Negative Slow Wave Research Articles

Changes of short latency somatosensory evoked potential in sleep

We studied how the first negative waves (frontal ‘N18’ and parietal ‘N20’) of median somatosensory evoked potentials (SEP) change from waking to sleep in 9 healthy volunteers. Frontal and parietal responses in awake subjects showed multiple fast frequency potentials (FFP) over the ascending and descending phases of the slow negative waves. The main frontal FFP consisted of N16, P17, N18, P18, N19 and P20, with an additional small FFP, n15, over the ascending phase of N16. The parietal FFP included 3 major peaks (N15, P18 and N20) and 3 small FFP (n17, n19 and n20). Frontal FFP, except for n15, were markedly attenuated or totally disappeared in stage II sleep. Only a few FFP were identified in stage IV. The FFP returned in REM sleep, but amplitude was smaller than the waking state. Parietal FFP were also attenuated in NREM and recovered in REM sleep, but these changes were less prominent compared to those of frontal FFP. Latencies of frontal P20 and parietal N20 were prolonged in NREM sleep with greater prolongation of P20 than N20. These returned to waking values in REM sleep. These findings suggest that the frontal and parietal major negative peaks (‘N18’ and ‘N20’) consist of multiple physioanatomical substrates mediated through complex thalamocortical projection systems, and that the FFP are closely related to the sleep-wake mechanism possibly reflected by mutual interaction between cortex and the thalamic reticular system.

Learning where to look: Electrophysiological and behavioral indices of visual search in young and old subjects

The present investigation explores the way young and elderly subjects use regularities in target location in a visual display to guide search for targets. Although both young and old subjects show efficient use of search strategies, slight but reliable differences in reaction times suggest decreased ability in the elderly to use complex cues. Event-related potentials were very different for the young and the old. In the young, P3 amplitudes were larger on trials where the rule that governed the location of the target became evident; this was interpreted as an effect of memory updating. Enhanced positive Slow Wave amplitude indicated uncertainty in random search conditions. Elderly subjects' P3 and SW, however, seemed unrelated to behavioral performance, and they showed a large negative Slow Wave at central and parietal sites to randomly located targets. The latter finding was tentatively interpreted as a sign of increased effort in the elderly to allocate attention in visual space. This pattern of behavioral and ERP results suggests that age-related differences in search tasks can be understood in terms of changes in the strategy of allocating visual attention.

Contingent negative variation in adults with Gilles de la Tourette syndrome.

Three deflections or waves of the Contingent Negative Variation (CNV): the Slow Negative Wave (SNW), the Terminal CNV (TCNV) and the Post Imperative Negative Variation (PINV) were studied in 18 adults with Gilles de la Tourette syndrome and in 15 controls. The patients showed a reduced SNW, a normal TCNV and an increased PINV. Moreover, at the right parietal region the patients demonstrated a decreased SNW, TCNV and PINV. The results are discussed in relation to behavioral and neuropsychological disturbances found in Gilles de la Tourette syndrome.

Spreading depression in the olfactory bulb of rats: Reliable initiation and boundaries of propagation

