P300 latency: abnormal in sleep apnea with somnolence and idiopathic hypersomnia, but normal in narcolepsy

Diagnostic challenges and burden of idiopathic hypersomnia: a systematic literature review

Idiopathic hypersomnia (IH) is a rare neurological sleep disorder, characterized by excessive daytime sleepiness despite normal sleep duration, that can significantly impact patient's lives. The burden of IH goes beyond excessive daytime sleepiness, pervading all aspects of everyday life. Characteristic and burdensome symptoms of IH include sleep inertia/drunkenness, long sleep duration, and daytime cognitive dysfunction. This systematic review assessed current knowledge regarding IH diagnostic challenges and burden of illness. Literature searches for original epidemiological, clinical, humanistic, or economic research relevant to IH published between 2012 and 2022 in MEDLINE, Embase, Cochrane, gray literature (diagnostic criteria and treatment guidelines), conferences (2019-2022), and clinical trial databases yielded 97 articles. Findings indicate that IH remains a poorly defined diagnosis of exclusion that is difficult to distinguish from narcolepsy type 2 because of symptom overlap and inadequacies of objective testing. Consequently, individuals with IH endure diagnostic delays of up to 9 years. The economic burden of IH has not been characterized to any appreciable extent. Pharmacological treatment options can improve symptoms and functional status, but rarely restores normal levels of functioning. These findings highlight the need to reclassify central disorders of hypersomnolence. Further collaboration is now required between research groups to identify and validate objective markers to help redefine diagnostic criteria for IH. This would move IH into a position that could benefit from future targeted therapeutic interventions. The study was funded by Takeda Development Center Americas, Inc.

Influence of obstructive sleep apnea on auditory event-related potentials

PURPOSE

To evaluate the influence of obstructive sleep apnea (OSA) on the P300 response of auditory event-related potentials (ERPs) and to correlate the electrophysiological findings with OSA severity.

METHODS

Patients with no OSA and mild, moderate, and severe OSA according to polysomnography (PSG) with normal hearing and no comorbidities were studied. Individuals with a body mass index (BMI) ≥ 40 kg/m², hypertension, diabetes, dyslipidemia, the use of chronic medications, and a risk of hearing loss were excluded. All patients underwent full PSG and auditory ERP measurement using the oddball paradigm with tone burst and speech stimuli. For P300 analysis (latencies and amplitudes), normal multiple linear regression models were adjusted with the groups (No OSA, Mild OSA, Moderate OSA, Severe OSA), age, BMI, and Epworth score as explanatory variables.

RESULTS

We studied 54 individuals (47 males) aged 35 ± 8 years with a BMI of 28.4 ± 4.3 kg/m². Patients were divided according to the apnea-hypopnea index (AHI) derived from PSG into no OSA (n = 14), mild (n = 16), moderate (n = 12), and severe OSA (n = 12) groups. Patients with severe OSA presented prolonged P300 latencies with tone burst stimuli compared to patients with no OSA and those with mild and moderate OSA.

CONCLUSION

Severe OSA is associated with impairment of the P300 response of auditory ERPs, suggesting a decrease in the processing speed of acoustic information that may be mediated by the level of somnolence.

Electrophysiological and neuropsychological outcomes of severe obstructive sleep apnea: effects of hypoxemia on cognitive performance

Obstructive sleep apnea syndrome (OSAS) is a sleep disorder characterized with upper airway obstructions. Some studies showed cognitive and electrophysiological changes in patients with OSAS; however, contradictory results were also reported. The purpose of the present study was twofold: (1) to investigate cognitive changes in severe OSAS patients by using neuropsychological tests and electrophysiological methods together, (2) to investigate influence of hypoxemia levels on cognition. Fifty-four severe OSAS patients and 34 age-, gender- and education matched healthy subjects were participated. OSAS patients were further divided into two subgroups according to minimum oxygen saturation levels. All participants underwent a detailed neuropsychological test battery. A classical visual oddball task was used to elicit ERP P300 and mean P300 amplitudes were measured from F_z, C_z and P_z electrode sites. OSAS patients showed reduced mean P300 amplitudes up to 43-51% on all electrode sites compared to healthy controls. Subgroup analysis revealed significant differences in neuropsychological test scores between healthy controls and high hypoxemia OSAS group, as well as between low and high hypoxemia groups. Moreover, both low and high hypoxemia OSAS groups had lower P300 amplitudes compared with healthy controls. P300 amplitudes showed a gradual decline in parallel with increasing hypoxemia severity; however, the difference between high and low hypoxemia OSAS groups did not reach significance. Moderate correlations were found between sleep parameters, neuropsychological test scores and P300 amplitudes. These results suggest that electrophysiological measures could be better indicators of cognitive changes than neuropsychological tests in OSAS, particularly in mildly affected patients.

