Sequence-related changes in sensory-evoked potentials in the dentate gyrus: a mechanism for item-specific short-term information storage in the hippocampus

Sensory-evoked potentials were recorded from the dentate gyrus of the rat hippocampus during performance of a differential auditory discrimination task. The short latency (20 ms) component (N1) of the sensory-evoked potential showed systematic amplitude fluctuations dependent upon the sequence of positive and negative trials preceding the presentation of a given trial and did not depend on the associated reward values of the individual tone stimuli which evoked the potential. The amplitude fluctuations could be accurately depicted by a model which retained the sequence for the five preceding trials in a "buffer" with exponentially decaying influence as a function of time of trial occurrence within the sequence. The results provide evidence that the hippocampus encodes accurate short-lasting representations of sensory events which can provide the basis for storage of information pertaining to past experiences.     

Practice evoking the flexor carpi radialis h-reflex: a guideline for proficiency

The purpose of this research was to identify the number of sessions required for a new investigator to become proficient at evoking an H-reflex in the flexor carpi radialis (FCR), in comparison to an experienced investigator. 31 students from Brock University in the greater Niagara region (16 women M age = 32.2, SD = 8.9 yr.; 15 men M age = 27.8, SD = 7.8 yr.) with no known neurological disorders volunteered and completed two test sessions performed by either an experienced or a novice investigator. In randomized order, both investigators stimulated each subject's median nerve 10 times, once every 15 sec. Each session included the measurement of the subject's flexor carpi radialis maximal M-wave amplitude and H-reflex amplitude and latency with surface electromyographic electrodes. The intraclass correlation coefficients (ICC) indicated an adequate correlation between investigators for both M-wave maximal amplitude and H-reflex at 5% of the M-wave maximal amplitude (.84 and .70, respectively). However, there was a low correlation (.38) between the latency values obtained by the two investigators. The peak-to-peak amplitudes of the H-reflex and M-wave do not appear to be influenced by experience of the tester. The latency of the response, however, appears to have an associated learning curve, improving in consistency with increasing practice of tester.     

Brainstem frequency-following response recorded from one vertical and three horizontal electrode derivations

The human brainstem frequency-following response reflects neural activity to periodic auditory stimuli. Responses were simultaneously recorded from one vertically oriented and three horizontally oriented electrode derivations. Nine participants each received a total of 16,000 tone repetitions, 4,000 for each of four stimulus frequencies: 222, 266, 350, and 450 Hz. The responses were digitally filtered, quantified by correlation and spectral analysis, and statistically evaluated by repeated measure analysis of variance. While the various horizontal derivation responses did not differ from each other in latency (values tightly clustered around M= 2.60 msec.), the vertical derivation response occurred significantly later (M=4.38 msec.). The smaller latency for the horizontal responses suggests an origin within the acoustic nerve, while the larger latency for the vertical response suggests a central brainstem origin. The largest response amplitude resulted from gold "tiptrode" electrodes placed in each auditory meatus, suggesting that this electrode derivation provided the most accurate (noninvasive) assessment of short-latency events originating at the level of the auditory nerve.     

A steady state visually evoked potential investigation of memory and ageing

Old age is generally accompanied by a decline in memory performance. Specifically, neuroimaging and electrophysiological studies have revealed that there are age-related changes in the neural correlates of episodic and working memory. This study investigated age-associated changes in the steady state visually evoked potential (SSVEP) amplitude and latency associated with memory performance. Participants were 15 older (59–67 years) and 14 younger (20–30 years) adults who performed an object working memory (OWM) task and a contextual recognition memory (CRM) task, whilst the SSVEP was recorded from 64 electrode sites. Retention of a single object in the low demand OWM task was characterised by smaller frontal SSVEP amplitude and latency differences in older adults than in younger adults, indicative of an age-associated reduction in neural processes. Recognition of visual images in the more difficult CRM task was accompanied by larger, more sustained SSVEP amplitude and latency decreases over temporal parietal regions in older adults. In contrast, the more transient, frontally mediated pattern of activity demonstrated by younger adults suggests that younger and older adults utilize different neural resources to perform recognition judgements. The results provide support for compensatory processes in the aging brain; at lower task demands, older adults demonstrate reduced neural activity, whereas at greater task demands neural activity is increased.     

