Changes In Response Latency Research Articles

Experiment for teaching virtual cathode in nerve conduction studies

The virtual cathode (VC) is a site near the anode where the nerve can be stimulated. Costimulation of neighboring nerves via the VC can affect recording and interpretation of responses. Hence, it is important to teach trainees the concept of the VC. The VC has been demonstrated previously with subtle changes in response latency, amplitude, and shape. Herein we describe an experiment that simply demonstrates a VC with its effects recognizable by gross changes in waveforms. Compound muscle action potentials of the abductor pollicis brevis were recorded using various placements of the cathode and anode at different stimulus intensity levels. Studies were performed in nine healthy subjects. Three patterns were observed that demonstrated no stimulation, partial stimulation, and complete nerve stimulation by the VC. Partial stimulation yielded responses with long duration and low amplitude. Response patterns also depended on stimulus strength and proximity of the nerve from the skin surface. This experiment demonstrates that nerve stimulation can occur near the anode when high-intensity stimulus is used. It also illustrates collision of action potentials. This exercise can help trainees understand potential pitfalls in nerve conduction studies, especially at very proximal stimulation sites or when high stimulus intensity is used.

The effects of guessing confidence on anticipatory behaviour in context understanding

Abstract The study investigates the anticipatory behaviour in a word guessing experiment with Slovak L2 speakers of English of varying proficiency levels. The L2 speakers are trying to correctly identify the word that the interlocutor is hinting at with two consecutive cues as soon as they are confident enough to provide the answer. This created a connection between anticipation and guessing confidence. The effect of guessing confidence on the anticipatory behaviour is measured through the change in response latency of how quickly the guessers produce their guesses after listening to the cues. The aim is to study how the response latencies of the listeners are affected by their previous correct or incorrect guesses. The findings suggest that the correctness of guesses has a measurable impact on response latency.

The development and validation of a short-duration sustained visual search task for process control environments

This study was designed to validate a short-duration sustained visual search task for the assessment of sustained attention in process control environments. The task consists of 10 short dynamic scenarios, which require participants (N = 121) to monitor simulated operating power transmission interfaces, and identify system faults. A vigilance decrement was demonstrated throughout the sustained visual search task, as evident in increased response latencies and decreased accuracy over time. Further, changes in response latency throughout the sustained visual search task were positively associated with changes in response latency during a 30-min, low signal probability task, a 45-min low signal probability task, and a 45-min high signal probability task. The findings indicate that the sustained visual search task may be a valid alternative to a longer-duration process control task for experimental studies, and is likely to be of value for assessments of the capacity for sustained attention of operators in process control environments.

A controlled clinical crossover trial of exercise training to improve cognition and neural communication in pediatric brain tumor survivors

ObjectiveTo assess the efficacy of aerobic exercise training to improve controlled attention, information processing speed and neural communication during increasing task load and rest in pediatric brain tumor survivors (PBTS) treated with cranial radiation. Methods: Participants completed visual-motor Go and Go/No-Go tasks during magnetoencephalography recording prior to and following the completion of 12-weeks of exercise training. Exercise-related changes in response accuracy and visual-motor latency were evaluated with Linear Mixed models. The Phase Lag Index (PLI) was used to estimate functional connectivity during task performance and rest. Changes in PLI values after exercise training were assessed using Partial Least Squares analysis. Results: Exercise training predicted sustained (12-weeks) improvement in response accuracy (p<0.05) during No-Go trials. Altered functional connectivity was detected in theta (4–7Hz) alpha (8–12Hz) and high gamma (60–100Hz) frequency bands (p<0.001) during Go and Go/No-Go trials. Significant changes in response latency and resting state connectivity were not detected. Conclusion: These findings support the efficacy of aerobic exercise to improve controlled attention and enhance functional mechanisms under increasing task load in participants. Significance: It may be possible to harness the beneficial effects of exercise as therapy to promote cognitive recovery and enhance brain function in PBTS.

Frequency-modulated up-chirps produce larger evoked responses than down-chirps in the big brown bat auditory brainstem.

