- Email: [email protected]
Spike-timing dependent plasticity at spinal motoneurons
Abstracts / Brain Stimulation 10 (2017) 346e540
alpha, theta and delta bands of the resting EEG. This study was conducted in awake volunteers under two different conditions: open and closed eyes. Participants and methods: Twenty-six healthy volunteers participated in the experiment (13 females and 13 males, mean age ¼ 23.5 ± 3.1 years). They attended two EEG recording sessions in a crossover, randomized, double-blind and counterbalanced design. During each session, the subject was exposed to 26 min of sham or real GSM RF exposure. Each recording session was composed of 3 experimental conditions: pre-exposure, exposure and postexposure. Recording consisted of resting EEG open eyes (3 min) and resting EEG closed eyes (3 min). A paired sample permutation test based on t-statistics was used to investigate the difference between sham/exposure conditions. Results: Comparison between the sham session and the exposure session showed a statistically significant (P < 0.0001) decrease of the alpha band spectral power during closed-eyes condition. This effect persisted in the post-exposure session (P < 0.0001). No differences were reported between the two sessions on the effect of GSM 900MHz on the theta or delta band. In conclusion, these results suggest that GSM-EMFs of a mobile phone affect the alpha band within spectral power of resting human EEG. Keywords: radiofrequency, EEG, Spectral power, alpha band [0219] IMPACT OF TDCS ON EXECUTIVE FUNCTIONING AND EXECUTIVE DOMAINS oret 1, 2. 1 Universite de Montreal, L. Dumont*1, S. El Mouderrib 1, 3, H. The Montr ^pital Ste-Justine, Canada; 3 Universit e du Qu ebec a eal, Canada; 2 Ho Canada Transcranial direct current stimulation (tDCS) over human dorsolateral prefrontal cortex (DLPFC) has been used to modulate executive function but has led to inconsistent results (Tremblay et al., 2014). Since most of these studies have used direct performance measures such as reaction times or number of errors as proxies for the cognitive functions that the task is thought to reflect, inconsistencies may be related to task impurity problems. To address this, we aimed to evaluate how psychometric measures of executive functions are affected by 15 minutes of unilateral anodal, cathodal and sham tDCS (1.5mA) over left DLPFC (F3). The NIH Examiner (Kramer et al., 2014) was used to assess executive function. This test calculates factorial scores both for general executive functioning and specific executive domains using item response theory and performance on 10 tasks. Twenty-four participants (14f, 21.17yo, SD 2.68) underwent six sessions, two by stimulation condition, where the tDCS protocol was followed by an half of each of the three versions of the NIH Examiner. Task version was counterbalanced with stimulation condition and task order in the battery was counterbalanced between participants but kept constant for each subject so that within the study each task had the same chance of directly following stimulation. Repeated measures ANOVAs yielded no significant effect of stimulation condition on executive function (F ¼ 0.334 ; p ¼ .718), and in the three executive domains (p > .746). There were also no significant differences when comparing the variables used to compute the factorial scores. The present results are in line with recent studies showing that tDCS can have limited, or widely varying, effects on neurophysiological and behavioral measures of prefrontal function. Stimulation parameters and participant characteristics may explain inconsistencies between studies, stressing the need for systematic evaluation of tDCS effects on cognitive function. Keywords: tDCS, Executive functions, DLPFC [0220] FACILITATING WORD MEMORIZING: FREQUENCY SPECIFICITY OF TRANSCRANIAL ALTERNATING CURRENT STIMULATION (TACS)? S. Weiss*1, 2, H.M. Müller 1. 1 Bielefeld University, Germany; 2 CITEC, Bielefeld University, Germany Although the most common brain oscillations associated with memory processes lay within the theta range (4-7 Hz) higher frequencies are involved too [1,2]. Particularly, beta oscillations (13-30 Hz) correlate with active maintenance of stimuli in verbal working memory [2]. In this study,
391
