Participants will be asked to take study medication each day for both 11-day study medication periods.

The study medication assignments for each participant in this project is randomized and counterbalanced. This means that approximately 50% of participants will take tolcapone during the first medication period, followed by the placebo in the second medication period. Alternatively, approximately 50% of participants will take the placebo during the first medication period, followed by tolcapone during the second medication period.

Subjects completed two, 11-day study medication periods (one taking active tolcapone; one taking placebo). On Day 8 of each period, after at least 24 hours of smoking abstinence, subjects had an fMRI scan to measure changes in brain activity that occur during a memory test. The subjects completed a commonly used working memory test referred to as the "N-back". This test presented complex geometric figures on a projection screen for 0.5 seconds; each figure is separated by 2.5 seconds of black screen. There were 4 conditions requiring increasing memory demands: 0-back, 1-back, 2-back, & 3-back. Subjects had to respond to the target geometric figure that was separated by 0, 1, 2, or 3 figures before it is repeated. Between each condition, there was a brief rest period.

To identify brain signal change, we calculated the difference in the amount of brain activity detected by the fMRI scan for each condition compared to the rest periods. This was a within-subject analysis.

Subjects completed two, 11-day study medication periods (one taking active tolcapone; one taking placebo). On Day 8 of each period, after at least 24 hours of smoking abstinence, subjects had an fMRI scan to measure changes in brain activity that occur during a memory test. The subjects completed a commonly used working memory test referred to as the "N-back". This test presented complex geometric figures on a projection screen for 0.5 seconds; each figure is separated by 2.5 seconds of black screen. There were 4 conditions requiring increasing memory demands: 0-back, 1-back, 2-back, & 3-back. Subjects had to respond to the target geometric figure that was separated by 0, 1, 2, or 3 figures before it is repeated. Between each condition, there was a brief rest period.

To identify brain signal change, we calculated the difference in the amount of brain activity detected by the fMRI scan for each condition compared to the rest periods. This was a within-subject analysis.

Subjects completed two, 11-day study medication periods (one taking active tolcapone; one taking placebo). On Day 8 of each period, after at least 24 hours of smoking abstinence, subjects had an fMRI scan to measure changes in brain activity that occur during a memory test. The subjects completed a commonly used working memory test referred to as the "N-back". This test presented complex geometric figures on a projection screen for 0.5 seconds; each figure is separated by 2.5 seconds of black screen. There were 4 conditions requiring increasing memory demands: 0-back, 1-back, 2-back, & 3-back. Subjects had to respond to the target geometric figure that was separated by 0, 1, 2, or 3 figures before it is repeated. Between each condition, there was a brief rest period.

To identify brain signal change, we calculated the difference in the amount of brain activity detected by the fMRI scan for each condition compared to the rest periods. This was a within-subject analysis.

Subjects underwent two, 11-day study medication periods (one taking active tolcapone; one taking placebo). On Day 8 of each study medication period, after at least 24 hours of smoking abstinence, subjects completed an fMRI brain scan. During these fMRI scan sessions, participants completed computer tasks that were designed to test working memory and attention. These tasks were similar to computer games, in that participants would push a button in response to the pictures they see.

Specifically, we tested whether subjects, while taking tolcapone, would display increased average reaction time (in milliseconds) during the N-back working memory task compared to their performance while they took the placebo. This was a within-subject analysis.

In order to determine if tolcapone (vs. placebo) would affect subject smoking behavior, we collected the daily number of cigarettes each subject smoked from Days 1 through 7 during each study medication period. This allowed us to calculate the average number of daily cigarettes smoked, across all subjects, during each study medication period (i.e., the average number of cigarettes/day smoked while all subjects took tolcapone and the average number of cigarettes/day smoked while all subjects took placebo). Then, we statistically assessed if there was a significant difference between these averages.

Subjective symptoms were assessed during each in-person session throughout each study medication period. During each visit, we asked subjects to complete the Questionnaire for Smoking Urges-Brief (QSU-B). Specifically, subjects completed the QSU-B at day 5, day 8 (fMRI scanning session 1), day 26 (day 5 of study medication period 2), and day 29 (day 8 of study medication period 2; fMRI scanning session 2).

The range of possible scores on the QSU-B is 10-70, with higher values indicating an increased craving for cigarettes. This range of scores represent a "total" score; there are no subscales.

While the QSU-B was collected at all in-person sessions, we only analyzed the scores collected from the fMRI scanning sessions of each period (day 8 and day 29). To analyze, we averaged the total scores across all 20 subjects from each fMRI scanning session and statistically analyzed for significant differences between these two averages. This was a within-subject analysis.

