ADHD Electrophysiological Subtypes and Implications in Transcranial Direct-current Stimulation
Condition: ADHD; ADD
Study type: Observational

Summary: 
      In the present study the aim is to examine whether transcranial direct-current stimulation
      (tDCS) generated excitability changes and induce modifications of functional cortical
      architecture in Attention Deficit Hyperactivity Disorder (ADHD) patients. To achieve this,
      the investigators used an event-related potential (ERP) analysis based on 20 channel EEG
      recordings in ADHD subjects before and after bipolar tDCS-anode stimulation over F3/F4 or
      T5/T6 or P4/P3, during resting state and measure clinical scores and visual CPT tasks
      changes. Time courses and topography of independent component visual ERPs were compared
      before and after tDCS.
    

Detailed description: 
      Important advances in the understanding of ADHD pathophysiology, such fMRI studies showing a
      focal frontotemporal loops dysfunction in brain activity, suggest that frontal brain
      stimulation might be helpful for the treatment of ADHD. In a recent study of Lyon's
      university with tDCS they concluded that tDCS is "cheaper and easier-use than transcranial
      magnetic stimulation (TMS) and the impact on symptomatology seems larger (impact on negative
      symptoms of schizophrenic patients) and longer (at least 3 months duration) than that TMS
      currently permits. It is possible that tDCS could in the future be used at home by patients
      themselves. The efficacy of tDCS depends of parameters like electrode position and current
      strength.

      In this trial, The investigators investigated the effects of 12 days of anodal stimulation of
      the left dorsolateral prefrontal cortex in ten patients with ADHD (aged 8 +/- 3 years). tDCS
      was applied through a saline-soaked pair of surface sponge electrodes (35 cm2). The anode
      electrode was placed over F3/F4 or T5/T6 or P4/P3(based on the 10-20 International EEG
      System) of each subject. The cathode was placed over the contralateral mastoid area. A
      constant current between 1.1 and 2.0 mA was applied for 25 min/day (administered for 12
      alternated days).

      Prior to the first session, ADHD subjects were asked to complete and return a series of
      questionnaires, including the Conners Brief Symptom Inventory, a health history
      questionnaire, and the QEEG questionnaire. Subjects were then tested in a first session which
      lasted approximately three hours. During this period, a comprehensive structured clinical
      interview was carried out, comprising of an assessment of current and past ADHD symptoms, the
      history of problems at school, the past psychiatric history (including drug and medication
      use), as well as past and present comorbidities. Subsequently, EEG data was acquired. EEG
      data was first recorded while the subject was in eyes-closed and eyes-open resting
      conditions, lasting four minutes each. Then data was recorded while subjects performed a
      visual continuous performance task (VCPT). The VCPT took approximately 22 minutes to
      complete. In addition, subjects randomly performed either an auditory or an emotional
      continuous performance task.

      The control group had a shortened procedure. Subjects were tested in a single session lasting
      approximately two and a half hours. During this period, a series of questionnaires (Brief
      Symptom Inventory, Health History questionnaire, Current Symptoms Scales) were filled out and
      thereafter, EEG data was acquired. Subsequently, a working memory task, which is not relevant
      here, was administered.

      EEG was recorded using a Mitsar 201 19-channel electroencephalographic system. The input
      signals referenced to the linked ears were filtered between 0.5 and 50 Hz and digitized at a
      sampling rate of 250 Hz. Impedance was kept below 5 kOhm for all electrodes. Electrodes were
      placed according to the International 10-20 system using a electrode cap. Quantitative data
      was calculated using WinEEG software. Linked ears reference montage was changed to average
      reference montage prior to data processing. Eye-blink artefacts were corrected by zeroing the
      activation curves of individual ICA component score responding to eye blinks. In addition,
      epochs of the filtered electroencephalogram with excessive amplitude (>100 μV) and/or
      excessive fast (>35 μV in 20 to 35 Hz band) and slow (>50 μV in 0 to 1 Hz band) activity were
      automatically marked and excluded from further analysis. Finally, EEG was manually inspected
      to verify artefact removal.

      Behavioral task

      The VCPT is a modification of the visual two-stimulus GO/NOGO paradigm. Three categories of
      visual stimuli were selected: 20 pictures of animals, 20 pictures of plants, and 20 pictures
      of humans (presented together with an artificial "novel" sound). The trials consisted of
      presentations of pairs of stimuli: animal-animal (GO trials), animal-plant (NOGO trials),
      plant-plant (IGNORE trials), and plant-human (NOVEL trials). The trials were grouped into
      four blocks. In each block a unique set of five animal stimuli, five plant stimuli and five
      human stimuli was selected. Each block consisted of a pseudo-random presentation of 100
      stimuli pairs with equal probability for each trial category.

      The task was to press a button as fast as possible in response to GO trials.

      According to the task design, two preparatory sets were distinguished in the trials. In the
      "Continue set" a picture of an animal is presented as the first stimulus and the subject is
      supposed to prepare to respond. In the "Discontinue set" a picture of a plant is presented as
      the first stimulus and the subject does not need to prepare to respond.

      During the task, subjects were seated in a comfortable chair, 1.5 m in front of a computer
      screen. The stimuli were presented on a 17 inch monitor using the Psytask (Mitsar Ltd.)
      software.

      The primary outcome was change in score on the QEEG Rating Scale (AMEN questionnaire). The
      ERP and questionnaire/behavioural assessments will be made at baseline (before
      stimulation)and 3 months after stimulation.

      This study involved 30 subjects, all aged between 7 and 13. All have been diagnosed with ADHD
      by a medical professional.
    

Intervention name(s): Active tDCS
Intervention type(s): Device
Intervention description(s): tDCS applied to left dorsolateral prefrontal scalp area through a saline-soaked pair of surface sponge electrodes (35 cm2). The anode electrode was placed over F3 (based on the 10-20 International EEG System) of each subject. The cathode was placed over the contralateral mastoid area. A constant current of 1.1 mA was applied for 25 min/day (administered for 12 alternated days).
Other intervention name(s): Chattanooga Iontophoresis
Observational model: Case-Control
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        ADHD children from 5 to 13 years old and controls
      
Keywords: tdcs; tms; qeeg; neuroplasticity; brain networks; add; adhs