Modafinil improves information processing speed and increases energetic resources for orientation of attention in narcoleptics: double-blind, placebo-controlled ERP studies with low-resolution brain electromagnetic tomography (LORETA)

BACKGROUND AND PURPOSE

Recent neuroimaging studies in narcolepsy discovered significant gray matter loss in the right prefrontal and frontomesial cortex, a critical region for executive processing. In the present study, event-related potential (ERP) low-resolution brain electromagnetic tomography (LORETA) was used to investigate cognition before and after modafinil as compared with placebo.

PATIENTS AND METHODS

In a double-blind, placebo-controlled cross-over design, 15 patients were treated with a 3-week fixed titration scheme of modafinil and placebo. The Epworth Sleepiness Scale (ESS), Maintenance of Wakefulness Test (MWT) and auditory ERPs (odd-ball paradigm) were obtained before and after the 3 weeks of therapy. Latencies, amplitudes and LORETA sources were determined for standard (N1 and P2) and target (N2 and P300) ERP components.

RESULTS

The ESS score improved significantly from 15.4 (+/- 4.0) under placebo to 10.2 (+/- 4.1) under 400mg modafinil (p=0.004). In the MWT, latency to sleep increased nonsignificantly after modafinil treatment (11.9+/-6.9 versus 13.3+/-7.1 min). In the ERP, N2 and P300 latencies were shortened significantly. While ERP amplitudes showed only minor changes, LORETA revealed increased source strengths: for N1 in the left auditory cortex and for P300 in the medial and right dorsolateral prefrontal cortex.

CONCLUSION

LORETA revealed that modafinil improved information processing speed and increased energetic resources in prefrontal cortical regions, which is in agreement with other neuroimaging studies.

The use of evoked potentials in sleep research

Averaged event-related potentials (ERPs) represent sensory and cognitive processing of stimuli during wakefulness independent of behavioral responses, and reflect the underlying state of the CNS (central nervous system) during sleep. Components measured during wakefulness which are reflective of arousal state or the automatic switching of attention are sensitive to prior sleep disruption. Components reflecting active attentional influences during the waking state appear to be preserved in a rudimentary form during REM sleep, but in a way that highlights the differences in the neurochemical environment between wakefulness and REM sleep. Certain ERP components only appear within sleep. These begin to emerge at NREM sleep onset and may reflect inhibition of information processing and thus have utility as markers of the functional status of sleep preparatory mechanisms. These large amplitude NREM components represent synchronized burst firing of large number of cortical cells and are a reflection of the nervous system's capacity to generate delta frequency EEG activity. As such they are useful in assessing the overall integrity of the nervous system in populations not showing substantial amounts of SWS as measured using traditional criteria. While requiring care in their interpretation, ERPs nonetheless provide a rich tool to investigators interested in probing the nervous system to evaluate daytime functioning in the face of sleep disruption, the ability of the sleeping nervous system to monitor the external environment, and the ability of the nervous system to respond to stimuli in a manner consistent with the initiation or maintenance of sleep.

Conditions of Primary Excessive Daytime Sleepiness

Excessive daytime somnolence is a prevalent problem in medical practice and in society. It exacts a great toll in quality of life, personal and public safety, and productivity. The causes of EDS are myriad, and careful evaluation is needed to determine the cause in each case. Although much progress has been made in discovering the pathophysiology of narcolepsy, much more remains to be understood, and far less is known about other primary conditions of EDS. Several methods have been developed to assess EDS, although each of them has limitations. Treatment is available for the great majority of cases.

