Imaging of hippocampal and neocortical neural activity following intravenous cocaine administration in freely behaving cats

We examined spatial-temporal patterns of neural activity, as inferred from 700 nm light reflectance, from the dorsal hippocampus and surrounding neocortex in seven freely behaving cats following 1.5, 2.5, 3.5 and 5.0 mg/kg intravenous cocaine administration. Images were acquired using a new technique which gathered reflected light from cortical and subcortical structures. Cardiac and respiratory patterning, collected simultaneously with optical images, revealed increased rates and diminished variation after intravenous cocaine administration. Cocaine increased reflectance correlates of hippocampal neural activity in a dose-dependent fashion over a 120 min period, with a lengthening time-to-peak effect (22-76 min). The largest dose resulted in an initial decrease, followed by the greatest enhancement in neuronal activity. Correlates of neural activation in the neocortex displayed an inverse dose-response curve to that found in the hippocampus; the time-to-peak effect was shorter (6-43 min) and the maximal change was reduced. Regional patches and bands of activation occurred during the period of the cocaine response, and were more pronounced in the hippocampus than the neocortex. Procaine, administered in a similar dose, slightly increased neural activity for 10 min in both the hippocampus and neocortex, and elicited a small increase in respiration. Cocaine induces a pronounced enhancement of neural activation in the neocortex and dorsal hippocampus; the time course of activation in the hippocampus parallels an increased respiratory pattern and outlasts the neocortical response. We speculate that hippocampal activation may be related to the profound respiratory acceleration found in response to cocaine.     

Contralateral evoked brainstem auditory potentials as an indicator of intraoperative brainstem manipulation in cerebellopontine angle tumors

Brainstem auditory evoked potentials (BAEP) were studied during operations to remove acoustic tumors using the retromastoid approach. BAEP were elicited from the side contralateral to the tumor, and changes in the latencies of peaks III and V of the BAEP were compared with changes in cardiovascular parameters throughout the operation. When the changes in the determined cardiovascular parameters were related to surgical manipulations, the related changes in the latencies of peaks III and V of the BAEP were more consistent than the changes in the cardiovascular parameters and they tended to occur earlier than the changes noted in the cardiovascular parameters.     

3-Methoxytyramine as an indicator of impulse-induced dopamine release in rat brain in vivo

Autotransfusions were performed in 80 patients operated upon for thyroid diseases at the Department of Surgery, Institute of Haematology in Warsaw. For autotransfusions patients were selected in good general condition and with haematological indices in the range accepted for blood donors. Planning of autotransfusion is purposeful only in these cases of thyroid disease in which the necessity of blood transfusion can be predicted in advance (e.g. Graves-Basedov-disease, retrosternal goitre, mediastinal goitre). The transfused volume may cover completely or partly the intraoperative blood loss. Autotransfusion protects the patients against possible isoimmunization which may develop after transfusion of blood from donors. Protection of patients against possible immunization is a problem of considerable value. It is important particularly in young subjects, especially young women who may become mothers. Operations connected with blood loss up to 500 ml do not require supplementary transfusions. Intraoperative blood loss in the range from 500 to 1000 ml requires supplementation. The risk of posttransfusion complications is lowest when autotransfusion is done.     

Involvement of brain serotonergic function in lidocaine-induced convulsions in mice

Influences of drug-induced manipulations of central serotonergic function on lidocaine- and pentylenetetrazol (PTZ)-induced convulsions were examined in mice. Agents that suppressed serotonergic transmission increased, whereas drugs that facilitated serotonin (5-HT) function decreased the incidence of lidocaine-induced convulsions. These treatments had similar influences on the incidence of PTZ-induced convulsions. Lidocaine (10(-5)-10(-3) M) reduced the stimulation evoked [3H]5-HT release from cortical slices, followed with an increased spontaneous [3H] overflow at higher concentrations. These results may suggest that brain 5-HT neurons are causally involved as inhibitory neurons in lidocaine-induced convulsions as in the case of PTZ-induced convulsions.     

