Functional connectivity analysis of the depression connectome provides potential markers and targets for transcranial magnetic stimulation

BACKGROUND

Despite efforts to improve targeting accuracy of the dorsolateral prefrontal cortex (DLPFC) as a repetitive transcranial magnetic stimulation (rTMS) target for Major Depressive Disorder (MDD), the heterogeneity in clinical response remains unexplained.

OBJECTIVE

We sought to compare the patterns of functional connectivity from the DLPFC treatment site in patients with MDD who were TMS responders to those who were TMS non-responders.

METHODS

Baseline anatomical T1 magnetic resonance imaging (MRI), resting-state functional MRI, and diffusion weighted imaging scans were obtained from 37 participants before they underwent a course of rTMS to left Brodmann area 46. A novel machine learning method was utilized to identify brain regions associated with each item of the Beck's Depression Inventory II (BDI-II), and for 26 participants who underwent rTMS treatment over the left Brodmann area 46, identify regions differentiating rTMS responders and non-responders.

RESULTS

Nine parcels of the Human Connectome Project Multimodal Parcellation Atlas matched to at least three items of the Beck's Depression Inventory II (BDI-II) as predictors of response to rTMS, with many in the temporal, parietal and cingulate cortices. Additionally, pre-treatment mapping for 17 items of the BDI-II demonstrated significant variability in symptom to parcel mapping. When parcels associated with symptom presence and symptom resolution were compared, 15 parcels were uniquely associated with resolution (potential targets), and 12 parcels were associated with both symptom presence and resolution (blockers or biomarkers).

CONCLUSIONS

Machine learning approaches show promise for the development of pathoanatomical diagnosis and treatment algorithms for MDD. Prospective studies are required to facilitate clinical translation.

Digitalized transcranial electrical stimulation: A consensus statement

OBJECTIVE

Although relatively costly and non-scalable, non-invasive neuromodulation interventions are treatment alternatives for neuropsychiatric disorders. The recent developments of highly-deployable transcranial electric stimulation (tES) systems, combined with mobile-Health technologies, could be incorporated in digital trials to overcome methodological barriers and increase equity of access. The study aims are to discuss the implementation of tES digital trials by performing a systematic scoping review and strategic process mapping, evaluate methodological aspects of tES digital trial designs, and provide Delphi-based recommendations for implementing digital trials using tES.

METHODS

We convened 61 highly-productive specialists and contacted 8 tES companies to assess 71 issues related to tES digitalization readiness, and processes, barriers, advantages, and opportunities for implementing tES digital trials. Delphi-based recommendations (>60% agreement) were provided.

RESULTS

The main strengths/opportunities of tES were: (i) non-pharmacological nature (92% of agreement), safety of these techniques (80%), affordability (88%), and potential scalability (78%). As for weaknesses/threats, we listed insufficient supervision (76%) and unclear regulatory status (69%). Many issues related to methodological biases did not reach consensus. Device appraisal showed moderate digitalization readiness, with high safety and potential for trial implementation, but low connectivity.

CONCLUSIONS

Panelists recognized the potential of tES for scalability, generalizability, and leverage of digital trials processes; with no consensus about aspects regarding methodological biases.

SIGNIFICANCE

We further propose and discuss a conceptual framework for exploiting shared aspects between mobile-Health tES technologies with digital trials methodology to drive future efforts for digitizing tES trials.

Sex Differences and the Influence of Sex Hormones on Cognition through Adulthood and the Aging Process

Hormones of the hypothalamic-pituitary-gonadal (HPG) axis that regulate reproductive function have multiple effects on the development, maintenance and function of the brain. Sex differences in cognitive functioning have been reported in both health and disease, which may be partly attributed to sex hormones. The aim of the current paper was to provide a theoretical review of how sex hormones influence cognitive functioning across the lifespan as well as provide an overview of the literature on sex differences and the role of sex hormones in cognitive decline, specifically in relation to Alzheimer’s disease (AD). A summary of current hormone and sex-based interventions for enhancing cognitive functioning and/or reducing the risk of Alzheimer’s disease is also provided.

