What this trial measures

• Craving for alcohol during the cue reactivity task as assessed by a rating scale28 minutes

  Participants will view blocks of pictures of alcohol and non-alcohol beverages, as well as control pictures and periods of rest. Participant rating of alcohol craving are obtained during the picture presentations using one of 5 buttons placed under their fingers, where 5 (thumb) = Extreme, 4=Severe, 3=Moderate, 2=Mild, 1=None

• Resting state functional connectivity during tDCS28 minutes

  Participants will rest quietly during tDCS administration

• Brain activation to alcohol cues28 minutes

  Participants will view blocks of pictures of alcohol and non-alcohol beverages, as well as control pictures and periods of rest. Brain activation will be measured from the fMRI signal on alcohol minus non-alcohol conditions.

• Brain functional connectivity to alcohol vs non-alcohol cues28 minutes

  A psychophysiological interaction (PPI) analysis will be used to determine if brain connectivity between the cerebellum and reward areas changes when viewing alcohol versus non-alcohol pictures

• Brain activation related to reward prediction during the monetary incentive task18 minutes

  The monetary incentive task is performed during fMRI scanning. Two different cue symbols (dollar sign vs circle) will cue participants to expect a $1 or $0 reward shortly after they press a button in response to seeing an "X" on the screen. These expectations will be learned in an initial Learning phase, where one symbol is always rewarded with $1 and the other with $0, and participants will be tested to ensure that they have learned the appropriate expectations. This Learning phase will be followed by a Testing phase in which the amount of reward (on reward trials) can be greater than, less than, or equal to expectation. Brain activation during reward prediction will be measured by the post-cue activation on dollar sign versus circle trials.

• Brain functional connectivity related to reward prediction during the monetary incentive task18 minutes

  The monetary incentive task is performed during fMRI scanning. Two different cue symbols (dollar sign vs circle) will cue participants to expect a $1 or $0 reward shortly after they press a button in response to seeing an "X" on the screen. These expectations will be learned in an initial Learning phase, where one symbol is always rewarded with $1 and the other with $0, and participants will be tested to ensure that they have learned the appropriate expectations. This Learning phase will be followed by a Testing phase in which the amount of reward (on reward trials) can be greater than, less than, or equal to expectation. Functional connectivity between the cerebellum and reward structures during reward prediction will be measured by a PPI analysis that measures post-cue functional connectivity on dollar sign versus circle trials.

• Brain activation to reward prediction error during the monetary incentive task18 minutes

  Two different symbols (circle vs triangle) will cue participants to expect a $1 or $0 reward shortly after they press a button in response to seeing an "X" on the screen. These expectations will be learned in an initial Learning phase, where one symbol is always rewarded with $1 and the other with $0, and participants will be tested to ensure that they have learned the appropriate expectations. This Learning phase will be followed by a Testing phase in which the amount of reward (on reward trials) can be greater than, less than, or equal to expectation. Brain activation to reward prediction error will be measured from the activation observed after the participant receives feedback on his/her winnings, by contrasting trials in which reward obtained is equal to the amount expected versus not equal to the amount expected.

• brain functional connectivity to reward prediction error during the monetary incentive task18 minutes

  Two different symbols (circle vs triangle) will cue participants to expect a $1 or $0 reward shortly after they press a button in response to seeing an "X" on the screen. These expectations will be learned in an initial Learning phase, where one symbol is always rewarded with $1 and the other with $0, and participants will be tested to ensure that they have learned the appropriate expectations. This Learning phase will be followed by a Testing phase in which the amount of reward (on reward trials) can be greater than, less than, or equal to expectation. Functional connectivity between the cerebellum and reward structures to reward prediction error will be measured using a PPI on the connectivity that is observed after the participant receives feedback on his/her winnings, by contrasting trials in which reward obtained is equal to the amount expected versus not equal to the amount expected.

• Percentage of trials with a conditioned response during the classical eyeblink conditional task21 minutes

  Eyeblink conditioning involves pairing a neutral stimulus, e.g. an auditory conditioned stimulus (CS), with an air puff to the eye region. This unconditioned stimulus (US) evokes an unconditioned response (UR) that is detected by measuring the eyeblink. After repeated pairings of the CS and US, participants learn to blink in response to the conditioned stimulus and before air puff onset. The CS-US pairing dependent eyeblink that anticipates the onset of the US is referred to as the conditioned response (CR).

• Mean time (in milliseconds) at which peak of conditioned response occurs during the classical eyeblink conditional task21 minutes

  Eyeblink conditioning involves pairing a neutral stimulus, e.g. an auditory conditioned stimulus (CS), with an air puff to the eye region. This unconditioned stimulus (US) evokes an unconditioned response (UR) that is detected by measuring the eyeblink. After repeated pairings of the CS and US, participants learn to blink in response to the conditioned stimulus and before air puff onset. The CS-US pairing dependent eyeblink that anticipates the onset of the US is referred to as the conditioned response (CR).