Tyrosine ameliorates heat induced delay in event related potential P300 and contingent negative variation

The efficacy of tyrosine, a catecholamine precursor, as a countermeasure in the reduction of cognitive decline during heat exposure (HE) using event-related potential P300, and contingent negative variation (CNV) was evaluated. Ten healthy males, age 20–30 years participated in the study. Volunteers received placebo or tyrosine (6.5 g) 90 min prior to HE (1.5 h in 45 °C + 30% RH). P300 latency was significantly increased (p < 0.01) during exposure with placebo, which was reduced significantly (p < 0.01) after tyrosine supplementation. There was an increase in CNV M100 latency (p < 0.05) and reaction time (p < 0.01) and decrease in M100 amplitude (p < 0.01) during HE with placebo, which returns to near normal level with the tyrosine administration. A significantly higher plasma norepinephrine (p < 0.05), dopamine and epinephrine levels were detected in tyrosine supplemented group post heat exposure. HE increases the brain catecholamine activity thereby reduces the plasma norepinephrine and dopamine level leading to a reduction in cognitive performances. Tyrosine supplementation increases the catecholamine level and reduces the impairment of cognitive performance during HE.     

The contingent negative variation laterality and dynamics in antisaccade task in normal and unmedicated schizophrenic subjects

Contingent negative variation (CNV) topography, hemispheric asymmetry and time-course were investigated in healthy subjects and non-medicated paranoid schizophrenic patients in two antisaccade paradigms with the short (800-1000 ms) and long (1200-1400 ms) durations of the fixation period. EEG and electrooculogram (EOG) were recorded. Saccade characteristics and mean amplitudes of slow cortical potentials time-locked to peripheral target were analyzed in 23 healthy volunteers and 19 schizophrenic patients. Compared to healthy control subjects, schizophrenic patients had significantly slower antisaccades and committed significantly more erroneous saccades in the both antisaccade tasks. The prolongation of the fixation period resulted in noticeable decrease of error percent in patients group. The analysis of CNV time-course has revealed two distinct stages in both groups. The early CNV stage was represented by a negative wave with the maximal amplitude over midline fronto-central area, and the late stage was characterized by increased CNV amplitude at the midline and left parietal electrode sites. In healthy subjects the simultaneous activation of frontal and parietal areas was observed in the paradigm with the shorter fixation interval; the increase of the fixation period produced consecutive activation of these areas. Schizophrenic patients' CNV amplitude was generally smaller than that of healthy subjects. The most pronounced between-group differences of the negative shift amplitude were revealed at frontal electrode sites during the early CNV stage in both modifications of the antisaccade task. The deficit of frontal activation revealed in patients at the early stage of antisaccade preparatory set in both antisaccadic paradigms may be related to pathogenesis of paranoid schizophrenia.     

Response speed, contingent negative variation and P300 in Alzheimer’s disease and MCI

Background

Decreased speed of information processing is a hallmark of Alzheimer’s disease (AD) and mild cognitive impairment (MCI). Recent studies suggest that response speed (RS) measures are very sensitive indicators of changes in longitudinal follow-up studies. Insight into the psycho-physiological underpinnings of slowed RS can be provided by measuring the associated event-related potentials (ERP).

Aims

The current study aims to investigate the relation between RS and its psycho-physiological correlates in AD and MCI.

Methods

Fifteen psychoactive drug-naïve AD patients, 20 MCI patients and twenty age-matched, healthy control subjects participated. Response speed was measured during a simple (SRT) and choice reaction time task (CRT). An oddball and contingent negative variation (CNV) paradigm were used to elicit ERP. To evaluate test-retest reliability (TRR), subjects underwent a similar assessment one week after the first.

Results

The SRT and CRT distinguished the patient groups significantly. The P300 amplitude and latency also distinguished the groups and showed a significant correlation with response speed. The CNV amplitude did not reveal a significant difference between groups and also showed a low TRR.The TRR of the SRT, CRT and P300 amplitude and latency in general was moderate to high.The current study suggests that response speed measures on a behavioural and psycho-physiological level deserve attention as a possible marker in the diagnosis and follow-up of AD.     

