Relationship of geniculate and occipital PGO waves and the effects of nonvisual sensory activity.

The nature of occipital PGO waves (REM) was addressed by comparing the occipital PGO waves measured at the marginal gyrus with the geniculate PGO waves and the occipital PGO waves "directly" transmitted to the occipital cortex. The directly transmitted PGO waves lack the first short positive-going spike that precedes the negative phase of the occipital PGO waves. The "directly" transmitted PGO wave was recorded from cats with either deafferented or excised LG nucleus. The "directly" transmitted PGO wave resembled pontine negative-going PGO wave more regarding amplitude and wave shape changes than the occipital PGO waves of intact cats. The ascending negativity of pontine PGO waves is indirectly transmitted through phasic increase of the local excitatory processes, more in the LG than in the occipital cortex. The PGO waves seem to be affected by endogenous and exogenous nonvisual processes, more in the LG than the occipital cells alone. The occipital PGO waves seem to result from the vectorial sum of geniculate and "directly" transmitted occipital PGO waves.     

The P300 wave of the human event-related potential.

The P300 wave is a positive deflection in the human event-related potential. It is most commonly elicited in an "oddball" paradigm when a subject detects an occasional "target" stimulus in a regular train of standard stimuli. The P300 wave only occurs if the subject is actively engaged in the task of detecting the targets. Its amplitude varies with the improbability of the targets. Its latency varies with the difficulty of discriminating the target stimulus from the standard stimuli. A typical peak latency when a young adult subject makes a simple discrimination is 300 ms. In patients with decreased cognitive ability, the P300 is smaller and later than in age-matched normal subjects. The intracerebral origin of the P300 wave is not known and its role in cognition not clearly understood. The P300 may have multiple intracerebral generators, with the hippocampus and various association areas of the neocortex all contributing to the scalp-recorded potential. The P300 wave may represent the transfer of information to consciousness, a process that involves many different regions of the brain.     

Current generators and properties of early components evoked in rat olfactory cortex

Depth-profile, current-source-density (CSD) and impedance analysis were used to determine the current generators of secondary waves "a" and "b" in the response evoked in pyriform cortex (PC) of the urethane anesthetized rat following OB or LOT stimulation. Positive peaks (sinks) in the second-derivative curves of the "a" and "b" waves were localized at 50-75 and 225-250 microns deep, respectively. Cortical impedance was significantly (p less than 0.01) correlated with the cell packing density of PC layers, being maximal close to the zero dipole point of the gross evoked response; magnitude of conductivity gradients was, however, insufficient to alter the interpretation of positive and negative peaks in terms of net membrane currents. Post-tetanic and/or frequency potentiation of PC responses but not long-term potentiation were found in the majority of animals tested. Recovery of the test "b" wave was faster when using paired-shock stimulation at 3.0 Hz than at 0.3 Hz; suppression of this component following a conditioning OB volley could be overcome and the "b" wave facilitated if either a long-latency component (i.e., 65-100 msec) was present in the priming response, or if the conditioning stimulus was delivered to the mediodorsal thalamic nucleus (MDT). These results confirm and extend similar ones in other species, suggesting that following OB or LOT stimulation three successive excitatory processes take place in PC neural elements of the rat under urethane anesthesia: an initial monosynaptic excitation of distal segments of apical dendrites of layer II cells, and to a lesser extent, also of layer III neurons ("a" wave), followed by action potentials in their respective somas (PS wave); subsequently, long association axons give rise to a di or polysynaptic compound EPSP in proximal apical and possibly also, in basal pyramidal dendrites ("b" wave; early reactivation process). Finally, a "late" reactivation takes place in PC involving neurons which participated in the early reactivation process (late component). In addition, heterosynaptic facilitation of the "b" wave in the PC evoked response follows MDT conditioning stimulation.     

Long-latency auditory-evoked potentials: Role of polysensory association cortex in the cat

The objective of this study has been to define the role of polysensory association cortex in the generation of "wave NA" and of "wave C," long-latency auditory-evoked potentials recorded from the vertex of conscious cats as, respectively, a marked negative potential of latency 30-48 msec followed by a broad positive wave of latency 50-75 msec. Wave C may represent the feline analogue of the longer latency human auditory-evoked potential wave P2, insofar as both waveforms are very large amplitude, long duration positivities characterized by long recovery cycles. Based on previous studies of wave C and the generators of other middle-latency evoked potentials, we hypothesized that both wave NA and wave C might reflect, at least in part, the cortical culmination of a nonlemniscal line auditory association system arising in reticulothalamic projections to intralaminar and associated ventral thalamic regions. Relays from these thalamic areas are known to project to polysensory association cortex, including pericruciate gyrus, anterolateral gyrus, and medial suprasylvian gyrus. Therefore we implemented a series of lesion experiments to characterize the role of each of these cortical areas in the production of wave NA and wave C. Our results indicate that all three polysensory association areas contribute significantly to both waves NA and C, although the largest effects followed ablation of the pericruciate area alone. Thus, the generator substrates of waves NA and C appear to involve a long-recovery cycle system which functionally incorporates activation of association cortex.     

