Baseline Latency Research Articles

Saccadic latency and choice in a concurrent random interval reinforcement schedule.

Conventional decision models view reaction time as a consequence of the duration of decision-making process. However, some studies have shown that reaction time distributions may be strongly affected by reinforcement contingencies (Madelain et al., 2007). Here, we probe the possibility to voluntarily control saccadic latencies in a choice paradigm. Three subjects (including the two authors) tracked a visual target stepping horizontally by 10 deg between two fixed locations on a screen. Any trial with saccadic latencies greater than 300 ms or shorter than 80 ms was interrupted. Using the first and last quartiles of individual baseline latency distributions, we first defined two classes, i.e. short and long saccadic latencies, respectively. We then concurrently reinforced each type of latencies in random interval reinforcement schedules: short and long latencies were reinforced with three different sets of probabilities such that the relative ratio of reinforcing short latencies was either 9/1, 1/9 or 1/1. After training (20 800 trials), we observed bimodal latency distributions –with a peak for short and another for long latencies– for two subjects and to a lesser extent for the third subject. To further probe the extent of control over saccadic latencies, we then analyzed the data using the generalized matching law (Baum, 1974) –which states that the relative proportion of choices made to an option matches the relative proportion of reinforcers earned from that option. We found an almost perfect match between the relative proportion of short and long latencies and the relative obtained reinforcement for two subjects (sensitivities were equal to 0.95 and 0.87) and typical undermatching parameter for the third one (sensitivity = 0.58). These results indicate that saccades may be allocated in time following the reinforcement contingencies in force, which support the idea of a voluntary control of saccadic reaction time.

Variability in response to 1 Hz repetitive TMS

Objective Responses to different plasticity-inducing brain stimulation protocols are highly variable. However there is little data available on the variability of response to 1 Hz repetitive transcranial magnetic stimulation (1 Hz rTMS). We tested the effects of 1 Hz rTMS over the motor cortex on corticospinal excitability. We examined whether an individual’s response could be predicted from measurements of onset latency of motor evoked potential (MEP) following stimulation with different coil orientations. Methods Thirty-two healthy subjects participated in a crossover-design. Baseline latency measurements with different coil orientations and MEPs were recorded from FDI muscle prior to the application of 900 pulses of 1 Hz rTMS with different stimulus intensities. Thirty MEPs were measured every 5 min for half an hour after the intervention. Results At the group level, there were no significant aftereffects of 1 Hz rTMS: about 50% individuals had only a minor or no response to 1 Hz rTMS whereas the remainders had a facilitatory effect. There was no significant correlation between the latency difference of MEPs (anterior-posterior stimulation minus latero-medial stimulation) and the response to 1 Hz rTMS. Conclusions This large variability is in line with similar studies using other forms of non-invasive brain stimulation. Individual factors may influence the responsiveness to these protocols.

Longitudinal Evaluation of Visual Function in Multiple Sclerosis.

To evaluate longitudinal changes of visual function in relapsing-remitting multiple sclerosis (RRMS). Multifocal visual evoked potential (mfVEP), contrast sensitivity (CS), and Humphrey visual fields (HVFs) were obtained at two visits (mean follow-up, 1.5 [±0.9] years) in both eyes of 57 RRMS patients (53 eyes with optic neuritis [ON]: 14 ON within 6 months of first visit [ON < 6 months] and 39 ON ≥ 6 months; 57 non-ON). Longitudinal changes were assessed using mfVEP amplitude (log signal-to-noise ratio [logSNR]), latency, CS, and HVF mean deviation based on established 95% tolerance limits of test-retest variability. A significant percentage of eyes in the ON < 6 months group exceeded 95% tolerance limits for mfVEP logSNR (21%, p < 0.05), latency (35%, p < 0.01), and CS (31% p < 0.001); more improved than worsened over time (14% vs. 7% for logSNR, 21% vs. 14% for latency, and 31% vs. 0% for CS). Multifocal visual evoked potential latency decreased in 11% of non-ON eyes and in 10% of eyes in the ON ≥ 6 months group, and increased in 21% and 10%, respectively (p < 0.01 for all). Latency changes correlated negatively with baseline latency (r = -0.43 and -0.45 for non-ON and ON ≥ 6 months; p = 0.0008). Although a nonsignificant percentage of non-ON and ON ≥ 6 months eyes exceeded tolerance limits for logSNR, CS, or HVF, logSNR and latency changes correlated, and both measures correlated with changes in CS (r = 0.47 to 0.79, p < 0.01). Multifocal visual evoked potential, particularly latency, is potentially useful for assessing neuroprotective and remyelinating strategies in RRMS.

