Event-related potential correlates of functional hearing loss: Reduced P3 amplitude with preserved Nl and N2 components in a unilateral case

Abstract A female patient exhibiting functional hearing loss in her left ear demonstrated reduced amplitude of P3 component in event-related potentials (ERP) to left monaural stimulation, with preserved N1 and N2 components to stimulation of either ear. This result suggested that stimuli in the affected ear were conducted successfully up to the auditory cortex but that further processing in higher brain regions was 'repressed'. Event-related potential examination for such hysterical disorders could be useful in clarifying their brain mechanism and offer a useful diagnostic clue to its nature.     

Macular oscillatory potentials in humans

Studies of the focal macular electroretinogram (ERG) have been made with special reference to oscillatory potentials (OPs) by using a fundus monitoring system in humans. Human macular OPs consist of 3 to 4 wavelets (mean peak interval, approximately 6.5 msec). The distribution of OPs in relation to those in a- and b-waves was studied. The amplitudes of a-waves, b-waves, and OPs of the upper macula were significantly larger than those of the lower macula. The distribution of OPs is relatively sparse in the fovea, becoming more dense than the a- and b-waves from the fovea toward the parafovea, and differing even more toward the perifovea. There was no statistical difference of amplitude in a- and b-waves between nasal and temporal macula. The amplitude of OPs in the temporal macula, however, was significantly larger than in the nasal macula. In some macular diseases, such as diabetic maculopathy, cystoid macular edema, or the convalescent stage of central serous chorioretinopathy, macular OPs were selectively reduced, leaving the a- and b-waves intact. Macular OPs can provide a new aspect of macular function and can be a sensitive indicator to assess that function in macular diseases.     

Pain-related somatosensory evoked potentials following CO2 laser stimulation in peripheral neuropathies

Pain-related somatosensory evoked potentials (pain SEPs) following CO2 laser stimulation were examined in 30 patients with peripheral neuropathies, and the results were compared with clinical sensory findings. Pain SEP findings showed a significant correlation with the clinical impairment of pain sensation, but not with the impairment of deep sensations. In contrast, conventional electrically-stimulated SEPs (electric SEPs) showed a significant correlation with deep sensations, but not with the impairment of pain sensation. Examinations of both pain SEPs and electric SEPs, therefore, are considered to be very useful to evaluate physiological functions of sensory nerves in patients with peripheral neuropathies.     

Effects of systemic clonidine on auditory event-related potentials in squirrel monkeys

Event-related potential (ERP), electroencephalographic (BEG), and behavioral data were collected from squirrel monkeys (Saimiri sciureus) in a 90−10 auditory oddball paradigm. Background or target tones were presented once every 2 s, and responses to the targets were rewarded. ERPs were recorded from epidural electrodes following systemic administration of clonidine (0.1 mg/kg) or a saline placebo. EEG power spectra and behavioral performance were assessed simultaneously as indices of behavioral state. Clonidine significantly decreased the area and increased the latency of a P300-like potential. The amplitudes and areas of the earlier P1, N1, and P2 components and a later slow wave-like potential were not reduced, nor were their latencies altered. Clonidine produced increased EEG power in the alpha range (7.5–12 Hz) and decreased power in the upper beta range (20–40 Hz) but did not affect performance in the oddball task. Because two major effects of clonidine are to substantially reduce activity in the noradrenergic nucleus locus coeruleus (LC) and to reduce norepinephrine (NE) release from axons, the present results support the hypothesis that the LC and its efferent projection system are important in modulating the activity of P300-like potentials.     

Effect of thoracic epidural etidocaine 1.5% on somatosensory evoked potentials, cortisol and glucose during cholecystectomy

The effect of thoracic (T7-8) epidural etidocaine 1.5%, 9 ml, and continuous per- and postoperative epidural infusion of etidocaine 1.5%, 4 ml/h, on early (less than 500 ms) somatosensory evoked potentials (SEPs), and cortisol and glucose in plasma during cholecystectomy, was examined in ten patients. Spread of analgesia (pin-prick) was T3 (T1-T3) to L2 (T11-L3) 35 min after injection of etidocaine, and T3 (T2-T4) to T12 (T8-L4) 3 h after surgical incision (median (range)). Before operation, epidural etidocaine had no significant effects on peak-to-peak amplitude of SEPs to electrical stimulation at the L1, T10 or T6 dermatomal level (P greater than 0.09). SEPs were abolished in only two patients at T6, and no patient had SEPs abolished at T10 or L1. The plasma concentrations of cortisol and glucose were significantly increased 20 min after surgical incision and remained increased throughout the study. No correlation was found between the block-induced decrease in the peak-to-peak amplitude at T6 or T10 and increase in plasma cortisol, except for a negative correlation at T10 and the initial increase in cortisol (Rs = 0.72, P = 0.03). In conclusion, thoracic epidural administration of 9 ml of etidocaine 1.5% does not provide total afferent somatic blockade assessed by SEP and the stress response to cholecystectomy.     