Early platelet-collagen interactions in whole blood and their modifications by aspirin and dipyridamole evaluated by a new method (BASIC wave)

It is shown that the supernatant of unstirred whole blood at 37 degrees C, stimulated by 1 microgram/ml of collagen for 10 sec, produces a rapid generation of pro and antiaggregatory compounds with a final proaggregatory activity which can be detected for more than 60 min on a platelet rich plasma (PRP) by turbidometric aggregometry. A reversible aggregation wave that we have called BASIC wave (for Blood Aggregation Stimulatory and Inhibitory Compounds) is recorded. The collagen stimulation of unstirred PRP produces a similar but smaller BASIC wave. BASIC's intensity increases if erythrocytes are added to PRP but decreases if white blood cells are added instead. Aspirin abolishes "ex vivo" the ability of whole blood and PRP to generate BASIC waves and dipyridamole "in vitro" significantly reduces BASIC's intensity in whole blood in every tested sample, but shows little effect in PRP.     

Seizures and pain

The findings of this case report do not answer the question of whether or not the slow wave discharge specifically represents a permutation of the K-complex. However, the slow wave discharge and the K-complex may be "bed partners" in part, with both residing in the same reticular activating system. It is therefore concluded that the reticular formation which harbors the arousal system also generates the slow wave discharges in this case. The discharge in turn activates the pain and other subsystems within the same reticular core to produce the associated somato-sensory, visceral and autonomic disturbances.     

Continuum model of mnemonic and amnesic phenomena.

Amnesia in its various forms is characterized by defects in one or more components of a complex system. Implantation of short-term memory occurs in the hippocampus, while long-term memory is essentially located in the neocortex; these regions are interconnected through complex synaptic structures. In the hippocampus, physiological data show that, as predicted by Hebb, excitatory synapses between nearby excitatory cells become strengthened by simultaneous activation. In contrast with this local process, the preponderance of clinical and experimental evidence indicates that cortical recall of a "memory" is the reconstruction of fragments stored in different synaptically distant brain regions. A mathematical model of memory must reconcile this apparent contradiction as well as explain how many different memories and "ideas" can be assembled within a given anatomical area. Continuum theory, which treats an ensemble of "cell assemblies" or neural networks, offers a step in this direction. Linear analysis using this approach shows that it is the nature of the neural continuum to generate activity waves of wavelength greater than synaptic connection ranges. These waves grow under certain circumstances, and their wavelength is controlled by the synaptic parameters. Both hippocampal and cortical tissue are subject to such wave growth. In the hippocampus, the local Hebbian strengthening controls the global wave growth, making the difference between wave decay and growth. The cortical wave structure can become very complex, so that reproducible memory recall as well as "creative thought" can be accommodated in the theory. Deficits in the functioning of the system may also be evaluated potentially by means of "goodness-of-fit" of the clinical and spatially resolved data with the model.     

Typology of nonlinear activity waves in a layered neural continuum

Neural tissue, a medium containing electro-chemical energy, can amplify small increments in cellular activity. The growing disturbance, measured as the fraction of active cells, manifests as propagating waves. In a layered geometry with a time delay in synaptic signals between the layers, the delay is instrumental in determining the amplified wavelengths. The growth of the waves is limited by the finite number of neural cells in a given region of the continuum. As wave growth saturates, the resulting activity patterns in space and time show a variety of forms, ranging from regular monochromatic waves to highly irregular mixtures of different spatial frequencies. The type of wave configuration is determined by a number of parameters, including alertness and synaptic conditioning as well as delay. For all cases studied, using numerical solution of the nonlinear Wilson-Cowan (1973) equations, there is an interval in delay in which the wave mixing occurs. As delay increases through this interval, during a series of consecutive waves propagating through a continuum region, the activity within that region changes from a single-frequency to a multiple-frequency pattern and back again. The diverse spatio-temporal patterns give a more concrete form to several metaphors advanced over the years to attempt an explanation of cognitive phenomena: Activity waves embody the "holographic memory" (Pribram, 1991); wave mixing provides a plausible cause of the competition called "neural Darwinism" (Edelman, 1988); finally the consecutive generation of growing neural waves can explain the discontinuousness of "psychological time" (Stroud, 1955).     