Acute motor, neurocognitive and neurophysiological change following concussion injury in Australian amateur football. A prospective multimodal investigation

OBJECTIVES

This multimodal study investigated the motor, neurocognitive and neurophysiological responses following a sports related concussion injury in the acute-phase (up to 10 days) in sub-elite Australian football players.

DESIGN

Between-group, repeated measures.

METHODS

Over the course of one season (six months), 43 male players from one football club (25.1 ± 4.5 years) were assessed for fine motor dexterity, visuomotor reaction time, implicit learning and attention. Motor cortex excitability and inhibition were assessed using transcranial magnetic stimulation.

RESULTS

Of the 43 players, eight suffered concussion injuries, and were compared to 15 non-concussed players (active control) who returned for follow up testing. Post-concussion assessments using the aforementioned tests were carried out at 48 and 96 h, and 10 days. Compared to the non-concussed players, those who suffered concussion showed slowed fine dexterity (P = 0.02), response (P = 0.02) and movement times (P = 0.01) 48 h post-concussion. Similarly, attentional performance was reduced in the concussed group at all time points (48 h: P < 0.01; 96 h: P < 0.01; and 10 days: P = 0.02) post-concussion. TMS revealed significantly increased corticospinal inhibition at 48 (P = 0.04) and 96 h post concussion (P = 0.02) with significant correlations between increased corticospinal inhibition and response (r = 0.48; P < 0.01), movement time (r = 0.42; P = 0.02), and attention performance (r = 0.44; P = 0.01).

CONCLUSIONS

This study has demonstrated that acutely concussed Australian football players show abnormalities in motor, cognitive and neurophysiological measures with variable rates of recovery. These findings suggest that measuring the recovery of concussed athletes should incorporate a range of testing modalities rather than relying on one area of measurement in determining return to play.

The long-term effects of sports concussion on retired Australian football players: a study using transcranial magnetic stimulation

This study investigated corticomotor excitability and inhibition, cognitive functioning, and fine motor dexterity in retired elite and amateur Australian football (AF) players who had sustained concussions during their playing careers. Forty male AF players who played at the elite level (n=20; mean age 49.7±5.7 years) or amateur level (n=20; mean age 48.4±6.9 years), and had sustained on average 3.2 concussions 21.9 years previously, were compared with 20 healthy age-matched male controls (mean age 47.56±6.85 years). All participants completed assessments of fine dexterity, visuomotor reaction time, spatial working memory (SWM), and associative learning (AL). Transcranial magnetic stimulation (TMS) was used to measure corticospinal excitability: stimulus-response (SR) curves and motor evoked potential (MEP) 125% of active motor threshold (aMT); and intracortical inhibition: cortical silent period (cSP), short-interval intracortical inhibition (SICI), and long-interval intracortical inhibition (LICI). Healthy participants performed better in dexterity (p=0.003), reaction (p=0.003), and movement time (p=0.037) than did both AF groups. Differences between AF groups were found in AL (p=0.027) and SWM (p=0.024). TMS measures revealed that both AF groups showed reduced cSP duration at 125% aMT (p>0.001) and differences in SR curves (p>0.001) than did healthy controls. Similarly, SICI (p=0.012) and LICI (p=0.009) were reduced in both AF groups compared with controls. Regression analyses revealed a significant contribution to differences in motor outcomes with the three measures of intracortical inhibition. The measures of inhibition differed, however, in terms of which performance measure they had a significant and unique predictive relationship with, reflecting the variety of participant concussion injuries. This study is the first to demonstrate differences in motor control and intracortical inhibition in AF players who had sustained concussions during their playing career two decades previously.

Can sleep disturbance in depression predict repetitive transcranial magnetic stimulation (rTMS) treatment response?

