Earlier Peak Latency Research Articles

Weak Transcranial Direct Current Effect on I Waves

Background: A single transcranial magnetic pulse over the motor cortex is known to generate repetitive descending activity along the corticospinal tract. With respect to the origin; the earliest volley is named direct wave and the subsequent activity forms indirect (I) waves. I waves are assumed to originate from corticocortical afferents; they can be modulated by several methods and are practical parameters for evaluating motor cortex excitability. Weak transcranial direct current stimulation (tDCS), which has been widely used in human studies since the early 2000s, is a noninvasive and painless modulatory method for studying cortical excitability. We aimed to investigate the modulatory effects of anodal and cathodal tDCS on I waves of healthy controls, as a component of the motor evoked potential response generator. Materials and Methods: Twelve healthy volunteers were enrolled in the study. One mA tDCS was applied for 10 min and; single motor unit (SMU) recording technique was used for the identification of I waves. Two conditions were analyzed for each SMU in both anodal and cathodal current polarities; before tDCS and after tDCS. Separate peristimulus time histograms were constituted for each condition. Total peak duration, early peak latency, early peak duration, and early peak discharge rate were calculated. Results: Total peak duration, early peak latency, and early peak duration did not differ between pre- and post-tDCS conditions in either polarity. However, I1 peak discharge rate was found to be significantly decreased after cathodal tDCS (P: 0.017) and increased after anodal tDCS (P: 0.003). Conclusion: Our results confirm polarity-specific effects of tDCS of the primary motor cortex on I waves. According to our knowledge, this is the first study evaluating modulatory effects of tDCS on I waves using SMU recording technique.

Response: Earlier Peak Latencies May not Fully Reflect the Robustness of Cervical Vestibular Evoked Myogenic Potential to CE-Chirp Stimulus.

Response: Earlier Peak Latencies May not Fully Reflect the Robustness of Cervical Vestibular Evoked Myogenic Potential to CE-Chirp Stimulus.

Earlier Peak Latencies May Not Fully Reflect the Robustness of Cervical Vestibular Evoked Myogenic Potential to CE-Chirp Stimulus.

Earlier Peak Latencies May Not Fully Reflect the Robustness of Cervical Vestibular Evoked Myogenic Potential to CE-Chirp Stimulus.

Critical Dynamics in Spontaneous Resting-State Oscillations Are Associated With the Attention-Related P300 ERP in a Go/Nogo Task.

Sustained attention is the ability to continually concentrate on task-relevant information, even in the presence of distraction. Understanding the neural mechanisms underlying this ability is critical for comprehending attentional processes as well as neuropsychiatric disorders characterized by attentional deficits, such as attention deficit hyperactivity disorder (ADHD). In this study, we aimed to investigate how trait-like critical oscillations during rest relate to the P300 evoked potential—a biomarker commonly used to assess attentional deficits. We measured long−range temporal correlations (LRTC) in resting-state EEG oscillations as index for criticality of the signal. In addition, the attentional performance of the subjects was assessed as reaction time variability (RTV) in a continuous performance task following an oddball paradigm. P300 amplitude and latencies were obtained from EEG recordings during this task. We found that, after controlling for individual variability in task performance, LRTC were positively associated with P300 amplitudes but not latencies. In line with previous findings, good performance in the sustained attention task was related to higher P300 amplitudes and earlier peak latencies. Unexpectedly, we observed a positive relationship between LRTC in ongoing oscillations during rest and RTV, indicating that greater criticality in brain oscillations during rest relates to worse task performance. In summary, our results show that resting-state neuronal activity, which operates near a critical state, relates to the generation of higher P300 amplitudes. Brain dynamics close to criticality potentially foster a computationally advantageous state which promotes the ability to generate higher event-related potential (ERP) amplitudes.