In many mammals, upward-sweeping frequency-modulated (FM) sounds (up-chirps) evoke larger auditory brainstem responses than downward-sweeping sounds (down-chirps). To determine if similar effects occur in FM echolocating bats, auditory evoked responses (AERs) in big brown bats in response to up-chirps and down-chirps at different chirp durations and levels were recorded. Even though down-chirps are the biologically relevant stimulus for big brown bats, up-chirps typically evoked larger peaks in the AER, but with some exceptions at the shortest chirp durations. The up-chirp duration that produced the largest AERs and the greatest differences between up-chirps and down-chirps varied between individual bats and stimulus levels. Cross-covariance analyses using the entire AER waveform confirmed that amplitudes were typically larger to up-chirps than down-chirps at supra-threshold levels, with optimal durations around 0.5-1 ms. Changes in response latencies with stimulus levels were consistent with previous estimates of amplitude-latency trading. Latencies tended to decrease with increasing up-chirp duration and increase with increasing down-chirp duration. The effects of chirp direction on AER waveforms are generally consistent with those seen in other mammals but with small differences in response patterns that may reflect specializations for FM echolocation.

Teacher-conducted trial-based functional analysis and treatment of multiply controlled challenging behavior.

We trained a public school teacher to conduct a trial-based functional analysis (FA) in her self-contained classroom during school hours with other children present. Using FA data as baseline, we validated our intervention by tracking changes in response latencies from the onset of relevant establis

Nucleus Accumbens Fast-Spiking Interneurons Constrain Impulsive Action

BackgroundThe nucleus accumbens (NAc) controls multiple facets of impulsivity but is a heterogeneous brain region with diverse microcircuitry. Prior literature links impulsive behavior in rodents to gamma-aminobutyric acid signaling in the NAc. Here, we studied the regulation of impulsive behavior by fast-spiking interneurons (FSIs), a strong source of gamma-aminobutyric acid–mediated synaptic inhibition in the NAc. MethodsMale and female transgenic mice expressing Cre recombinase in FSIs allowed us to identify these sparsely distributed cells in the NAc. We used a 5-choice serial reaction time task to measure both impulsive action and sustained attention. During the 5-choice serial reaction time task, we monitored FSI activity with fiber photometry calcium imaging and manipulated FSI activity with chemogenetic and optogenetic methodology. We used electrophysiology, optogenetics, and fluorescent in situ hybridization to confirm these methods were robust and specific to FSIs. ResultsIn mice performing the 5-choice serial reaction time task, NAc FSIs showed sustained activity on trials ending with correct responses, but FSI activity declined over time on trials ending with premature responses. The number of premature responses increased significantly after sustained chemogenetic inhibition or temporally delimited optogenetic inhibition of NAc FSIs, without any changes in response latencies or general locomotor activity. ConclusionsThese experiments provide strong evidence that NAc FSIs constrain impulsive actions, most likely through gamma-aminobutyric acid–mediated synaptic inhibition of medium spiny projection neurons. Our findings may provide insight into the pathophysiology of disorders associated with impulsivity and may inform the development of circuit-based therapeutic interventions.

Motor adaption during repeated motor control testing: Attenuated muscle activation without changes in response latencies

With repeated exposure to postural perturbations the human postural control system can adapt and create efficient strategies to counteract these perturbations. The Motor Control Test (MCT) is commonly used to elicit reactionary postural movements. Though this device has been assessed for possible learning effects and reliability of composite scores, yet no study has evaluated possible neuromuscular alterations repeated bouts might elicit. Twenty participants (age: 25 ± 4.73 years; height: 183.8 ± 8.5 cm; mass: 85.2 ± 15.6 kg) volunteered and, following familiarization, performed five full-randomized MCTs over six testing sessions. The first five sessions occurred on consecutive days, with the sixth occurring two days later. Electromyography (EMG) was recorded on right lower extremity knee flexors and extensors, and ankle plantarflexors and dorsiflexors. Response latencies and Mean and RMS muscle activity were calculated and analyzed using 1 × 5 (within days) and 1 × 6 (across days) RM ANOVA. Decreases in muscle activation of proximal musculature were noted between days and trials within days, however these changes were not maintained after the two-day retention period. No differences were detected for MCT scores. These results suggest repeated MCT exposure modifies neuromuscular responses to maintain similar reaction time through a postural control strategy shift.