Impact of Aspiration Pneumonia on the Clinical Course of Progressive Supranuclear Palsy: A Retrospective Cohort Study.

IntroductionAlthough aspiration pneumonia is the most common complication of progressive supranuclear palsy (PSP), the clinical impact of aspiration pneumonia on disease course and survival has not been fully estimated. Thus, we retrospectively analyzed the prognostic factors and clinical consequences of pneumonia in PSP.MethodsThe clinical course of patients with aspiration pneumonia was surveyed. The association between baseline clinical features (2 years from disease onset) and latency to the initial development of pneumonia was investigated using survival time and Cox regression analyses.ResultsNinety patients with a clinical diagnosis of PSP were observed for 5.1±3.8 years (mean±SD), and 22 had aspiration pneumonia. Subsequently, 20 patients (91%) had to discontinue oral feeding entirely and 13 (59%) died, whereas, of 68 patients without pneumonia, only three patients (4%) died. Time to initial development of pneumonia was strongly correlated with survival time (Spearman R = 0.92, P<0.001), with a mean latency of 2.3 years to death. Among baseline clinical features, early fall episodes and cognitive decline were significant predictors of pneumonia (P = 0.001 and P<0.001, respectively, log rank test). Cox regression analysis demonstrated that early fall episodes (adjusted hazard ratio: 3.9, 95% confidence interval: 1.2–12.5, P = 0.03) and cognitive decline (adjusted hazard ratio: 5.2, 95% confidence interval: 1.4–19.3, P = 0.02) independently predicted pneumonia. By contrast, dysphagia was not associated with pneumonia (P = 0.2, log rank test).ConclusionInitial development of pneumonia indicates an unfavorable clinical course and predicts survival time (mean survival time 2.3 years). Patients with early falls and cognitive decline were at high risk of early development of pneumonia.

Variability in response to 1 Hz repetitive TMS

Objective Responses to different plasticity-inducing brain stimulation protocols are highly variable. However there is little data available on the variability of response to 1 Hz repetitive transcranial magnetic stimulation (1 Hz rTMS). We tested the effects of 1 Hz rTMS over the motor cortex on corticospinal excitability. We examined whether an individual’s response could be predicted from measurements of onset latency of motor evoked potential (MEP) following stimulation with different coil orientations. Methods Thirty-two healthy subjects participated in a crossover-design. Baseline latency measurements with different coil orientations and MEPs were recorded from FDI muscle prior to the application of 900 pulses of 1 Hz rTMS with different stimulus intensities. Thirty MEPs were measured every 5 min for half an hour after the intervention. Results At the group level, there were no significant aftereffects of 1 Hz rTMS: about 50% individuals had only a minor or no response to 1 Hz rTMS whereas the remainders had a facilitatory effect. There was no significant correlation between the latency difference of MEPs (anterior-posterior stimulation minus latero-medial stimulation) and the response to 1 Hz rTMS. Conclusions This large variability is in line with similar studies using other forms of non-invasive brain stimulation. Individual factors may influence the responsiveness to these protocols.