Involvement of cortical, thalamic and midbrain reticular formation neurons in spike and wave discharges: extracellular study in feline generalized penicillin epilepsy

Extracellular activity of single units, simultaneously recorded in cortex, thalamus, and midbrain reticular formation was investigated during feline generalized penicillin epilepsy. The firing activity of neurons recorded in the cortex was invariably and consistently enhanced in coincidence with the positive peak and the positive-negative transient of the "spike" of the spike and wave complex, and it was greatly decreased during the wave. In the nonspecific thalamic nuclei three classes of neurons were identified according to their patterns of activity during the spike and wave complex: (i) neurons behaving like cortical units, (ii) neurons with enhanced firing activity during the wave and a decreased activity during the "spike," and (iii) unmodified neurons. In the nucleus lateralis posterior neurons of the third class were not found. Most midbrain reticular neurons could be classified in the same three classes of the nonspecific thalamic nuclei; however, 11% of those units increased their activity 20 to 30 ms earlier than did the cortical units (class IV). Investigation of the activities of all these neuronal populations immediately prior to a spike and wave discharge showed that the rhythmic cycle of excitation-inhibition commenced earlier in the cortical neurons than in any other subcortical neuron. Moreover, there were some nonspecific thalamic neurons of class II with an inhibitory phase exactly coincident with the activation of class IV midbrain reticular neurons. These data suggest (i) a leading role of cortical neurons in initiating and maintaining a spike and wave burst; (ii) the involvement of a corticothalamocortical circuit in timing the bursts, and (iii) an accessory reticulothalamic loop also involved in regulating the intraburst frequency of the spike and wave complex.     

Electroconvulsive therapy-induced Wolff–Parkinson–White syndrome: a case report

Objective

Wolff–Parkinson–White (WPW) syndrome is characterized by premature ventricular excitation due to the presence of an abnormal accessory pathway. Electrocardiography (ECG) of patients with WPW syndrome portrays a short PR interval and a wide QRS interval with a delta wave.

Methods

Herein, we report the case of a patient with schizophrenia who developed a wide QRS interval with a delta wave immediately following electroconvulsive therapy (ECT).

Results

Initially, the delta wave disappeared within 2 days after ECT. However, the duration of the delta wave increased exponentially to 4 months when ECT was repeated.

Conclusion

Although the patient's cardiocirculatory dynamics remained normal, we continued to monitor her ECG until the delta wave disappeared because WPW syndrome can lead to serious arrhythmia.     

Periodic lateralized epileptiform discharges. I. Clinical and electroencephalographic aspects

In a two-years period, from a total of 5481 EEGs, we could select 25, corresponding to 22 patients, with PLEDs (prevalence of 0.45%). The group was composed by 13 males and 9 females, with age ranging from 5 months to 85 years. Main diagnosis was epilepsy of unknown etiology and brain tumor (22% each). The localization of PLEDs was mainly temporal region (54% of the whole group) and more frequent morphology was "delta triphasic wave" (a graphic pattern resembling sharp wave, but with longer duration) (1/3 of total), followed by sharp biphasic wave and sharp wave-slow wave (29% each). Although 9 patients died it was not possible to determine prognostic value of PLEDs specifically for each pathological condition.     

Sulthiame therapy for continuous spike and wave in slow-wave sleep

Corticosteroids are often considered as the first therapeutic choice in children with continuous spike and wave in slow-wave sleep on electroencephalogram; however, they are associated with significant adverse effects. "Idiopathic" forms of continuous spike and wave in slow-wave sleep may represent the severe end of the spectrum of benign rolandic epilepsy of childhood. This report describes a 5-year-old male with language delay who presented with a single focal-onset, nocturnal seizure and had continuous spike and wave in slow-wave sleep on electroencephalography. After 1 month of sulthiame therapy, his electroencephalographic abnormality had resolved, and his language development improved.     

Neuronal activities in human epileptic foci and surrounding areas.

1. Extracellular microelectrode recording was carried out in human epileptogenic cortex and in the area surrounding the focus in three cases and in the hippocampus of two cases. 2. It was impossible to identify primary "epileptic" or "pacemaker" neurons. Emphasis is placed on the interactions among the neuronal aggregates at the focus for generating the epileptic discharges in the interictal stage. The possibility of plasticity in each neuronal element in the epileptogenicity is considered. Surround inhibition was not observed. The slow wave burst was accompanied by a long repetitive rhythymic burst of unitary discharge. It was shown that the slow wave burst was a modified feature of epileptic activity. 3. Various types of activity of hippocampal neurons are described, which are, however, considered as normal discharges of those neurons.     

