Targeting Individual Alpha Frequencies to Enhance Perceptual Timing
Condition: Psychosis; Schizophrenia; Schizo Affective Disorder
MeSH terms: Schizophrenia; Psychotic Disorders; Mental Disorders; Mood Disorders
Study type: Observational

Summary: 
      This is a single-blind randomized within-subject crossover design study that will be
      conducted in 2 phases. In Phase 1, up to 50 participants, after signing informed consent and
      determining eligibility, will undergo a baseline EEG and cognitive assessment. In Phase 2
      participants will undergo tACS at IAF+2Hz, IAF-2Hz, and IAF during a double-flash illusion
      task in a randomized order. The tACS will be applied with a current of 1-2 mA (milliamperes)
      via two saline soaked electrode sponges (25 cm²) applied to the back of the head. The
      investigator's hypothesis is that participant's will perform better on the visual task while
      tACS is set to 2 Hz above their IAPF, relative to tACS set to 2 Hz below their IAPF.
    

Detailed description: 
      The proposed pilot study will assess the feasibility of transcranial alternating current
      stimulation (tACS) to enhance aspects of attention in people with psychotic disorders.

      If a participant agrees to participate in this research, they will be asked to visit the
      study site to complete the activities listed below. These study activities will take about
      5.5 hours to complete. The activities can be divided into up to 3 separate sessions as
      needed, but all activities should be completed within approximately one week.

      Phase 1:

        -  A clinical interview including an abbreviated MINI, consisting of the mood, mania,
           suicide, and psychosis modules to either: confirm a diagnosis of a psychotic disorder in
           Psychosis Subject recruits; or confirm no diagnosis of a psychotic disorder in Control
           Subject recruits. If any suicidal ideation is expressed on the suicide module, study
           staff will administer the C-SSRS.

        -  All participants will complete the Wechsler Test of Adult Reading (WTAR) to obtain an
           estimate of average IQ, the Brief Assessment of Cognition (BAC app; including Verbal
           Learning, Digit Sequencing, Token Motor, Semantic Fluency, Symbol Coding, and Tower of
           London), the Edinburgh Handedness Inventory, and a brief demographic questionnaire.

        -  Participants with psychosis will complete the PANSS clinical interview to assess
           psychosis symptoms. Controls will not complete the PANSS.

        -  Next, participants will undergo a baseline EEG that includes measures of resting EEG
           (once at the beginning and once more at the end of the session) and a Double-Flash
           Fusion Illusion Task.

      Phase 2:

        -  Participants will undergo a shortened version of the Double-Flash task without any tACS
           stimulation.

        -  Participants will then undergo 3 shortened versions of the Double-Flash Fusion Illusion
           task while simultaneously undergoing tACS. In counterbalanced order, participants will
           have tACS set at their IAF (obtained from the subject's resting EEG signal), their IAF +
           2Hz and their IAF - 2 Hz. Each task run is expected to last 10-20 minutes. In the first
           ~1 minute of stimulation before starting the task, we will ask participants to report
           whether they are perceiving phosphenes. We will turn down the stimulation in .1 mA
           increments until the participant is no longer perceiving bothersome phosphenes before
           starting the task. Participants will have a ~40 minute break between task sessions.

        -  During one of the 40 minute between session breaks, participants will be asked to
           perform two assessment versions of a time-order frequency judgment task: Sound Sweeps
           (auditory frequency modulation time-order judgement) and Visual Sweeps (visual gabor
           frequency modulation time-order judgement).

        -  Following the third stimulation/task session, participants will respond to a
           questionnaire about the tolerability of the stimulation and whether they experienced any
           immediate adverse effects.

             -  Currently, subjects will only undergo Phase 1 of the study to optimally pilot test
                the task and EEG procedures prior to enrolling subjects to both Phases which
                involves an experimental manipulation of the Double-Flash task. Phase 2 will be
                initiated at the discretion of the PI.
    

Intervention name(s): Transcranial alternating current stimulation
Intervention type(s): Device
Intervention description(s): The tACS will be applied with a current of 1-2 mA (milliamperes) via two saline soaked electrode sponges (25 cm²) applied to the back of the head. The anode will be located at Oz and the cathode will be located at Cz.
Other intervention name(s): tACS
Observational model: Case-Control
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        This study will study individuals who experience psychosis, including schizophrenia,
        schizoaffective disorder, and bipolar disorder with psychosis.
      
Keywords: tacs; neuromodulation; psychosis; schizophrenia