Modifying excitability of trigemino-facial reflex circuits with transcranial direct current stimulation

s / Brain Stimulation 8 (2015) 378e394 384 Background: Responses to a number of different plasticityinducing brain stimulation protocols are highly variable. However there is little data available on the variability of response to 1 Hertz repetitive transcranial magnetic stimulation (1Hz rTMS). Objective: We tested the effects of 1Hz rTMS over the motor cortex on corticospinal excitability. We also examined whether an individual’s response could be predicted frommeasurements of onset latency of motor evoked potential (MEP) following stimulationwith different orientations of monophasic transcranial magnetic stimulation (TMS). Methods: Thirty-two healthy subjects (mean age 30.3 years, SD 11.0; 13 females) participated in a crossover-design. Baseline latency measurements with different coil orientations and MEPs were recorded from the first dorsal interosseous muscle prior to the application of 900 pulses of 1Hz rTMS with two different stimulus intensities, i.e. 90% resting motor threshold (RMT) and 115%RMT. Thirty MEPs were measured every 5 min for up to half an hour after the intervention to assess after-effects on corticospinal excitability. Results: At the group level, there were no significant aftereffects of 1Hz rTMS for both stimulus intensities: about 50% individuals had only a minor or no response to 1Hz rTMS whereas the remainders had a facilitatory effect to both forms of stimulation. There was no significant correlation between the latency difference of MEPs (anterior-posterior stimulation minus latero-medial stimulation) and the response to 1Hz rTMS. Conclusions: The large variability in response to 1Hz rTMS is in line with similar studies using other forms of non-invasive brain stimulation. These results highlight the importance of individual factors influencing the responsiveness to these protocols.

Oral self-administration of buprenorphine in the diet for analgesia in mice.

Postsurgical oral self-administration of analgesics in rodents is an interesting technique of providing analgesia, avoiding the negative effects of manipulation. Several strategies, using gelatin or nutella, have already been described. However, rodents require some habituation period to reach a good intake because of their neophobic behavior. The current study aimed to explore whether buprenorphine when mixed with an extruded diet offers a potential treatment option in the pain management of mice using a triple approach: by measuring the spontaneous intake in healthy animals; by using the hot-plate test; and finally by assessing the drug's ability to provide postoperative analgesia in a surgical intervention of moderate severity (intra-utero electroporation). Mice consumed during 20 hours, similar amounts of extruded diet alone, mixed with glucosaline, and mixed with buprenorphine (0.03 mg per pellet) or meloxicam (0.25 mg per pellet) both of which were diluted in glucosaline, showing that no neophobia was associated with these administrations. Relative increase from baseline latency (% maximal possible effect) in the hot-plate test at 20 h of administration was significantly higher for oral buprenorphine in diet 0.03 mg/pellet, and diet 0.15 mg/pellet, compared with placebo and no differences were found between those oral administrations and subcutaneous buprenorphine 0.1 mg/kg measured 3 h later. The treatment was also effective in attenuating the reductions in food consumption and body weight that occur after surgery. These data suggest that providing buprenorphine with the diet is a feasible and effective way of self-administration of analgesia in mice and does not cause neophobia and may easily contribute to the refinement of surgical procedures.

Antiallodynic and antihyperalgesic activity of 3-[4-(3-trifluoromethyl-phenyl)-piperazin-1-yl]-dihydrofuran-2-one compared to pregabalin in chemotherapy-induced neuropathic pain in mice