tACS with theta (4 Hz) and beta (18 Hz) was applied during the memorization of words in order for testing, which stimulation frequency corresponds to better verbal memory performance. Twelve participants had to memorize 600 different visually presented concrete words (300 nouns, 300 verbs; each randomly presented in blocks a 25 words for two times) and freely recall them after each block. 20min tACS was applied via electrodes placed at left frontal and temporo-parietal sites. tACS in the theta (4Hz) and beta (18 Hz) range as well as sham stimulation was applied in a double-blind design (ABDCEF or AECDBF) on 5 different days (incl. pre/post block). Current intensity was 1000 mA (or below individual phosphene threshold). A significant difference between stimulation (theta and beta) and sham was found which differed for nouns and verbs. During theta stimulation participants showed a 12% increase of verbs recalled from the first to the second learning block (13% for nouns), during beta stimulation a 9% (10% for nouns), and during sham a 3% increase for verbs (9% for nouns). These improvements highly correlated with current intensity applied (r2¼.80, p >.015). Results support the notion that a direct relation between single frequencies and single cognitive processes seems unrealistic [3]. Rather, different rhythms are associated with different components of a cognitive operation, with multiple rhythms potentially playing multiple roles. Keywords: brain oscillations, theta, beta, memory, language References [1] Weiss, S & Müller, HM (2012). Front Psychol 3: 1-15. [2] Kopell, N, Whittington, MA et al. (2011). PNAS 108: 3779-3784. [3] Weiss, S, Müller, HM et al. (2005). Int J Psychophysiol 57: 129-141. [0221] SPIKE-TIMING DEPENDENT PLASTICITY AT SPINAL MOTONEURONS A. Yamashita*1, 2, T. Murakami 3, S. Kadowaki 3, K. Yoshida 3, E. Ito 3, N. F. Chang 3, N. Hattori 1, I. Miyai 1, Y. Matsuda 3, Ugawa 3. 1 Neurorehabilitation Research Institute, Morinomiya Hospital, Japan; 2 Bobath Memorial Hospital, Japan; 3 Fukushima Medical University, Japan Introduction: Paired-associative stimulation (PAS), repeated transcranial magnetic stimulation (TMS) pairing with electrical peripheral nerve stimulation (ES), leads to synaptic plasticity at the cortical level. The direction and magnitudes of induced plasticity are dependent on interstimulus intervals. Here we investigated synaptic plasticity at spinal motoneurons (SMs) using a modified PAS protocol, named as SM-PAS. Methods: Eleven right-handed healthy volunteers participated in the present study. Motor-evoked potentials (MEPs) were recorded from right first dorsal interosseous muscle (FDI). ES were delivered on right ulnar nerve at the wrist, and stimulus intensity was set at supramaximal intensity. TMS was applied over the left primary motor cortex hand area, and stimulus intensity was set at 120% resting motor threshold in the right FDI. We measured TMS-evoked MEP and F-wave latencies in each subject and calculated timing overlapping between TMS-induced descending volleys and ES-induced antidromic inputs at the SM synapses. We performed SMPAS (180 pairs at 0.2 Hz) at different intervals of TMS and ES pairing. For evaluating corticospinal-motoneuronal synaptic excitability at the spinal level, single-pulse TMS was delivered at cervicomedullary junction level during brief contraction of FDI, and MEP was recorded before and after SMPAS. We also measured compound muscle action potential (CMAP) and Fwaves of FDI to ulnar nerve stimulation at the wrist and obtained F/M ratio. Results: When the interval was set at the timing at which antidromic inputs in the motoneurons axons reached the neurons just before the corticospinal descending volley arrived at the presynaptic terminal, SMPAS facilitated MEPs for 60 min. Inversely, SM-PAS reduced MEPs for 60 min when antidromic inputs reached the postsynaptic terminal 9 ms after the descending volleys arrival (Fig1). CMAP and F/M ratio remained unchanged after SM-PAS (Fig2-3). Discussion: The findings indicate that the SM-PAS can induce bidirectional plasticity at the corticospinal-motoneuonal synapses following the spike timing dependent plasticity rule. Keywords: SM-PAS, spinal motoneurons, spike timing dependent plasticity, bidirectional plasticity
392
Abstracts / Brain Stimulation 10 (2017) 346e540
ĂFig1. MEP ratio on the SM-PASLTP / SM-PASLTD conditions.means±SEM.