The anticipatory potential (contingent negative variation) as an indicator of neuronal information processing in relation to changes in slow potentials in the EEG

The aim of this study was to investigate the interaction between spontaneous Slow Potential Shifts (SPSs) and the probability effect on CNV amplitudes. Fifteen right-handed volunteers participated in this experiment. The presentation of the stimuli was triggered by spontaneous SPSs (duration: 2 seconds, mean-amplitude: 10 microV) in the EEG signal at Cz. Thus, two different S1s (S1a: 1500 Hz, S1b: 2000 Hz) were presented in a random order with a fixed probability of occurrence of 0.8 for S1a and 0.2 for S1b. Each S1 was followed by a light stimulus (S2) with a constant ISI of 4 seconds. According to the cue, the subjects had to push the left (S1a) or the right (S1b) response button as fast as possible with their right index finger. The order of the 4 experimental conditions (stimulus presentation triggered by negative or positive shifts and recording of negative or positive shifts without any stimuli) in which each subject participated was balanced across subjects. Several significant effects could be found by means of a two-way ANOVA for repeated measures (condition x recording site): Negative shifts were accompanied by smaller CNVs as well as PINVs (resolution deficits) at all recording sites; the probability effect was found to be significant in the positive shift condition at F3, F4, and Cz, but not in the negative shift condition except at Cz for the E-wave. CNVs triggered by negative shifts only showed a significant correlation (-.55) with reaction time. These results together favor a two-component model suggesting that SPSs, spontaneous and evoked, are largely generated by glia depolarization, which is evoked by but outlasts neuronal activity.     

Effects of positive and negative verbal reinforcement on performance as a function of extraversion-introversion: Some tests of Gray's theory

Matched groups of extraverts and introverts performed under positive or negative verbal reinforcement in: (1) a computer game involving initiation of cursor movements on a VDU to find a hidden target; (2) a task involving recoding of decimal numbers into, and performing calculations in, a base-6 arithmetic with the letters A–F representing the decimal digits 1–6. In both tasks, consistent with the predictions from Gray's theory, there was a complete absence of main effects distinguishing between either type of personality or type of reinforcement. However, there was a highly significant interaction between these variables; extraverts performed better under positive than negative reinforcement, whilst introverts performed better under negative than positive reinforcement. Whilst the results appear to support Gray's theory that extraverts are differentiated from introverts by a reversal in the balance between the sensitivities of the behavioural activation (BAS) and behavioural inhibition systems (BIS), the covert nature of cognitive operations carried out in the experimental tasks precludes unequivocal attribution of superior task performance in negatively reinforced introverts to the accentuated excitation of the BIS.     

关联负变化(CNV)与反应时的关系

本实验采用选择性叠加方法,研究了关联负变化(Contingent NegativVariation以下简称CNV)与反应时的关系。证明:最长、最短反应时差异显著时,相对应的CNV面积差异也显著。CNV的这种差异主要表现在CNV面积的后半部分。对形成这种现象的原因作了讨论。     

Study habits and Eysenck's theory of extraversion-introversion

Predictions derived from Eysenck's theory of personality were tested in two samples by relating extraversion scores to library study locations, frequency of study breaks, and self-report of factors which influence study location. The predicted main effects for study location were found, with extraverts occupying locations that provided greater external stimulation. Positive correlations were consistently found between extraversion and preferred level of noise, preferred level of socializing opportunities, and rated importance of socializing opportunities. The prediction that extraverts would take more frequent study breaks was supported in Sample 1 but not replicated in Sample 2. The data are interpreted as providing direct support for Eysenck's theory of behavioral differences and mixed indirect support for his theory of neurological differences between introverts and extraverts.     

Chimpanzee (Pan troglodytes) intentional communication is not contingent upon food

Studies of great apes have revealed that they use manual gestures and other signals to communicate about distal objects. There is also evidence that chimpanzees modify the types of communicative signals they use depending on the attentional state of a human communicative partner. The majority of previous studies have involved chimpanzees requesting food items from a human experimenter. Here, these same communicative behaviors are reported in chimpanzees requesting a tool from a human observer. In this study, captive chimpanzees were found to gesture, vocalize, and display more often when the experimenter had a tool than when she did not. It was also found that chimpanzees responded differentially based on the attentional state of a human experimenter, and when given the wrong tool persisted in their communicative efforts. Implications for the referential and intentional nature of chimpanzee communicative signaling are discussed.     

