Neuropsychopharmacology
February 2012
Jatin G Vaidya, Robert I Block, Daniel S O'Leary et al.
Marijuana (MJ) acutely acts on cannabinoid receptors that are found in numerous brain regions, including those involved in reward processing and decision-making. However, it remains unclear how long-term, chronic MJ use alters reward-based decision-making. In the present study, using [(15)O]water PET imaging, we measured brain activity in chronic MJ users, who underwent monitored abstinence...
Journal of the American Academy of Child and Adolescent Psychiatry
April 14, 2010
Gerry Jager, Robert I Block, Maartje Luijten et al.
Objective: Early-onset cannabis use has been associated with later use/abuse, mental health problems (psychosis, depression), and abnormal development of cognition and brain function. During adolescence, ongoing neurodevelopmental maturation and experience shape the neural circuitry underlying complex cognitive functions such as memory and executive control. Prefrontal and temporal regions are...
Human psychopharmacology
April 2007
Daniel S O'Leary, Robert I Block, Julie A Koeppel et al.
Using an attention task to control cognitive state, we previously found that smoking marijuana changes regional cerebral blood flow (rCBF). The present study measured rCBF during tasks requiring attention to left and right ears in different conditions. Twelve occasional marijuana users (mean age 23.5 years) were imaged with PET using [15O]water after smoking marijuana or placebo cigarettes as...
Neuroreport
June 11, 2003
Daniel S O'Leary, Robert I Block, Beth M Turner et al.
The effects of marijuana on brain perfusion and internal timing were assessed using [15O] water PET in occasional and chronic users. Twelve volunteers who smoked marijuana recreationally about once weekly, and 12 volunteers who smoked daily for a number of years performed a self-paced counting task during PET imaging, before and after smoking marijuana and placebo cigarettes. Smoking marijuana...
Neuropsychopharmacology
June 2002
Daniel S O'Leary, Robert I Block, Julie A Koeppel et al.
The effects of smoking marijuana on regional cerebral blood flow (rCBF) and cognitive performance were assessed in 12 recreational users in a double-blinded, placebo-controlled study. PET with [(15)Oxygen]-labeled water ([(15)O]H(2)O) was used to measure rCBF before and after smoking of marijuana and placebo cigarettes, as subjects repeatedly performed an auditory attention task. Smoking...
Pharmacology, Biochemistry, and Behavior
May 2002
Robert I Block, Daniel S O'Leary, Richard D Hichwa et al.
It is uncertain whether frequent marijuana use adversely affects human brain function. Using positron emission tomography (PET), memory-related regional cerebral blood flow was compared in frequent marijuana users and nonusing control subjects after 26+ h of monitored abstention. Memory-related blood flow in marijuana users, relative to control subjects, showed decreases in prefrontal cortex,...
Human Psychopharmacology: Clinical and Experimental
December 1, 1988
Robert I Block, Mohamed M Ghoneim, James V. Hinrichs et al.
AbstractSubjects (16 men and 16 women) breathing 30 per cent nitrous oxide in oxygen, or 100 per cent oxygen, were tested to see if the effects of nitrous oxide on memory varied with different types of auditory stimuli and memory‐testing procedures. The drug produced substantial memory impairments. These impairments were milder in forced‐choice recognition than in yes/no recognition and for...