Intersession Interval Research Articles

Human Brain Networks in Physiological and Pathological Aging: Reproducibility of Electroencephalogram Graph Theoretical Analysis in Cortical Connectivity.

Background: Physiological and pathological brain aging plays a central role in brain network modulation. The aim of the present article was to assess the stability of a proposed method for evaluation of small-world (SW) characteristics for the study of the human connectome. Subjects and Methods: Eighty subjects were recruited: 36 young healthy controls, 32 elderly healthy controls, and 12 patients affected by Alzheimer's disease (AD). Electroencephalograms (EEGs) were recorded during six separate sessions (480 recordings) at an average intersession interval of 3.8 ± 0.2 days. We applied graph theory functions to the weighted and undirected networks obtained by the lagged linear coherence estimated by exact low-resolution electromagnetic tomography (eLORETA). We explored the following frequency bands: delta (2-4 Hz), theta (4-8 Hz), alpha 1 (8-10.5 Hz), alpha 2 (10.5-13 Hz), beta 1 (13-20 Hz), beta 2 (20-30 Hz), and gamma (30-40 Hz). Results: The proposed method for evaluation of SW characteristics exhibited good reproducibility and stability. Furthermore, results showed the pattern, Young>Elderly>AD, in low-frequency delta and theta bands and vice versa in the higher alpha band. Finally, a correlation with age was confirmed in healthy subjects, showing that the older the age, the higher the SW values for alpha 2. Discussion: Evidences from the present study confirm the stability of the SW index and suggest that the analysis of connectivity patterns evaluated from EEGs can be supported by the graph theory. The proposed method for evaluation of SW characteristics has shown good reproducibility and stability. This technique, applied to patient data, could provide more information on the pathophysiological processes underlying age-related brain disconnection, as well as on administration of rehabilitation treatments at the right time, which could allow patients to avoid unnecessary interventions. Impact statement The graph analysis tools described in this study represent an interesting approach to study the distinctive characteristics of physiological aging by focusing on functional connectivity networks. The proposed method for evaluation of small-world characteristics has shown good reproducibility and stability. This technique, applied to patient data, could provide more information on the pathophysiological processes underlying age-related brain disconnection, as well as on delivery of rehabilitation treatments at the right time, which could allow patients to avoid unnecessary interventions.

The distributed practice effects of speaking task repetition

AbstractThis study examined the distributed practice effects on L2 speaking task repetition (TR). Previous research indicated that speaking TR has beneficial effects on learners’ later speech. To examine the distributed practice effects on learners’ second repetition and post‐repetition speech, 38 university students were engaged in cartoon narrations. The procedure included: a pre‐test, two repetition tasks with a 1‐week intersession interval (spaced practice group) or without an interval (massed practice group), and a post‐test. The grammatical complexity, grammatical accuracy, fluency, and lexical variety of learners’ performances were examined using ANCOVA. The lexical variety scores increased more in the spaced practice group than the massed practice group in the pre‐ and post‐test comparisons, indicating that spaced TR may induce lexical variety in post‐repetition speech.

A reproducible systematic map of research on the illusory truth effect

People believe information more if they have encountered it before, a finding known as the illusory truth effect. But what is the evidence for the generality and pervasiveness of the illusory truth effect? Our preregistered systematic map describes the existing knowledge base and objectively assesses the quality, completeness and interpretability of the evidence provided by empirical studies in the literature. A systematic search of 16 bibliographic and grey literature databases identified 93 reports with a total of 181 eligible studies. All studies were conducted at Western universities, and most used convenience samples. Most studies used verbatim repetition of trivia statements in a single testing session with a minimal delay between exposure and test. The exposure tasks, filler tasks and truth measures varied substantially across studies, with no standardisation of materials or procedures. Many reports lacked transparency, both in terms of open science practices and reporting of descriptive statistics and exclusions. Systematic mapping resulted in a searchable database of illusory truth effect studies (https://osf.io/37xma/). Key limitations of the current literature include the need for greater diversity of materials as stimuli (e.g., political or health contents), more participants from non-Western countries, studies examining effects of multiple repetitions and longer intersession intervals, and closer examination of the dependency of effects on the choice of exposure task and truth measure. These gaps could be investigated using carefully designed multi-lab studies. With a lack of external replications, preregistrations, data and code, verifying replicability and robustness is only possible for a small number of studies.