cannabinoids; and (ii) characterize fatigue, a symptom frequently reported in this interesting population. The natural course of progressive MS was found to be associated with changes in motor cortex excitability, involving pyramidal cells and inhibitory circuits. In the context of MS relapses, it was demonstrated that the rapid improvement observed following high-dose steroid administration would result from modification in the excitability of cortical circuitry; such mechanism appears to precede the remyelination and axonal regeneration processes. As for fatigue, its correlation with changes in intracortical inhibition remains controversial and requires to be readdressed in future works. Conclusion and perspectives: These results altogether plead for an important and promising role of excitability measures in the characterization of MS evolution and its various treatments. Further studies are still needed before adopting these parameters as reliable biomarkers in this domain. Keywords: Multiple sclerosis, Cortical Excitability, TMS [0223] ELECTROCONVULSIVE THERAPY AS A TREATMENT OPTION FOR INTRACTABLE EPILEPSY: A CASE REPORT A. Ragab*1, A. Elaghoury 2. 1 Cairo University School of Medicine, Egypt; Abbassia Mental Hospital, Egypt
2
ĂFig2. CMAP amplitude ration under the SM-PASLTP condition.means±SEM.
[0224] SEIZURE THRESHOLD INCREASES ARE PREDICTED BY EEG QUALITY IN RIGHT UNILATERAL ULTRABRIEF ECT
ĂFig3. F/M ratio under the SM-PASLTP condition.means±SEM.
[0222] CORTICAL EXCITABILITY WHERE DO WE STAND?
PARAMETERS
IN
MULTIPLE
Introduction: Central to the practice of the electroconvulsive therapy (ECT) is the concept of the seizure threshold (ST), which has been an object of research since the 1940s. During the ECT course, there is a cumulative increase in the ST, suggesting an anticonvulsant action of ECT. The purpose is to report the safety and efficacy of the ECT in an adolescent with intractable epilepsy, and psychiatric morbidity from our practice. Methods: Right unilateral (RUL), ultrabrief ECT course was delivered to an adolescent boy. A literature review was done through the PubMed and clincaltrials.gov with the Keywords: “electroconvulsive therapy,” “seizure threshold” and “intractable epilepsy.” Results: the boy received 15 sessions safely, with improvement in both the seizure frequency and the psychiatric morbidity. These results are in agreement with those obtained from the previous literature. No registered ongoing study for the ECT in epileptic patients from clincaltrials.gov. Discussion: Electroconvulsive therapy is safe in epileptic patients. They may get benefit from the rising seizure threshold during the ECT course, with reduced seizure frequency and improved psychiatric morbidity, commonly associated with those patients. The current data highlight the importance of ECT as a viable therapeutic option for intractable epilepsy. Keywords: electroconvulsive therapy, intractable epilepsy, seizure threshold, adolescence
SCLEROSIS:
ange 1, J.-P. Lefaucheur 1. 1 Henri Mondor S.S. Ayache*1, 2, M.A. Chalah 1, A. Cre Hospital - Paris Est University, France; 2 Lebanese American University Medical Center-Rizk Hospital, Lebanon Introduction: The transcranial magnetic stimulation (TMS) is a noninvasive technique that continues to attract the attention of scientists and researchers. When applied to the cerebral cortex, TMS can activate the corticospinal pathways and generate motor evoked potentials in the corresponding muscle. Besides the activation of pyramidal tracts, the development of paired-pulse paradigms has opened the way to the exploration of inhibitory and excitatory circuits of the motor cortex, and the comprehension of pathophysiological mechanisms of several neuropsychiatric diseases. Among the latter, multiple sclerosis (MS) has gained a growing interest over the last decade. Hence, our aim is to shed the light on the utility of excitability measures in examining different aspects of MS. Methods and results: A thorough review of the literature reveals that cortical excitability parameters were mainly studied to (i) better understand the natural evolution of progressive forms of MS; (ii) evaluate the efficacy of several therapeutic strategies, namely steroids and