Spreading depression in the olfactory bulb of rats is an elusive phenomenon, the demonstration of which requires specific conditioning procedures. The present paper describes a simple technique for reliable initiation of bulbar spreading depression with microinjections of potassium acetate. Adult hooded rats were anesthetized with pentobarbital (50 mg/kg) and slow potential changes accompanying spreading depression were recorded with capillary microelectrodes stereotaxically inserted into the olfactory bulb and adjacent forebrain structures. KCl microinjection (0.5–1.0 μl, 0.134–0.670 mol/l) into the olfactory bulb elicited local depolarization which only exceptionally developed into a propagating spreading depression. Potassium acetate (0.5–1.0 μl, 0.15 mol/l) injected into the rostral olfactory bulb evoked a negative slow potential wave (amplitude of around 25 mV and duration 30–50 s) propagating at a rate of 3–4 mm/min through all the olfactory bulb layers. Low positive (5 mV) instead of negative waves were recorded in the superficial olfactory nerve layer with reversal in the glomerular layer (200–300 μm). The slow potential decreased in the rostrocaudal direction and expired at the caudal boundary of the olfactory bulb. Bulbar spreading depression never spread to neocortex, and cortical spreading depression never entered into the olfactory bulb but stopped in the anterior olfactory nucleus 7 mm rostral to bregma. Repeated potassium acetate injections into the olfactory bulb occasionally elicited a series of spreading depression waves recurring at regular intervals, probably reflecting reverberation of scroll-shaped waves around the rostrocaudal axis of the olfactory bulb. It is argued that the low susceptibility of the olfactory bulb to spreading depression is due to powerful GABAergic inhibition which can be weakened by (Cl −) e reduction after potassium acetate injections.

Postsynaptic neuronal response of a cat sensorimotor cortex during evoked and self-sustained rhythmic "spike and wave" activity

Intracellular correlates of complex sets of rhythmic cortical "spike and wave" potentials evoked in sensorimotor cortex and of self-sustained rhythmic "spike and wave" activity were examined during acute experiments on cats immobilized by myorelaxants. Rhythmic spike-wave activity was produced by stimulating the thalamic relay (ventroposterolateral) nucleus (VPLN) at the rate of 3 Hz; self-sustained afterdischarges were recorded following 8–14 Hz stimulation of the same nucleus. Components of the spike and wave afterdischarge mainly correspond to the paroxysmal depolarizing shifts of the membrane potential of cortical neurons in length. After cessation of self-sustained spike and wave activity, prolonged hyperpolarization accompanied by inhibition of spike discharges and subsequent reinstatement of background activity was observed in cortical neurons. It is postulated that the negative slow wave of induced spike and wave activity as well as slow negative potentials of direct cortical and primary response reflect IPSP in more deep-lying areas of the cell bodies, while the wave of self-sustained rhythmic activity is due to paroxysmal depolarizing shifts in the membrane potential of cortical neurons.

Event-related potentials in children at risk for schizophrenia during two versions of the continuous performance test

Event-related potentials (ERPs) were recorded from children of schizophrenic parents, children of parents with affective disorders, and children of parents without a history of psychiatric illness. ERPs were elicited during two versions of the continuous performance test (CPT), which differed in their level of processing complexity. The data were recorded from electrodes located at midline frontal, central, parietal, and occipital scalp sites. Diagnostic assessments of the parents were performed using the Schedule for Affective Disorders and Schizophrenia-Lifetime Version and Research Diagnostic Criteria. Clinical assessments of the children were made with a modified version of the Global Assessment Scale. ERP amplitudes for six electrophysiological events were compared among groups for target and nontarget stimuli using analyses of variance of both factor score and baseline to peak measures. There was one isolated between-group finding: frontal negative slow wave recorded at F z was of greater magnitude in the high risk (HR) than in either the psychiatric (PC) or normal control (NC) groups. Since only a small percentage of children at risk will eventually develop schizophrenia, ERP amplitude deviance and frequency distribution analyses were also performed and compared among groups. ERP component amplitudes did not distinguish the groups when each component was considered separately. Deviance analyses, using a combination of the amplitudes of the six ERP components, also did not provide evidence of a deviant subgroup within any of the three groups. There appeared to be no relationship between ERP component amplitudes and behavioral adjustment in adolescence. Some evidence of a relationship between deviant attentional functioning and ERP component amplitude was found, but the pattern of findings within the attentionally deviant HR subgroup was opposite to that found for the HR group as a whole and more consistent with the pattern found for the NC group.