Modulation of linguistic prediction by TDCS of the right lateral cerebellum

It has been postulated recently that the cerebellum contributes the same prediction and learning functions to linguistic processing as it does towards motor control. For example, repetitive TMS over posterior-lateral cerebellum caused a significant loss in predictive language processing, as assessed by the latency of saccades to target items of spoken sentences, using the Visual World task. We aimed to assess the polarity-specific effects of cerebellar TDCS, hypothesising that cathodal TDCS should impair linguistic prediction, and anodal TDCS facilitate it. Our design also tested whether TDCS modulated associative learning in this task. A between groups (sham, anodal, cathodal) design was used, with concurrent stimulation during performance of a manual variation of the Visual World paradigm, and with assessment of latency reduction over repeated presentations of the spoken sentences. Mixed model ANOVA was used to analyse change in response latency. Cathodal TDCS decreased participants’ response time advantage for the predictable sentence items without change for non-predictable items, consistent with the previous TMS results. Furthermore, anodal stimulation enhanced the response time advantage for the predictable items, again without change in latencies for non-predictive items. We found a clear practice-based effect over 4 blocks. However, this difference was not significantly modulated by either anodal or cathodal stimulation. Our results therefore support the hypothesis that cerebellum contributes to predictive language processing, mirroring its predictive role in motor control, but we do not yet have evidence that the learning process was affected by cerebellar TDCS.

The effect of acute tyrosine phenylalanine depletion on emotion-based decision-making in healthy adults

Despite interest in dopamine's role in emotion-based decision-making, few reports of the effects of dopamine manipulations are available in this area in humans. This study investigates dopamine's role in emotion-based decision-making through a common measure of this construct, the Iowa Gambling Task (IGT), using Acute Tyrosine Phenylalanine Depletion (ATPD). In a between-subjects design, 40 healthy adults were randomized to receive either an ATPD beverage or a balanced amino acid beverage (a control) prior to completing the IGT, as well as pre- and post-manipulation blood draws for the neurohormone prolactin. Together with conventional IGT performance metrics, choice selections and response latencies were examined separately for good and bad choices before and after several key punishment events. Changes in response latencies were also used to predict total task performance. Prolactin levels increased significantly in the ATPD group but not in the control group. However, no significant group differences in performance metrics were detected, nor were there sex differences in outcome measures. However, the balanced group's bad deck latencies speeded up across the task, while the ATPD group's latencies remained adaptively hesitant. Additionally, modulation of latencies to the bad decks predicted total score for the ATPD group only. One interpretation is that ATPD subtly attenuated reward salience and altered the approach by which individuals achieved successful performance, without resulting in frank group differences in task performance.

The effects of subthalamic and pallidal deep brain stimulation on postural responses in patients with Parkinson disease

The effect of deep brain stimulation (DBS) for Parkinson disease (PD) on balance is unclear. The goal of this study was to investigate how automatic postural responses (APRs) were affected in patients randomized to either subthalamic nucleus (STN) or globus pallidus internus (GPi) surgery. The authors tested 24 patients with PD who underwent bilateral DBS, 9 control patients with PD who did not undergo DBS, and 17 age-matched control volunteers. The electrode placement site was randomized and blinded to the patients and to the experimenters. Kinematic, kinetic, and electromyographic recordings of postural responses to backward disequilibrium via forward translations of the standing surface were recorded in the week prior to surgery while the patients were off (OFF) and on (ON) antiparkinsonian medication (levodopa), and then 6 months after surgery in 4 conditions: 1) off medication with DBS switched off (OFF/OFF); 2) off medication with DBS on (DBS); 3) on medication with DBS off (DOPA); and 4) with both medication and DBS on (DBS+DOPA). Stability of the automatic postural response (APR) was measured as the difference between the displacement of the center of pressure and the projected location of the center of body mass. Patients with PD had worse APR stability than controls. Turning the DBS on at either site improved APR stability compared with the postoperative OFF condition by lengthening the tibialis response, whereas medication did not show an appreciable effect. The STN group had worse APR stability in their best functional state (DBS+DOPA) 6 months after the DBS procedure compared with their best functional state (ON levodopa) before the DBS procedure. In contrast, the GPi group and the PD control group showed no change over 6 months. The APR stability impairment in the STN group was associated with smaller tibialis response amplitudes, but there was no change in response latency or coactivation with gastrocnemius. Turning the DBS current on improved APR stability for both STN and GPi sites. However, there was a detrimental DBS procedural effect for the STN group, and this effect was greater than the benefit of the stimulating current, making overall APR stability functionally worse after surgery for the STN group.