BackgroundAnticancer drugs — oxaliplatin (OXPT) and paclitaxel (PACLI) cause painful peripheral neuropathy activating Transient Receptor Potential (TRP) channels. Here we investigated the influence of 3-[4-(3-trifluoromethyl-phenyl)-piperazin-1-yl]-dihydrofuran-2-one (LPP1) and pregabalin on nociceptive thresholds in neuropathic pain models elicited by these drugs. Pharmacokinetics of LPP1 and its ability to attenuate neurogenic pain caused by TRP agonists: capsaicin and allyl isothiocyanate (AITC) were also investigated. MethodsAntiallodynic and antihyperalgesic effects of intraperitoneally administered LPP1 and pregabalin were tested in the von Frey, hot plate and cold water tests. The influence of LPP1 on locomotor activity and motor coordination was assessed using actimeters and rotarod. Serum and tissue concentrations of LPP1 were measured using the HPLC method with fluorimetric detection. ResultsIn OXPT-treated mice LPP1 and pregabalin dose-dependently reduced tactile allodynia (41–106% and 6–122%, respectively, p<0.01). At the dose of 10mg/kg LPP1 attenuated cold allodynia. In PACLI-treated mice LPP1 and pregabalin reduced tactile allodynia by 12–63% and 8–50%, respectively (p<0.01). Both drugs did not affect cold allodynia, whereas pregabalin (30mg/kg) attenuated heat hyperalgesia (80% vs. baseline latency time; p<0.01). No motor impairments were observed in LPP1 or pregabalin-treated neuropathic mice in the rotarod test, while severe sedation was noted in the locomotor activity test.LPP1 reduced pain induced by capsaicin (51%; p<0.01) and AITC (41%; p<0.05). The mean serum concentration of LPP1 measured 30min following i.p. administration was 7904.6±1066.1ng/ml. Similar levels were attained in muscles, whereas brain concentrations were 62% lower. Relatively high concentrations of LPP1 were also determined in the cerebrospinal fluid and the sciatic nerve. ConclusionsLPP1 and pregabalin reduce pain in OXPT and PACLI-treated mice. This activity of LPP1 might be in part attributed to the inhibition of TRPV1 and TRPA1 channels, but also central mechanisms of action cannot be ruled out.

Fentanyl produces an anti-hyperalgesic effect through the suppression of sodium channels in mice with painful diabetic neuropathy

Diabetic neuropathy is one of the most frequent complications of diabetes mellitus. Therefore, the present study was designed to investigate the anti-hyperalgesic mechanism of fentanyl in a mouse model of streptozotocin-induced diabetic neuropathy. The antinociceptive response was assessed by recording the latency in a tail-flick test. The tail-flick latency in diabetic mice was significantly shorter than that in non-diabetic mice. Fentanyl, at doses of 3 and 10μg/kg, s.c., produced a dose-dependent increase in the tail-flick latencies in diabetic mice. While fentanyl (3μg/kg, s.c.) did not produce a significant inhibition of the tail-flick response in non-diabetic mice, it significantly prolonged the tail-flick latency in diabetic mice to the same level as the baseline latency in non-diabetic mice. Although pretreatment with naloxone (3mg/kg, s.c.) completely antagonized fentanyl-induced antinociception in non-diabetic mice, it had no effect on the antinociceptive effect of fentanyl in diabetic mice. Pretreatment with either of the voltage-gated sodium channel openers fenvarelarte and veratridine practically abolished the antinociceptive effects of fentanyl in diabetic mice. However, neither fenvarelate nor veratridine affected the antinociceptive effect of fentanyl in non-diabetic mice. These results suggest that the anti-hyperalgesic effect of fentanyl is mediated through the blockade of sodium channels in diabetic mice, whereas opioid receptors mediate the antinociceptive effect of fentanyl in non-diabetic mice.

Quit Now? Quit Soon? Quit When You’re Ready? Insights About Target Quit Dates for Smoking Cessation From an Online Quit Date Tool