Subjective symptoms were assessed during each in-person session throughout each study medication period. During each visit, we asked subjects to complete the Minnesota Nicotine Withdrawal Scale - Revised version (MNWS). The scale assesses eight DSM-IV items of nicotine withdrawal. The range of possible total scores on the MNWS is 0-60, with higher values indicating an increased nicotine withdrawal. This range of scores represent a "total" score; there are no subscales. The MNWS-N (right now/at the moment) was assessed during each fMRI scanning session visit (Day 8).

To assess if tolcapone (vs. placebo) affect withdrawal symptoms, we statistically analyzed the average of the total MNWS scores across, all 20 subjects, for each study medication period. Specifically, we analyzed for significant differences between reported withdrawal symptoms while taking tolcapone vs. taking placebo.

Determined by the Fagerstrom Test for Nicotine Dependence (FTND). The FTND is a 6-item, self-report measure of nicotine dependence derived from the Fagerstrom Tolerance Questionnaire. Scores range from 0-10; higher FTND scores indicate greater difficulty in quitting smoking. All subjects completed the FTND during the medical screening visit.

During the medical screening visit, subjects were asked to self-report the number of cigarettes they smoked on an average day.

During the medical screening visit, subjects were asked to self-report the number of years they have been a regular smoker (defined as smoking at least one cigarette per day).

Subjects underwent two, 11-day study medication periods (one taking active tolcapone; one taking placebo). On Day 8 of each study medication period, after at least 24 hours of smoking abstinence, subjects completed an fMRI brain scan. During these fMRI scan sessions, participants completed computer tasks that were designed to test working memory and attention. These tasks were similar to computer games, in that participants would push a button in response to the pictures they see.

Specifically, we tested whether subjects, while taking tolcapone, would display increased accuracy during the N-back working memory task compared to their performance while they took the placebo. We measured accuracy by counting the absolute number of true positives scored (the number each subject got correct during the task). This was a within-subject analysis.

29 subjects completed both fMRI scan sessions; however, data from 9 subjects were excluded from analysis, due to either poor fMRI data quality, low task accuracy (defined as task scores falling two standard deviations below the mean), or a failure to respond to more than 30% of the task's items. Below, we report on the 20 remaining subjects.

Subjects underwent two, 11-day study medication periods (one taking active tolcapone; one taking placebo). On Day 8 of each study medication period, after at least 24 hours of smoking abstinence, subjects completed an fMRI brain scan. During these fMRI scan sessions, participants completed computer tasks that were designed to test working memory and attention. These tasks were similar to computer games, in that participants would push a button in response to the pictures they see.

Specifically, we tested whether subjects, while taking tolcapone, would display increased average reaction time (in milliseconds) during the N-back working memory task compared to their performance while they took the placebo. This was a within-subject analysis.

29 subjects completed both fMRI scan sessions; however, data from 9 subjects were excluded from analysis, due to either poor fMRI data quality, low task accuracy (defined as task scores falling two standard deviations below the mean), or a failure to respond to more than 30% of the task's items. Below, we report on the 20 remaining subjects.

In order to determine if tolcapone (vs. placebo) would affect subject smoking behavior, we collected the daily number of cigarettes each subject smoked from Days 1 through 7 during each study medication period. This allowed us to calculate the average number of daily cigarettes smoked, across all subjects, during each study medication period (i.e., the average number of cigarettes/day smoked while all subjects took tolcapone and the average number of cigarettes/day smoked while all subjects took placebo). Then, we statistically assessed if there was a significant difference between these averages.

29 subjects completed both fMRI scan sessions; however, data from 9 subjects were excluded from analysis, due to either poor fMRI data quality, low task accuracy (defined as task scores falling two standard deviations below the mean), or a failure to respond to more than 30% of the task's items. Below, we report on the 20 remaining subjects.

Subjective symptoms were assessed during each in-person session throughout each study medication period. During each visit, we asked subjects to complete the Questionnaire for Smoking Urges-Brief (QSU-B). Specifically, subjects completed the QSU-B at day 5, day 8 (fMRI scanning session 1), day 26 (day 5 of study medication period 2), and day 29 (day 8 of study medication period 2; fMRI scanning session 2).

The range of possible scores on the QSU-B is 10-70, with higher values indicating an increased craving for cigarettes. This range of scores represent a "total" score; there are no subscales.

While the QSU-B was collected at all in-person sessions, we only analyzed the scores collected from the fMRI scanning sessions of each period (day 8 and day 29). To analyze, we averaged the total scores across all 20 subjects from each fMRI scanning session and statistically analyzed for significant differences between these two averages. This was a within-subject analysis.

29 subjects completed both fMRI scan sessions; however, data from 9 subjects were excluded from analysis, due to either poor fMRI data quality, low task accuracy (defined as task scores falling two standard deviations below the mean), or a failure to respond to more than 30% of the task's items. Below, we report on the 20 remaining subjects

Subjective symptoms were assessed during each in-person session throughout each study medication period. During each visit, we asked subjects to complete the Minnesota Nicotine Withdrawal Scale - Revised version (MNWS). The scale assesses eight DSM-IV items of nicotine withdrawal. The range of possible total scores on the MNWS is 0-60, with higher values indicating an increased nicotine withdrawal. This range of scores represent a "total" score; there are no subscales. The MNWS-N (right now/at the moment) was assessed during each fMRI scanning session visit (Day 8).