Effects of corticotropin-releasing factor on brain serotonergic activity

The serotonergic dorsal raphe nucleus is innervated by corticotropin-releasing factor (CRF) and expresses CRF receptors, suggesting that endogenous CRF impacts on this system. The present study characterized interactions between CRF and the dorsal raphe serotonin (5-HT) system. The effects of intracerebroventricularly (i.c.v.) administered CRF on microdialysate concentrations of 5-HT in the lateral striatum of freely moving rats were determined. CRF had biphasic effects, with 0.1 and 0.3 microgram decreasing, and 3.0 micrograms increasing 5-HT dialysate concentrations. i.c.v. administration of CRF inhibited neuronal activity of the majority of dorsal raphe neurons at both low (0.3 microgram) and high (3 micrograms) doses. Likewise, intraraphe administration of CRF (0.3 and 1.0 ng) had predominantly inhibitory effects on discharge rate. Together, these results suggest that CRF is positioned to regulate the function of the dorsal raphe serotonergic system via actions within the cell body region. This regulation may play a role in stress-related psychiatric disorders in which 5-HT has been implicated.     

Interpretation bias in social anxiety as detected by event-related brain potentials.

Little is known about psychophysiological correlates of interpretation bias in social anxiety. To address this issue, the authors measured event-related brain potentials (ERPs) in high and low socially anxious individuals during a task wherein ambiguous scenarios were resolved with either a positive or negative ending. Specifically, the authors examined modulations of the P600, an ERP that peaks approximately 600 ms following stimulus onset and indexes violations of expectancy. Low-anxious individuals were characterized by an increased P600 to negative in comparison with positive sentence endings, suggesting a positive interpretation bias. In contrast, the high-anxious group evidenced equivalent P600 magnitude for negative and positive sentence endings, suggesting a lack of positive interpretation bias. Similar, but less reliable results emerged in earlier time windows, that is, 200-500 ms poststimulus. Reaction time, occurring around 900 ms poststimulus, failed to show a reliable interpretation bias. Results suggest that ERPs can detect interpretation biases in social anxiety before the emission of behavioral responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pharmacological evidence for the central serotonergic effects of monomethoxyamphetamines

The effects of three monomethoxyamphetamines, dl-para-methoxyamphetamine (dl-PMA), dl-meta-methoxyamphetamine (dl-MMA) and dl-ortho-methyoxyamphetamine (dl-OMA), and d-amphetamine (d-A) on the myoclonic twitch activity (MTA) of PMA, MMA and d-A were found to increase the MTA but OMA was ineffective. The increased MTA induced by d-A was not influenced by the blockade of 5-hydroxytryptamine (5-HT) receptor by methysergide or inhibition of 5-HT synthesis by para chlorophenylalamine (PCPA) but was reduced by haloperidol which blocked the dopamine receptor. On the other hand, the increased MTA produced by PMA was not influenced by haloperidol but was reduced by methysergide and PCPA. The increased MTA induced by MMA was not effectively blocked by either PCPA or haloperidol but was blocked by the combination of both PCPA and haloperidol. The results indicate that whereas the increased MTA produced by d-A is not dependent on the availability of 5-HT, PMA exerts by a release of 5-HT and that the MMA effect is due to a release of both 5-HT and dopamine. High doses of PMA and MMA increased the locomotor activity arevious biochemical findings that PMA releases 5-HT in brain tissue and suggests that PMA exerts its pharmacological effects by releasing 5-HT.     

Response preparation begins before mental rotation is finished: evidence from event-related brain potentials

Behavioral data (response time (RT) and accuracy) and psychophysiological data (event-related brain potentials of ERPs, and lateralized readiness potential or LRP) were studied in an experiment in which rotated alphanumeric characters were presented normally or mirror-reversed. In half of the trials, character classification (letter versus digit) determined whether or not the response was to be executed (go versus nogo) and parity determined the responding hand. In the other half, classification determined the responding hand and parity determined go versus nogo. LRP data indicated that response preparation occurred before mental rotation was finished. These data contradict strictly sequential discrete models of information processing and suggest continuous flow of information.     