Reliability and Reproducibility of Hadamard Encoded Pseudo-Continuous Arterial Spin Labeling in Healthy Elderly.

The perfusion parameters cerebral blood flow (CBF) and arterial transit time (ATT) measured with arterial spin labeling (ASL) magnetic resonance imaging (MRI) provide valuable essentials to assess the integrity of cerebral tissue. Brain perfusion changes, due to aging, an intervention, or neurodegenerative diseases for example, could be investigated in longitudinal ASL studies with reliable ASL sequences. Generally, pseudo-continuous ASL (pCASL) is preferred because of its larger signal-to-noise ratio (SNR) compared to pulsed ASL (PASL) techniques. Available pCASL versions differ regarding their feature details. To date only little is known about the reliability and reproducibility of CBF and ATT measures obtained with the innovative Hadamard encoded pCASL variant, especially if applied on participants in old age. Therefore, we investigated an in-house developed Hadamard encoded pCASL sequence on a group of healthy elderly at two different 3 Tesla Siemens MRI systems (Skyra and mMR Biograph) and evaluated CBF and ATT reliability and reproducibility for several regions-of-interests (ROI). Calculated within-subject coefficients of variation (wsCV) demonstrated an excellent reliability of perfusion measures, whereas ATT appeared to be even more reliable than CBF [e.g., wsCV(CBF) = 2.9% vs. wsCV(ATT) = 2.3% for a gray matter (GM) ROI on Skyra system]. Additionally, a substantial agreement of perfusion values acquired on both MRI systems with an inter-session interval of 78 ± 17.6 days was shown by high corresponding intra-class correlation (ICC) coefficients [e.g., ICC(CBF) = 0.704 and ICC(ATT) = 0.754 for a GM ROI]. The usability of this novel Hadamard encoded pCASL sequence might improve future follow-up perfusion studies of the aging and/or diseased brain.

The Trajectory of Truth: A Longitudinal Study of the Illusory Truth Effect.

Repeated statements are rated as subjectively truer than comparable new statements, even though repetition alone provides no new, probative information (the illusory truth effect). Contrary to some theoretical predictions, the illusory truth effect seems to be similar in magnitude for repetitions occurring after minutes or weeks. This Registered Report describes a longitudinal investigation of the illusory truth effect (n = 608, n = 567 analysed) in which we systematically manipulated intersession interval (immediately, one day, one week, and one month) in order to test whether the illusory truth effect is immune to time. Both our hypotheses were supported: We observed an illusory truth effect at all four intervals (overall effect: χ2(1) = 169.91; Mrepeated = 4.52, Mnew = 4.14; H1), with the effect diminishing as delay increased (H2). False information repeated over short timescales might have a greater effect on truth judgements than repetitions over longer timescales. Researchers should consider the implications of the choice of intersession interval when designing future illusory truth effect research.

Effects of Intermittent Theta Burst Stimulation on the Clock Drawing Test Performances in Patients with Alzheimer's Disease.

The clock drawing test (CDT) is widely used in clinical neuropsychological practice. However, its neuroanatomical correlates have not been well established. This study investigated the effects of theta burst stimulation (TBS) applied over different brain regions on CDT scores in patients with Alzheimer's disease (AD). The 10-20 positions F3, F4, T3, T4, TP3, TP4, P3, P4, as determined by a 10-20 positioning cap, were targeted. Excitatory intermittent TBS (iTBS) was given over the above-mentioned eight regions to ten AD patients and ten control subjects on separate days. CDT was administered at baseline (T0), during the 5min following the TBS (T1) and 60min after TBS (T2), with an inter-session interval of at least 4days. iTBS over TP4 and P4 transiently increased Rouleau CDT score in AD patients. When targeting TP4 and P4, mainly the area of the supramarginal/angular gyrus and the inferior parietal lobe, corresponding respectively to the Brodmann areas 40/39 and 7/40, are reached. iTBS thus seems able to modulate activity of the right posterior parietal cortex in AD patients performing the CDT. Our results provide physiological evidence that those parietal regions are functionally important for the execution of the Rouleau CDT. This finding suggests that CDT has reliable neuroanatomical correlates, and support the notion that this test can be used as a good marker of right parietal brain dysfunction. The present study also highlights the therapeutic potential of the induction of neuromodulatory effects using non-invasive brain stimulation techniques.

