Clinical effectiveness of active Alpha-Stim AID versus sham Alpha-Stim AID in major depression in primary care in England (Alpha-Stim-D): a multicentre, parallel group, double-blind, randomised controlled trial.

BACKGROUND: Randomised sham-controlled trials of cranial electrostimulation with the Alpha-Stim Anxiety Insomnia and Depression (AID) device have reported improved anxiety and depression symptoms; however, no adequately powered sham-controlled trials in major depression are available. We investigated whether active Alpha-Stim AID is superior to sham Alpha-Stim AID in terms of clinical effectiveness for depression symptoms in major depression. METHODS: The Alpha-Stim-D trial was a multicentre, parallel group, double-blind, randomised controlled trial, recruiting participants from 25 primary care centres in two regions in England, UK. Eligible participants were aged 16 years or older with a current diagnosis of primary major depression, a score of 10-19 on the nine-item Patient Health Questionnaire, and had been offered or prescribed and reported taking antidepressant medication for at least 6 weeks in the previous 3 months. Main exclusion criteria were contraindications to Alpha-Stim AID device use, having persistent suicidal ideation or self-harm, neurological conditions, a substance use disorder or dependence, an eating disorder, bipolar disorder, or non-affective psychosis, or receiving psychological treatment in the past 3 months. Eligible participants were randomly assigned (1:1, minimised by region, anxiety disorder, and antidepressant use) to 1 h daily use of active (100 µA) or sham Alpha-Stim AID treatment for 8 weeks. Randomisation was via an independent web-based system, with participants, outcome assessors, and data analyst masked to treatment assignment. The primary outcome was change from baseline in score on the 17-item Hamilton Depression Rating Scale (HDRS-17, GRID version) at 16 weeks after randomisation, with participants analysed by intention to treat (ITT; all randomly assigned participants). Safety was assessed in all randomly assigned participants. The trial is registered with the ISRCTN registry (ISRCTN11853110); status completed. FINDINGS: Between Sept 8, 2020, and Jan 14, 2022, 236 eligible participants were randomly assigned to active or sham Alpha-Stim AID (n=118 each). 156 (66%) participants were women, 77 (33%) were men, and three (1%) self-reported as other gender; 200 (85%) were White British or Irish; and the mean age was 38·0 years (SD 15·3; range 16-83). 102 (86%) participants in the active Alpha-Stim AID group and 98 (83%) in the sham group were followed up 16 weeks after randomisation. In the ITT population, mean change in GRID-HDRS-17 at 16 weeks was -5·9 (95% CI -7·1 to -4·8) in the active Alpha-Stim AID group and -6·5 (-7·7 to -5·4) in the sham group (mean change difference -0·6 [95% CI -1·0 to 2·2], p=0·46). Among the 236 participants, 17 adverse events were reported in 17 (7%) participants (nine [8%] participants in the active Alpha-Stim AID group; and eight [7%] participants in the sham group). One serious adverse event of suicidal ideation leading to hospitalisation was reported in the sham group, which was judged to be unrelated to the device. INTERPRETATION: Active Alpha-Stim AID was safe and acceptable, but no more clinically effective than sham Alpha-Stim AID in major depression. FUNDING: National Institute for Health Research Applied Research Collaboration East Midlands and Electromedical Products International.

A randomised controlled trial investigating the clinical and cost-effectiveness of Alpha-Stim AID cranial electrotherapy stimulation (CES) in patients seeking treatment for moderate severity depression in primary care (Alpha-Stim-D Trial).

BACKGROUND: Major depression is the second leading cause of years lost to disability worldwide and is a leading contributor to suicide. However, first-line antidepressants are only fully effective for 33%, and only 40% of those offered psychological treatment attend for two sessions or more. Views gained from patients and primary care professionals are that greater treatment uptake might be achieved if people with depression could be offered alternative and more accessible treatment options. Although there is evidence that the Alpha-Stim Anxiety Insomnia and Depression (AID) device is safe and effective for anxiety and depression symptoms in people with anxiety disorders, there is much less evidence of efficacy in major depression without anxiety. This study investigates the effectiveness of the Alpha-Stim AID device, a cranial electrotherapy stimulation (CES) treatment that people can safely use independently at home. The device provides CES which has been shown to increase alpha oscillatory brain activity, associated with relaxation. METHODS: The aim of this study is to investigate the clinical and cost-effectiveness of Alpha-Stim AID in treatment-seeking patients (aged 16 years upwards) with moderate to moderately severe depressive symptoms in primary care. The study is a multi-centre parallel-group, double-blind, non-commercial, randomised controlled superiority trial. The primary objective of the study is to examine the clinical efficacy of active daily use of 8 weeks of Alpha-Stim AID versus sham Alpha-Stim AID on depression symptoms at 16 weeks (8 weeks after the end of treatment) in people with moderate severity depression. The primary outcome is the 17-item Hamilton Depression Rating Scale at 16 weeks. All trial and treatment procedures are carried out remotely using videoconferencing, telephone and postal delivery considering the COVID-19 pandemic restrictions. DISCUSSION: This study is investigating whether participants using the Alpha-Stim AID device display a reduction in depressive symptoms that can be maintained over 8 weeks post-treatment. The findings will help to determine whether Alpha-Stim AID should be recommended, including being made available in the NHS for patients with depressive symptoms. TRIAL REGISTRATION: ISRTCN ISRCTN11853110 . Registered on 14 August 2020.

Asymmetries in the representation of space in the human auditory cortex depend on the global stimulus context.