Event-related potentials during forced awakening: a tool for the study of acute sleep inertia

Sleep propensity and sleep inertia were assessed in 43 patients with excessive daytime sleepiness (EDS) and 21 sleep-deprived controls, using a forced awakening test under continuous electroencephalographic (EEG) recording. Event-related potentials (ERPs) were first obtained in waking, while participants performed a target detection auditory task. Subjects were then allowed to take a nap with lights off and sleep latency was calculated. After 3 min of continuous sleep, frequent and rare tones were suddenly presented again (and ERPs recorded) in a forced awakening condition, which was repeated a second time if patients fell asleep. ERPs in pre-nap wakefulness did not differ in patients and controls. On forced awakening, almost half (48%) of EDS patients retained morphologically normal ERPs, but showed a significant delay of P300 relative to waking. In the other half of the patients (and none of the controls), the N200/P300 complex to targets was replaced on forced awakening by high-amplitude negative waves ('sleep negativities'). Single subject analysis showed that 65% of patients had abnormal responses during forced awakening (significant P3 delay or sleep negativities), while only three of them (7%) had abnormal ERPs on wakefulness. The presence of sleep negativities was associated with shorter sleep latencies and increased target detection errors on forced awakening. Sleep negativities were more prevalent in narcolepsy and idiopathic hypersomnia than in EDS associated to psychiatric disorders. By combining sleep latency and ERP measures, the forced awakening test provided a robust and relatively rapid tool (45-60 min) to evaluate both sleep propensity and sleep inertia within a single recording session. The test allows each subject to act as his/her own control, thus increasing sensitivity. In the present series, it proved to be much more discriminative than waking ERPs alone to demonstrate specific abnormalities in patients complaining of excessive daytime sleepiness.

Sleep and respiratory stimulus specific dampening of cortical responsiveness in OSAS

The application of inspiratory occlusion stimuli produces cortical responses called respiratory-related evoked potentials (RREPs). During wakefulness the RREP waveform consists of early P1 and Nf components, an N1 and a P300. During non-REM sleep the predominant component is an N550, best seen in the averages of elicited K-complexes. Obstructive sleep apnea syndrome (OSAS) patients have been previously shown to have a normal wake RREP but to have a reduced amplitude N550 and a smaller proportion of elicited K-complexes than controls. The present study tested the hypothesis that this reflects a sleep-specific dampening peculiar to inspiratory effort-related stimuli, by assessing both respiratory and auditory evoked potentials (AEPs) during wakefulness and non-REM sleep in OSAS patients and controls. Auditory tones were presented in an oddball sequence during wakefulness and as a monotonous series during stage 2 sleep. Inspiratory occlusions, delivered for 500 msec via an nCPAP mask were also presented during wakefulness and stage 2 sleep, every three to five breaths. Data were collected from ten OSAS patients and ten controls. There were no significant differences in the amplitudes of the auditory N1 and P3 or the respiratory P1, Nf, N1 or P3 components during wakefulness. The amplitude of the auditory N550 and the proportion of elicited K-complexes did not differ between groups for auditory stimuli presented during stage 2 sleep. The respiratory N550 and K-complex elicitation rate were both significantly reduced in the OSAS group, despite there being no differences in the mask occlusion pressure response to the occlusion. The results confirm a blunted cortical response to inspiratory occlusions that is specific to sleep. The absence of significant group differences in the responses to auditory stimuli highlight that the sleep-related differences seen in OSAS patients are specific to the processing of inspiratory effort related stimuli.

Evidence of a sleep-specific blunted cortical response to inspiratory occlusions in mild obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS) patients have elevated non-rapid eye movement (REM) sleep arousal thresholds to inspiratory loading. To test the hypothesis that this is due to sleep-specific dampening of cortical responses to inspiratory effort, respiratory-related evoked potentials (RREPs) were evaluated in six mild OSAS patients and six age- and body mass index-matched controls during wakefulness and Stage 2 non-REM sleep. Electroencephalogram was recorded from six scalp sites (Fz, FCz, Cz, CPz, Pz, and O(2)). Electrooculogram, electromyogram, and mask pressure signals were also recorded. During sleep, pharyngeal pressure was recorded using a Millar pressure catheter placed 2 cm below the glottis. The RREP waveform was broadly similar in the two groups during wakefulness, but was markedly different during Stage 2 non-REM sleep. During wakefulness, only the N1 component showed reduced amplitude in the OSAS group. During sleep, the occlusion stimulus elicited fewer K-complexes in the OSAS patients. In addition, the N550 component in the average of K-complex responses was smaller in amplitude in the OSAS group. The data suggest that patients with mild OSAS have a "blunted" response to the respiratory occlusion stimulus. This appears not to be related to compromised mechanoreceptor function, as the RREP was normal in the patients when they were awake.