Treatment for depression is not effective in all patients and it is therefore important to identify factors that can be used to tailor treatments. One potential factor is insomnia. Several repetitive transcranial magnetic stimulation (rTMS) studies have reported on this symptom, however, they did not take into account the presence of hypersomnia or that insomnia was related to their outcome measure. Our aim was to investigate whether baseline sleep disruption was related to rTMS treatment response. We pooled data from four clinical trials using rTMS to treat depression, including 139 subjects in data analysis. Insomnia was measured using the Hamilton Depression Rating Scale (HamD) sleep questions and hypersomnia from the Beck Depression Inventory (BDI). To reduce the possible impact of insomnia on our treatment response outcome we created an adjusted HamD score which omitted sleep items. Sleep disturbances were common in our study: 66% had insomnia and 38% hypersomnia. Using regression analysis with our adjusted HamD score we found no relation between baseline insomnia or hypersomnia and rTMS treatment response. Our data are consistent with previous studies; however, this is the first rTMS study to our knowledge that has attempted to dissociate baseline insomnia from the HamD outcome measure and to report no relationship between hypersomnia and rTMS outcome.

A randomized trial of unilateral and bilateral prefrontal cortex transcranial magnetic stimulation in treatment-resistant major depression

BACKGROUND

Although several studies have reported that repetitive transcranial magnetic stimulation (rTMS) treatment has demonstrable efficacy in patients with depression, the parameters needed to optimize therapeutic efficacy remain unclear. To this end we determined the efficacy of low-frequency right rTMS to the dorsolateral prefrontal cortex (DLPFC) compared to two forms of bilateral rTMS to the DLPFC: (1) sequential low-frequency right-sided followed by high-frequency left-sided rTMS and (2) sequential low-frequency rTMS to both hemispheres.

METHOD

A total of 219 patients with treatment-resistant depression (TRD) were randomized to a 4-week course of rTMS applied with one of the three treatment conditions. Outcomes were assessed with standard rating scales.

RESULTS

Overall, slightly more than 50% of the patients achieved clinical response criteria. There was no substantial difference in response between the unilateral and bilateral treatment groups. Successful response to rTMS was predicted by a greater degree of baseline depression severity.

CONCLUSIONS

There is no substantial difference in efficacy between unilateral right-sided rTMS and the two forms of bilateral rTMS assessed in the study. Furthermore, our results call into question the specificity between frequency and laterality and rTMS response.

A study of the effectiveness of high-frequency left prefrontal cortex transcranial magnetic stimulation in major depression in patients who have not responded to right-sided stimulation

The objective of this study was to explore the response rate to high-frequency left-sided repetitive transcranial magnetic stimulation (rTMS) in patients who had failed to respond to right-sided low-frequency stimulation, and to investigate whether there was differential efficacy between stimulation at 5 or 10 Hz. Data from two randomized controlled trials were pooled. In both studies a group of patients were randomized to receive either 5- or 10-Hz left prefrontal rTMS after failing to respond to right-sided stimulation. These patients received blinded 5- or 10-Hz stimulation (but without a sham control) for a period of up to 4 weeks and outcomes were compared. There was a small but significant overall response to left-sided rTMS but no difference in response between the 5- and 10-Hz treatment conditions. There appears to be a significant but modest likelihood of response to left-sided TMS in patients who fail right-sided stimulation, but there is no difference in efficacy between 5- and 10-Hz stimulation.

A randomized trial of the anti-depressant effects of low- and high-frequency transcranial magnetic stimulation in treatment-resistant depression

BACKGROUND

The majority of studies investigating the effectiveness of repetitive transcranial magnetic stimulation (rTMS) as a treatment for major depression have focused on high-frequency rTMS to the left prefrontal cortex (HFL-rTMS). In addition, low-frequency right prefrontal rTMS (LFR-rTMS) has also been shown to have antidepressant properties. To date only a small number of studies have directly compared the efficacy of these two approaches.

METHODS

The aim of this study, therefore, was to investigate further whether LFR-rTMS is as effective as HFL-rTMS in the treatment of major depression. Twenty-seven patients were randomized to one of two treatment arms (HFL-rTMS or LFR-rTMS) for 3 weeks with a possible 1-week extension. Non-responders were offered the opportunity of crossing over to the other treatment type. Stimulation parameters for HFL-rTMS were 30 stimulation trains of 5 s duration at 100% of the resting motor threshold (RMT); for LFR-rTMS, stimulation was applied in four trains of 180 s duration (30 s inter-train interval) at 110% of the RMT. Stimulation was provided 5-week days per week.