Time distribution and intentional vocabulary learning through repeated reading: a partial replication and extension

The aim of this study is to analyze the effect of different schedules of repeated reading practice on intentional vocabulary learning, and constitutes a partial replication and extension of the authors’ previous study on incidental vocabulary learning. Two groups of Taiwanese EFL learners (n = 72) engaged in five repeated reading sessions; one group had the sessions on consecutive days (1-day intersession interval, ISI), whereas the other had them once a week (7-day ISI). Apart from reading for meaning, the students were also asked to focus on 36 target words. The students were tested before and immediately after the treatment. Moreover, a delayed posttest was scheduled at a retention interval (RI) of 4 and 28 days for the intensive group and spaced group respectively (considering an ISI/RI ratio of 25%). The results indicate that the short-spaced repeated reading sessions had a significantly more positive effect on vocabulary learning on both immediate and delayed posttest than the long-spaced sessions. The benefits of the short-spaced schedule were clearer in the current study on intentional vocabulary learning than in the authors’ previous study on incidental learning through repeated reading.

Learning the same motor task twice impairs its retention in a time- and dose-dependent manner.

Anterograde interference emerges when two differing tasks are learned in close temporal proximity, an effect repeatedly attributed to a competition between differing task memories. However, recent development alternatively suggests that initial learning may trigger a refractory period that occludes neuroplasticity and impairs subsequent learning, consequently mediating interference independently of memory competition. Accordingly, this study tested the hypothesis that interference can emerge when the same motor task is being learned twice, that is when competition between memories is prevented. In a first experiment, the inter-session interval (ISI) between two identical motor learning sessions was manipulated to be 2 min, 1 h or 24 h. Results revealed that retention of the second session was impaired as compared to the first one when the ISI was 2 min but not when it was 1 h or 24 h, indicating a time-dependent process. Results from a second experiment replicated those of the first one and revealed that adding a third motor learning session with a 2 min ISI further impaired retention, indicating a dose-dependent process. Results from a third experiment revealed that the retention impairments did not take place when a learning session was preceded by simple rehearsal of the motor task without concurrent learning, thus ruling out fatigue and confirming that retention is impaired specifically when preceded by a learning session. Altogether, the present results suggest that competing memories is not the sole mechanism mediating anterograde interference and introduce the possibility that a time- and dose-dependent refractory period-independent of fatigue-also contributes to its emergence. One possibility is that learning transiently perturbs the homeostasis of learning-related neuronal substrates. Introducing additional learning when homeostasis is still perturbed may not only impair performance improvements, but also memory formation.

Evaluation of a 5 day accelerated 1 Hz repetitive transcranial magnetic stimulation protocol in major depression: A feasibility study