Awakening from sleep

Awakening is a crucial event for the organism. The transition from sleep to waking implies physiological processes which lead to a new behavioural state. Spontaneous awakenings have varying features which may change as a function of several factors. The latter include intrasleep architecture, circadian phase, time awake, age, or disordered sleep. Despite its clear theoretical and clinical importance, the topic of awakening (in humans) has received little attention so far. This contribution focuses on major issues which relate to awakening from both basic (experimental) and clinical research. Recent knowledge on neurophysiological mechanisms is reported. The experimental data which provide in the human suggestions on the regulation of awakening are discussed, mainly those concerning sleep architecture and homeostatic/circadian factors also in a life-span perspective, since age is a powerful factor which may influence awakening. Clinical contributions will examine two main sleep disorders: insomnia and hypersomnia. Daytime functioning is shown in insomniac patients and compared to other pathologies like sleep apnea. A final section evokes links between some types of night waking and psychological factors.

Assessment of sleepiness in children

Excessive sleepiness is a common but under-recognized problem in children. This article examines the clinical and laboratory evaluation of sleepiness in children, including the use of polysomnography, the multiple sleep latency test, and other varieties of neurophysiologic testing. Where applicable, technical aspects of laboratory testing are reviewed. Alternative laboratory and neurobehavioral techniques used to investigate daytime sleepiness are also briefly covered.

Idiopathic Hypersomnia

In contrast to narcolepsy and the Kleine-Levin syndrome, idiopathic hypersomnia is a recently described sleep disorder. Absence of associated clinical features such as cataplexy or megaphagia and characteristic polysomnographic features such as sleep-onset REM episodes render positive diagnosis more uncertain in idiopathic hypersomnia than in the fwo former conditions. Consequently there has been an unfortunate tendency to label all difficult to classify cases of excessive daytime sleepiness as idiopathic hypersomnia. At present due to the description of new disorders such as upper airway resistance syndrome, narcolepsy without cataplexy, delayed sleep phase syndrome, all of which were formerly confused with idiopathic hypersomnia and the clear identification of a "polysymptomatic" or "classic" form of idiopathic hypersomnia, the limits of the disorder become more precise. Still there are a number of cases of isolated excessive daytime sleepiness with no prolonged night sleep, no difficulty waking up, which lay between narcolepsy and genuine idiopathic hypersomnia. Thus there is a definite need to further develop laboratory investigations to help identify and classify these cases. Moreover pathophysiology and pathogenesis are still in their infancy and efforts have to be pursued in this direction. Treatment has not made consistent progress except for the use of a new wake promoting compound, modafinil, which has not yet been evaluated in controlled studies.

Attentive and preattentive processing in narcolepsy as revealed by event-related potentials (ERPs)

Narcolepsy is a neurological disorder, characterised by excessive daytime sleepiness, sleep attacks, cataplexy and abnormal manifestations of rapid eye movement sleep. Recent studies suggest that neuropsychological impairments in narcolepsy may include memory and attention deficits due to a monoaminergic or cholinergic transmitter dysfunction. To explore the nature of cognitive problems, the P300 and mismatch negativity (MMN) event-related potentials were investigated in narcoleptic patients and matched controls. Narcoleptics showed significantly increased P300 amplitudes relative to controls, especially at frontal recording sites. While control subjects exhibited typically larger MMN over the right than the left hemisphere, in particular at frontal and central electrodes, narcoleptics did not show this asymmetry. These results are interpreted as possible alterations in cognitive preattentive and attentive processing associated with altered functioning of the prefrontal cortex in narcolepsy.

Cerebral metabolic impairment in patients with obstructive sleep apnoea: an independent association of obstructive sleep apnoea with white matter change

OBJECTIVES

To determine the relation between severity of obstructive sleep apnoea (OSA) and degree of cerebral metabolic impairment.

METHODS

Fifty five patients with habitual snoring and excessive daytime sleepiness underwent standard overnight polysomnography and magnetic resonance spectroscopy separately. Proton MR spectra were measured with two dimensional chemical shift imaging (repetition time; 1500 ms, echo time; 135 ms). Severity of cerebral metabolic impairment was assessed by the N-acetylaspartate (NAA)/choline ratios for the cerebral cortex and white matter. Severity of OSA was assessed by the apnoea-hypopnoea index (AHI) and the minimum value of peripheral oxyhaemoglobin saturation. All patients were evaluated for the presence or absence of comobidities including hypertension, cardiac disease, diabetes mellitus, and hyperlipidaemia. Univariate analysis of variance (ANOVA) and mulitple linear regression analysis were used for statistical analyses.

