Poster presentation given at McLean Hospital Research Day 2014.

1.  Marijuana (MJ) is the most widely used illicit drug both worldwide and in the United
States. Results from the 2012 national survey performed by the Substance Abuse and
Mental Health Services Administration indicate that:
• MJ use in the United States continues to rise with 18.1 million Americans reporting
past month use in 2011, an increase from 14.5 million in 2007.
• 5.4 million people aged 12 or older used MJ on a daily or almost daily basis in 2011
(i.e. 300 or more days within that period), and 39.1% (approximately 7.1 million
people) used MJ on 20 or more days in the past month.
• The perception of risk associated with MJ has reached an all-time historic low
amongst the nation’s emerging adults. The percentage of youths aged 12-17
perceiving great risk in smoking MJ once or twice a week decreased from 54.6% in
2007 to 44.8% in 2011.
 These trends are unfolding against a growing body of literature that suggests chronic MJ
use is linked with cognitive impairments (Pope & Yurgelun-Todd 1996; Bolla et al. 2002,
Gruber et al. 2011).
• Studies report differences on a range of cognitive processes, including impairments
in executive functioning, reaction time, impulsivity, and attention.
• Combined, these cognitive processes are crucial for behavior monitoring, decision-
making, abstract thinking, rule acquisition and inhibiting inappropriate actions.
 Previous investigations focused on substance use/abuse have utilized traditional Go/No
Go tasks to measure subjects’ inhibitory function, specifically impulse control, and the
ability to refrain from making inappropriate responses.
• A number of Go/No Go tasks exist, including a version specifically designed to
assess nicotine-salient stimuli (Luijten et al. 2011).
• Pilot research from our lab has indicated that on a traditional geometric Go/No Go
task, there were no significant performance differences for accuracy or reaction time
between controls and MJ smokers.
 We developed an MJ specific Go/No Go task similar to Luijten’s nicotine Go/No Go task
and hypothesized that we would see impaired performance in MJ smokers compared to
controls.
 As hypothesized, results suggest a general pattern of slower response time and
more errors throughout the MJ Go/No Go task for MJ smokers relative to control
subjects.
 These findings are consistent with the growing literature that chronic MJ use is
associated with compromised ability to perform tasks requiring cognitive control as
well as greater difficulty regulating impulse control (Eldreth et al.,2004; Gruber &
Yurgelun-Todd, 2005; Pillay et al., 2004; Tapert et al., 2007).
 Further, the use of a novel Go/No Go task was able to detect specific MJ-related
bias in the smoking group as compared to control subjects. Specifically, MJ smokers
performed better in the presence of MJ stimuli, highlighting an attentional bias.
 These results are particularly compelling as previous work with similar groups which
utilized a traditional Go/No Go task yielded no between group differences,
suggesting the salience of the stimuli facilitates a between group distinction.
 Future research can incorporate this MJ specific Go/No Go task during fMRI
scanning to determine if the task successfully activates brain regions previously
implicated in the processing of Go/No Go tasks, which include the anterior cingulate
cortex (ACC), the dorsolateral prefrontal cortex (DLPFC), and the inferior frontal
gyrus (IFG).
Why So Slow?
Slower Reaction Times To Marijuana Stimuli During a Novel Marijuana Go/No Go Task
MW Dreman1
, KA Sagar1
, MK Dahlgren1
, MT Racine1
, & SA Gruber1,2
1
Cognitive and Clinical Neuroimaging Core, McLean Imaging Center, McLean Hospital, Belmont, MA
2
Department of Psychiatry, Harvard Medical School, Boston, MA
Bolla, K. I., Brown, K., Eldreth, D., Tate, K., & Cadet, J. L. (2002). Dose-related neurocognitive effects of
marijuana use. Neurology, 59, 1337–1343.
Eldreth, D. A., Matochik, J. A., Cadet, J. L., & Bolla, K. I. (2004). Abnormal brain activity in prefrontal brain
regions in abstinent marijuana users. NeuroImage, 23, 914–920.
Gruber, S. A., Silveri, M.M., Dahlgren, M.K., & Yurgelun-Todd, D. A. (2011). Why So Impulsive? White Matter
Alterations Are Associated With Impulsivity in Chronic Marijuana Smokers. Experimental and Clinical
Psychopharmacology, 19, 231-242.