RESULTS

There were significant improvements seen from baseline to end point irrespective of group and on all clinical outcome measures. In addition, there was no deterioration in any of the measures used to assess cognitive change, and significant improvements were seen on measures of immediate verbal memory and verbal fluency.

CONCLUSIONS

HFL-rTMS and LFR-rTMS appear to be equally efficacious in treating major depression. This study adds to the growing literature supporting LFR-rTMS as an additional viable method of rTMS delivery in the treatment of depression.

A randomized trial of rTMS targeted with MRI based neuro-navigation in treatment-resistant depression

The aim of this study is to investigate whether repetitive transcranial magnetic stimulation (rTMS) targeted to a specific site in the dorsolateral prefrontal cortex (DLPFC), with a neuro-navigational method based on structural MRI, would be more effective than rTMS applied using the standard localization technique. Fifty-one patients with treatment-resistant depression were randomized to receive a 3-week course (with a potential 1-week extension) of high-frequency (10 Hz) left-sided rTMS. Thirty trains (5 s duration) were applied daily 5 days per week at 100% of the resting motor threshold. Treatment was targeted with either the standard 5 cm technique (n=27) or using a neuro-navigational approach (n=24). This involved localizing the scalp location that corresponds to a specific site at the junction of Brodmann areas 46 and 9 in the DLPFC based on each individual subject's MRI scan. There was an overall significant reduction in the Montgomery-Asberg Depression Rating Scale scores over the course of the trial, and a better outcome in the targeted group compared with the standard localization group at 4 weeks (p=0.02). Significant differences were also found on secondary outcome variables. The use of neuro-navigational methods to target a specific DLPFC site appears to enhance response to rTMS treatment in depression. Further research is required to confirm this in larger samples, or to establish whether an alternate method based on surface anatomy, including measurement from motor cortex, can be substituted for the standard 5 cm method.

Cortical inhibition in motor and non-motor regions: a combined TMS-EEG study

A number of studies using paired pulse transcranial magnetic stimulation (TMS) have demonstrated that cortical inhibition (CI) of the motor cortex can be recorded and also gauged through surface electromyography. However, recording CI from other brain regions that are more directly related with the pathophysiology of some neurologic and psychiatric disorders (e.g., dorsolateral prefrontal cortex (DLPFC) in schizophrenia) was previously fraught with technical difficulties. This study was therefore designed to examine, through a combination of TMS with EEG, whether CI could be measured directly from the motor cortex, DLPFC, and another non-motor region. To index CI, long interval cortical inhibition (LICI; a TMS paradigm) was used in the motor cortex and DLPFC in 14 healthy subjects, and in the parietal lobe in 5 of those subjects. In the motor cortex, LICI resulted in a significant suppression in mean cortical evoked activity on EEG (37.31 +/- 47.51%). In the DLPFC, LICI resulted in a significant suppression (32.45 +/- 47.86%) in mean cortical evoked activity and did not correlate with LICI in the motor cortex although they did not significantly differ. In the parietal lobe, LICI resulted in significant suppression (47.76 +/- 44.70%) in mean cortical evoked activity. In conclusion, CI in the dorsolateral prefrontal cortex, motor cortex and parietal cortex were similar at 120% of motor threshold. These data suggest that CI can be recorded by combining TMS with EEG and may facilitate future research attempting to ascertain the role of CI in the pathophysiology of several neurologic and psychiatric disorders.

A comparative study of the effects of repetitive paired transcranial magnetic stimulation on motor cortical excitability

OBJECTIVES

Various methods of application of repetitive transcranial magnetic stimulation (TMS) have been evaluated for their potential capacity to alter motor cortical excitability. Initial research suggests that the repetitive application of paired TMS pulses (repetitive paired pulse TMS (rppTMS)) may have greater effects on cortical excitability, perhaps through the facilitation of I-wave interaction. We aimed to compare the post-train effects of 15 min trains of rppTMS to investigate the potential therapeutic application of this technique as well as to compare it to a standard high frequency repetitive TMS paradigm.