Postsynaptic reactions of neurons of the sensomotor cortex of the cat during evoked and self-sustained rhythmic activity of the "peak-wave" type

Intracellular correlates of evoked rhythmic cortical "spike-and-wave" potentials produced in sensorimotor cortex during 3/s stimulation of the thalamic relay nucleus (VPL) and of self-sustained "spike-and-wave" afterdischarges following 8-14/s stimulation of the same nucleus were studied in acute experiments on cats immobilized by myorelaxants. Intracellular recordings of pyramidal tract neurons revealed that different components of evoked "spike-and-wave" potentials, i. e. the spike-like negative wave and the long lasting negative wave, are postsynaptic in origin: the first is due to EPSPs with spike discharges, and the latter--to IPSPs of cortical neurons. Components of "spike-and-wave" afterdischarge mostly reflect the paroxysmal depolarizing shifts of the membrane potential of cortical neurons. After cessation of sustained "spike-and-wave" activity the long-lasting hyperpolarization accompanied by inhibition of spike discharges and subsequent recovery was observed in cortical neurons. It is presumed that the negative wave of the evoked "spike-and-wave" potential as well as slow negative potentials of direct cortical and primary responses reflect IPSPs of deeper parts of pyramidal tract neurons, while the waves of the sustained "spike-and-wave" afterdischarges are due to paroxysmal depolarizing shifts in cortical neurons.     

Generalized epilepsy with bilateral synchronous spike and wave discharge. New findings concerning its physiological mechanisms.

A hypothesis for the mechanism of generalized spike and wave discharge in human generalized epilepsy is proposed in the light of findings obtained in feline generalized penicillin epilepsy. It is postulated that generalized bilaterally synchronous spike and wave discharge depends upon a diffuse and relatively mild state of cortical hyperexcitability which increases the responsiveness of cortical neurons. Afferent thalamo-cortical volleys normally involved in the genesis of spindles and recruiting responses are most likely to precipitate spike and wave discharges under these conditions. The spike and wave pattern probably results from the activation of a recurrent intracortical inhibitory pathway which becomes activated when cortical neurons discharge in greater number and more repetitively than is normally the case. During spike and wave discharges a large number of neurons oscillate between short periods of excitation, corresponding to the spike, and longer periods of inhibition, corresponding to the slow wave component of the spike and wave complex. This disrupts the normal transactional processes of cortical neurons which are presumably responsible for mental activity, particularly for the close integration of perception, cognition and voluntary motor responsiveness. The degree of this interference varies greatly and in mild absence seizure it is not justified to speak of "loss of consciousness". The fundamental disturbance in absence seizures brought about by the generalized cortical spike and wave discharges is therefore better regarded as a "clouding of the mind". Loss of consciousness can be said to occur only when the interference with mental activity becomes particularly intense. Loss of consciousness in absence seizures can therefore not be used as an argument in favor of primary involvement of higher brain-stem mechanisms.     

Developmental change of short latency somatosensory evoked potential waves between P3 and N1 components in children

We attempted to isolate and identify the negative waves between the conventional P3 and N1 components of short latency somatosensory evoked potentials (S-SEPs) in children. Twenty normal children ranging in age from 3 months to 12 years, and 11 adolescents and adults were studied. The median nerve was stimulated and recordings from F (F3 or F4) and C' (1-2 cm posterior to C3 or C4) contralateral to the stimulation site were simultaneously obtained in order to identify each negative wave in the C' recording. The wave of C' coincident with that of F was regarded as the far-field potential, and the wave of C' that diverged from F as the near-field potential at the scalp. There were one negative wave (N1) in the far-field potential and 2 negative waves (N2 and N1(3)) in the near-field potential, after the P3 component. "N1(3)" was conventional N1 and "N2" was the negative wave just before N1(3). In infants and younger children, the interpeak latencies of P3-N1(3) and P3-N2 were markedly elongated in comparison with that in older children. These interpeak latencies may be useful as an index of cerebral maturation.     