• rTMS is an effective intervention in major depressive disorder, but has limited accessibility. • Shortening rTMS courses while retaining similar effectiveness would increase scalability. • We delivered 8 daily sessions of 1 Hz rTMS over 5 days. • Treatment was safe, well-tolerated and effective. • Validation in a randomized trial will be required. Repetitive transcranial magnetic stimulation (rTMS) is an effective intervention in major depressive disorder (MDD) but requires daily travel to a treatment clinic over several weeks. Shorter rTMS courses retaining similar effectiveness would thus increase the practicality and scalability of the technique, and therefore its accessibility. We assessed the feasibility of a novel 5 day accelerated 1 Hz rTMS protocol. We hypothesized that this novel rTMS protocol would be safe and well-tolerated while shortening the overall treatment course. We conducted a prospective, single-arm, open-label feasibility study. Thirty (30) participants received a one-week (5 days) accelerated (8 sessions per day, 40 sessions total) course of 1 Hz rTMS (600 pulses per session, 50-minute intersession interval) over the right dorsolateral prefrontal cortex (R-DLPFC) using a figure-of-eight coil at 120% of the resting motor threshold (rMT). Primary outcomes were response and remission rates on the Beck Depression Inventory-II (BDI-II). Response and remission rates 1 week after treatment were 33.3% and 13.3% respectively and increased to 43.3% and 30.0% at follow-up 4 weeks after treatment. No serious adverse events occurred. All participants reported manageable pain levels. 1 Hz rTMS administered 8 times daily for 5 days is safe and well-tolerated. Validation in a randomized trial will be required. ClinicalTrials.gov Identifier: NCT04376697.

THE EFFECT OF INPUT SPACING ON EFL LEARNERS' VOCABULARY KNOWLEDGE

The lag or the intersession interval (ISI) is the gap between two learning sessions. Lag effects are one of those effects that few studies have examined. Moreover, albeit a huge bulk of research on input spacing (i.e., phenomenon of distributed learning conditions) has been done in laboratory setting, few studies have directly examined this issue within real contexts. Therefore, the purpose of this study was to examine the impact of not only spaced-short but also spaced-long condition on the vocabulary knowledge of EFL learners. To achieve this goal, 37 intermediate level EFL learners were selected from four intact classes. The whole process took place in nine weeks; two testing sessions for pretest and a 28-day delayed posttest, two learning sessions and a final review session. Learning was done in two sessions. In this process, 20 target items were divided into 10 target words from each two lists. The first 10 words were studied during the first session, and reviewed during the review session. Eight days (intersession interval) ISI was specified for the spaced-long condition. Finally, a 1-day ISI was specified for the spaced-short condition. To do so, the second 10 words during the second session were studied, and then they were reviewed during the review session. The results of paired samples t-test revealed that spaced-long input was more effective than the space-short. Spaced-long condition could help learners for conceptual understanding to develop, reduce forgetting and provide opportunities for learners to learn more efficiently.

Distributed Practice in Math Facts Fluency: A Comparative Analysis of Varied Intersession Intervals

We examined the math facts fluency growth of students receiving explicit timing practice in either a massed, short-distributed, or long-distributed fashion. In a repeated measures group design, 43 Midwestern third-grade students completed four 1-min math probes each day for 20 days. Hierarchical linear modeling revealed that students who received practice separated by a 3-hr interval grew significantly more than students who practiced with a 10-min distribution or a massed presentation. Impact Statement Our study found further support that separating math fact fluency practice by an interval of at least 3 hr leads to greater learning than practicing for the same amount of overall time but without separating the practice.

S195. ROLE OF BOOSTER SESSION TRANSCRANIAL DIRECT CURRENT STIMULATION (TDCS) FOR PERSISTENT AUDITORY HALLUCINATIONS IN SCHIZOPHRENIA