V. Galvez*1, 2, S. Waite 3, D. Hadzi-Pavlovic 1, 2, C.K. Loo 1, 2. 1 University of New South Wales, Australia; 2 Black Dog Institute, Australia; 3 Queen Elisabeth Hospital, Australia Introduction: Increases in seizure threshold (ST) can occur over a brief pulse ECT course and are associated with decreases in seizure quality. No data exists on the relationship between ST increases and EEG indices in Right Unilateral Ultrabrief (RUL UB) ECT, a novel form of ECT that is gaining popularity in clinical practice. Methods: Electroencephalographic (EEG), clinical, demographic and ECT treatment data from 16 subjects in a RCT and 19 subjects collected as a part of a clinical protocol in a clinical hospital were included. RUL UB ECT was administered. Subjects were titrated at ECT course commencement and had a second titration at ECT 7. Treatment dosing was given at 6-8 times ST and was maintained stable between the first and last suprathreshold sessions. Seizure quality indices (slow wave onset, amplitude, regularity, stereotypy and post-ictal suppression) were rated at the first and last suprathreshold sessions, through a structured rating scale (MacPherson, 2010) by a single blinded trained rater. The association between ST changes and EEG quality was examined with logistic regression analysis. Results: Twenty one subjects (60%) presented an increase in ST, while 14 subjects (40%) did not. The mean percentage of change in ST for the whole
alpha, theta and delta bands of the resting EEG. This study was conducted in awake volunteers under two different conditions: open and closed eyes. Participants and methods: Twenty-six healthy volunteers participated in the experiment (13 females and 13 males, mean age ¼ 23.5 ± 3.1 years). They attended two EEG recording sessions in a crossover, randomized, double-blind and counterbalanced design. During each session, the subject was exposed to 26 min of sham or real GSM RF exposure. Each recording session was composed of 3 experimental conditions: pre-exposure, exposure and postexposure. Recording consisted of resting EEG open eyes (3 min) and resting EEG closed eyes (3 min). A paired sample permutation test based on t-statistics was used to investigate the difference between sham/exposure conditions. Results: Comparison between the sham session and the exposure session showed a statistically significant (P < 0.0001) decrease of the alpha band spectral power during closed-eyes condition. This effect persisted in the post-exposure session (P < 0.0001). No differences were reported between the two sessions on the effect of GSM 900MHz on the theta or delta band. In conclusion, these results suggest that GSM-EMFs of a mobile phone affect the alpha band within spectral power of resting human EEG. Keywords: radiofrequency, EEG, Spectral power, alpha band [0219] IMPACT OF TDCS ON EXECUTIVE FUNCTIONING AND EXECUTIVE DOMAINS oret 1, 2. 1 Universite de Montreal, L. Dumont*1, S. El Mouderrib 1, 3, H. The Montr ^pital Ste-Justine, Canada; 3 Universit e du Qu ebec a eal, Canada; 2 Ho Canada Transcranial direct current stimulation (tDCS) over human dorsolateral prefrontal cortex (DLPFC) has been used to modulate executive function but has led to inconsistent results (Tremblay et al., 2014). Since most of these studies have used direct performance measures such as reaction times or number of errors as proxies for the cognitive functions that the task is thought to reflect, inconsistencies may be related to task impurity problems. To address this, we aimed to evaluate how psychometric measures of executive functions are affected by 15 minutes