METHODS

Ten normal subjects received three 15 min sessions of rppTMS, 5 Hz high frequency rTMS and sham TMS in randomised order. rppTMS consisted of a single train of 180 pulse pairs (0.2 Hz, 1.5 ms inter-stimulus interval, supra-threshold intensity) administered over 15 min. The rTMS condition involved 750 pulses provided in 5s 5 Hz trains with a 25s inter-train interval at 90% of the RMT. Motor evoked potential size and cortical silent period duration were assessed before and after each session.

RESULTS

There were no significant changes in cortical excitability produced by any of the stimulation conditions. Five hertz rTMS produced an increase in cortical silent period duration (p=0.004) which was not affected by rppTMS.

CONCLUSIONS

Fifteen minutes trains of 1.5ms rppTMS do not substantially increase post train cortical excitability. Repetitive brief trains of 5Hz rTMS also do not alter excitability but appear to effect cortical inhibition.

Effect of moderate exercise on blood flow in the gastrointestinal tract in trained conscious miniature swine

AIM

To examine how moderate exercise affects the blood flow in the gastrointestinal tract.

MATERIALS AND METHODS

Twelve miniature swine weighing 38-43 kg were used. All animals were trained on a cardiac exercise treadmill. Blood flow measurements were done on conscious animals using labeled microspheres with a diameter of 16.5 +/- 0.1 (SD) microm. The first flow was measured while the animal was awake and resting, the second flow after 15 min of exercise, the third flow after 30 min of rest.

RESULTS

Flow in the oesophagus at rest was 19.5 +/- 1.3 (SEM) ml/min/100 g. During exercise the flow decreased to 13.3 +/- 1.2 (SEM) ml/min/100 g (ns). After 30 min of rest the flow was 9.9 +/- 1.2 (SEM) ml/min/100 g (p < 0.05 when comparing the flow before and after exercise). Flow in the cardia at rest was 23.1 +/- 1.3 (SEM) ml/min/100 g. During exercise the flow decreased to 14.0 +/- 1.2 (SEM) ml/min/100 g (p < 0.05). After 30 min of rest the flow was 15.0 +/- 1.2 (SEM) ml/min/100 g. Flow in the pylorus at rest was 38.9 +/- 1.1 (SEM) ml/min/100 g. During exercise the flow decreased to 24.6 +/- 1.1 (SEM) ml/min/100 g (p < 0.01). After 30 min of rest the flow was 26.9 +/- 1.2 (SEM) ml/min/100 g. Blood flow in the small and large intestine was mainly unaffected by moderate exercise.

CONCLUSION

Under moderate exercise, blood flow in the upper part of the gastrointestinal tract declines while it is mainly unaffected in the duodenum, small and large intestine.

Unexplained disturbance in body weight regulation: diagnostic outcome assessed by doubly labeled water and body composition analyses in obese patients reporting low energy intakes

SUBJECTS

Ten patients who had long-term disturbances in body weight regulation, were referred over a 3-year period for obesity evaluation, and reported low energy intakes (< 1,200 kcal/day).

OBJECTIVE

To ascertain whether these patients had a low energy expenditure and thus reduced energy requirement, and/or whether they were misreporting their energy intake.

DESIGN

Comparison of outcome measures in referred patients and in obese control patients who did not report low energy intakes and disturbances in body weight regulation.

MAIN OUTCOME MEASURES

Low energy expenditure was evaluated with serum thyroid hormone levels, resting metabolic rate (RMR), thermic effect of food (TEF), and total energy expenditure (TEE) by doubly labeled water technique. Misreporting of energy intake was evaluated by comparing patients' self-reported energy intake with energy intake estimated by doubly labeled water and body composition analyses over a 14-day period.

STATISTICAL ANALYSES PERFORMED

Low energy expenditure was considered present in a patient if RMR or TEE was more than 15% below predicted values according to results from the control group. Patient group TEF was compared with TEF results observed in the control group.