Effects of Tai Chi on pre-landing muscle response latency during stepping down while performing a concurrent mental task in older adults

To investigate whether elderly Tai Chi practitioners are better able to descend a step while performing a concurrent mental task than non-practitioners. The design includes cross-sectional study. The setting includes university-based rehabilitation center. The subjects were 16 young women, 29 elderly women, and 31 elderly women who had been practicing Tai Chi regularly for at least half a year. Pre-landing muscle response latencies in their tibialis anterior (TA) and medial gastrocnemius (MG) muscles were measured during stepping down (single task) and stepping down while performing a concurrent mental activity (dual tasking). The non-practitioners had earlier onset of muscle activity in the TA in preparation for landing than the other subjects. The response latency of the Tai Chi practitioners was not significantly different from that of the young controls. When the cognitive task was added, the pre-landing response in the TA was significantly altered in both elderly groups. Response was significantly delayed among the non-practitioners, but significantly earlier among the Tai Chi subjects. The average change in response latency was significantly greater in the non-Tai Chi group compared with the young subjects and the Tai Chi practitioners (p = 0.006). Such findings suggest that practicing Tai Chi helps the elderly maintain the same strategy as much as younger subjects during stepping down. Tai Chi practitioners seem to have a greater capacity to shift attention between mental and physical tasks than other elderly women.

Prenatal IV Cocaine: Alterations in Auditory Information Processing.

One clue regarding the basis of cocaine-induced deficits in attentional processing is provided by the clinical findings of changes in the infants’ startle response; observations buttressed by neurophysiological evidence of alterations in brainstem transmission time. Using the IV route of administration and doses that mimic the peak arterial levels of cocaine use in humans, the present study examined the effects of prenatal cocaine on auditory information processing via tests of the auditory startle response (ASR), habituation, and prepulse inhibition (PPI) in the offspring. Nulliparous Long–Evans female rats, implanted with an IV access port prior to breeding, were administered saline, 0.5, 1.0, or 3.0 mg/kg/injection of cocaine HCL (COC) from gestation day (GD) 8–20 (1×/day-GD8–14, 2×/day-GD15–20). COC had no significant effects on maternal/litter parameters or growth of the offspring. At 18–20 days of age, one male and one female, randomly selected from each litter displayed an increased ASR (>30% for males at 1.0 mg/kg and >30% for females at 3.0 mg/kg). When reassessed in adulthood (D90–100), a linear dose–response increase was noted on response amplitude. At both test ages, within-session habituation was retarded by prenatal cocaine treatment. Testing the females in diestrus vs. estrus did not alter the results. Prenatal cocaine altered the PPI response function across interstimulus interval and induced significant sex-dependent changes in response latency. Idazoxan, an α2-adrenergic receptor antagonist, significantly enhanced the ASR, but less enhancement was noted with increasing doses of prenatal cocaine. Thus, in utero exposure to cocaine, when delivered via a protocol designed to capture prominent features of recreational usage, causes persistent, if not permanent, alterations in auditory information processing, and suggests dysfunction of the central noradrenergic circuitry modulating, if not mediating, these responses.

Silver exposure in developing zebrafish produces persistent synaptic and behavioral changes

Environmental silver exposures are increasing due to the use of silver nanoparticles, which exert antimicrobial actions by releasing Ag +, a suspected developmental neurotoxicant. We evaluated the long-term neurochemical and behavioral effects of embryonic Ag + exposure in zebrafish at concentrations that had no overt effects on morphological development. Exposure to 0.03, 0.1 or 0.3 μM Ag + during the first five days post-fertilization caused elevations in both dopamine and serotonin turnover in the adult zebrafish brain without affecting basal neurotransmitter levels. Consistent with these synaptic effects, Ag +-exposed fish showed a faster acquisition of avoidance behavior in a three-chamber test apparatus, without any change in response latency or overall swimming ability. Our results indicate that Ag + is a developmental neurotoxicant that causes persistent neurobehavioral effects, reinforcing health concerns about Ag + released from silver nanoparticles.