of unilateral anodal, cathodal and sham tDCS (1.5mA) over left DLPFC (F3). The NIH Examiner (Kramer et al., 2014) was used to assess executive function. This test calculates factorial scores both for general executive functioning and specific executive domains using item response theory and performance on 10 tasks. Twenty-four participants (14f, 21.17yo, SD 2.68) underwent six sessions, two by stimulation condition, where the tDCS protocol was followed by an half of each of the three versions of the NIH Examiner. Task version was counterbalanced with stimulation condition and task order in the battery was counterbalanced between participants but kept constant for each subject so that within the study each task had the same chance of directly following stimulation. Repeated measures ANOVAs yielded no significant effect of stimulation condition on executive function (F ¼ 0.334 ; p ¼ .718), and in the three executive domains (p > .746). There were also no significant differences when comparing the variables used to compute the factorial scores. The present results are in line with recent studies showing that tDCS can have limited, or widely varying, effects on neurophysiological and behavioral measures of prefrontal function. Stimulation parameters and participant characteristics may explain inconsistencies between studies, stressing the need for systematic evaluation of tDCS effects on cognitive function. Keywords: tDCS, Executive functions, DLPFC [0220] FACILITATING WORD MEMORIZING: FREQUENCY SPECIFICITY OF TRANSCRANIAL ALTERNATING CURRENT STIMULATION (TACS)? S. Weiss*1, 2, H.M. Müller 1. 1 Bielefeld University, Germany; 2 CITEC, Bielefeld University, Germany Although the most common brain oscillations associated with memory processes lay within the theta range (4-7 Hz) higher frequencies are involved too [1,2]. Particularly, beta oscillations (13-30 Hz) correlate with active maintenance of stimuli in verbal working memory [2]. In this study,
391
tACS with theta (4 Hz) and beta (18 Hz) was applied during the memorization of words in order for testing, which stimulation frequency corresponds to better verbal memory performance. Twelve participants had to memorize 600 different visually presented concrete words (300 nouns, 300 verbs; each randomly presented in blocks a 25 words for two times) and freely recall them after each block. 20min tACS was applied via electrodes placed at left frontal and temporo-parietal sites. tACS in the theta (4Hz) and beta (18 Hz) range as well as sham stimulation was applied in a double-blind design (ABDCEF or AECDBF) on 5 different days (incl. pre/post block). Current intensity was 1000 mA (or below individual phosphene threshold). A significant difference between stimulation (theta and beta) and sham was found which differed for nouns and verbs. During theta stimulation participants showed a 12% increase of verbs recalled from the first to the second learning block (13% for nouns), during beta stimulation a 9% (10% for nouns), and during sham a 3% increase for verbs (9% for nouns). These improvements highly correlated with current intensity applied (r2¼.80, p >.015). Results support the notion that a direct relation between single frequencies and single cognitive processes seems unrealistic [3]. Rather, different rhythms are associated with different components of a cognitive operation, with multiple rhythms potentially playing multiple roles. Keywords: brain oscillations, theta, beta, memory, language References [1] Weiss, S & Müller, HM (2012). Front Psychol 3: 1-15. [2] Kopell, N, Whittington, MA et al. (2011). PNAS 108: 3779-3784. [3] Weiss, S, Müller, HM et al. (2005). Int J Psychophysiol 57: 129-141. [0221] SPIKE-TIMING DEPENDENT PLASTICITY AT SPINAL MOTONEURONS A. Yamashita*1, 2, T. Murakami 3, S. Kadowaki 3, K. Yoshida 3, E. Ito 3, N. F. Chang 3, N. Hattori 1, I. Miyai 1, Y. Matsuda 3, Ugawa 3. 