Luijten, M., Little, M., Franken, I. (2011) Deficits in Inhibitory Control in Smokers During a Go/NoGo Task: An
Investigation Using Event-Related Brain Potentials. PLOS One, 6, 1-7.
Pillay, S. S., Rogowska, J., Kanayama, G., Jon, D. I., Gruber, S.,Simpson, N., Yurgelun-Todd, D. A. (2004).
Neurophysiology of motor function following cannabis discontinuation in chronic cannabis smokers: An
fMRI study. Drug and Alcohol Dependence, 76, 261–271.
Pope, H.G., Yurgelun-Todd, D.A. (1996) The residual cognitive effects of heavy marijuana use in college
students. JAMA 275:521-527.
Ramaekers, J. G., Kauret, G., van Ruitenbeek, P., Theunissen, E. L., Schneider, E., Moeller, M. R. (2006).
High-potency marijuana impairs executive function and inhibitory control. Neuropsychopharmacology, 31,
2296–2303.
Substance Abuse and Mental Health Services Administration (2012). Results from the 2011 National Survey on
Drug Use and Health: Summary of National Findings (NSDUH Series H-44, HHS Publication No. SMA 12-
4713). Rockville, MD.
Tapert, S. F., Schweinsburg, A. D., Drummond, S. P. A., Paulus, M. P., Brown, S. A., Yang, T. T., & Frank, L.
R. (2007). Functional MRI of inhibitory processing in abstinent adolescent marijuana users.
Psychopharmacology, 194, 173–183.
Results
Discussion
References
Introduction
Methods
We designed a MJ-specific Go/No Go task which included MJ-salient images to measure
subject’s inhibitory function. The task was administered to 15 chronic, heavy MJ smokers
and 9 non-MJ smoking control subjects, all between the ages of 17-35.
9 healthy control subjects:
No Axis I pathology and did not meet criteria for current or past drug/alcohol abuse or
dependence
15 well-characterized, chronic, heavy MJ smokers:
2,000+ lifetime uses of MJ and used MJ at least 5 days a week
Tested positive for urinary cannabinoids and negative for other illicit drugs
No Axis I pathology and did not meet criteria for current or previous drug/alcohol abuse
or dependence (excluding MJ)
This study was supported by NIDA grant R01 DA032646-01 to Dr. Gruber
MJ SMOKERS vs. CONTROLS
Overall, task accuracy for both subject groups was high, suggesting that participants were
attuned to the task (MJ Smokers: mean = 95.94%; Controls: mean = 97.98%)
Relative to controls, MJ smokers had significantly slower reaction times in response to all
stimuli, t(20)=2.109, p=.024. (Figure 2)
MJ Go/No Go:
• Fifteen pairs of neutral stimuli and MJ-related stimuli were matched on the basis of
content, color, and composition (Figure 1).
• A red or green border was added to each stimulus set. The stimuli were
randomized with a ratio of 3 Go stimuli for every 1 No Go stimuli, as per traditional
Go/No Go protocol.
• Subjects are instructed to push a response button as quickly as possible for all
stimuli with a green border, and to withhold responses for those with a red border.
• Stimuli are presented for 350 milliseconds followed by an interstimulus interval (ISI)
of 1650 milliseconds.
Figure 1: MJ Go/No Go Stimuli WITHIN GROUP ANALYSES: MJ STIMULI vs. NEUTRAL STIMULI
Within-group analysis showed that both MJ smokers t(12)=5.312, p <.001) and
controls t(8)= 6.000, p<.001) demonstrated significantly longer reaction times for MJ
stimuli relative to neutral stimuli (Figure 4).
 In a trend that approaches significance, MJ smokers spent longer on the marijuana-
related stimuli relative to the controls, t(20)= 1.493, p = .076.
WITHIN GROUP ANALYSES: MJ Smokers Accuracy
 Within the MJ group, there was a significant difference in accuracy according to
stimulus type. The MJ subjects had better total percent accuracy for MJ stimuli
(96.69 ± 3.60) compared to neutral stimuli (95.10 ± 5.27); t(12)= 2.106, p=.0285)
(Figure 3).
**
**
*p<0.001
*p<0.05
*p<0.05
Figure 2: MJ Smoker vs. Control Total Reaction Time
Figure 3: MJ Smoker vs. Control : Percent Accuracy
Figure 4: MJ Smoker vs. Control Reaction Time