The validity of a visual searching task as an indicator of brain damage.

Required 17 brain-damaged patients, 17 non-brain-damaged psychiatric patients, and 17 nonpatient normal controls to perform a visual search. The task discriminated among the Ss at a statistically significant level. Using an optimal cut-off point, the task was 94.1% accurate in differentiating between brain-damaged and normal Ss and 79.4% accurate in differentiating between psychiatric and brain-damaged Ss. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social interactions in cats: regional brain monoamine distribution in dominant and submissive cats

Immunological memory has been ascribed to the presence of long-lived memory cells. The mechanisms underlying their generation are not completely understood, but dependence on antigen persistence has been discussed in this regard. However, in spite of in vivo evidence favoring this model, studies on TCR/CD3 stimulation of T cell lines or unseparated peripheral blood T cell in vitro have failed to demonstrate prolonged survival of preactivated cells. We have examined the dose-dependent effect of TCR/CD3 engagement mimicked by immobilized anti-CD3 antibody. To this end, well-defined populations of CD4+ and CD8+ lymphoblasts isolated from bulk cultures of preactivated PBMCs by flow sorting were examined. These cells were restimulated with immobilized anti-CD3 in the presence or absence of various costimulatory factors, and were analyzed for their viability state, as well as their apoptotic and proliferative behavior. We have shown that inhibition of apoptosis following CD3 stimulation occurs at submitogenic concentrations, while activation-driven apoptosis requires high-density TCR/CD3 activation. Prevention of apoptosis by submitogenic CD3 stimulation was, however, observed only when CD4+ but not when CD8+ cells were investigated, and was not readily influenced by other costimulatory factors present in cultures. This observation points to the importance of antigen persistence in regulating survival of memory CD4+ but not CD8+ cells.     

Neural correlates of depth of processing effects on recollection: evidence from brain potentials and positron emission tomography

The probability that words would be recollected during tests of recognition memory was varied by manipulating depth of processing at study. Experiment 1 employed scalp-recorded event-related potentials (ERPs), and identified as a correlate of recollection a late (onset c. 500 ms), strongly left-lateralized positive-going modulation of the ERP waveform. The findings from experiment 2, which employed positron emission tomography (PET), indicated that recollection was associated with activation of the left hippocampal formation together with an extensive region of left temporal and frontal cortex. The findings support current ideas about the role of the hippocampal formation in episodic memory retrieval, and provide complementary information about the time course and localization of the cortical correlates of the recollection of recently experienced words.     

Lasting cytotoxic edema as an indicator of irreversible brain damage: a case of neonatal stroke

We describe a case of neonatal stroke in the territory of the left middle cerebral artery. Although the ischemic lesion appeared rather homogeneously hyperintense on T2-weighted MR images, corresponding diffusion-weighted images clearly delineated two separate zones of different cellular swelling and, thus, different prognoses. Lasting cytotoxic edema heralded infarction. We believe that the different rates of disintegration of neurons and glial cells may have caused the change from intracellular to interstitial volume fraction during the evolution of edema.     

Monoamine changes in the brain of cats during slow-wave sleep

We have found that the metabolism of 5-hydroxytryptamine increases in the hippocampus and that the metabolism of dopamine decreases in the striatum and thalamus during slow-wave sleep, and we suggest that these changes are related to this stage of sleep. We have also found that the concentration of dopamine increases in the hippocampus during slow-wave sleep, and suggest that this may be related to the subsequent appearance of paradoxical sleep. These data raise new questions on the hippocampal role in the sleep-wakefulness cycle.     

