Thalamic EEG Research Articles

Hemodynamics in hemorrhagic infarction--an experimental study.

Using the canine thalamic infarction model, hemodynamics, CO2 responses and thalamic EEG changes were studied in 7 dogs. Of the 7 animals, 4 showed hemorrhagic infarction and 3 did not, following recirculation after 6 hours of vascular occlusion. 1) The rCBF threshold for producing hemorrhagic infarction when recirculation following 6 hours of vascular occlusion was approximately 50% of the pre-occlusion level. 2) rCBF of the animals showing hemorrhagic infarction included hyperperfusion due to recirculation, and then fell to a level below the pre-occlusion level in a relatively short period. The CO2 response became disturbed both during occlusion and after release of occlusion. Thalamic EEG was nearly flat during vascular occlusion and recovery was not seen following recirculation. 3) rCBF of the animals not showing hemorrhagic infarction recovered rapidly to the pre-occlusion level due to recirculation. The CO2 response was somewhat disturbed during occlusion, but recovered following recirculation. Thalamic EEG was well preserved both during occlusion and after release.

Transition from spindles to generalized spike and wave discharges in the cat: Simultaneous single-cell recordings in cortex and thalamus

The relationships between the activity of the cortex and that of a “specific” (n. lateralis posterior, LP) and an intralaminar thalamic nucleus (n. centralis medialis, NCM) were studied in the cat during the transition from spontaneous spindles to generalized spike and wave (SW) discharge following i.m. penicillin injection. The EEG and extracellular single-unit activity were recorded in cortex and thalamus during the spindle stage and at different intervals after penicillin until well developed SW discharges were present. Computer-generated EEG averages and histograms of single-unit activity were triggered by either peaks of cortical or thalamic EEG transients or by cortical or thalamic action potentials. In agreement with previous observations, cortical neurons increasingly fired during the spindle wave as it was transformed into the “spike” of the SW complex, while a period of neuronal silence gradually developed as the “wave” of the SW complex emerged. Similar changes developed in the thalamus, particularly in LP, either concurrently with or more often after the onset of the changes in the cortex. Most neurons in NCM, continued to fire randomly even after well developed SWs and rhythmic neuronal discharges had developed in cortex and LP. Only 4 11 NCM neurons did ultimately exhibit a rhythmic firing pattern similar to that seen in the cortex and LP. The correlation between cortical and thalamic unit activity was low during spindles, but gradually increased during the development of SW discharges. These data confirm that the cortex is the leading element in the transition from spindles to SWs. Increasingly, in the course of this transition, cortical and thalamic neuronal firing becomes more intimately phase-locked. This mutual interrelationship appears to be more pronounced between cortex and “specific” than intralaminar thalamic nuclei.

Simultaneous recording of cortical and thalamic EEG and single neuron activity in the cat association system during spindles

Simultaneous recording of the EEG and single unit activity in cortex and thalamus shows that during spindles the cortical and thalamic EEGs within a given thalamocortical sector are highly correlated, but that the firing of only a fraction of cortical and thalamic neurons shows a close mutual correlation or exhibits a close relationship to the cortical and thalamic EEGs. Thus, only a fraction of thalamic and cortical neurons is involved in generating spindles. The synchronized activity of these neurons, even if some of it is subliminal for action potential discharge, suffices to produce a recordable EEG signal.

Wakefulness-sleep modulation of thalamic multiple unit activity and EEG in man

Quantitative changes in the number of EEG waves and MUA neuronal spikes of various thalamic nuclear groups were studied during steady and transitional wakefulness-sleep states in a group of patients with implanted electrodes, used as an electrophysiological procedure for the surgical treatment of unilateral tremor and rigidity. Thalamic nuclei included ventroposterolateral (VPL), ventrolateral (VL) and centromedian (CM). Steady-states included initial wakefulness (W1), slow wave sleep (SWS) I, II, IV and IIL, paradoxical sleep phasic (PSP) and tonic (PST) and final wakefulness (W2). Transitional states included transition from SWS to PSP (transition) and from sleep to W2 (arousal). 1. (1) There was a significant correlation in EEG and MUA between different thalamic nuclei simultaneously recorded in the same patient during different steady-states. 2. (2) Thalamic MUA significantly decreased from W to SWS, increased from SWS to PS and SWS to W2, while thalamic EEG significantly decreased from W to SWS, increased from SWS to W2 but was not significantly modified from SWS to PS, consecutive steady-state shifts. 3. (3) Thalamic MUA significantly decreased while EEG remained unchanged from PSP to PST consecutive steady-state shifts. 4. (4) Both thalamic MUA and EEG significantly decreased from SWS II to IIL while they were not systematically modified from W1 to W2 indirect steady-state shifts. 5. (5) Thalamic MUA significantly increased 1 sec before transition and arousal while EEG increased 5 sec after arousal and did not change during transition.