Chimpanzees (Pan troglodytes) do not develop contingent reciprocity in an experimental task

Chimpanzees provide help to unrelated individuals in a broad range of situations. The pattern of helping within pairs suggests that contingent reciprocity may have been an important mechanism in the evolution of altruism in chimpanzees. However, correlational analyses of the cumulative pattern of interactions over time do not demonstrate that helping is contingent upon previous acts of altruism, as required by the theory of reciprocal altruism. Experimental studies provide a controlled approach to examine the importance of contingency in helping interactions. In this study, we evaluated whether chimpanzees would be more likely to provide food to a social partner from their home group if their partner had previously provided food for them. The chimpanzees manipulated a barpull apparatus in which actors could deliver rewards either to themselves and their partners or only to themselves. Our findings indicate that the chimpanzees’ responses were not consistently influenced by the behavior of their partners in previous rounds. Only one of the 11 dyads that we tested demonstrated positive reciprocity. We conclude that contingent reciprocity does not spontaneously arise in experimental settings, despite the fact that patterns of behavior in the field indicate that individuals cooperate preferentially with reciprocating partners.     

Threats may be negative promises (but warnings are more than negative tips)

In everyday situations conditional promises, threats, tips, and warnings are commonplace. Previous research has reported disruption to eye movements during reading when conditional promises are produced by someone who does not have control over the conditional outcome event, but no such disruption for the processing of conditional tips. In the present paper, we examine how readers process conditional threats and warnings. We compare one account which views conditional threats and warnings simply as promises and tips with negative outcomes, with an alternative account which highlights their broader pragmatic differences. In an eye-tracking experiment we find evidence suggesting that, in processing terms, while threats operate like negative promises, warnings are more than negative tips.     

Religion as a source of variation in the experience of positive and negative emotions

In a series of three studies, we examined the ways in which religion informs the individual experience and valuation of emotions. In Study 1, Christian, Muslim, Hindu, Buddhist and Jewish participants (N = 7231) in 49 nations reported the frequency with which they experienced nine discrete emotions. Results indicate group level differences in the frequency with which different emotions are experienced. Study 2 examined whether the patterns of emotional experiences found in Study 1 replicated in the valuation of those emotions by the adherents of those different religious traditions. Study 3 experimentally manipulated the salience of religious identity to examine the effect of religion on the current experience of emotions. Across the studies, findings provide evidence that religion (e.g., Christianity, Buddhism, etc) is related to the experience of, and beliefs about, emotional states. Implications for the study of happiness and positive psychology are discussed in light of the findings.     

Persistence of simple and contingent motion aftereffects

Jones and Holding (1975) showed that orientation-contingent color aftereffects can persist for at least 3 months, but are depleted by repeated testing. We applied the same paradigm to a simple motion aftereffect (MAE) and found that it can persist for up to 1week and is only slightly diminished by testing. It was further found that simple MAEs appear to persist longer than color-contingent MAEs, although when procedures for inducing and measuring both kinds of aftereffect are equalized, contingent MAEs last longer. Finally, no tendency was found for color-contingent MAEs to diminish with repeated testing. Although both simple and color-contingent MAEs can be relatively persistent, there are certain differences between them. Furthermore, contingent aftereffects should not be considered interchangeable, as there appear to be large differences in the persistence of orientation-contingent color aftereffect and color-contingent MAEs.     

Discriminative activation and maintenance of contingent self-reinforcement

The present experiment studied the process by which environmental events come to exercise some degree of control over the activation of contingent self-reinforcement. Through differential training, animals learned to impose performance requirements for self-reward in certain environmental contexts but not in others. Both contextual influences and periodic negative consequences for noncontingent self-reward increased adherence to response requisites for self-reinforcement.