BackgroundSetting a target quit date (TQD) is often an important component in smoking cessation treatment, but ambiguity remains concerning the optimal timing (ie, quitting spontaneously versus delaying to prepare).ObjectiveWe examined four questions about the timing of TQDs and smoking outcomes in secondary analyses of The iQUITT Study, a randomized trial of Internet and telephone treatment for cessation: (1) What are the characteristics of TQDs set using an online interactive quit date tool?, (2) What are the characteristics of individuals who use a quit date tool and do they differ from those who do not?, (3) Are there differences in smoker characteristics, treatment utilization, and cessation outcomes based TQD timing?, and (4) Is maintenance of an initial TQD predictive of abstinence or do changes to TQDs lead to cessation?MethodsA total of 825 adult current cigarette smokers were randomized to enhanced Internet or enhanced Internet plus telephone counseling. Latency to TQD in days was calculated as the date difference between the initial TQD and enhanced Internet registration; prospective TQD setters were stratified into four latency groups (0, 1-14, 15-28, 29+ days). Baseline variables, website utilization, and 3-month cessation outcomes were examined between prospective TQD groups. Desire and confidence to quit, number of TQDs, and website logins were tested as predictors of 30-day point prevalence abstinence (ppa) at 3 months (responder-only analyses). Classification and regression tree (CART) analysis explored interactions among baseline variables, website utilization, and latency to TQD as predictors of 30-day ppa.ResultsThere were few baseline differences between individuals who used the quit date tool and those who did not. Prospective TQDs were set as follows: registration day was 17.1% (73/427), 1-14 days was 37.7% (161/427), 15-28 days was 18.5% (79/427), and 29+ days was 26.7% (114/427). Participants with a TQD within 2 weeks had higher baseline self-efficacy scores but did not differ on smoking variables. Individuals whose TQD was the same day as registration had the highest logins, page views, number of TQDs set using the tool, and messages sent to other members. Logistic regression revealed a significant interaction between number of TQDs and website logins for 30-day ppa (P=.005). Among those with high logins, 41.8% (33/79) with 1 TQD were abstinent versus 25.9% (35/135) with 2+TQDs. Logins and self-efficacy predicted 30-day ppa in the CART model.ConclusionsTQD timing did not predict cessation outcomes in standard or exploratory analyses. Self-efficacy and an apparent commitment to an initial TQD were the components most highly related to abstinence but only via interactions with website utilization. Findings highlight the importance of feeling efficacious about handling specific smoking situations and engaging with treatment. Additional research focused on increasing engagement in Web-based cessation studies is needed.Trial RegistrationClinicalTrials.gov: NCT00282009; http://clinicaltrials.gov/show/NCT00282009 (Archived by WebCite at http://www.webcitation.org/6Kt7NrXDl).

Variability in Response to Transcranial Direct Current Stimulation of the Motor Cortex

Responses to a number of different plasticity-inducing brain stimulation protocols are highly variable. However there is little data available on the variability of response to transcranial direct current stimulation (TDCS). We tested the effects of TDCS over the motor cortex on corticospinal excitability. We also examined whether an individual's response could be predicted from measurements of onset latency of motor evoked potential (MEP) following stimulation with different orientations of monophasic transcranial magnetic stimulation (TMS). Fifty-three healthy subjects participated in a crossover-design. Baseline latency measurements with different coil orientations and MEPs were recorded from the first dorsal interosseous muscle prior to the application of 10 min of 2 mA TDCS (0.057 mA/cm2). Thirty MEPs were measured every 5 min for up to half an hour after the intervention to assess after-effects on corticospinal excitability. Anodal TDCS at 2 mA facilitated MEPs whereas there was no significant effect of 2 mA cathodal TDCS. A two-step cluster analysis suggested that approximately 50% individuals had only a minor, or no response to TDCS whereas the remainder had a facilitatory effect to both forms of stimulation. There was a significant correlation between the latency difference of MEPs (anterior-posterior stimulation minus latero-medial stimulation) and the response to anodal, but not cathodal TDCS. The large variability in response to these TDCS protocols is in line with similar studies using other forms of non-invasive brain stimulation. The effects highlight the need to develop more robust protocols, and understand the individual factors that determine responsiveness.

Predictors of Treatment Response to Brief Behavioral Treatment of Insomnia (BBTI) in Older Adults

The extant literature on predictors of treatment response to behavioral treatments for insomnia is equivocal and limited in scope. The current study examined demographic, clinical, and sleep characteristics as predictors of clinically significant treatment response to brief behavioral treatment of insomnia (BBTI) in older adults with insomnia. Thirty-nine older adults with insomnia (67% females, mean age: 72.54 years) were randomized to BBTI treatment. Treatment outcomes were defined according to 2 criteria: (1) "response," defined as change in Pittsburgh Sleep Quality Index (PSQI) score ≥ 3 points or increase in sleep diary sleep efficiency ≥ 10%); or (2) remission, defined as absence of a clinical diagnosis of insomnia according to standard diagnostic criteria. Logistic regression examined whether baseline demographic, clinical, or sleep characteristics predicted treatment outcomes at 1 month follow-up. Demographic variables did not predict treatment outcomes for either criterion. Higher anxiety, depression, poorer sleep quality, and longer polysomnography (PSG)-assessed sleep latency predicted greater likelihood of response at follow-up (p < 0.05). Longer sleep duration at baseline (measured by sleep diary and PSG) predicted greater likelihood of the remission at follow-up (p < 0.05). Patients with insomnia who have greater distress at baseline or prolonged sleep latency are more likely to show positive response to BBTI. In contrast, short sleepers at baseline are less likely to have resolution of insomnia diagnosis following BBTI, perhaps due to the sleep restriction component of the treatment. Identifying the characteristics that predict positive BBTI treatment outcomes can facilitate personalized behavioral treatments to improve outcomes.

