 age-matched control subjects during a two-tone discrimination task. Major findings were that the schizophrenic patients had reduced P300, N200 and N100 amplitudes and an increased P300 latency. The P300 amplitude was negatively correlated with age in patients. The P200 latency was negatively correlated with the PANSS positive syndrome score. The ERP abnormalities shown in this study appear to be enduring traits of the disorder as they persist in stabilized patients even after drug withdrawal.

Order effects in response times of parkinsonian patients and normal controls.

Response latencies were measured in 6 parkinsonian patients and 6 normal subjects in a choice reaction task requiring the discrimination of two different tones with different probabilities of occurrence (frequent and rare). Response latency was measured from stimulus onset to onset of electromyographic activity in the responding muscle. Rare-tone responses were separated on the basis of the number of frequent tones intervening between the rare tone of interest and the immediately preceding rare tone (defined as rare-tone position). Frequent-tone responses were separated by the number of consecutive frequent tones occurring either before or after a rare tone (defined as frequent-tone position). Rare- and frequent-tone position had a significant impact on response latency. Both patients and controls had the shortest response latencies to rare tones when four frequent tones (the median interval for these experiments) intervened. Similarly, the response latency to frequent tones increased at approximately this same median interval after a rare event for both patients and controls. These findings suggest that normal controls utilize probability information about both global probabilities and their immediate past experience in order to modify upcoming responses. Our findings also indicate that patients with Parkinson's disease do not differ from normal subjects in this regard, and thus that even subtle attributes of preprogramming are not affected in Parkinson's disease, despite suggestions by others to the contrary.

Effects of interstimulus interval on auditory event-related potentials in congenitally blind and normally sighted humans

To test the hypothesis of auditory compensation after early visual deprivation, congenitally blind and sighted adults performed an auditory discrimination task. They had to detect a rare target tone among frequent standard tones. Stimuli were presented with different interstimulus intervals (ISIs) (200, 1000, 2000 ms) and the auditory-event related potentials to all tones and reaction times to targets were recorded. Increasing ISIs resulted in an increasing amplitude of the vertex response (N1-P2) in both groups, but this amplitude recovery was more pronounced in the blind. Furthermore, targets elicited larger and more posteriorly distributed N2 responses in the blind than in the sighted. Since target detection times were shorter in the blind as well, these findings imply compensatory adaptations within the auditory modality in humans blind from birth.

Interhemispheric asymmetry of event-related fields concerned with logical processing during auditory oddball stimulation.

This study investigated the cortex during logical processing of auditory information using a 122-channel dc-SQUID gradiometer. The experimental task was designed to require a simple logical decision prior to counting rare paired tones, which consisted of two different pitches and were presented to separate ears. Among six subjects, left and right predominant dipolar activity was observed in three subjects each. When the dipolar sources were superimposed on MR images, the inferior region of the supramarginal gyrus showed activation, suggesting that logical processing occurred in the association cortex but not in the auditory cortex. We propose a modified cognitive sequence model in which auditory information processed in Heschl's gyri is transmitted to the supramarginal gyrus to commence automatic detection processing.

Processing of auditory stimuli during visual attention in patients with schizophrenia

Background: The aim of this study was to evaluate attentional functioning in patients with schizophrenia with an emphasis on automatic processes using the mismatch negativity (MMN) component of the event-related brain potential. Methods: Participants were asked to perform a challenging visual discrimination task and simultaneously ignore auditory stimuli presented in the background. In different blocks of trials, the background was either a sequence of tones that included rare deviant tones differing in pitch or a sequence of tones that alternated regularly in pitch with occasional deviant repetitions. In a second experiment, participants were asked to actively respond to auditory deviant stimuli. Results: Visual targets generated smaller N1, N2, and P3b deflections in patients than in control subjects, suggesting deficits in controlled attentional processes. Auditory deviant stimuli elicited an MMN that varied in scalp distribution as a function of the deviant-type (pitch vs. pattern). In patients with schizophrenia, impaired auditory discrimination was associated with altered MMN topography and reduced MMN amplitude. Conclusions: These findings are consistent with impaired automatic processes in patients with schizophrenia, which may contribute to their difficulties in processing complex auditory sequences. The timing and scalp topography are consistent with impaired auditory pattern analysis in posterior association cortices.