Four-dimensional tractography animates propagations of neural activation via distinct interhemispheric pathways

ObjectiveTo visualize and validate the dynamics of interhemispheric neural propagations induced by single-pulse electrical stimulation (SPES). MethodsThis methodological study included three patients with drug-resistant focal epilepsy who underwent measurement of cortico-cortical spectral responses (CCSRs) during bilateral stereo-electroencephalography recording. We delivered SPES to 83 electrode pairs and analyzed CCSRs recorded at 268 nonepileptic electrode sites. Diffusion-weighted imaging (DWI) tractography localized the interhemispheric white matter pathways as streamlines directly connecting two electrode sites. We localized and visualized the putative SPES-related fiber activation, at each 1-ms time window, based on the propagation velocity defined as the DWI-based streamline length divided by the early CCSR peak latency. ResultsThe resulting movie, herein referred to as four-dimensional tractography, delineated the spatiotemporal dynamics of fiber activation via the corpus callosum and anterior commissure. Longer streamline length was associated with delayed peak latency and smaller amplitude of CCSRs. The cortical regions adjacent to each fiber activation site indeed exhibited CCSRs at the same time window. ConclusionsOur four-dimensional tractography successfully animated neural propagations via distinct interhemispheric pathways. SignificanceOur novel animation method has the potential to help investigators in addressing the mechanistic significance of the interhemispheric network dynamics supporting physiological function.

Speech auditory brainstem responses in adult hearing aid users: Effects of aiding and background noise, and prediction of behavioral measures

The aim of the study was to investigate the effect of aiding (hearing aids) and background noise on Auditory Brainstem Responses to short consonant vowel speech (Speech-ABRs), and to assess the predictive value of these responses in adults with a bilateral sensorineural hearing loss. Speech-ABRs evoked by a 40-ms [da] were recorded from 98 adult hearing-aid users via loudspeaker stimulus presentation with and without a hearing aid, in quiet and in 2-talker babble using a two-channel vertical electrode montage. Behavioral speech perception in noise and/or aided self-reported speech understanding were assessed. Aided speech-ABRs had earlier peak latencies, larger peak amplitudes, and larger F0 encoding amplitudes compared to unaided speech-ABRs. Background noise resulted in later F0 encoding latencies but did not have an effect on peak latencies and amplitudes, or on F0 encoding amplitudes. Speech-ABRs were not a significant predictor of any of the behavioral or self-report measures. Speech-ABRs are not a good predictor measure of speech-in-noise performance or self-reported speech understanding with hearing aids. However, they may have potential for clinical application as an objective measure of speech detection with hearing aids. [Work supported by EPSRC EP/M026728/1, Saudi Arabian Ministry of Education, NIHR MBRC.]

Age Related Decline in Cortical Multifocal Flash VEP: Latency Increases Shown to Be Predominately Magnocellular.

As the visual system ages, flicker sensitivity decreases and the latencies of cortical visual evoked potentials (VEP) increase. However, the extent to which these effects reflect age-related changes in the magnocellular (M) and or parvocellular (P) pathways remain unclear. Here, we investigated the relation between flicker fusion frequencies and VEP non-linearities induced by rapid stimulation, as a function of age over 6 decades. The approach, using Wiener kernel analysis of multifocal flash (mf)VEP, allows the extraction of signatures of both M and P processing and hence establishing a neural basis of the known decline in flicker fusion threshold. We predicted that, in a sample of 86 participants, age would be associated with a latency increase in early mfVEP response components and that flicker fusion thresholds, for both low and high contrast stimuli, would relate to the temporal efficiency of the M-generated VEP component amplitudes. As expected, flicker fusion frequency reduced with age, while latencies of early second order peaks of the mfVEP increased with age, but M temporal efficiency (amplitude ratio of first to second order peaks) was not strongly age-related. The steepest increases in latency were associated with the M dominated K2.1 (second order first slice) N70 components recorded at low and high contrast (6.7 and 5.9 ms/decade, respectively). Interestingly, significant age-related latency shifts were not observed in the first order responses. Significant decreases in amplitude were found in multiple first and second order components up to 30 years of age, after which they remained relatively constant. Thus, aging and decline in visual function appears to be most closely related to the response latencies of non-linearities generated by the M pathway.

Speech Auditory Brainstem Responses in Adult Hearing Aid Users: Effects of Aiding and Background Noise, and Prediction of Behavioral Measures.