Observations upon the evoked responses to natural vestibular stimulation

Repetitive rotational stimuli simulating natural head movements have been applied to the study of the vestibular evoked response in normal subjects and 12 patients with complete loss of vestibular function. Special precautions were taken to eliminate all possible sources of artefacts, in particular, all eye movements were restrained by requiring the subject to fixate upon a target light attached to the rotating chair throughout the course of the test. With a stimulus of 2 sec duration the typical response took the form of a slow negative wave with a mean peak amplitude of approximately 24 μV and maximally recorded from the vertex. It was characteristically absent in the patient group. Occasionally, both in normal subjects and patients it was preceded by a long latency complex thought to be non-vestibular in origin. Tests carried out both in total darkness and in the light show a statistically significant increase in the potential in the latter condition indicating an influence of the optokinetic effect exerted by the visual surround. Further studies have explored the phase changes brought about by varying the amplitude and duration of the stimulus. These have revealed certain parallels in the results of recent animal experimental studies.

Human sympathetic electrical activity recorded with skin surface electrodes

Spontaneous electrical activity correlated to cardiac rhythm has been recorded with electrodes placed on the surface of the human arm or using the rabbit hindlimb. The signal-to-noise ratio has been improved using record averaging synchronized with the ECG. The recorded activity in man is a slow negative wave of sinusoid-like shape with a mean peak amplitude 0.08 ± 0.03 μV. The sympathetic origin of this activity is suggested by the facts that its time course and conduction velocity are similar to those of integrated spontaneous electrical activity, recorded directly from postganglionic sympathetic fibers in the rabbit, and that it can be recorded from skin surface as a response to direct electrical stimulation of sympathetic nerve fibers in the same animal.

The effects of handedness on event-related potentials in a rhyme-matching task

Event-related potentials (ERPs) were recorded from one midline and three pairs of homotopic lateral sites while subjects determined whether or not sequentially presented words rhymed. ERPs from left-handed males with a family history of sinistrality were compared with those from 12 right-handers, none of whom had such a family history. As in previous work (e.g. Rugg, M. D. Neuropsychologia 22, 435–443, 1984) the slow negative wave developing during the interval in which subjects waited for the final word was more negative from left-hemisphere electrodes, and the rhyme/non-rhyme differences in the ERPs following this word were greater over the right hemisphere. Neither of these asymmetries differed between the left and right-handers. Possible reasons for the occurrence of these ERP asymmetries during rhyme-matching are discussed, and it is suggested that the aspect(s) of linguistic processing tapped by this task, and influencing concurrently recorded ERPs, may be similarly lateralised in the brains of left- and right-handers.

Alterations in transient visual-evoked potentials induced by clonazepam and sodium valproate.

The transient visual-evoked potentials (VEP), recorded in patients suffering from generalized epilepsy, can be characterized by a duplication of the negative peak with a latency of 70-100 ms, a strong increase in amplitude of the negative peak between 80 and 130 ms and the development of a high amplitude slow negative wave following the primary complex. In this study we have investigated to which degree these changes are influenced by the intravenous administration of clonazepam and sodium valproate. Therefore, VEPs were registered in 30 patients, suffering from generalized epilepsy, just before and immediately after the intravenous injection of 0.4-0.8 mg clonazepam and further at 15, 30 and 16 min thereafter. The same procedure was applied on 10 patients treated with an intravenous injection of 400 mg sodium valproate. In both groups we found more or less a reduction in number and degree of the mentioned VEP changes. The improvement was associated with a strong decrease in amplitude of the VEP components in the group treated with clonazepam but was not seen in the sodium valproate group.

Changes in latency of evoked potentials after caudate nucleus stimulation

The activation of the head of the caudate nucleus in cats which have undergone transection of the spinal cord at C1 produces inhibition of evoked potentials in the motor area (pre-cruciate region) and also reduces the peak latency of the negative slow wave. The results of decreased latency are discussed with reference to variations in intensity of the stimulation activating the motor cortex. The role played by the caudate nucleus in the control of the motor system is emphasized.