Psychiatric hospitalization during the two SARS-CoV-2 pandemic waves: New warnings for acute psychotic episodes and suicidal behaviors

BACKGROUNDThe subsequent waves of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic have represented a dramatic health emergency characterized by significant consequences on mental health. Diachronic variations in the incidence rates of acute relapse of psychiatric disorders may represent significant "sentinel events" for assessing the mental health response to an unprecedented stressful event.AIMTo investigate the variation in psychiatric hospitalization rates and differences in sociodemographic and clinical-psychopathological peculiarities at Bologna "Maggiore" General Hospital Psychiatric Ward (GHPW) between the first two waves SARS-CoV-2 pandemic and the same periods of the previous 3 years. The secondary purpose of the study was to suggest a diachronic response pathway to stress by reporting additional literature data on coping strategies.METHODSThis observational and retrospective study collected information on admission to the GHPW at the "Maggiore" Hospital in Bologna in the index periods defined as follows: the first period between February 24, 2020 and April 30, 2020 (first epidemic wave) and the second period between October 8, 2020, and January 7, 2021 (second pandemic wave). Absolute numbers and proportion of admitted patients, their sociodemographic and clinical-psychopathological characteristics were compared with the same parameters recorded in the two same periods of the previous 3 years. No strict inclusion or exclusion criteria were provided in the data collection to collect information on all patients requiring acute psychiatric hospitalization.RESULTSDuring the first wave, there was a significant reduction in hospitalization rates, although there was a simultaneous increase in compulsory hospitalizations and the acute relapse of schizophrenia spectrum and other psychotic disorders. During the second wave, hospitalization rates reached those recorded during the same period of the previous 3 years, mainly due to the rise of bipolar and related disorders, depressive disorders, anxiety disorders, trauma- and stressor-related disorders and suicidal behaviors.CONCLUSIONThe coping strategies adopted during the first wave of the SARS-CoV-2 pandemic protected the vulnerable population from the general risk of clinical-psychopathological acute relapse, even if they increased the susceptibility to run into schizophrenia spectrum and other psychotic disorder relapses. In the medium-long term (as in the second pandemic wave), the same strategies do not play protective roles against the stress associated with the pandemic and social restriction measures. Indeed, during the second wave of the SARS-CoV-2 pandemic, an increase in total hospitalization rate, suicidal behaviors and the incidence rate of bipolar and related disorders, depressive disorders, anxiety disorders, trauma- and stressor-related disorders was observed.     

Effect of paclitaxel administration on P wave duration and dispersion

Abstract. The prototypic taxane paclitaxel, which disrupts tubulin dynamics, has been widely used in the treatment of solid malignancies. However, it has been associated with adverse cardiac effects. Therefore, the effect of the paclitaxel infusion on P wave duration and dispersion (PWD) was investigated. Twelve-lead surface ECGs were recorded twice from 12 patients with breast, ovarian and non-small-cell lung carcinoma: one just before paclitaxel infusion and the other 1 hour after the end of the infusion. The changes in maximum (Pmax) and minimum P wave duration (Pmin) were measured manually and the difference between the two values was defined as PWD. The mean heart rate, Pmin, did not change after the infusion. However, Pmax, PWD and the average P wave duration significantly increased after infusion (122 ± 5 vs. 125 ± 5 p = 0.001 and 46 ± 7 vs. 53 ± 9 p = 0.03, 97 ± 5 vs. 101 ± 5ms p = 0.02 respectively). We found that paclitaxel infusion increased PWD and this may be a result of the drugs effect on cardiac autonomic modulation.     

Midlatency auditory-evoked responses: effect of scopolamine in the cat and implications for brain stem cholinergic mechanisms

The objective of this study has been to define the role of cholinergic mechanisms in the generation of "wave A," a middle latency auditory-evoked potential recorded as a positivity with a 20-25 ms peak latency from the vertex of conscious cats. Wave A and its generator system have particular significance as an experimental model of the human middle latency component "P1." Both the feline wave A and the human P1 are characterized by a long recovery cycle, disappearance during slow wave sleep, and reappearance during rapid eye movement (REM) sleep and during wakefulness. The orchestration of several phenomena of REM sleep are known to involve muscarinic cholinergic mechanisms in the brain stem. Therefore, middle latency auditory-evoked potentials were studied in awake cats before and after injection of a cholinergic antagonist, scopolamine. Wave A and the successive negative potential were abolished by scopolamine in a dose-dependent fashion. This effect occurred within 5-15 min and was spontaneously reversible within a few hours. Although individual subjects were differentially susceptible to lower doses of the drug, all six subjects in this study demonstrated a well-defined statistically significant response at higher doses of the drug. In addition, careful parametric baseline studies were performed in each cat to strengthen the evidentiary linkage between wave A as recorded from the vertex in these experiments and previous studies describing the origin and trajectory of wave A in the brainstem reticular formation and several regions of thalamus, including the intralaminar nuclei. Thus, we conclude that the production of wave A depends substantially on the postsynaptic activation of muscarinic cholinergic receptors whose cells of origin lie within the brainstem reticular formation.