Effects of electrical stimulation of dorsal raphe nucleus on neuronal response properties of barrel cortex layer IV neurons following long-term sensory deprivation

To evaluate the effect of electrical stimulation of dorsal raphe nucleus (DRN) on response properties of layer IV barrel cortex neurons following long-term sensory deprivation. Male Wistar rats were divided into sensory-deprived (SD) and control (unplucked) groups. In SD group, all vibrissae except the D2 vibrissa were plucked on postnatal day one, and kept plucked for a period of 60 d. After that, whisker regrowth was allowed for 8-10 d. The D2 principal whisker (PW) and the D1 adjacent whisker (AW) were either deflected singly or both deflected in a serial order that the AW was deflected 20 ms before PW deflection for assessing lateral inhibition, and neuronal responses were recorded from layer IV of the D2 barrel cortex. DRN was electrically stimulated at inter-stimulus intervals (ISIs) ranging from 0 to 800 ms before whisker deflection. PW-evoked responses increased in the SD group with DRN electrical stimulation at ISIs of 50 ms and 100 ms, whereas AW-evoked responses increased at ISI of 800 ms in both groups. Whisker plucking before DRN stimulation could enhance the responsiveness of barrel cortex neurons to PW deflection and decrease the responsiveness to AW deflection. DRN electrical stimulation significantly reduced this difference only in PW-evoked responses between groups. Besides, no DRN stimulation-related changes in response latency were observed following PW or AW deflection in either group. Moreover, condition test (CT) ratio increased in SD rats, while DRN stimulation did not affect the CT ratio in either group. There was no obvious change in 5-HT(2A) receptor protein density in barrel cortex between SD and control groups. These results suggest that DRN electrical stimulation can modulate information processing in the SD barrel cortex.

Contrast induced changes in response latency depend on stimulus specificity

Neurones in visual cortex show increasing response latency with decreasing stimulus contrast. Neurophysiological recordings from neurones in inferior temporal cortex (IT) and the superior temporal sulcus (STS), show that the increment in response latency with decreasing stimulus contrast is considerably greater in higher visual areas than that seen in primary visual cortex. This suggests that the majority of the latency change is not retinal or V1 in origin, instead each cortical processing area adds latency at low contrast. I show that, as in earlier visual areas, response latency is more strongly dependent on stimulus contrast than stimulus identity. There is large variation in the extent to which response latency increases with decreasing stimulus contrast. I show that this between cell variability is, at least in part, related to the stimulus specificity of the neurones: the increase in response latency as stimulus contrast decreases is greater for neurones that respond to few stimuli compared to neurones that respond to many stimuli.

Changes in chromatic pattern-onset VEP with full-body inversion

Intra-ocular pressure (IOP) increases to double that of its normal level under full-body inversion, in part simulating high IOPs found in glaucoma and ocular hypertension. Inversion also simulates negative g-forces experienced in aerobatic maneuvers such as those produced during aerial combat. Studies using achromatic pattern-reversal visual evoked potentials (VEPs) have shown losses in response amplitude when subjects are inverted and IOP is increased. In other studies, chromatic, pattern-onset VEPs have been shown to be a sensitive and objective indicator of ocular and systemic pathology. Thus, chromatic pattern-onset VEPs may also show changes in amplitude and/or latency when subjects are subjected to full-body inversion. In this study we employed chromatic, pattern-onset VEPs to determine if there were changes in response latency for the different visual pathways with healthy subjects during full-body inversion. Stimuli were 1 cpd horizontal sine-wave patterns presented in an onset mode (100 ms on/400 ms off). Subjects (n = 7) were tested at low to medium contrast levels, which were subjectively equated across chromatic pathways (S, LM, and achromatic). Patterns were presented using LCD goggles. All subjects showed a small but statistically significant increase in latency in the large negative component (CII) for both L - M and S - (L + M) pathways during inversion. The achromatic pathway also showed a statistically significant increase in latency to the positive component (CI) during inversion. These results demonstrate that changes in ocular and/or systemic physiology during full-body inversion can result in increased latencies of chromatic and achromatic pattern-onset VEPs.