Evaluation of patients who are unable to provide behavioral responses on standard clinical measures is challenging due to the lack of standard objective (non-behavioral) clinical audiological measures that assess the outcome of an intervention (e.g., hearing aids). Brainstem responses to short consonant-vowel stimuli (speech-auditory brainstem responses [speech-ABRs]) have been proposed as a measure of subcortical encoding of speech, speech detection, and speech-in-noise performance in individuals with normal hearing. Here, we investigated the potential application of speech-ABRs as an objective clinical outcome measure of speech detection, speech-in-noise detection and recognition, and self-reported speech understanding in 98 adults with sensorineural hearing loss. We compared aided and unaided speech-ABRs, and speech-ABRs in quiet and in noise. In addition, we evaluated whether speech-ABR F0 encoding (obtained from the complex cross-correlation with the 40 ms [da] fundamental waveform) predicted aided behavioral speech recognition in noise or aided self-reported speech understanding. Results showed that (a) aided speech-ABRs had earlier peak latencies, larger peak amplitudes, and larger F0 encoding amplitudes compared to unaided speech-ABRs; (b) the addition of background noise resulted in later F0 encoding latencies but did not have an effect on peak latencies and amplitudes or on F0 encoding amplitudes; and (c) speech-ABRs were not a significant predictor of any of the behavioral or self-report measures. These results show that speech-ABR F0 encoding is not a good predictor of speech-in-noise recognition or self-reported speech understanding with hearing aids. However, our results suggest that speech-ABRs may have potential for clinical application as an objective measure of speech detection with hearing aids.

The N2pc component reliably captures attentional bias in social anxiety.

We systematically compared different measures of attentional bias (i.e., reaction times, the N2pc component in the EEG, and explicit stimulus ratings) on their ability to reveal attentional engagement to threatening versus neutral facial stimuli in a Dot Probe Task and tested their relation to trait measures of general and social anxiety. We found that the N2pc component reflects a bias toward angry faces with excellent internal consistency. Similar results were obtained for explicit ratings. Reaction time (RT) differences, however, were not indicative of attentional biases and showed zero odd-even reliability. We further found that both higher (i.e., more negative) N2pc amplitudes and earlier peak latencies were associated with more severe symptoms of social anxiety even when controlling for general trait anxiety. The explicit rating biases were also specifically associated with social anxiety. Conversely, the RT bias was not related to social anxiety levels but to general trait anxiety. This highlights the importance of valid and reliable outcome measures for interventions such as attentional bias modification protocols. Mutual exclusivity of different bias operationalizations is discussed.

Are speech-evoked auditory brainstem response (speech-ABR) outcomes influenced by ethnicity?

Due to its objective nature, auditory brainstem response (ABR) evoked by complex stimuli has been gaining attention lately. The present study aimed to compare the speech-evoked auditory brainstem response (speech-ABR) results between two ethnic groups: Malay and Chinese. In addition, it was also of interest to compare the speech-ABR outcomes obtained from the present study with the published Caucasian data. Thirty healthy male adults (15 Malay and 15 Chinese) were enrolled in this comparative study. Speech syllable/da/presented at 80 dBnHL was used to record speech-ABR waveforms from the right ear of each subject. Amplitudes and latencies of speech-ABR peaks (V, A, C, D, E, F and O), as well as composite onset measures (V/A duration, V/A amplitude and V/A slope) were computed and analyzed. When the two ethnic groups were compared, all speech-ABR results were not statistically different from each other (p>0.05). When the data from the present study were compared with the published Caucasian data, most of the statistical analyses were significant (p<0.05). That is, Asian subjects revealed significantly higher peak amplitudes, earlier peak latencies, higher V/A amplitudes and steeper V/A slopes than that of Caucasians. The speech-ABR results between Malay and Chinese were found to be essentially similar due to anatomical similarities. Nevertheless, specific normative data for Asian adults are required as their speech-ABR results are different from that of Caucasian males. This issue should be addressed before it can be applied holistically in multiracial countries.