BackgroundAuditory verbal hallucinations (AH), one of the hallmark symptoms, are present in 60–80% of schizophrenia (SZ) patients. 25% of patients suffering from AH in schizophrenia fail to respond to any psychotropic medication. Non-invasive brain stimulation techniques like transcranial direct current stimulation (tDCS), with cathodal electrode placement on the left temporoparietal junction (TPJ) is known to alleviate such symptoms in SZ. In this study, we describe the effects of booster tDCS after relapse of AH in patients. The pattern and effectiveness of booster treatment cycles for alleviation of AH in a naturalistic clinical setting are explored in this study.MethodsPatients with persistent AH (n=15) received an initial course (cycle) of add-on tDCS with cathode at left TPJ and anode over left dorsolateral prefrontal cortex (L-DLPFC) with 2mA current, twice-daily 20-minute sessions for 5 days with intersession interval of 3-hours. Clinical global impression- improvement scale (CGI-I) was rated at the end of the course for every patient. All the patients who were found to show response (“much improved” and “very much improved”) received repeat cycles of add-on booster tDCS after a varying duration ranging from 1–32 months from initial treatment course, due to relapse/persistence of AH. Thirteen out of fifteen patients received one booster cycle while one patient received 3 booster cycles and another received 12 booster cycles. We conducted a spearman’s rank correlation test to determine the correlation between CGI-I score rating at the end of add-on tDCS, and the duration of maintenance of improvement before relapse/ worsening of AH.ResultsSix of the fifteen patients (40%) had responded “very much improved” and nine (60%) patients had responded “much improved” to tDCS in the initial cycle. It was found that 50% of the initial “very much improved” responders (n=3) had a comparable response to tDCS after booster sessions for relapse of symptoms while 50% of patients showed “much improved” (n=2) and “minimally improved” (n=1) response in the booster sessions. Among the nine patients who showed “much improved” response from the initial cycle, one patient showed better response than initial cycle (“very much improved”) to booster session. Five patients showed “minimally changed” response in the second cycle in the booster sessions while three patients had comparable responses. The average duration of symptom free interval/ maintenance of improvement with initial cycle of tDCS was found to be 10.46± 9.23 months. The CGI improvement from the initial add-on tDCS course and the duration of the maintenance of improvement/symptom-free interval before the booster session was not found to be significantly correlated (r=0.332, p=0.226)DiscussionA reduction in hallucinations was noted with booster tDCS in patients who had responded to the initial course of add-on tDCS. Booster tDCS is a feasible option and given its cost-effectiveness and ease of administration, booster sessions of tDCS can be considered for resurgence of symptoms. Future studies are recommended in systematically exploring maintenance tDCS as an add-on treatment for persistent/recurring AVH in schizophrenia.

Level of immersion affects spatial learning in virtual environments: results of a three-condition within-subjects study with long intersession intervals

Virtual reality and immersive technologies are used in a variety of learning and training applications. However, higher levels of immersion do not always improve learning. The mixed results in the literature may partly arise from the use of between-subjects designs, insufficient time intervals between sessions in within-subjects designs, and/or overreliance on binary comparisons of immersion levels. Our study examined the influence of three levels of audiovisual immersive technology on spatial learning in virtual environments, using a within-subjects design with long intersession intervals. Performance on object recognition and discrimination was improved in the highest immersion condition, whereas performance on directional bearings showed a U-shaped relationship with level of immersion. Examination of our data suggests that these results likely would not have been found had we used a between-subjects design or a binary comparison, thus demonstrating the value of our approach. Results suggest that different levels of immersion may be better suited to more or less cognitively complex types of spatial learning. We discuss challenges and opportunities for future work.

The temporal effect of hippocampal Arc in the working memory paradigm during novelty exploration

Arc (activity-regulated cytoskeleton-associated protein) is one of the neuronal Immediate Early Genes (IEG), which is involved in the consolidation of memory and is an essential factor in the induction of Long-term Potentiation (LTP), Long-term Depression (LTD) and homeostatic synaptic plasticity. It has also been implicated in the increased familiarization of novel environments during reference memory paradigms. However, the Arc associated temporal effects in a working memory paradigm during novelty exploration are not well studied. Therefore, in the present study, we used spontaneous alternation behavior (SAB) test along with the expression analysis of Arc to study its temporal effects on the working memory paradigms. Using a modified SAB test, we found that the increase in the duration of exposure to a novel environment in the short time-scale (<min) increases the alternations showing that short-term habituation increases the alternation rate. Additionally, during repeated exposure to a novel environment, the alternation rates decrease after shorter inter-session interval. Parallelly, we observed the upregulation of Arc mRNA and protein level 30 min after the SAB test in the cortex and hippocampus of mice, which returns to near-basal level after two hours. The novel experience, associated with the enhanced expression of Arc, helps in the decrease of alternations in subsequent sessions. This change in alternations was absent if the environment was familiar. Further, the role of Arc during these SAB test was confirmed by the inhibition of hippocampal Arc protein through the stereotaxic infusion of Arc antisense oligodeoxynucleotides. We observed that the Arc is involved in the temporal decrease of spontaneous alternations during a series of exposures to a novel environment. Finally, the significance of these results has been discussed in the light of Wagner’s Sometimes Opponent Processes model, where we suggest that Arc reduces the ability for short-term habituation during repeated exposures in the working memory paradigm, and the loss of this ability is more prominent when subjected to a novel environment.