Neural Prostheses: Electrophysiological and Histological Evaluation of Central Nervous System Alterations Due to Long-Term Implants of Sieve Electrodes to Peripheral Nerves in Cats

We have investigated the alterations that the long-term implant of sieve electrodes to the peripheral nerves could evoke in the central nervous system by studying the neural activity at various levels of the somatosensory system [the implanted nerves, the dorsal column nuclei (DCN), and the primary somatosensory cortex (SI)] up to 30 months after implantation of the electrode in the distal median nerve in adult cats. This long survival period, which could correspond to 15 years within a human lifespan, enabled us to confirm the biocompatibility of the electrode. We also performed histological and molecular studies on sections of the spinal cord, DCN, and SI and electrophysiological recordings on of DCN and SI. Although in the "implanted" regions (ipsilateral nerve, ipsilateral DCN, and contralateral SI) there was apparently a good recovery of a number of molecular markers, mostly related to local metabolism and neurotransmission in central relay structures, the expression of calcium-binding proteins in the cortex, which identifies inhibitory interneurons, remained clearly abnormal, although they were never as altered as in case of irreversible, chronic denervations. Also, prominent anatomical disorganization was detected in the normal spatial arrangement of neural clusters within the DCN. With respect to the electrical activity the "implanted side" showed minor changes in response latency, intensity, and somatotopy, compared to control recordings. These findings show that central sensory-processing structures achieve fair, but not complete, levels of structural and functional reorganization following chronic intraneural implants of sieve electrodes.

Age-related differences in sensitivity to small changes in frequency assessed with cortical evoked potentials

As part of an ongoing study of age-related changes in auditory processing, sensitivity to small changes in frequency were assessed using the cortical auditory evoked potential, P1-N1-P2, in younger and older adults with normal hearing. Behavioral measures have shown age-related differences in intensity and frequency discrimination that are larger at lower than higher frequencies. However, substantial individual differences and equivocal results among studies have been reported. This variability may reflect differences in tasks and procedures, as well as subject variables, such as hearing sensitivity and level of attention. To minimize these subject variables, the P1-N1-P2 response was investigated using a passive listening paradigm. Subjects were 10 younger and 10 older adults. The P1-N1-P2 was elicited by a 150-ms change in frequency in otherwise continuous 500-Hz and 3000-Hz pure tones presented at 70 dB SPL. P1-N1-P2 threshold was defined as the smallest change in frequency needed to evoke a P1-N1-P2 response. Furthermore, a frequency-dependent aging effect was observed for P1-N1-P2 thresholds, such that older subjects were significantly less sensitive to the frequency change than younger subjects, with significantly larger age-related differences at 500 Hz than at 3000 Hz. Age-related changes in response latencies and amplitude of the P1-N1-P2 response were also evident at 500 and 3000 Hz. These results are consistent with age-related changes in the central auditory system and suggest that changes in frequency discrimination abilities of older adults may be, in part, related to changes in preattentive levels of auditory processing.

Abnormal associative encoding in orbitofrontal neurons in cocaine-experienced rats during decision-making.

Recent evidence has linked exposure to addictive drugs to an inability to employ information about adverse consequences, or outcomes, to control behavior. For instance, addicts and drug-experienced animals fail to adapt their behavior to avoid adverse outcomes in gambling and reversal tasks or after changes in the value of expected rewards. These deficits are similar to those caused by damage to the orbitofrontal cortex, suggesting that addictive drugs may cause long-lasting changes in the representation of outcome associations in a circuit that includes the orbitofrontal cortex. Here we test this hypothesis by recording from orbitofrontal neurons in a discrimination task in rats previously exposed to cocaine (30 mg/kg i.p. for 14 days). We found that orbitofrontal neurons recorded in cocaine-experienced rats failed to signal the adverse outcome at the time a decision was made in the task. The loss of this signal was associated with abnormal changes in response latencies on aversive trials. Furthermore, upon reversal of the cue-outcome associations, orbitofrontal neurons in cocaine-treated rats with enduring reversal impairments failed to reverse their cue-selectivity, while orbitofrontal neurons in cocaine-treated rats with normal performance showed an increase in the plasticity of cue-selective firing after reversal. These results provide direct neurophysiological evidence that exposure to cocaine can cause behaviorally relevant changes in the processing of associative information in a circuit that includes the orbitofrontal cortex.