A neurophysiological study of the medullary sympathetic pathway to the adrenal gland (1131.7)

Neurons in the rostral ventrolateral medulla (RVLM) control adrenaline secretion from the adrenal gland and participate in glucose homeostasis. Here, we examined sympathetic evoked responses recorded from the adrenal sympathetic nerve in response to intermittent stimulation of the RVLM. All experiments were performed using isoflurane/urethane‐anaesthetised, artificially‐ventilated, paralysed, male Sprague‐Dawley rats. The RVLM was first identified by extracellular single unit recording combined with field potential mapping of the facial nucleus. We compared the latencies of the evoked adrenal sympathetic nerve (ASNA) response to the lumbar sympathetic nerve (LSNA) response upon electrical stimulation of RVLM (0.5 Hz, 1 ms pulse width, 50‐300 μA) after conversion to urethane (1.4 g/kg, i.v.). RVLM stimulation elicited an evoked ASNA response that depended on whether the recording was primarily pre‐ or post‐ganglionic activity as judged by the effect of the ganglion blocker hexamethonium (Hex; 20‐40 mg/kg, i.v.). Pre‐ganglionic ASNA consisted of an early peak (latency ‐ 79±9 ms, n=4) and a late peak (latency ‐ 149±6 ms). Lumbar sympathetic nerve activity exhibited a prominent early peak (latency ‐ 87±7 ms; n = 5) that was eliminated by Hex. Pre‐ganglionic ASNA was reduced by 62 % after intrathecal kynurenate (0.5 μmole/10 μl; P&lt;0.01, late peak, n=3). The early peak may represent sympathetic vasomotor activity in both the adrenal and lumbar sympathetic nerves. However, the late sympathetic response noted in the adrenal nerve is mediated by a glutamatergic input and may be involved in the control of catecholamine secretion from adrenal chromaffin cells.Grant Funding Source: National Health and Medical Research Council of Australia

Shortened conditioned eyeblink response latency in male but not female Wistar-Kyoto hyperactive rats.

Reductions in the volume of the cerebellum and impairments in cerebellar-dependent eyeblink conditioning have been observed in attention-deficit/hyperactivity disorder (ADHD). Recently, it was reported that subjects with ADHD as well as male spontaneously hypertensive rats (SHR), a strain that is frequently employed as an animal model in the study of ADHD, exhibit a parallel pattern of timing deficits in eyeblink conditioning. One criticism that has been posed regarding the validity of the SHR strain as an animal model for the study of ADHD is that SHRs are not only hyperactive but also hypertensive. It is conceivable that many of the behavioral characteristics seen in SHRs that seem to parallel the behavioral symptoms of ADHD are not solely due to hyperactivity but instead are the net outcome of the interaction between hyperactivity and hypertension. We used Wistar-Kyoto Hyperactive (WKHA) and Wistar-Kyoto Hypertensive (WKHT) rats (males and females), strains generated from recombinant inbreeding of SHRs and their progenitor strain, Wistar-Kyoto (WKY) rats, to compare eyeblink conditioning in strains that are exclusively hyperactive or hypertensive. We used a long-delay eyeblink conditioning task in which a tone conditioned stimulus was paired with a periorbital stimulation unconditioned stimulus (750-ms delay paradigm). Our results showed that WKHA and WKHT rats exhibited similar rates of conditioned response (CR) acquisition. However, WKHA males displayed shortened CR latencies (early onset and peak latency) in comparison to WKHT males. In contrast, female WKHAs and WKHTs did not differ. In subsequent extinction training, WKHA rats extinguished at similar rates in comparison to WKHT rats. The current results support the hypothesis of a relationship between cerebellar abnormalities and ADHD in an animal model of ADHD-like symptoms that does not also exhibit hypertension, and suggest that cerebellar-related timing deficits are specific to males.

Abnormal topography and altered acquisition of conditioned eyeblink responses in a rodent model of attention-deficit/hyperactivity disorder.