Effects of distributed practice and criterion level on word retrieval in aphasia

This study examined how the distribution and amount of practice affect word retrieval in aphasia as well as how such factors relate to the efficiency of learning. The central hypothesis was that factors that enhance the learning of new knowledge also enhance persistent access to existing, but inconsistently available, word representations. The study evaluated the impact of learning principles on word retrieval by manipulating the timing and amount of retrievals for items presented for naming. Nine people with chronic aphasia with naming impairment completed the experiment. Training materials involved proper noun entities assigned to six conditions formed by crossing a 2-level factor of spacing of sessions, i.e., intersession interval (1 day versus 7 days between sessions) with a 3-level factor of number of correct retrievals per item per session, i.e., criterion level (Criterion-1, Criterion-2, and Criterion-4). Each intersession interval condition comprised three training sessions and a one-month retention test. Increasing the criterion level enhanced naming performance after short (1 day, 7 days) and long (one month) retention intervals, but these advantages came at the cost of many additional training trials. In most cases, later naming success was superior when the same number of correct retrievals of an item was distributed across multiple sessions rather than administered within one session. The substantial advantages for across-session spacing were gained at little cost in terms of additional training trials. At one-month retention, naming accuracy was numerically but not significantly higher in the 7-day versus 1-day intersession interval condition. Implications for theories of lexical access and naming treatment in aphasia are discussed.

Tolerance of transcranial direct current stimulation in psychiatric disorders: An analysis of 2000+ sessions

Transcranial direct current stimulation (tDCS), a non-invasive, neuromodulatory technique, is being increasingly applied to several psychiatric disorders. In this study, we describe the side-effect profile of repeated tDCS sessions (N = 2005) that were administered to 171 patients (156 adults and 15 adolescents) with different psychiatric disorders [schizophrenia [N = 109], obsessive-compulsive disorder [N = 28], alcohol dependence syndrome [N = 13], mild cognitive impairment [N = 10], depression [N = 6], dementia [N = 2] and other disorders [N = 3]]. tDCS was administered at a constant current strength of 2 mA with additional ramp-up and ramp-down phase of 20 s each at the beginning and end of the session, respectively. Other tDCS protocol parameters were: schizophrenia and obsessive-compulsive disorder: 5-days of twice-daily 20-min sessions with an inter-session interval of 3-h; Mild cognitive impairment/dementia and alcohol dependence syndrome: at least 5-days of once-daily 20-min session; Depression: 10-days of once-daily 30 min session. At the end of each tDCS session, any adverse event observed by the administrator and/or reported by the patient was systematically assessed using a comprehensive questionnaire. The commonly reported adverse events during tDCS included burning sensations (16.2%), skin redness (12.3%), scalp pain (10.1%), itching (6.7%), and tingling (6.3%). Most of the adverse events were noted to be mild, transient and well-tolerated. In summary, our observations suggest that tDCS is a safe mode for therapeutic non-invasive neuromodulation in psychiatric disorders in adults as well as the adolescent population.

Short-Interval periodic transcranial direct current stimulations may induce long-term remission of symptoms in a patient with poststroke depression