Effects of 4-aminopyridine on the field potentials of hippocampal slices

In addition to promoting long-lasting negative (and positive) dendritic field potentials elicited by stimulation of Schaffer collaterals in hippocampal slices, 4-aminopyridine causes a slow negative wave which may have another origin than the dendritic potentials.

Visual evoked potentials and nociceptive thresholds in high and low self-stimulators

Tail flick latencies (TFL) were examined in order to distinguish between rats from genetically high (HI) and low (LO) self-stimulation lines (LC2-HI and LC2-LO). In addition, slow secondary negative wave (SNW) of the visual evoked potential, which is considered to be a sensitive index of normal and pharmacologically-induced behavioral arousal, was analysed. Small, albeit statistically significant enhancement of SNW was obtained in LO rats. Unlike LO animals, HI rats gained in SNW amplitude during repeated photic stimulation. The difference between the lines was highly significant. TFL assessment yielded slightly reduced (NS) values for HI rats. However, when TFL and SNW data were compared it appeared that TFL vary as a function of SNW amplitude in LO but not in HI rats, (r=0.9). SNW may be employed as a predictor of the nociceptive threshold in rats.

Somatosensory evoked potentials from the human brain-stem: Origins of short latency potentials

Short latency somatosensory evoked potentials (SEPs) were recorded in man from an array of electrodes within the IVth (the pons) and IIIrd ventricles (the thalamus) and the aqueduct of Sylvius (the midbrain). The slow negative (N15 and N20) and positive (P22) waves were preceded by 4 small positive (P9, P11, P13, and P14) waves of approximately 1 msec duration in scalp recordings. The sources of these waves have been differentiated on the basis of their timing and spatial gradients of corresponding intracranial potentials. While P11 is identified as volume conducted from below the brain-stem, P13 and P14 reflect synchronized volleys of the medial lemniscus and its branches to the various pontine and mecencephalic nuclei. In contrast to these earlier positive wavelets arising from fiber tracts, N15 may represent post-synaptic activities within these pontine and midbrain nuclei. N20 and P22 are the initial responses of the juxtarolandic cortex.

Visual evoked potentials in rats selected for high or low self-stimulation

Visual evoked potentials (VEPs) were analyzed in order to distinguish between rats from genetically high (HI) and low (LO) self-stimulation lines (LC2-HI and LC2-LO). Secondary VEP components - slow secondary negative wave (SNW) and sensory afterdischarge (SAD) - which are considered to be most sensitive indices of normal and pharmacologically-induced behavioral changes, were used for the comparison. Small, albeit statistically significant enhancement of SNW and SAD was obtained in LO rats. Unlike LO animals, HI rats gained in SNW amplitude and SAD area during repeated photic stimulation. The difference being highly significant. d,l-Amphetamine (1 mg/kg, i.p.) suppressed SAD and reduced the SNW amplitude in both HI and LO animals, although the predrug difference in their values remained practically unaltered. Apomorphine (0.25, 2.75, 5.25 mg/kg i.p.) had no measurable effect on VEP parameters even though it caused a regular picture of dose-related enhancement of locomotion and stereotypy. The effect of amphetamine can, therefore, be attributed to the activation of the norepinephrinergic system. Correspondingly, VEP variance in the two lines of rats is interpreted as related to the peculiarities of norepinephrine modulation of neocortical activity.

Cognitive brain potential components in adolescents.

ABSTRACTEvent‐related potentials (ERPs) were recorded in a cross‐sectional study from 70 adolescents ranging in age from 11 to 18. A paradigm was used in which background, standard auditory events (66 percent occurrence) were randomly replaced by either a change in pitch, or a missing stimulus, each occurring 17 percent of the time. Subjects were instructed to respond to one of the infrequent events, with each designated as relevant (i.e., a target) on alternate blocks of trials. Factor score analyses showed that P300 and frontal negative slow wave were larger to relevant than irrelevant events, whereas parietal positive slow wave was not. Both N200 and frontal negative slow wave showed modest age effects. Significant effects of sex, mainly for the exogenous components, were also found. These data highlight the importance of the negative task‐related potentials as correlates of development. They also point to the functional independence of P300 and slow wave and add to the evidence for the functional distinction between the frontal negative and parietal positive aspects of slow wave.