The spontaneously hypertensive rat (SHR) has been suggested as a possible animal model of attention-deficit/hyperactivity disorder (ADHD). Reductions in the volume of the cerebellum and impairments in cerebellar-dependent eyeblink conditioning have been observed in ADHD, prompting investigation into whether SHRs also exhibit eyeblink conditioning impairments. In Experiment 1, SHRs and a control strain, Wistar, were trained on a long-delay eyeblink conditioning task in which a tone conditioned stimulus was paired with a periorbital stimulation unconditioned stimulus (750-ms delay paradigm). SHRs exhibited faster acquisition of eyeblink conditioned responses (CRs) and displayed mistimed (early onset and peak latency) and larger CRs in comparison with Wistar rats. In subsequent extinction training, SHRs were slower to extinguish CRs. The authors conducted Experiment 2 using separate rats to rule out the possibility that the results of Experiment 1 were due to nonassociative responding. SHRs and Wistar rats were presented with explicitly unpaired tone and periorbital stimulation stimuli. There was no evidence of conditioning in either group, nor were there differences between the groups in terms of the number of eyeblink responses elicited by the tone. The current results support the hypothesis of cerebellar abnormalities in this rodent model of ADHD.

Neural mechanisms of auditory sensory processing in children with high intelligence

To investigate the differences in event-related potential parameters related to children's intelligence, 18 intellectually gifted children and 18 average children participated in this study. The electroencephalograms were recorded the auditory sensory memory that elicited the mismatch negativity (MMN) and late discriminative negativity (LDN), as well as involuntary attention switch that elicited the P3a and early MMN were analyzed. The results indicated that children with high intelligence had comparatively larger MMN, LDN, early MMN, P3a amplitudes, and earlier peak latency in LDN than average children. The enhanced neural function of the intellectually gifted children might be due to more spatially and temporally coordinated neural network, faster neural processing speed and more efficient neural activation functions.

Predictive information and error processing: The role of medial‐frontal cortex during motor control

We have recently provided evidence that an error-related negativity (ERN), an ERP component generated within medial-frontal cortex, is elicited by errors made during the performance of a continuous tracking task (O.E. Krigolson & C.B. Holroyd, 2006). In the present study we conducted two experiments to investigate the ability of the medial-frontal error system to evaluate predictive error information. In two experiments participants used a joystick to perform a computer-based continuous tracking task in which some tracking errors were inevitable. In both experiments, half of these errors were preceded by a predictive cue. The results of both experiments indicated that an ERN-like waveform was elicited by tracking errors. Furthermore, in both experiments the predicted error waveforms had an earlier peak latency than the unpredicted error waveforms. These results demonstrate that the medial-frontal error system can evaluate predictive error information.

Motor evoked potentials in rats with congenital hydrocephalus

Motor evoked potential (MEP) by focal transcranial magnetic stimulation was used to test the functional integrity of the motor cortex in congenital hydrocephalic rats. Magnetic MEPs, using a figure-eight coil above the head, were recorded in the tibialis anterior muscle. The latency of transcranial magnetic MEP was 3.4 msec in nonhydrocephalic rats. In the hydrocephalic rats, the MEP had a lower threshold than in nonhydrocephalic rats, and showed two peaks. Latencies of early and late peaks were 3.9 msec and from 5.4 msec to 10.0 msec, respectively. Our findings suggest that hydrocephalus in rats is associated with changes in pyramidal cell excitability in the motor cortical area, probably induced by the fluctuations in cortical excitability and synaptic interaction in hydrocephalic rats.

Pattern‐reversal visual evoked potentials in infants: gender differences during early visual maturation

This paper investigates gender differences in the peak latency and amplitude of the P1 component of the pattern‐reversal visual evoked potential (pattern‐reversal VEP) recorded in healthy term infants. Pattern‐reversal VEPs in response to a series of high contrast black and white checks (check widths 120′, 60′, 30′, 24′, 12′, 6′) were recorded in 50 infants (20 males, 30 females) at 50 weeks post‐conceptional age (PCA) and in 49 infants (22 males, 27 females) at 66 weeks PCA. Peak latency of the major component, P1, was considerably shorter in female compared with male infants. Differences in head circumference do not entirely account for the gender differences in peak latency reported here. A gender difference in P1 amplitude was not detected. These findings stress the importance of considering gender norms as well as age‐matched norms when utilizing the pattern‐reversal VEP in clinical investigations. Studies including a wider range of ages are clearly necessary in order to establish whether the earlier peak latencies in female infants represents a difference in the onset or rate of visual maturation.