Use of the bulbocavernosus reflex system in assessing voiding dysfunction

The Bulbocavernosus Reflex System (BRS) (Laborie, Canada) is an office-based procedure used to measure the bulbocavernosus reflex (BCR) latency period. The aim of this study is to evaluate the BCR as a predictor of specific voiding dysfunction patterns confirmed by urodynamics (UDS). A total of 87 men were evaluated with BRS, UDS, and electromyography at Weill Cornell Medical College from March to August 2010. Baseline characteristics, demographics, UDS, and latency parameters were recorded. Multivariate logistic regression analysis was performed to evaluate prolonged BCR (latency >45 ms) as a predictor of specific voiding dysfunction patterns. The median age of men was 70.4 years (IQR 57.6-75.6). Based on UDS, 60 men were given a primary or secondary diagnosis of bladder outlet obstruction (BOO), 43 a diagnosis of detrusor overactivity (DO), 11 a diagnosis of intrinsic sphincter deficiency (ISD), and 4 a diagnosis of detrusor sphincter dyssynergia (DSD). Median BCR latency was 57.0 ms (IQR 47.5-76.5) and 68 (78%) men demonstrated a prolonged latency. In multivariate analysis, latency period was not significantly associated with DO, BOO, ISD, or DSD (p = 0.067, 0.696, 0.999, 0.971, respectively). Prolonged bulbocavernosus reflex latency was not associated with DO, BOO, ISD, or DSD. Although evidence in the literature suggests a link between this reflex arc and voiding, its specific diagnostic role remains unclear. Large prospective trials are needed to further explore the role of BCR in the evaluation of patients with voiding dysfunction.

Differential Control of Opioid Antinociception to Thermal Stimuli in a Knock-In Mouse Expressing Regulator of G-Protein Signaling-Insensitive GαoProtein

Regulator of G-protein signaling (RGS) proteins classically function as negative modulators of G-protein-coupled receptor signaling. In vitro, RGS proteins have been shown to inhibit signaling by agonists at the μ-opioid receptor, including morphine. The goal of the present study was to evaluate the contribution of endogenous RGS proteins to the antinociceptive effects of morphine and other opioid agonists. To do this, a knock-in mouse that expresses an RGS-insensitive (RGSi) mutant Gαo protein, Gαo(G184S) (Gαo RGSi), was evaluated for morphine or methadone antinociception in response to noxious thermal stimuli. Mice expressing Gαo RGSi subunits exhibited a naltrexone-sensitive enhancement of baseline latency in both the hot-plate and warm-water tail-withdrawal tests. In the hot-plate test, a measure of supraspinal nociception, morphine antinociception was increased, and this was associated with an increased ability of opioids to inhibit presynaptic GABA neurotransmission in the periaqueductal gray. In contrast, antinociception produced by either morphine or methadone was reduced in the tail-withdrawal test, a measure of spinal nociception. In whole-brain and spinal cord homogenates from mice expressing Gαo RGSi subunits, there was a small loss of Gαo expression and an accompanying decrease in basal G-protein activity. Our results strongly support a role for RGS proteins as negative regulators of opioid supraspinal antinociception and also reveal a potential novel function of RGS proteins as positive regulators of opioid spinal antinociceptive pathways.

Is the Relationship between Race and Continuous Positive Airway Pressure Adherence Mediated by Sleep Duration?