RESULTS

All patients had normal serum thyroid hormone levels. Eight patients had RMR and TEE values within 15% of predicted values and were substantially underreporting their energy intake. One patient had low TEE (-19%) and a normal RMR, a finding that implies a low level of physical activity. This patient also underreported energy intake as estimated by the doubly labeled water technique during the study (-38%). The 10th patient had a low RMR (-23.2%) and TEE (-25.0%), the mechanism of which was uncertain. This patient's reported food intake over the 14-day period was accurate but was less than her long-term intake over months or years as suggested by doubly labeled water TEE estimates. The TEF response in patients was not significantly different from that observed in the control group.

CONCLUSIONS

Underreporting of energy intake from foods is a frequent finding in patients with disturbances in body weight regulation who are referred for obesity evaluation. Severe underreporting may be detectable by means of screening measures available to most dietitians. Low energy expenditure, due either to physical inactivity or to metabolic factors, is also observed. Modern evaluation methods provide new insights into patients with weight regulatory disturbances and at the same time stimulate important new research questions.

Regulation of cyclic AMP levels by phorbol esters in bovine adrenal medullary cells

Cyclic AMP responses to phorbol esters were studied in cultured bovine adrenal medullary cells. Phorbol esters that activate protein kinase C (PKC: phorbol 12,13-dibutyrate, phorbol 12,13-didecanoate) increased cellular cyclic AMP levels by up to 100% over 5 min, and this was maintained for up to 3 h. The effect was mimicked by 1,2-dioctanoyl-sn-glycerol but not by inactive phorbol esters. The effect of active phorbol esters was concentration dependent over the range 50-500 nM, and was abolished by the PKC inhibitor, Ro 31-8220 (10 microM). The response was enhanced by 3-isobutyl-1-methylxanthine (1 mM) and by forskolin (0.3 microM), was enhanced following pertussis toxin pretreatment (100 ng/ml, 7.5 h) and was unaffected by removing extracellular Ca2+. The phorbol ester cyclic AMP response was additive with that to K+ depolarisation, and synergised with those to prostaglandin E1 and dimaprit. The results indicate PKC activation increases cyclic AMP formation in bovine adrenal medullary cells, probably by a direct action on adenylate cyclase or Gs.

Perinatal salt intake alters blood pressure and salt balance in hypertensive rats

Blood pressure and the rate of excretion of an oral salt load were examined in spontaneously hypertensive rats of the Okamoto strain after exposure in utero and during suckling to a high salt (3% NaCl, wt/wt), low salt (0.1%), control salt (0.8%), or high potassium (2.2% KCl, wt/wt) [corrected] maternal diet. After weaning, all offspring were given a diet containing 0.8% NaCl. There were small but significant differences in growth rate among offspring groups over the 60 weeks of observation, with rats exposed to perinatal low salt and high salt diet being lighter than those given control or high potassium diet. There were positive, significant correlations between body weight and blood pressure in all dietary groups at 8 weeks of age but not 16 or 24 weeks. Rats exposed to perinatal low salt diet had significantly lower blood pressures than the other three groups, which had similar blood pressures. Low salt rats also exhibited an exaggerated natriuresis after a single, oral salt load (0.15 M saline, 1% body weight) compared with the other three diet groups, which were not different from each other. High potassium rats had a reduced kaliuresis and diuresis after the salt load when compared with the other three groups. At 60 weeks of age, rats that received perinatal low salt diet had significantly heavier adrenal glands when compared with the other groups, and the high potassium group had significantly elevated plasma renin concentrations. Thus, maternal electrolyte intake during the perinatal phase may alter body fluid homeostasis in genetically susceptible individuals at maturity.

Release of gas residues from an ethylene oxide sterilized haemodialyser

Ethylene oxide, a toxic gas used as sterilant for medical devices, is absorbed in plastic materials. The gas is desorbed from the sterilized devices occasionally leading to injuries to the users. A photoionization detector, being specific and sensitive, is used for measurement of liberated ethylene oxide from a haemodialyser. The detector, used as a flow through cell direct connected to the haemodialyser, enables measurement of ethylene oxide in quantities ten times smaller than the maximum daily exposure.