Event-related potential measures of attention in moderately depressed subjects

Prior research has inferred attentional changes related to depression from evidence concerning other cognitive processes. The present experiment investigated attentional changes related to depression in a more direct manner. Subjects were 32 young adults attending college. Depression was measured by self-report measures. In an auditory selective attention task similar to that of Hansen and Hillyard (1980), auditory event-related potentials(ERPs) were recorded from central (Cz) and frontal (Fz) scalp locations. Evidence for selective attention was manifest as the difference wave (Nd), which showed larger mean and peak amplitudes for the less difficult of two attention conditions. Nd was also shown to have an earlier peak latency at the Cz scalp location. However, there was no significant difference between the Depressed and Control groups as measured by the Nd wave. Significant differences were found between groups for the amplitude of the N1 peak of the ERP at the Fz scalp location. This suggests that the Depressed group differed in arousal level or sensory sensitivity from the Control group.

"Virtual N400" and Slow Wave Topography to Auditory Sentence Incongruence

In a simple auditory sentence paradigm, two ERP components were found to be sensitive to violations of sentence congruence: a "virtual N400" and the Slow Wave (SW). Unlike previous studies, the N400 was found to occur very early (peak latency of 250 msec) and have a short duration (196-287 msec), while maintaining the previously described slightly asymmetric right central-parietal negative topography. Because of the early latency, this component was referred to as a "virtual N400." The SW (418-530 msec) was also enhanced and topographically shifted to incongruent sentence terminal words. Its topography consisted of a symmetric frontal minimum and posterior maximum. Although the difference map was also symmetric, a t value map of the congruence effect was maximal over the left posterior temporal area. The very early latency of the "virtual N400" and its decreased duration were produced by a paradigm that allowed for very early recognition of a semantic violation, even before the spoken word was complete. It is postulated that the "virtual N400" indexes word recognition. Semantic processing is indexed by the "virtual N400" as well, but the left posterior temporal asymmetry in the t maps of the Slow Wave may be of even greater import.

Temporal features of the responses of primate spinothalamic neurons to noxious thermal stimulation of hairy and glabrous skin.

Extracellular recordings were made from 81 primate spinothalamic (STT) neurons in the L7-S1 segments of the spinal cord. The majority of the sample was recorded from within laminae IV-V. The temporal features of the responses to noxious thermal stimulation of glabrous and hairy skin were studied in an attempt to determine whether natural groupings of STT neurons could be identified on the basis of response time course alone and whether these groups were skin type dependent. The relationship between these groups and those based on static response features (37) was also explored in an attempt to define more fully their potential functional roles. In most STT neurons, the thermally evoked responses typically appeared to have two response components, particularly at stimulus temperatures above 49 degrees C. The first response phase typically peaked within 1-12 s of stimulus onset and then adapted. The second phase slowly rose to a maximum, typically 15-30 s following stimulus onset. The existence of natural groupings of STT neurons based upon the characteristics of these two response components was assessed with a k-means cluster analysis. On the basis of the onset and early peak latencies, two well-defined short and long latency neuronal clusters were found in the responses evoked from both glabrous and hairy skin; these were referred to as the SP1 and LP1 classes, respectively. The glabrous and hairy skin SP1 classes did not differ significantly in either onset or early peak latency for stimuli of 47-55 degrees C. However, the hairy skin LP1 class had significantly shorter onset latencies than the glabrous skin LP1 class for stimuli of 49-53 degrees C, as well as shorter peak latencies for stimuli of 49 and 51 degrees C. The SP1 class constituted 62% of the hairy skin subset, whereas the LP1 class constituted 57% of the glabrous skin subset. A cluster analysis of the late-peak latencies also revealed two subgroups. In the responses evoked from both glabrous and hairy skin, the longer latency classes (LP2) constituted more than 80% of the samples. With one exception, no dependence upon the type of skin that was stimulated was found in the latencies of either the LP2 class or the shorter latency SP2 class. Prior conditioning of the skin with a 30-s thermal pulse of 51-55 degrees C led to a suppression of the early response phase and an enhancement of the late phase in nearly all cases examined (n = 11). This pattern was independent of skin type.(ABSTRACT TRUNCATED AT 400 WORDS)