Black race has been associated with decreased continuous positive airway pressure (CPAP) adherence. Short sleep duration, long sleep latency, and insomnia complaints may affect CPAP adherence as they affect sleep and opportunity to use CPAP. We assessed whether self-reported sleep measures were associated with CPAP adherence and if racial variations in these sleep characteristics may explain racial differences in CPAP adherence. Analysis of data from a randomized controlled trial (HomePAP), which investigated home versus laboratory-based diagnosis and treatment of obstructive sleep apnea. Seven American Academy of Sleep Medicine-accredited sleep centers in five cities in the United States. Enrolled subjects (n = 191) with apnea-hypopnea index ≥ 15 and sleepiness (Epworth Sleepiness Scale > 12). N/A. Multivariable regression was used to assess if subjective sleep measures and symptoms predicted 3-mo CPAP use. Mediation analysis was used to assess if sleep measures mediated the association of race with CPAP adherence. Black participants reported shorter sleep duration and longer sleep latency at baseline than white and Hispanic participants. Shorter sleep duration and longer sleep latency predicted worse CPAP adherence. Sleep duration mediated the association of black race with lower CPAP adherence. However, insomnia symptoms were not associated with race or CPAP adherence. Among subjects with similar severity of obstructive sleep apnea and sleepiness, baseline self-reported sleep duration and latency, but not perceived insomnia, predicted CPAP adherence over 3 mo. Sleep duration explains some of the observed differences in CPAP use by race. Sleep duration and latency should be considered when evaluating poor CPAP adherence. PORTABLE MONITORING FOR DIAGNOSIS AND MANAGEMENT OF SLEEP APNEA (HOMEPAP) URL: http://clinicaltrials.gov/show/NCT00642486. NIH clinical trials registry number: NCT00642486.

Recovery cycle times of inferior colliculus neurons in the awake bat measured with spike counts and latencies

Neural responses in the mammalian auditory midbrain (inferior colliculus; IC) arise from complex interactions of synaptic excitation, inhibition, and intrinsic properties of the cell. Temporally selective duration-tuned neurons (DTNs) in the IC are hypothesized to arise through the convergence of excitatory and inhibitory synaptic inputs offset in time. Synaptic inhibition can be inferred from extracellular recordings by presenting pairs of pulses (paired tone stimulation) and comparing the evoked responses of the cell to each pulse. We obtained single unit recordings from the IC of the awake big brown bat (Eptesicus fuscus) and used paired tone stimulation to measure the recovery cycle times of DTNs and non-temporally selective auditory neurons. By systematically varying the interpulse interval (IPI) of the paired tone stimulus, we determined the minimum IPI required for a neuron's spike count or its spike latency (first- or last-spike latency) in response to the second tone to recover to within ≥50% of the cell's baseline count or to within 1 SD of it's baseline latency in response to the first tone. Recovery times of shortpass DTNs were significantly shorter than those of bandpass DTNs, and recovery times of bandpass DTNs were longer than allpass neurons not selective for stimulus duration. Recovery times measured with spike counts were positively correlated with those measured with spike latencies. Recovery times were also correlated with first-spike latency (FSL). These findings, combined with previous studies on duration tuning in the IC, suggest that persistent inhibition is a defining characteristic of DTNs. Herein, we discuss measuring recovery times of neurons with spike counts and latencies. We also highlight how persistent inhibition could determine neural recovery times and serve as a potential mechanism underlying the precedence effect in humans. Finally, we explore implications of recovery times for DTNs in the context of bat hearing and echolocation.