Long latency auditory evoked potentials

Experiment 1 elicited the P1, N1, P2, and N2 components of the long latency auditory evoked potential (AEP) using a 1000 Hz tone presented at 30, 50, or 70 dB SPL and 1-, 3-, or 5- second inter-stimulus intervals to assess the relative effects of the combination of these variables on component amplitude and latency. Four blocks of 16 tone presentations each were recorded from each subject to determine if changes in the AEP would occur because of short-term habituation. Both stimulus factors interacted significantly in a systematic fashion for the amplitude measures, with increases in latency also associated with increases in intensity and inter-stimulus interval. Only minor changes across the four trial blocks for either the amplitude or latency measures were observed over the various stimulus presentation conditions. Experiment 2 employed the same tone stimulus presented at 50 dB SPL and a 3-second inter-stimulus interval. Eight blocks of 64 trials were recorded from each subject on each day for four days to investigate long-term habituation effects. No substantial changes in any of the component amplitudes or latencies were obtained across the 32 trial blocks. It was concluded that intensity and inter-stimulus interval interact to determine AEP amplitude as well as latency values and that the constituent components do not change appreciably with repeated stimulus presentations, even after several days.     

Evoked potentials in cat auditory nerve: Suppression by prior tonal stimulation

Action potentials (AP) recorded from the eighth nerve of a cat to a tone pip, S₁, were suppressed when preceded by a monotic or dichotic conditioning tone, Tc. The suppression increased when (1) the interval between Tc and S1 was decreased, (2) either the intensity or the duration of Tc was increased, or (3) the difference in frequency between the two stimuli was reduced. Thus the nerve action potential amplitude correlates strongly, but inversely, with the loudness enhancement effects seen in man (Galambos, Bauer, Picton, Squires & Squires,Journal of the Acoustical Society of America, 1972, 52). Since Coats and Dickey (Journal of the Acoustical Society of America, 1972, 52) found that the human AP can be diminished by a preceding noise without reducing the loudness of a click, the available results suggest that a central mechanism functions to compensate for the reduction in AP amplitude. The dichotic effects could be accounted for by cross-hearing, thereby providing no evidence for a role of the olivocochlear bundle in the effects observed.

     

智力与心理速度的关系研究述评

目前在智力研究领域出现了一种新的研究趋势,研究者开始关注心理计量学智力与认知或生理心理学变量的相关,考察的重点是心理速度,相应的测量指标主要有检测时（IT）、反应时、ERP或神经传导速度,等等。在运用IT任务进行的ERP研究中发现,ERP波幅和潜伏期的不同往往能够反映出智力上的差异。信息加工速度和神经传导速度均与一般智力因素（g因素）存在较高的相关。上述研究发现促进了智力与心理速度关系的跨学科研究,成为智力研究领域中的热点     

内隐自尊的ERP研究

研究使用GNAT范式对内隐自尊的ERP进行研究。结果发现：在自我-积极与自我-消极的感受性指标（d’）和反应时上存在显著差异;他人-积极与他人-消极的差异仅在d＇上;自我-积极与自我-消极的P3在潜伏期和振幅上存在显著差异;他人-积极与他人-消极的P3之间的差异仅表现在潜伏期上。     

Effects of caffeine on the trigeminal blink reflex

The acoustic startle and trigeminal blink reflexes share the same motor output. Since caffeine has been shown to augment the startle reflex, it was proposed that caffeine would also increase the trigeminal blink reflex. In 6 humans, the effects of caffeine (100 mg) on the trigeminal blink reflex were investigated. Reflex blinks were elicited by stimulation of the supraorbital branch of the trigeminal nerve. Following ingestion of caffeinated coffee, reflex blinks increased in amplitude and duration and occurred at a shorter latency than reflex blinks following ingestion of decaffeinated coffee. Since the blink reflex is a brainstem reflex, these results suggest that the psychomotor effects of caffeine facilitate brainstem processing.     