Amygdala Kindling in the Classical Conditioning Paradigm

The hypothesis was tested that epileptiform alterations of brain excitability may be elicited by a conditioning stimulus (CS) in a classical conditioning paradigm. Fifteen male albino rats were chronically implanted with electrodes in the amygdala and over the visual cortex. A train of six stroboscopic flashes served as the CS and the unconditioned stimulus was the amygdaloid electrical stimulation, delivered together with the sixth flash in the course of the kindling procedure. Rats were randomly assigned to two groups. Rats in Group 1 were exposed to one or two kindling sessions per day, and those in Group 2 were exposed to 10 such sessions every day. All rats in Group 1 showed fully mature seizures within 15 +/- 5.5 sessions, whereas none of those in Group 2 displayed kindled seizures. There was no evidence of amygdaloid afterdischarges or enhanced spiking as a response to the CS. A gradual selective suppression of the visual evoked potentials (VEP) secondary components, i.e., slow negative wave and sensory afterdischarge, paralleled kindling in Group 1. This effect was weak in Group 2. There was no change in the primary response of VEPs in either group. No recovery of VEPs followed the extinction of conditioning.

Analysis of long-latency components of field potentials evoked by stimulation of the cerebral cortex and nerves in the cerebellar paramedian lobule

Field potentials evoked in the graunular layer of the cerebellar paramedian lobule of unanesthetized cats in response to stimulation of the sensomotor cortex and limb nerves contained slow negative waves, appearing after a long latent period, which were generated by granule cells. In the case of nerve stimulation this component was recorded both inside and outside the projection zone of the corresponding limb. Cortical stimulation by single stimuli or series of stimuli not more than 1.8–2.5 times above threshold strength led to the appearance of evoked potentials only inside the corresponding projection zone. The long-latency component of field potentials evoked by cerebral stimulation followed high frequencies of repetitive stimulation and was less sensitive to the action of barbital anesthesia than the analogous component of potentials evoked by nerve stimulation. In the case of combined cerebral and nerve stimulation the long-latency components underwent summation. It is concluded that mossy fibers of slowly-conducting spino- and cerebrocerebellar tracts innervate different granule cells in the cerebellar cortex.

Interpretation of brainstem auditory evoked potentials: results from intracranial recordings in humans.

The results of recording intracranially from the auditory nerve, lower brainstem nuclei, and the inferior colliculus in more than 40 patients operated upon for hemifacial spasm and trigeminal neuralgia are presented. Recordings from the auditory nerve have shown that the auditory nerve is the neural generator of the first two peaks in the human ABR. Recordings from the entrance of the eighth nerve into the brainstem and locations close to that reveal potentials; the latencies of the peaks in these potentials match those of peaks III and IV. These peaks are therefore assumed to have their source in second-and third-order neurons of the ascending auditory pathway. Recordings from the inferior colliculus show a surface-positive deflection followed by a slow negative wave usually with several undulations. The latency of the positive peak matches that of wave V of the scalp-recorded ABR. It is assumed that the neural generator of this component of the potential recorded from the inferior colliculus is the lateral lemniscus and that the slow, surface-negative potential originates in the inferior colliculus. The latency of this slow potential is too long to explain that nucleus as the neural generator of peak V, as was assumed previously.

The effect of attentional effort on visual evoked potential N1 latency

The latency of the visual evoked potential N1 component evoked by nontarget stimuli increases with an increased attention to nontarget stimuli. The latency increase seems related to a general effort at processing, rather than any early filtering. This phenomenon is illustrated in one study of hyperactive children and another of normal young adults. The literature of this phenomenon is reviewed, and various explanations are considered. It does not appear to be a result of a slow negative wave, but rather a genuine effect of one aspect of attention on N1.