Noninvasive Brain Stimulation to Enhance Cognitive Training in Older Adults

This research study explores the feasibility of pairing computer-based cognitive training (CBCT) with transcranial direct current stimulation (tDCS), a form of non-invasive brain stimulation, in order to enhance and preserve mental skills in older adults. The investigators aim to enhance participants ability to perform tasks of memory, attention, processing speed and other areas of cognition. Additionally, researchers are interested in the ability of the brain to adapt to change-neuroplasticity. Neuroplasticity is thought to impact how individuals respond to cognitive training and tDCS. In order to look at individual differences in neuroplasticity transcranial magnetic stimulation (TMS), a noninvasive brain stimulation technique, will be used. Individual responses to TMS can be used as a marker of neuroplastic changes in brain function, in order to reveal the relationship between brain plasticity and tDCS-induced changes in cognitive ability.

Promising evidence suggests that cognitive training regimens may have some beneficial effects on cognition in older adults. However, the improvement from computer-based cognitive training (CBCT) diminish over time which highlights a fundamental challenge for CBCT interventions. Transcranial direct current stimulation (tDCS) can enhance certain cognitive skills, particularly when stimulation is combined with rehearsal of relevant behaviors. Importantly, these benefits have been shown to persist up to 2 months after the intervention.

This study will lay the groundwork for larger scale studies that will combine CBCT with neuromodulation, potentially leading to the development of a persistent, transferrable, multimodal technique to preserve cognition in older adults. In this study, participants will be randomly assigned to receive either real or sham tDCS for 5 consecutive days in conjunction with CBCT. The participant's cognition will be assessed with a neuropsychological assessment at baseline, 1 week, 2 weeks, and 2 months in order to determine any changes.

Additionally, transcranial magnetic stimulation (TMS) will be used to characterize the relationship between baseline differences in brain plasticity and cognitive changes induced by tDCS+CBCT. The effects of TMS on cortical activity have been shown to depend on a variety of neuroplasticity-related mechanisms. In this study, changes in motor physiology (called motor evoked potentials (MEPs)) induced by TMS will be used. Stimulation of the motor cortex with TMS induces robust, transient, and readily quantifiable changes in motor excitability, which are sensitive to changes in the mechanisms of neuroplasticity. Investigators hypothesize that individual variability in brain plasticity, measured by changes in MEP response to TMS, will predict the degree of cognitive benefit afforded by tDCS+CBCT.

Study Visits:

---------------- Visit 1 - Consent and Screening (2 hours) Review enrollment documents and conduct baseline neuropsychological assessment

---------------- Visit 2 - Visit 5 - tDCS + CBCT (30 minutes) Subjects will receive either real or sham stimulation along with cognitive training

--------------- Visit 6 - tDCS + CBCT \& Follow-up (3 hours) Subjects will receive either real or sham stimulation along with cognitive training \& follow-up neurospychological assessment

--------------- Visit 7 - TMS (3 hours) Subjects will receive TMS in order to induce MEPs

------------ Visit 8 - 2 week follow-up (1 .5 hours) Follow-up neuropsychological assessment

----------- Visit 9 - 2 month follow-up (1.5 hours) Follow-up neuropsycological assessment

Eligibility Criteria:
Inclusion Criteria:

* Normal cognition
* English as their native language

Exclusion Criteria:

1. . History of neurological disorders
2. . History of head injury with unconsciousness lasting more than 5 minutes
3. . History of psychiatric disorders
4. . Currently abusing alcohol or drugs (prescription or otherwise)
5. . History of epilepsy or seizures within the past 6 months
6. . Previous brain surgery
7. . Pacemaker