P3 event-related potentials and childhood maltreatment in successful and unsuccessful psychopaths

Although P3 event-related potential abnormalities have been found in psychopathic individuals, it is unknown whether successful (uncaught) psychopaths and unsuccessful (caught) psychopaths show similar deficits. In this study, P3 amplitude and latency were assessed from a community sample of 121 male adults using an auditory three-stimulus oddball task. Psychopathy was assessed using the Psychopathy Checklist-Revised (Hare, 2003) while childhood physical maltreatment was assessed using the Conflict Tactic Scale (Straus, 1979). Results revealed that compared to normal controls, unsuccessful psychopaths showed reduced parietal P3 amplitudes to target stimuli and reported experienced more physical abuse in childhood. In contrast, successful psychopaths exhibited larger parietal P3 amplitude and shorter frontal P3 latency to irrelevant nontarget stimuli than unsuccessful psychopaths. This is the first report of electrophysiological processing differences between successful and unsuccessful psychopaths, possibly indicating neurocognitive and psychosocial distinctions between these two subtypes of psychopathy.     

Inhibition of return from stimulus to response

In a standard inhibition-of-return (IOR) paradigm using a manual key-press response, we examined the effect of IOR both on the amplitude of early sensory event-related brain potential (ERP) components and on the motor-related lateralized readiness potential (LRP). IOR was associated with a delay of premotor processes (target-locked LRP latency) and reduced sensory ERP activity. No effect of IOR was found on motor processes (response-locked LRP latency). Thus, IOR must arise at least in part from changes in perceptual processes, and, at least when measured with manual key presses, IOR does not arise from inhibition of motor processes. These results are consistent with the results of attention-orienting studies and provide support for an inhibition-of-attention explanation for IOR.     

Behavioral and electrophysiological evidence of species-specific face processing

Several recent reports suggest that the behavioral and cortical specificity of face processing may be influenced by experience. To test this hypothesis, behavioral and electrophysiological data were recorded from adults in response to human and monkey faces differing in familiarity and orientation. An analysis of event-related potential and behavioral data revealed differentiation across species, familiarity, and orientation. Behavioral measures were correlated with amplitude and latency measures for each factor of interest. These analyses revealed that accuracy was positively related to the amplitude of the vertex positive potential in the human face task but not in the monkey face task. These findings suggest that previous experience with different categories of faces modulates the link between behavioral and electrophysiological measures of face processing.     

Event-related brain potentials and subjective probability in a learning task

In a paired associate learning task, subjects responded to each presentation of a nonsense syllable by typing both a three-letter associate and a rating of their confidence that this response was correct or incorrect. Average event-related potentials (ERPs) elicited by the subsequent presentation of the actual paired syllable varied with the interaction of confidence and trial outcome. A larger amplitude P300 was elicited by syllables that informed subjects that they were correct when they thought they were incorrect or that they were incorrect when they thought they were correct than by syllables that confirmed subjects expectations. That this average ERP result was indeed an effect on P300 amplitude, and not an artifact of single-trial variability in P30O latency, was confirmed with a trial-by-trial latency adjustment procedure. Consistent with findings from other tasks, P300 amplitude varied inversely with the subj ective probability of the ERP-eliciting events.     