RESULTS

Univariate ANOVA disclosed significant effects of AHI, age, and the presence or absence of hypertension on the NAA/choline ratio for cerebral white matter (p=0.011, p=0.028, p=0.0496, respectively). The AHI had a significant negative association with the NAA/choline ratio for cerebral white matter, independent of age and the presence or absence of cardiac disease, in the final multivariate regression model (standardised partial regression coefficient=-0.417, p<0.001). No significant relation was found between severity of OSA and the NAA/choline ratio for the cerebral cortex. Age alone had a significant effect on the NAA/choline ratio for the cerebral cortex on univariate ANOVA (p<0.001) and a significant negative association with the NAA/choline ratio for the cerebral cortex in the regression model (r=-0.552, p<0.001).

CONCLUSIONS

A significant relation exists between AHI and the degree of metabolic impairment in cerebral white matter in patients with OSA.

Visual P300 latency predicts treatment response to modafinil in patients with narcolepsy

OBJECTIVE

To evaluate the hypothesis that visual P300 latency (VL) predicts treatment response to modafinil (a new wake-promoting agent) in patients with narcolepsy.

METHODS

DESIGN

Comparison of responders and non-responders in a double-blind randomized placebo-controlled trial.

SETTING

Private practice referral sleep disorders center.

PATIENTS

Twenty one patients with narcolepsy (ages 17-65 years).

INTERVENTIONS

Auditory and visual P300 testing using 31 evenly spaced scalp electrodes, and baseline polysomnograms and objective and subjective tests of daytime sleepiness, followed by modafinil treatment for 9 weeks. Polysomnograms and tests of sleepiness were then repeated.

MAIN OUTCOME MEASURE

The Maintenance of Wakefulness Test (MWT). Response defined as a final MWT > 7.3min (normative sample mean - 3 SD), plus an increase > 1SD based on normative sample (3.6 min) over baseline MWT.

RESULTS

Non-responders had longer age-adjusted 31-electrode mean VL (448.4 ms vs. 410.8 ms, P = 0.024), and larger auditory P300 amplitude, with no topographical P300 differences. Non-responders and responders did not differ on any other baseline clinical variable. Using a cut-off of 0.5 SE from normal regression constant, shorter age-adjusted VL predicted modafinil response, with specificity of 0.71 and sensitivity of 0.86.

CONCLUSIONS

VL predicts treatment response to modafinil in patients with narcolepsy.

Longer auditory and visual P300 latencies in patients with narcolepsy

To compare auditory and visual P300 amplitude and latency magnitudes and topographies in patients with narcolepsy and normal subjects, 20 patients with polysomnographically-confirmed narcolepsy and 40 normal subjects were administered auditory and visual P300 testing using 31 evenly spaced scalp electrodes. Patients with narcolepsy were then administered baseline polysomnograms and objective (MSLT, Maintenance of Wakefulness Test or MWT) and subjective tests (Epworth Sleepiness Scale, Clinical Global Impression) of daytime sleepiness. Patients had longer 31-electrode mean age-adjusted auditory P300 latencies (406.0 +/- 27.8 vs. 385.7 +/- 28.9 ms, p = 0.012) and visual P300 latencies (427.3 +/- 29.0 vs. 411.4 +/- 27.7 ms., p = 0.044) than 40 normal subjects in the same age range. Age-adjusted auditory P300 latency was correlated with MWT (r = -0.49, p = 0.028), but not with any other clinical variable or measure of sleepiness. Age-adjusted visual P300 latency was not correlated with any clinical variable or measure of sleepiness. Patients with narcolepsy had longer auditory and visual P300 latencies than normal subjects.

Measurement of P300 and sleep characteristics in patients with hypersomnia: do P300 latencies, P300 amplitudes, and multiple sleep latency and maintenance of wakefulness tests measure different factors?