Studies on humans and other mammals have provided evidence for a two-channel or three-channel representation of horizontal space in the auditory system, with one channel maximally responsive to each of the left hemispace, the right hemispace and, possibly, the midline. Mammalian studies have suggested that the contralateral channel is larger in both cortices, but human studies have found this contralateral preference in only one of the cortices. However, human studies are in conflict as to whether the contralateral preference is in the left or the right auditory cortex, and there are a number of methodological differences that this conflict could be attributed to. A key difference between studies is the duration of the silent interval preceding each stimulus and any perception of sound-source movement that the absence of a silent interval creates. We presented auditory noises that alternated between -90° (left) and +90° (right) and recorded neural responses (event-related potentials) using electroencephalography. We randomly varied the duration of the silent interval preceding each stimulus to create a condition with an immediate (local) stimulus context similar to that used in a study reporting contralateral preference in the left auditory cortex, a condition with a local context similar to that in a study reporting contralateral preference in the right auditory cortex, and an intermediate condition. Surprisingly, we found that both auditory cortices exhibited a similarly strong contralateral preference under all conditions, with responses 27% greater, on average, to the contralateral than the ipsilateral space. This suggests that both the cortices can exhibit a contralateral preference, but whether these preferences manifest depends on the global, rather than the local, stimulus context.

Age-related deterioration of the representation of space in human auditory cortex.

One of the principal auditory disabilities associated with older age is difficulty in locating and tracking sources of sound. This study investigated whether these difficulties are associated with deterioration in the representation of space in the auditory cortex. In psychophysical tests, half of a group of older (>60 years) adults displayed spatial acuity similar to that of young adults throughout the frontal horizontal plane. The remaining half had considerably poorer spatial acuity at the more peripheral regions of frontal space. Computational modeling of electroencephalographic responses to abrupt location shifts demonstrated marked differences in the spatial tuning of populations of cortical neurons between the older adults with poor spatial acuity on the one hand, and those with good spatial acuity, as well as young adults, on the other hand. In those with poor spatial acuity, cortical responses contained little information with which to distinguish peripheral locations. We demonstrate a clear link between neural responses and spatial acuity measured behaviorally, and provide evidence for age-related changes in the coding of horizontal space.

Mechanisms of adaptation in human auditory cortex.

This study investigates the temporal properties of adaptation in the late auditory-evoked potentials in humans. The results are used to make inferences about the mechanisms of adaptation in human auditory cortex. The first experiment measured adaptation by single adapters as a combined function of the adapter duration and the stimulus onset asynchrony (SOA) and interstimulus interval (ISI) between the adapter and the adapted sound ("probe"). The results showed recovery from adaptation with increasing ISI, as would be expected, but buildup of adaptation with increasing adapter duration and thus SOA. This suggests that adaptation in auditory cortex is caused by the ongoing, rather than the onset, response to the adapter. Quantitative modeling indicated that the rate of buildup of adaptation is almost an order of magnitude faster than the recovery rate of adaptation. The recovery rate suggests that cortical adaptation is caused by synaptic depression and slow afterhyperpolarization. The P2 was more strongly affected by adaptation than the N1, suggesting that the two deflections originate from different cortical generators. In the second experiment, the single adapters were replaced by trains of two or four identical adapters. The results indicated that adaptation decays faster after repeated presentation of the adapter. This increase in the recovery rate of adaptation might contribute to the elicitation of the auditory mismatch negativity response. It may be caused by top-down feedback or by local processes such as the buildup of residual Ca(2+) within presynaptic neurons.

Evidence for pitch chroma mapping in human auditory cortex.

Some areas in auditory cortex respond preferentially to sounds that elicit pitch, such as musical sounds or voiced speech. This study used human electroencephalography (EEG) with an adaptation paradigm to investigate how pitch is represented within these areas and, in particular, whether the representation reflects the physical or perceptual dimensions of pitch. Physically, pitch corresponds to a single monotonic dimension: the repetition rate of the stimulus waveform. Perceptually, however, pitch has to be described with 2 dimensions, a monotonic, "pitch height," and a cyclical, "pitch chroma," dimension, to account for the similarity of the cycle of notes (c, d, e, etc.) across different octaves. The EEG adaptation effect mirrored the cyclicality of the pitch chroma dimension, suggesting that auditory cortex contains a representation of pitch chroma. Source analysis indicated that the centroid of this pitch chroma representation lies somewhat anterior and lateral to primary auditory cortex.

Evidence for opponent process analysis of sound source location in humans.

Research with barn owls suggested that sound source location is represented topographically in the brain by an array of neurons each tuned to a narrow range of locations. However, research with small-headed mammals has offered an alternative view in which location is represented by the balance of activity in two opponent channels broadly tuned to the left and right auditory space. Both channels may be present in each auditory cortex, although the channel representing contralateral space may be dominant. Recent studies have suggested that opponent channel coding of space may also apply in humans, although these studies have used a restricted set of spatial cues or probed a restricted set of spatial locations, and there have been contradictory reports as to the relative dominance of the ipsilateral and contralateral channels in each cortex. The current study used electroencephalography (EEG) in conjunction with sound field stimulus presentation to address these issues and to inform the development of an explicit computational model of human sound source localization. Neural responses were compatible with the opponent channel account of sound source localization and with contralateral channel dominance in the left, but not the right, auditory cortex. A computational opponent channel model reproduced every important aspect of the EEG data and allowed inferences about the width of tuning in the spatial channels. Moreover, the model predicted the oft-reported decrease in spatial acuity measured psychophysically with increasing reference azimuth. Predictions of spatial acuity closely matched those measured psychophysically by previous authors.