Concurrent deployment of visual attention and response selection bottleneck in a dual-task: Electrophysiological and behavioural evidence

Visual attention and response selection are limited in capacity. Here, we investigated whether visual attention requires the same bottleneck mechanism as response selection in a dual-task of the psychological refractory period (PRP) paradigm. The dual-task consisted of an auditory two-choice discrimination Task 1 and a conjunction search Task 2, which were presented at variable temporal intervals (stimulus onset asynchrony, SOA). In conjunction search, visual attention is required to select items and to bind their features resulting in a serial search process around the items in the search display (i.e., set size). We measured the reaction time of the visual search task (RT2) and the N2pc, an event-related potential (ERP), which reflects lateralized visual attention processes. If the response selection processes in Task 1 influence the visual attention processes in Task 2, N2pc latency and amplitude would be delayed and attenuated at short SOA compared to long SOA. The results, however, showed that latency and amplitude were independent of SOA, indicating that visual attention was concurrently deployed to response selection. Moreover, the RT2 analysis revealed an underadditive interaction of SOA and set size. We concluded that visual attention does not require the same bottleneck mechanism as response selection in dual-tasks.     

Extraversion and the effects of frequency and intensity on the auditory brainstem evoked response

Extraversion was positively correlated with the latency of wave I of the auditory brainstem evoked response (BER) at 75, 80 and 85 dB of intensity. Extraverts also tended to display longer latency for wave V than introverts to high frequency, 80-dB tone bursts and to click stimuli at intensity levels which ranged from 55 to 85 dB (SPL). These results are consistent with reports of greater auditory sensitivity (d') and enhanced amplitude of the late (N₁–P₂) cortical evoked response for introverts. The absence of differences in interpeak latency, or central transmission time. center the effects on wave I which is thought to be generated by the cochlear nerve. The present findings may require the elaboration of the neurophysiological bases of extraversion, which presently focuses on differences in cortico-reticular arousal systems, to accomodate individual differences in axonal or synaptic transmission.     

儿童青少年大脑认知功能事件相关电位P_（300）的年龄特征

从发展心理学的角度．对幼儿到大学六个年龄组的儿童青少年进行了事件相关电位Ｐ_（３００）测定．结果发现：反映大脑认知功能的事件相关电位Ｐ_（３００）各成分随着年龄增长而发展的趋势十分明显,从而进一步说明了认知发展的特点与大脑高级神经系统活动功能发展特点的密切关系。     

The effect of movement amplitude and target diameter on reaction time

Henry's (Henry & Rogers, 1960) memory drum model of neuromotor reaction, which predicts an increased response latency for more complicated movements, was tested by examining the effects of variations in movement amplitude and target diameter on choice RT. RT tended to increase with decreasing target diameter, and varied as a U-shaped function with amplitude. Such findings were in only partial support of the memory of drum notion. The data were discussed in relation to information processing, muscle activation, and subjects' expectations for executing responses along the range of movement amplitude.     

Computer signal detection by monitoring auditory evoked potentials

A digital computer, using a simple decision algorithm, attempted to determine when an acoustical signal had been presented to a cat by monitoring the amplitude of the evoked potentials (EP) at brainstem auditory nuclei. The signal-to-noise level at threshold and the shape and range of the decision model “psychometric functions” were similar to those obtained from humans in the same task. In addition, the detection performance obeys Weber’s law, the mean amplitude of the EP increases monotmonically with signal level, the variance of the amplitude is independent of both signal and noise level, and both the mean latency and the variance of the latency of the peaks decrease with increasing signal level. These findings suggest that the synchronization in firing of a population of single units plays a part in determining the amplitude of the EP. Interaural effects in detection performance were found at the inferior colliculus and, to a lesser extent, at the superior olive.     

Electrophysiological manifestations of typicality judgment

Ten male subjects participated in an event-related potential study of typicality judgment of words that were of either high or low frequency of usage. The amplitude of a negative wave with an average peak latency of 490 msec (N400) correlated with the goodness-of-fit of a word to a particular category independent of frequency, with poor examples of the category evoking a significantly more negative waveform. The relative insensitivity of the N400 to word frequency suggests that the N400 reflects some postlexical evaluation rather than lexical access.