To explore further the relationship between ease of falling asleep, ability to maintain wakefulness, attention and information processing in sleep apnea and other sleep disorders, we conducted a thorough analysis of the similarities, differences and correlations between auditory and visual P300 amplitudes and latencies, and tests of sleepiness. The 283 consecutive patients presenting with hypersomnia were administered nocturnal polysomnography. Next day they underwent auditory and visual P300 recordings, Multiple Sleep Latency Test (MSLT) and Maintenance of Wakefulness Test (MWT). Correlation coefficients were calculated between auditory and visual P300 amplitudes and latencies, respiratory disturbance index (RDI), sleep efficiency, % stage 1, and the tests for sleepiness. Factor analysis was performed with data from P300 testing, MSLT and MWT. Auditory P300 amplitude was correlated with sleep efficiency. Auditory P300 latency was correlated with % stage 1, RDI, MSLT and MWT. Visual P300 latency was correlated with % stage 1, sleep efficiency and MWT. MSLT but not MWT was negatively correlated with sleep efficiency. Factor analysis suggests three factors: attention, information processing, and sleepiness. We conclude that P300 latencies and tests of sleepiness (MSLT and MWT) measure different abilities in patients with diagnosable disorders of daytime sleepiness.

Obstructive sleep apnea and abnormal P300 latency topography

This study was conducted to evaluate cognitive abnormalities in obstructive sleep apnea (OSA) using cognitive evoked potentials (P300), and to clarify if such cognitive dysfunction is related to the OSA itself or to the hypersomnolence in OSA. Subjects were administered a polysomnogram, auditory and visual P300 testing using 31 scalp electrodes, and the multiple sleep latency test. There were 40 normal subjects ages 26 to 75. Of 143 consecutive OSA patients ages 26 to 75, 56 had severe OSA (Respiratory Disturbance Index or RDI 40-80/h sleep) with objective somnolence (Mean Sleep Latency < 5 min). Thirty-three had severe OSA without objective somnolence. Fifty-four had profound OSA (RDI > 80/h sleep) with or without objective somnolence. The normals and the three OSA groups did not differ in age. Patients with profound OSA or with severe OSA without somnolence had longer visual P300 latency than normals. The groups also differed in visual P300 latency topography. OSA patients had significantly longer latencies frontally than normals. Thus, OSA, even in the absence of hypersomnolence, is associated with abnormalities in cognitive evoked potentials. Visual P300 latency at frontal electrodes seems to be a neurophysiological index of dysfunction in OSA that is independent of tests of sleepiness.

Topography of auditory and visual P300 in normal adults

Auditory and visual P300 recordings were performed on 40 normal, right-handed individuals from age 16 through 65, using 31 evenly spaced scalp electrodes. Amplitude at the P300 peak and latency to this peak at each electrode site were measured. Age was significantly correlated with the 31-electrode mean for auditory and visual P300 amplitudes and auditory and visual P300 latencies. The younger age group (16-40) had shorter auditory and visual P300 latencies than the older group (41-65). Visual P300 amplitudes were of an overall larger magnitude than auditory P300 amplitudes. There were no other differences in P300 amplitudes or latencies by gender, modality, or side of scalp, and no significant topographical differences in P300 amplitudes or latencies by gender, age-group, modality, or side of scalp. Radial current density maps on group-averaged auditory and visual P300 waveforms at the group mean P300 latency at Cz, showed a right centroparietal sink surrounded by sources. This suggests a major right centroparietal P300 generator. Except for the change in P300 amplitudes with age, and the direction of the change in P300 latencies with age, these data on adults are similar to our previous description of P300 topography in normal children. Description of the normal topography of the P300, and demonstration of the lack of topographic differences by gender, age group, modality, or side of scalp, may facilitate the meaningful examination of P300 topography in cognitive disorders. Such an examination might lead to better diagnostic tools and more appropriate treatment of cognitive disorders in adults.

Abnormal auditory P300 topography in attention deficit disorder predicts poor response to pemoline

P300 is a cognitive evoked potential that evaluates attention and information processing. This study uses auditory and visual P300 topography to develop a classification of attention deficit disorder (ADD), and to find predictors of treatment response to the stimulant pemoline. Forty-five ADD children ages 6 to 15 were administered auditory and visual P300 using 31 scalp electrodes. They were compared with 39 normals. Patients were treated with pemoline, and good and poor responders compared. There were no P300 differences between normals and ADD patients. Good and poor responders to pemoline were clinically identical. Poor pemoline responders had smaller right fronto-central auditory P300 amplitudes than good responders. The ratio of right fronto-central to parietal auditory P300 amplitude, had a sensitivity of 0.70 and specificity of 0.76, as a test for good pemoline response. A ratio greater than 0.5 predicted good response to pemoline, while a ratio less than 0.5 predicted poor response. Treatment with pemoline produced no P300 changes. We conclude that P300 topography classifies ADD into group 1 with normal P300 topography and good response to pemoline, and group 2 with small right fronto-central auditory P300 amplitudes and poor response to pemoline.