Concurrent visual task effects on evoked and emitted auditory p300 in adolescents

Using an oddball stimulus presentation paradigm, the effects of divided attention on auditory P300s were studied. Auditory attention was either divided or focused, depending on the demands placed on subjects during the performance of a concomitantly presented visual task. Two types of auditory tasks were performed under each of the two auditory attention conditions. In one, subjects responded to infrequently presented high pitched tones (oddball stimuli). In the other they responded to the occasional omission of a stimulus in an otherwise rhythmically presented chain of stimuli. P300s and reaction times were recorded to both the rare tones and the omissions. The Sternberg visual memory task was used to manipulate the subject's auditory attention state. Subjects actively performed the Sternberg task during the divided auditory attention condition, whereas during the focused attention condition they were not required to respond to the visual stimuli. During focused auditory attention, evoked auditory P300s were both larger and faster than their emitted counterparts. During divided attention, auditory P300s were reduced in amplitude but latency was unaffected. Evoked auditory P300s showed evidence of containing P300a as well as P300b components, particularly when attention was shared with the visual task.

First-episode schizophrenic psychosis differs from first-episode affective psychosis and controls in P300 amplitude over left temporal lobe.

Schizophrenia is associated with central (sagittal) midline reductions of the P300 cognitive event-related potential and topographic asymmetry of P300, with reduced left temporal voltage. This P300 asymmetry is, in turn, linked to tissue volume asymmetry in the posterior superior temporal gyrus. However, it is unknown whether P300 asymmetry is specific to schizophrenia and whether central and lateral P300 abnormalities are due to chronic morbidity, neuroleptic medication, and/or hospitalization, or whether they are present at the onset of illness. P300 was recorded in first-episode schizophrenia, first-episode affective psychosis, and control subjects (n = 14 per group). Subjects silently counted rare (15%) target tones (1.5 kHz) among trains of standard tones (1.0 kHz). Averages were constructed from brain responses to target tones. Peak amplitude of P300 and integrated voltage over 300 to 400 milliseconds were significantly different between first-episode schizophrenics and controls over the posterior sagittal midline of the head. First-episode schizophrenics displayed smaller amplitudes over the left temporal lobe than first-episode affective psychotics and controls, but the groups showed no differences over the right temporal lobe. Left-sided P300 abnormality in first-episode schizophrenia relative to first-episode affective psychosis and controls suggests that P300 asymmetry is specific to schizophrenic psychosis and present at initial hospitalization. This P300 asymmetry suggests left temporal lobe dysfunction at the onset of schizophrenia.

A topographical ERP study of healthy premature 5 year old children in the auditory and visual modalities

The aim of this research is to study the impact of extreme prematurity on the cognitive development of the child as assessed at age 5 years 9 months. Our samples include 15 healthy prematures born between 25 and 28 weeks of gestational age carefully matched with 15 full-term controls. In the first experiment, two different auditory stimuli were presented to the subjects who listened passively without instruction. The second experiment consisted of a standard visual oddball task in which the subjects were instructed to `catch' two different animals, by pushing a left or right button for a moose ( n=120) or a raccoon ( n=40), respectively. In the auditory task, 3 ERP peaks were analyzed (frontal N100 and P3a, temporal P2). All premature children demonstrated normal early frontal N100 and temporal P2 responses. The group differences were apparent in the late positivity (P3a) where controls showed a larger amplitude to the rare tones applied evenly to both ears. In contrast, the prematures did not show sensitivity to rare tones but showed a larger P3a upon left ear stimulation, when compared to the right. Also, the ERPs to the visual oddball task showed normal early positivities (P250–300) in the premature group. Once again, deviations from the normal were evident in late waves. The ERPs recorded from prematures showed a more diffuse topography especially between 500 and 600 ms post-stimulus and around the posterior area (P550). The succeeding negativity (SW) was not altered in the premature group. The ERP data suggest that premature children, even without clinically apparent problems, convey specific ERP singularity when engaged in a task that involves complex processing.