Transcranial direct current stimulation (tDCS) has been shown to be effective in the management of patients with poststroke depression (PSD) but with a high relapse rate. We present a report of a patient with PSD who had long-term mood improvement upon receiving periodic tDCS sessions with short inter-session intervals following a relapse of symptoms at 3 weeks after improvement due to stimulations with long inter-sessions intervals. A 60-year-old patient presented with moderate PSD, having a Beck Depression Inventory (BDI) score of 25. She received anodal tDCS to the left dorsolateral prefrontal cortex using two different application protocols. Initially, a stimulation session of 2 mA intensity for 20 min was given every working day for 2 weeks. After 3 weeks, she then received seven sessions of periodic stimulations of 2 mA intensity for 13 min each with 20 min inter-sessions interval. BDI score was taken before the intervention, immediately after, and at 3 weeks and 6 months postintervention. Immediately following the last session of the initial protocol of stimulation, the BDI score reduced from 25 to 7. However, the symptoms relapsed at 3 weeks postintervention to the initial BDI score of 25. There was no change in the BDI score immediately after follow-up with short interval periodic stimulations. Nevertheless, the BDI score improved to 18 at 3 weeks and later to 7 at 6 months postintervention. Series of periodic tDCS with short-intersession intervals may be more effective in inducing long-term mood improvement in patients with PSD.

Number and time in acquisition, extinction and recovery.

We measured rate of acquisition, trials to extinction, cumulative responses in extinction, and the spontaneous recovery of anticipatory hopper poking in a Pavlovian protocol with mouse subjects. We varied by factors of 4 number of sessions, trials per session, intersession interval, and span of training (number of days over which training extended). We find that different variables affect each measure: Rate of acquisition [1/(trials to acquisition)] is faster when there are fewer trials per session. Terminal rate of responding is faster when there are more total training trials. Trials to extinction and amount of responding during extinction are unaffected by these variables. The number of training trials has no effect on recovery in a 4-trial probe session 21 days after extinction. However, recovery is greater when the span of training is greater, regardless of how many sessions there are within that span. Our results and those of others suggest that the numbers and durations and spacings of longer-duration "episodes" in a conditioning protocol (sessions and the spans in days of training and extinction) are important variables and that different variables affect different aspects of subjects' behavior. We discuss the theoretical and clinical implications of these and related findings and conclusions-for theories of conditioning and for neuroscience.

Effects of decreasing intersession interval duration on graduated exposure treatment during simulated routine dental care.

Reports suggest that individuals with developmental disabilities often engage in behavior during dental visits that precludes regular dental care. Graduated exposure therapies are an effective treatment for avoidant behavior in people with developmental delays, and some studies show that the duration of the intersession interval (ISI) can impact the effectiveness of graduated exposure treatments for typically developing individuals. The current study examined the effects of decreasing ISI on outcomes of a graduated exposure treatment during simulated routine dental care for 3 individuals diagnosed with autism. Treatment consisted of graduated exposure and extinction for disruptive behavior. Initially, sessions were conducted once per week. In subsequent conditions, treatment sessions were conducted 3-5 times per week. A nonconcurrent multiple baseline across subjects design was used to demonstrate experimental control. Results suggest that decreasing ISI durations can produce improved treatment outcomes.

Reliability of transcranial magnetic stimulation measures of afferent inhibition

Short-latency afferent inhibition (SAI) and long-latency afferent inhibition (LAI) are well-known transcranial magnetic stimulation (TMS) paradigms used to probe the sensorimotor system. To date, there is a paucity of research examining the reliability of these neurophysiological measures. This information is required to validate the utility of afferent inhibition as a biomarker of neural function. The goal of this study was to quantify the absolute reliability, relative reliability, and smallest detectable change (SDC) of SAI and LAI using a test-retest paradigm. 30 healthy individuals (20.9 ± 2.5 years) participated in two sessions (intersession interval of ~7 days). Reliability was assessed with intraclass correlation coefficients (ICC), standard error of measurement (SEMeas), and SDC. The results show that LAI and SAI had poor-to-moderate relative reliability as determined by the ICC, with digital nerve LAI displaying the highest relative reliability (highest ICC with smallest confidence interval). The %SEMeas indicated a large amount of measurement error in all measures of afferent inhibition, with LAI exhibiting more measurement error than SAI. The SDC was large at the individual level (SDCindiv), but analyses showed that the SDC is significantly reduced at the group-level (SDCgroup). Our results indicate that digital nerve LAI is the most reliable outcome to differentiate between individuals within a sample. Further, results suggest that SAI and LAI are not appropriate indicators of individual neurophysiological change across time but can reliably detect changes in group-averaged data providing sample sizes are sufficient.