Simple reaction time event-related potentials: Effects of alcohol and diazepam

1. 1. Acute effects of alcohol and diazepam on reaction time (RT) and event-related potential (ERP) measures were examined in 108 healthy male volunteers.

2. 2. The subjects engaged in a simple RT task at two levels of stimulus intensity during baseline and treatment sessions.

3. 3. Lower stimulus intensity produced increased RTs, increased ERP peak latencies, and suppression of peak amplitudes.

4. 4. Moderate and high doses of alcohol, and high doses of diazepam produced increased RTs. Alcohol suppressed P100 and N100 amplitudes, while diazepam suppressed P100 amplitudes only. P100 amplitudes were correlated to RTs under baseline and treatment conditions.

5. 5. These results were taken as evidence for impaired stimulus detection during alcohol and diazepam intoxication, with both drugs influencing sensory-perceptual processes and alcohol alone influencing the degree of attentiveness.

Biological correlates of deliberate self-harm behaviour: a study of electroencephalographic,biochemical and psychological variables in parasuicide

Clinical, electroencephalographic and biochemical variables were measured in 40 patients who attempted suicide and 27 age-matched controls. Patients had significantly higher scores for depression, hopelessness, neuroticism and psychoticism and lower scores for extraversion than controls. They also had significantly lower contingent negative variation (CNV), higher postimperative negative variation and lower whole blood serotonin values than controls. Within the patient group, vulnerability to parasuicide, as determined by previous or repeated acts of deliberate self-harm, was associated with higher scores for hopelessness and suicide intent, lower scores for extraversion and decreased CNV. Factor analysis revealed significant correlations between psychological variables and auditory evoked potential amplitudes for the vulnerable group. A profile of variables associated with increased risk of self-harm in patients presenting with attempted suicide is proposed from our data.     

Inhibitory motor control in children with attention-deficit/hyperactivity disorder: event-related potentials in the stop-signal paradigm.

BACKGROUND: The aim of the study was to investigate the inhibitory control of an ongoing motor response and to identify underlying neural deficiencies, manifested in event-related potentials, that cause poorer inhibitory performance in children with attention-deficit/hyperactivity disorder. METHODS: A stop-signal paradigm with a primary visual task and auditory stop signal was used to compare performance in 13 children with attention-deficit/hyperactivity disorder and 13 control children, while event-related potentials were recorded simultaneously. RESULTS: Children with attention-deficit/hyperactivity disorder showed poorer inhibitory performance through a slower inhibitory process. Inhibitory processing of auditory stop signals was marked by a frontal N2 component that was reduced in the attention-deficit/hyperactivity disorder group relative to controls. A central positive component (P3) was associated with the success of inhibiting a response, but there were no group differences in its amplitude or latency. CONCLUSIONS: Findings support the hypothesis of deficient inhibitory control in children with attention-deficit/hyperactivity disorder. Slower inhibitory processing appears to be due to a specific neural deficiency that manifests in the processing of the stop signal as attenuated negativity in the N2 latency range.     

Electrochemistry of Anticonvulsants: Electron Transfer as a Possible Mode of Action

Reduction potentials were determined for various anticonvulsants, including progabide, SL 75.102, CGS 9896, pyridazines, zonisamide, 1,2,3-triazoles, and copper complexes. The values generally were in the range of about -0.1 to -0.6 V for the protonated drugs and the metal complexes. Reduction potentials provide information on the feasibility of electron transfer (ET) in vivo. If the value is relatively positive (greater than about -0.6 V), the agent can act catalytically as an electron acceptor from an appropriate cellular donor. A concomitant favorable influence on abnormal neuronal processes associated with epilepsy could occur. We describe ET as a possible mode of action of anticonvulsants as well as some antiepileptic agents with no electrochemical data based on this hypothetical ET approach.