The time course of brain activations during response inhibition: evidence from event-related potentials in a go/no go task

The cortical organization of executive control was investigated using event-related potentials (ERPs). ERPs were collected while subjects performed a go/no go task that required response inhibition. First, around 260 ms after stimulus onset, an effect of response inhibition on ERPs was observed over inferior prefrontal areas. Generators in these regions were confirmed by source analysis. Later, between 300-600 ms after stimulus onset, a left lateralized fronto-central ERP effect was found which differed in topography from a non-specific effect of task difficulty. Source analysis indicated that generators in anterior cingulate and left premotor areas also contributed to this effect. Orchestrated activation of prefrontal areas and the anterior cingulate subserves executive function whereas relatively late activity of the left premotor cortex is involved in motor control.     

Effect of atropine on intracortical evoked potentials during classical aversive conditioning in cats.

In this article, intracortical evoked potentials (EPs) were recorded simultaneously from six different depths of the auditory cortex of freely moving cats. The effect of (a) different states of vigilance and that of atropine, (b) classical aversive conditioning, and (c) the effect of atropine during conditioning was studied on the intracortical EP profiles. Atropine induced EP changes that were similar to those seen in slow wave sleep. During classical aversive conditioning signal stimuli elicited a middle-latency negative EP component which was localized to the superficial cortical layers. Atropine (2 mg/kg body weight) did not abolish the appearance of this component but only increased its latency. It is proposed that the cholinergic part of the ascending activating system did not play an essential role in its generation. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Event-related brain potentials and case information in syntactic ambiguities

In an ERP study, German sentences were investigated that contain a case-ambiguous NP that may be assigned accusative or dative case. Sentences were disambiguated by the verb in final position of the sentence. As our data show, sentences ending in a verb that assigns dative case to the ambiguous NP elicit a clear garden-path effect. The garden-path effect was indicated by a broad centro-posterior negative shift that occurred between 300 and 900 msec after the dative-assigning verb was presented. No enhanced P600 following the misanalysis was observed. Noun phrases whose case ambiguity was resolved in favor of accusative case and unambiguously dative-marked NPs did not trigger significant ERP differences. We will discuss the implications of our results for parsing and its neuropsychological correlates. The results of this study support a parser design according to which the so-called structural case (nominative or accusative) is assigned without any delay in the absence of morpho-lexical counterevidence. It is argued that the enhancement of a negative ERP component with a "classical" N400 topography reflects the difficulty of reanalysis due to reaccessing morpho-lexical information that lies outside the domain of the parsing module. Consequently, ERP responses to garden-path effects are not confined to a late positivity but vary depending on the level of processing involved in reanalysis. The fact that garden-path effects may also elicit an N400 can be linked to the nonhomogeneous linguistic properties of the constructions from which they arise.     

A spatio-temporal analysis of recognition-related event-related brain potentials

Words correctly recognized as previously studied (i.e. old) elicit greater amounts of positive event-related brain potential (ERP) activity over posterior scalp between 400 and 800 ms than do previously unstudied (i.e. new) words. While investigators have reported that this old/new effect consists of more than one subcomponent, the spatio-temporal parameters of these possible subcomponents, as well as any other patterns of brain activity associated with recognition, remain incompletely specified. Thus, ERPs were recorded from 32 scalp sites while 13 subjects performed four repetitions of a study-test recognition paradigm. The subjects' task was to decide whether each word was old or new and press the appropriate button as quickly as possible. The timing and topography of the ERPs elicited by old and new words was assessed with topographic profile comparisons on the areas with a variety of temporal windows, and visualized with potential and CSD maps. The results revealed that seven patterns of ERP activity, dissociable on the basis of their topography, timing and response to experimental variables, were elicited between 300 and 2000 ms. Three of these appeared as subcomponents of the old/new effect (maximal over left medial frontal, left parietal-occipital and right central-frontal scalp), another was related to decision confidence and/or memory trace strength (maximal over left central scalp) and three others appeared to be related to more general aspects of recognition (maximal over the frontal poles, midline frontal scalp and right frontal scalp). Taken together, the seven distinct patterns of neural generator activity described here support the hypothesis that retrieval of information from episodic memory depends on a collection of different processes that occur in a temporally and spatially distributed neural circuit.