This study is being completed to learn if high-definition transcranial direct current stimulation (HD-tDCS) has an effect on visual and thinking abilities in persons with posterior cortical atrophy (PCA). Participants will be randomized to receive real or sham HD-tDCS (8 sessions over 4 days).
Following the randomized treatment, participants will have optional open-label phase with real HD-tDCS up to 26 weeks and other possible testing.
Diagnosis or symptoms consistent with PCA
Fluent in English
HD-tDCS compatible
Stable on relevant medications for at least approximately 4 weeks prior to study enrollment
Other relevant neurological disease (e.g., epilepsy) or injuries (e.g., large vessel stroke, moderate-severe traumatic brain injury) viewed as primary to deficits since these could interfere with etiologic considerations and confound study results
Active, relevant psychiatric conditions (e.g., bipolar disorder, schizophrenia) since the symptoms of these conditions may confound study participation.
A recent (e.g., within the past 2 years) significant history of, or current, alcohol or drug abuse/dependence. Remote history of abuse/dependence is not exclusionary as long as it is not considered to be the primary etiology for visuospatial deficits.
Women that are lactating/breastfeeding, pregnant, or may potentially be pregnant will be excluded from the study.
Parallel
HD-tDCS sessions
DeviceThis project translates decades of observational neuroimaging research into a biologically plausible stimulation target (i.e., DAN) and uses functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) to plan personalized brain stimulation and to ensure target engagement. When available; those not MRI compatible will receive a standard montage with per channel amplitudes of up to 5 milliamperes (mA) or a montage derived from other imaging methods. Participants will receive 4 days of HD-tDCS sessions in person. During these sessions participants will have electrodes placed on different areas of the head and held in place with headgear. Participants may also have memory and thinking tests during and after the sessions as well as questionnaires about the experience. Additionally, on the fourth day participants may have repeat immersive virtual reality (iVR) as well as other study activities.
Sham HD-tDCS sessions
DeviceParticipants will receive 4 days of sham HD-tDCS sessions in person. During these sessions participants will have electrodes placed on different areas of the head and held in place with headgear. Participants may also have memory and thinking tests during and after the sessions as well as questionnaires about the experience. Additionally, on the fourth day participants may have repeat immersive virtual reality (iVR) as well as other study activities.
HD-tDCS sessions - Open-label (after randomized treatment)
DeviceOptional 26 weeks of additional HD-tDCS sessions. Participants can complete up to 5 days per week, but most people will complete about 3 days per week. The study team may also collect audio recordings of these sessions. Participants can complete this in person or at-home via using a secure, HIPAA-compliant videoconferencing with the supervision of a research staff member. Participant's that decide to complete the additional sessions at home, a research staff member will train a study partner during the first 4 HD-tDCS sessions in the office. This option may not be available or appropriate for all participants and the study team member will discuss this with participant's and study partners.
Change in network connectivity measured via fMRI
Functional connectivity measures whether activity in different brain regions show similar patterns of change over time. Graph theory metrics of resting-state fMRI can characterize functional connectivity within the Dorsal Attention Network (DAN).
Measure of form coherence
This will evaluate dorsal and ventral visual stream functioning using a visual paradigm.
Long-term change in network connectivity via fMRI
Functional connectivity measures whether activity in different brain regions show similar patterns of change over time. Graph theory metrics of resting-state fMRI can characterize functional connectivity within the Dorsal Attention Network.
Measures of motion tasks
This will evaluate dorsal and ventral visual stream function. Motion coherence is measured using a visual paradigm.
Measures of motion tasks
This will evaluate dorsal and ventral visual stream function. Motion coherence is measured using a visual paradigm.
Measure of form coherence tasks
Form coherence is measured using a visual paradigm.
Eye tracking - Number of fixations
The study team will quantify the number and duration of fixations, while the participants perform visual search, reading, or other visual tasks affected by PCA.
Eye tracking - Number of fixations
The study team will quantify the number and duration of fixations, while the participants perform visual search, reading, or other visual tasks affected by PCA.
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