Re-evaluation of estrogen-induced cortical and thalamic paroxysmal EEG activity in the cat

Conjugated estrogens (Premarin), piperazine-esterone-sulfate (Ogen) and esterone-3-sulfate were applied bilaterally or unilaterally to sensory-motor cortex in locally anesthetized, paralyzed cats. All these agents (1–2% concentration) initiated paroxysmal activity characterized by 2–3 c/sec spike and wave discharge that was generalized bilaterally over cortex and in the nuclei ventralis anterior, medialis dorsalis and centrum medianum of thalamus. In contrast, unilateral micro-injection (2%, 0.01 cc) of conjugated estrogens into thalamic nuclei resulted in 7–20 c/sec poly-spike activity recorded bilaterally over cortex and in the contralateral thalamus. Spike and wave discharges were not observed following thalamic injection of estrogens. Ipsilateral electrolytic lesions of either ventralis anterior or centrum medianum failed to decrease spike and wave discharge originating from a cortical focus. In chronically-isolated slabs of suprasylvian cortex, topically applied conjugated estrogens induced 1–3 c/sec spike and wave activity restricted to the isolated tissue in the absence of spread of activity to surrounding intact cortex. In contrast to the estrogenic steroids, progesterone, testosterone and diethylstillbesterol failed to initiate paroxysmal activity after bilateral topical application in concentrations of 10% although the application of either testosterone or progesterone was associated with spindle formation in some animals. These findings demonstrate a capacity of cerebral cortex to generate spike and wave discharge in the absence of subcortical influences, a generalization of spike and wave discharge from a unilateral cortical focus and an epileptogenic specificity of estrogens. The experimental spike and wave complex produced by topically-applied estrogens is discussed in reference to the epileptiform EEG of clinical petit mal or petit mal variant.

Thalamic EEG recordings in patients with chronic pain.

Thalamic EEG recordings were made in 10 patients; the therapeutic goal of the implantation was the electrical stimulation treatment for pain. The patients' ages ranged from 37 to 72 years; seven patients had thalamic pain (Dejerine-Roussy syndrome), two had chronic spinal arachnoiditis and one had facial anaesthesia dolorosa. Platinum-iridium electrodes were stereotaxically inserted; the ventrobasal complex of the thalamus including the ventral posterior zone was the target of the implant. Excessive thalamic slowing was found in four of seven patients with Dejerine-Roussy syndrome and also in two of three cases with other causes of pain. One patient had marked rhythmical intermittent delta activity in the thalamus which was often triggered by arousing stimuli. Thalamic spindle activity was sometimes noted without concomitant spindle activity on the scalp and would occasionally occur in states of early drowsiness.

“Mittens” in Thalamic EEG Depth Recordings

“Mittens” in Thalamic EEG Depth Recordings

ELECTROENCEPHALOGRAPHIC STUDIES OF ANTIPYRETIC ANALGESICS: REPORT 2. THE EFFECT OF AMINOPYRINE ON THE RABBIT

The mechanism of action of the antipyretic drugs has been discussed from the point of view based mainly on the hypothalamic thermoregulatory center. Since the introduction of Mayer's classical theory (1), many authors (2-6) have attributed the site of action of the drugs to the hypothalamus and other basal nuclei from their extensive studies. In the previous paper the author has studied on the effects of aminopyrine on the electroencephalogram in cats (7). The results that the manifestation of the seizure discharge of the spontaneous EEG in cat in response to aminopyrine was preceded by the manifestation of the seizure discharge or spike waves of the hypothalamic and thalamic EEG have suggested the primary site of action of aminopyrine on the diffuse region of the anterior hypothalamus. However, the electrophysiological studies of aminopyrine by Fujita et al. (8, 9) have shown the diffuse dimensions of the site of action within the brain. The effects of aminopyrine shown by the authors, according to the general consideration, may include various aspects of the drug effects such as analgesic, antipyretic and other side effects as well as the secondary or rebound effects. In the current report attempts were made to differentiate the unique antipyretic effect of aminopyrine from the other effects either dependent or independent on the antipyresis by comparing the time course of the EEG changes. Moreover, the effects of aminopyrine on the EEG were also studied in the rabbit which had received the pyretic doses of 2, 4-dinitrophenol.

A STUDY OF SPONTANEOUS SPINDLE WAVES IN SENSORIMOTOR CORTEX OF CAT

A STUDY OF SPONTANEOUS SPINDLE WAVES IN SENSORIMOTOR CORTEX OF CAT