To assess if tolcapone (vs. placebo) affect withdrawal symptoms, we statistically analyzed the average of the total MNWS scores across, all 20 subjects, for each study medication period. Specifically, we analyzed for significant differences between reported withdrawal symptoms while taking tolcapone vs. taking placebo.

29 subjects completed both fMRI scan sessions; however, data from 9 subjects were excluded from analysis, due to either poor fMRI data quality, low task accuracy (defined as task scores falling two standard deviations below the mean), or a failure to respond to more than 30% of the task's items. Below, we report on the 20 remaining subjects.

Subjects completed two, 11-day study medication periods (one taking active tolcapone; one taking placebo). On Day 8 of each period, after at least 24 hours of smoking abstinence, subjects had an fMRI scan to measure changes in brain activity that occur during a memory test. The subjects completed a commonly used working memory test referred to as the "N-back". This test presented complex geometric figures on a projection screen for 0.5 seconds; each figure is separated by 2.5 seconds of black screen. There were 4 conditions requiring increasing memory demands: 0-back, 1-back, 2-back, & 3-back. Subjects had to respond to the target geometric figure that was separated by 0, 1, 2, or 3 figures before it is repeated. Between each condition, there was a brief rest period.

To identify brain signal change, we calculated the difference in the amount of brain activity detected by the fMRI scan for each condition compared to the rest periods. This was a within-subject analysis.

See previous sections.

Subjects completed two, 11-day study medication periods (one taking active tolcapone; one taking placebo). On Day 8 of each period, after at least 24 hours of smoking abstinence, subjects had an fMRI scan to measure changes in brain activity that occur during a memory test. The subjects completed a commonly used working memory test referred to as the "N-back". This test presented complex geometric figures on a projection screen for 0.5 seconds; each figure is separated by 2.5 seconds of black screen. There were 4 conditions requiring increasing memory demands: 0-back, 1-back, 2-back, & 3-back. Subjects had to respond to the target geometric figure that was separated by 0, 1, 2, or 3 figures before it is repeated. Between each condition, there was a brief rest period.

To identify brain signal change, we calculated the difference in the amount of brain activity detected by the fMRI scan for each condition compared to the rest periods. This was a within-subject analysis.

See previous sections.

Subjects completed two, 11-day study medication periods (one taking active tolcapone; one taking placebo). On Day 8 of each period, after at least 24 hours of smoking abstinence, subjects had an fMRI scan to measure changes in brain activity that occur during a memory test. The subjects completed a commonly used working memory test referred to as the "N-back". This test presented complex geometric figures on a projection screen for 0.5 seconds; each figure is separated by 2.5 seconds of black screen. There were 4 conditions requiring increasing memory demands: 0-back, 1-back, 2-back, & 3-back. Subjects had to respond to the target geometric figure that was separated by 0, 1, 2, or 3 figures before it is repeated. Between each condition, there was a brief rest period.

To identify brain signal change, we calculated the difference in the amount of brain activity detected by the fMRI scan for each condition compared to the rest periods. This was a within-subject analysis.

See previous sections.

Subjects completed two, 11-day study medication periods (one taking active tolcapone; one taking placebo). On Day 8 of each period, after at least 24 hours of smoking abstinence, subjects had an fMRI scan to measure changes in brain activity that occur during a memory test. The subjects completed a commonly used working memory test referred to as the "N-back". This test presented complex geometric figures on a projection screen for 0.5 seconds; each figure is separated by 2.5 seconds of black screen. There were 4 conditions requiring increasing memory demands: 0-back, 1-back, 2-back, & 3-back. Subjects had to respond to the target geometric figure that was separated by 0, 1, 2, or 3 figures before it is repeated. Between each condition, there was a brief rest period.

To identify brain signal change, we calculated the difference in the amount of brain activity detected by the fMRI scan for each condition compared to the rest periods. This was a within-subject analysis.

See previous sections.

11-day phase, tapered dosing scheduled (Day 1: 100mg three times daily, Days 2-8: 200mg three times daily, Day 9: 200mg twice daily, Day 10: 200mg once daily, Day 11: 100mg once daily); oral dosing; medication is encapsulated by the University of Pennsylvania's Investigational Drug Service (IDS)

Tolcapone: Participants will be asked to take study medication each day for both 11-day study medication periods.

The study medication assignments for each participant in this project is randomized and counterbalanced. This means that approximately 50% of participants will take tolcapone during the first medication period, followed by the placebo in the second medication period. Alternatively, approximately 50% of participants will take the placebo during the first medication period, followed by tolcapone during the second medication period.