Microneurographic identification of spontaneous activity in C-nociceptors in neuropathic pain states in humans and rats

C-nociceptors do not normally fire action potentials unless challenged by adequate noxious stimuli. However, in pathological states nociceptors may become hyperexcitable and may generate spontaneous ectopic discharges. The aim of this study was to compare rat neuropathic pain models and to assess their suitability to model the spontaneous C-nociceptor activity found in neuropathic pain patients. Studies were performed in normal rats (n = 40), healthy human subjects (n = 15), peripheral neuropathic pain patients (n = 20), and in five rat neuropathic pain models: nerve crush (n = 24), suture (n = 14), chronic constriction injury (n = 12), STZ-induced diabetic neuropathy (n = 56), and ddC-induced neuropathy (n = 15). Microneurographic recordings were combined with electrical stimulation to monitor activity in multiple C fibers. Stimulation at 0.25 Hz allowed spontaneous impulses to be identified by fluctuations in baseline latency. Abnormal latency fluctuations could be produced by several mechanisms, and spontaneous activity was most reliably identified by the presence of unexplained latency increases corresponding to two or more additional action potentials. Spontaneous activity was present in a proportion of mechano-insensitive C-nociceptors in the patients and all rat models. The three focal traumatic nerve injury models provided the highest proportion (59.5%), whereas the two polyneuropathy models had fewer (18.6%), and the patients had an intermediate proportion (33.3%). Spontaneously active mechano-sensitive C-nociceptors were not recorded. Microneurographic recordings of spontaneous activity in diseased C-nociceptors may be useful for both short- and long-term drug studies, both in animals and in humans.

Lack of relationship between acoustic startle and cognitive variables in schizophrenia and control subjects

Measures of acoustic startle such as prepulse inhibition (PPI) and startle latency have been found to be impaired in schizophrenia, and are commonly thought to be related to cognitive deficits in this disease. However, findings about the relationship between startle variables and cognitive performance have been equivocal. In this study, we examined correlations between startle measures (baseline startle magnitude, latency, habituation and PPI) and cognitive performance (using the Benton Visual Retention Test, Conner's Continuous Performance Test, California Verbal Learning Test, Finger Tapping Test, and Wisconsin Card Sort Test) in 107 schizophrenia patients and 94 healthy controls. Overall, there was a lack of any significant relationship between these constructs in both populations when correcting for multiple comparisons. This suggests that alterations in startle measures seen in schizophrenia may not reflect elements of information processing that cause cognitive deficits in the disease.

Anxiety-like behavior in weanling and young adult male and female malnourished rats

The present study determined whether protein-calorie malnutrition alters anxiety-like behavior in weanling and young adult, male and female malnourished rats. On the day of birth, litters of Wistar rats were divided into Control (C) and Malnutrition (M) groups. In the C group, litters were fed by dams receiving ad libitum lab chow, whereas in the M group, litters were fed by dams receiving 40% of the total amount of the diet offered to dams in the C group. After weaning (PND21) until PND50, animals received the same food as theirs mothers (i.e., ad libitum access in the C group and 40% of the C group food in the M group). On PND21 and PND50, independent C (male [CM] and female [CF]) and M (male [MM] and female [MF]) groups were exposed to the elevated T-maze. The time taken to withdraw four paws from this arm was recorded (baseline latency [BL]). The same measurement was repeated twice at 30s intervals (avoidance trial 1 [AT1] and avoidance 2 [AT2]). The cutoff time in each trial was 300s. ANOVA indicated a four-way age×diet×sex×trials interaction. Post hoc comparisons revealed that PND50 rats had a lower BL and AT1 latency compared with PND21 rats. Training increased both AT1 and AT2 latencies compared with BL in both the CM and CF groups. Weanling malnourished rats exhibited reduced anxiety-like behavior and young adult male rats presented less anxiety-like behavior than young adult female rats in this experimental model.

*Poster 47: Correlations Between Recovery of Ambulatory Capacity and Lower-Limb Somatosensory Evoked Potentials in Incomplete Spinal Cord Injury

Objective: To study relationships between posterior tibial (PT) nerve somatosensory evoked potentials (SEP) and recovery of ambulatory capacity in patients with incomplete spinal cord injury (SCI) participating in Lokomat training. Design: Correlation study of functional clinical outcome with quantitative electrophysiological measures of sensory processing. Setting: Queen Elizabeth National Spinal Injuries Unit, Scotland. Participants: 13 acute and 5 chronic incomplete SCI patients. Intervention: 30 hours Lokomat Training over a 6-week period.