1 Neurorehabilitation Research Institute, Morinomiya Hospital, Japan; 2 Bobath Memorial Hospital, Japan; 3 Fukushima Medical University, Japan Introduction: Paired-associative stimulation (PAS), repeated transcranial magnetic stimulation (TMS) pairing with electrical peripheral nerve stimulation (ES), leads to synaptic plasticity at the cortical level. The direction and magnitudes of induced plasticity are dependent on interstimulus intervals. Here we investigated synaptic plasticity at spinal motoneurons (SMs) using a modified PAS protocol, named as SM-PAS. Methods: Eleven right-handed healthy volunteers participated in the present study. Motor-evoked potentials (MEPs) were recorded from right first dorsal interosseous muscle (FDI). ES were delivered on right ulnar nerve at the wrist, and stimulus intensity was set at supramaximal intensity. TMS was applied over the left primary motor cortex hand area, and stimulus intensity was set at 120% resting motor threshold in the right FDI. We measured TMS-evoked MEP and F-wave latencies in each subject and calculated timing overlapping between TMS-induced descending volleys and ES-induced antidromic inputs at the SM synapses. We performed SMPAS (180 pairs at 0.2 Hz) at different intervals of TMS and ES pairing. For evaluating corticospinal-motoneuronal synaptic excitability at the spinal level, single-pulse TMS was delivered at cervicomedullary junction level during brief contraction of FDI, and MEP was recorded before and after SMPAS. We also measured compound muscle action potential (CMAP) and Fwaves of FDI to ulnar nerve stimulation at the wrist and obtained F/M ratio. Results: When the interval was set at the timing at which antidromic inputs in the motoneurons axons reached the neurons just before the corticospinal descending volley arrived at the presynaptic terminal, SMPAS facilitated MEPs for 60 min. Inversely, SM-PAS reduced MEPs for 60 min when antidromic inputs reached the postsynaptic terminal 9 ms after the descending volleys arrival (Fig1). CMAP and F/M ratio remained unchanged after SM-PAS (Fig2-3). Discussion: The findings indicate that the SM-PAS can induce bidirectional plasticity at the corticospinal-motoneuonal synapses following the spike timing dependent plasticity rule. Keywords: SM-PAS, spinal motoneurons, spike timing dependent plasticity, bidirectional plasticity
392
Abstracts / Brain Stimulation 10 (2017) 346e540
ĂFig1. MEP ratio on the SM-PASLTP / SM-PASLTD conditions.means±SEM.
cannabinoids; and (ii) characterize fatigue, a symptom frequently reported in this interesting population. The natural course of progressive MS was found to be associated with changes in motor cortex excitability, involving pyramidal cells and inhibitory circuits. In the context of MS relapses, it was demonstrated that the rapid improvement observed following high-dose steroid administration would result from modification in the excitability of cortical circuitry; such mechanism appears to precede the remyelination and axonal regeneration processes. As for fatigue, its correlation with changes in intracortical inhibition remains controversial and requires to be readdressed in future works. Conclusion and perspectives: These results altogether plead for an important and promising role of excitability measures in the characterization of MS evolution and its various treatments. Further studies are still needed before adopting these parameters as reliable biomarkers in this domain. Keywords: Multiple sclerosis, Cortical Excitability, TMS [0223] ELECTROCONVULSIVE THERAPY AS A TREATMENT OPTION FOR INTRACTABLE EPILEPSY: A CASE REPORT A. Ragab*1, A. Elaghoury 2. 1 Cairo University School of Medicine, Egypt; Abbassia Mental Hospital, Egypt
2
ĂFig2. CMAP amplitude ration under the SM-PASLTP condition.means±SEM.
[0224] SEIZURE THRESHOLD INCREASES ARE PREDICTED BY EEG QUALITY IN RIGHT UNILATERAL ULTRABRIEF ECT
ĂFig3. F/M ratio under the SM-PASLTP condition.means±SEM.
[0222] CORTICAL EXCITABILITY WHERE DO WE STAND?
PARAMETERS
IN
MULTIPLE
Introduction: Central to the practice of the electroconvulsive therapy (ECT) is the concept of the seizure threshold (ST), which has been an object of research since the 1940s. During the ECT course, there is a cumulative increase in the ST, suggesting an anticonvulsant action of ECT. The purpose is to report the safety and efficacy of the ECT in an adolescent with intractable epilepsy, and psychiatric morbidity from our practice. Methods: Right unilateral (RUL), ultrabrief ECT course was delivered to an adolescent boy. A literature review was done through the PubMed and clincaltrials.gov with the Keywords: “electroconvulsive therapy,” “seizure threshold” and “intractable epilepsy.” Results: the boy received 15 sessions safely, with improvement in both the seizure frequency and the psychiatric morbidity. These results are in agreement with those obtained from the previous literature. No registered ongoing study for the ECT in epileptic patients from clincaltrials.gov. Discussion: Electroconvulsive therapy is safe in epileptic patients. They may get benefit from the rising seizure threshold during the ECT course, with reduced seizure frequency and improved psychiatric morbidity, commonly associated with those patients. The current data highlight the importance of ECT as a viable therapeutic option for intractable epilepsy. Keywords: electroconvulsive therapy, intractable epilepsy, seizure threshold, adolescence
SCLEROSIS:
ange 1, J.-P. Lefaucheur 1. 1 Henri Mondor S.S. Ayache*1, 2, M.A. Chalah 1, A. Cre Hospital - Paris Est University, France; 2 Lebanese American University Medical Center-Rizk Hospital, Lebanon Introduction: The transcranial magnetic stimulation (TMS) is a noninvasive technique that continues to attract the attention of scientists and researchers. When applied to the cerebral cortex, TMS can activate the corticospinal pathways and generate motor evoked potentials in the corresponding muscle. Besides the activation of pyramidal tracts, the development of paired-pulse paradigms has opened the way to the exploration of inhibitory and excitatory circuits of the motor cortex, and the comprehension of pathophysiological mechanisms of several neuropsychiatric diseases. Among the latter, multiple sclerosis (MS) has gained a growing interest over the last decade. Hence, our aim is to shed the light on the utility of excitability measures in examining different aspects of MS. Methods and results: A thorough review of the literature reveals that cortical excitability parameters were mainly studied to (i) better understand the natural evolution of progressive forms of MS; (ii) evaluate the efficacy of several therapeutic strategies, namely steroids and
V. Galvez*1, 2, S. Waite 3, D. Hadzi-Pavlovic 1, 2, C.K. Loo 1, 2. 1 University of New South Wales, Australia; 2 Black Dog Institute, Australia; 3 Queen Elisabeth Hospital, Australia Introduction: Increases in seizure threshold (ST) can occur over a brief pulse ECT course and are associated with decreases in seizure quality. No data exists on the relationship between ST increases and EEG indices in Right Unilateral Ultrabrief (RUL UB) ECT, a novel form of ECT that is gaining popularity in clinical practice. Methods: Electroencephalographic (EEG), clinical, demographic and ECT treatment data from 16 subjects in a RCT and 19 subjects collected as a part of a clinical protocol in a clinical hospital were included. RUL UB ECT was administered. Subjects were titrated at ECT course commencement and had a second titration at ECT 7. Treatment dosing was given at 6-8 times ST and was maintained stable between the first and last suprathreshold sessions. Seizure quality indices (slow wave onset, amplitude, regularity, stereotypy and post-ictal suppression) were rated at the first and last suprathreshold sessions, through a structured rating scale (MacPherson, 2010) by a single blinded trained rater. The association between ST changes and EEG quality was examined with logistic regression analysis. Results: Twenty one subjects (60%) presented an increase in ST, while 14 subjects (40%) did not. The mean percentage of change in ST for the whole