Grace Fong

All Publications

• Amphetamine modulates human incentive processing NEURON Knutson, B., Bjork, J. M., Fong, G. W., Hommer, D., Mattay, V. S., Weinberger, D. R. 2004; 43 (2): 261-269

  Abstract

  Research suggests that psychostimulants can physiologically alter dopamine kinetics in the ventral striatum (VS) and psychologically enhance mood and attention. Using event-related functional magnetic resonance imaging (fMRI), we conducted a within-subject, double-blind, placebo (PLAC)-controlled study of the effects of oral dextroamphetamine (AMPH, 0.25 mg/kg) treatment on brain activity and affect during incentive processing. In two counterbalanced scanning sessions 60-180 min after ingesting AMPH or PLAC, 8 healthy volunteers played a game involving anticipation and receipt of monetary gains and losses. Group and volume of interest analyses suggested that by enhancing tonic over phasic activation, AMPH treatment "equalized" levels of VS activity and positive arousal during anticipation of both gain and loss. These findings suggest that therapeutic effects of amphetamine on incentive processing may involve reducing the difference between anticipation of gains and losses.

  View details for DOI 10.1016/j.neuron.2004.06.030

  View details for Web of Science ID 000222905400014

  View details for PubMedID 15260961

• Amphetamine modulates human incentive processing NEURON Knutson, B., Bjork, J. M., Fong, G. W., Hommer, D., Mattay, V. S., Weinberger, D. R. 2004; 43 (2): 261-269

  Abstract

  Research suggests that psychostimulants can physiologically alter dopamine kinetics in the ventral striatum (VS) and psychologically enhance mood and attention. Using event-related functional magnetic resonance imaging (fMRI), we conducted a within-subject, double-blind, placebo (PLAC)-controlled study of the effects of oral dextroamphetamine (AMPH, 0.25 mg/kg) treatment on brain activity and affect during incentive processing. In two counterbalanced scanning sessions 60-180 min after ingesting AMPH or PLAC, 8 healthy volunteers played a game involving anticipation and receipt of monetary gains and losses. Group and volume of interest analyses suggested that by enhancing tonic over phasic activation, AMPH treatment "equalized" levels of VS activity and positive arousal during anticipation of both gain and loss. These findings suggest that therapeutic effects of amphetamine on incentive processing may involve reducing the difference between anticipation of gains and losses.

  View details for Web of Science ID 000222905400014

  View details for PubMedID 15260961

• Voxel-based homogeneity probability maps of grapy matter in groups: assessing the reliability of functional effects NEUROIMAGE Momenan, R., Rawlings, R., Fong, G., Knutson, B., Hommer, D. 2004; 21 (3): 965-972

  Abstract

  A subject of increasing importance in magnetic resonance imaging (MRI) is the analysis of intersubject structural differences, particularly when comparing groups of subjects with different conditions or diagnoses. On the other hand, determining structural homogeneity across subjects using voxel-based morphological (VBM) methods has become even more important to investigators who test for group brain activation using functional magnetic resonance images (fMRI) or positron emission tomography (PET). In the absence of methods that evaluate structural differences, one does not know how much reliability to assign to the functional differences. Here, we describe a voxel-based method for quantitatively assessing the homogeneity of tissues from structural magnetic resonance images of groups. Specifically, this method determines the homogeneity of gray matter for a group of subjects. Homogeneity probability maps (HPMs) of a given tissue type (e.g., gray matter) are generated by using a confidence interval based on binomial distribution. These maps indicate for each voxel the probability that the tissue type is gray for the population being studied. Therefore, HPMs can accompany functional analyses to indicate the confidence one can assign to functional difference at any given voxel. In this paper, examples of HPMs generated for a group of control subjects are shown and discussed. The application of this method to functional analysis is demonstrated.

  View details for DOI 10.1016/j.neuroimage.2003.10.038

  View details for Web of Science ID 000220148900017

  View details for PubMedID 15006663

• Incentive-elicited brain activation in adolescents: Similarities and differences from young adults JOURNAL OF NEUROSCIENCE Bjork, J. M., Knutson, B., Fong, G. W., Caggiano, D. M., Bennett, S. M., Hommer, D. W. 2004; 24 (8): 1793-1802

  Abstract

  Brain motivational circuitry in human adolescence is poorly characterized. One theory holds that risky behavior in adolescence results in part from a relatively overactive ventral striatal (VS) motivational circuit that readily energizes approach toward salient appetitive cues. However, other evidence fosters a theory that this circuit is developmentally underactive, in which adolescents approach more robust incentives (such as risk taking or drug experimentation) to recruit this circuitry. To help resolve this, we compared brain activation in 12 adolescents (12-17 years of age) and 12 young adults (22-28 years of age) while they anticipated the opportunity to respond to obtain monetary gains as well as to avoid monetary losses. In both age groups, anticipation of potential gain activated portions of the VS, right insula, dorsal thalamus, and dorsal midbrain, where the magnitude of VS activation was sensitive to gain amount. Notification of gain outcomes (in contrast with missed gains) activated the mesial frontal cortex (mFC). Across all subjects, signal increase in the right nucleus accumbens during anticipation of responding for large gains independently correlated with both age and self-rated excitement about the high gain cue. In direct comparison, adolescents evidenced less recruitment of the right VS and right-extended amygdala while anticipating responding for gains (in contrast with anticipation of nongains) compared with young adults. However, brain activation after gain outcomes did not appreciably differ between age groups. These results suggest that adolescents selectively show reduced recruitment of motivational but not consummatory components of reward-directed behavior.

  View details for DOI 10.1523/JNEUROSCI.4862-03.2004

  View details for Web of Science ID 000189210300001

  View details for PubMedID 14985419

• A region of mesial prefrontal cortex tracks monetarily rewarding outcomes: characterization with rapid event-related fMRI NEUROIMAGE Knutson, B., Fong, G. W., Bennett, S. M., Adams, C. M., Homme, D. 2003; 18 (2): 263-272

  Abstract

  The function of the mesial prefrontal cortex (MPFC: including Brodman areas 10/12/32) remains an enigma. Current theories suggest a role in representing internal information, including emotional introspection, autonomic control, and a "default state" of semantic processing. Recent evidence also suggests that parts of this region may also play a role in processing reward outcomes. In this study, we investigated the possibility that a region of the MPFC would be preferentially recruited by monetary reward outcomes using a parametric monetary incentive delay (MID) task. Twelve healthy volunteers participated in functional magnetic resonance scans while playing the MID task. Group analyses indicated that while the ventral striatum was recruited by anticipation of monetary reward, a region of the MPFC instead responded to rewarding monetary outcomes. Specifically, volume-of-interest analyses indicated that when volunteers received $5.00 after anticipating a $5.00 win, MPFC activity increased, whereas when volunteers did not receive $5.00 after anticipating a $5.00 win, MPFC activity decreased, relative to outcomes with no incentive value. These findings suggest that in the context of processing monetary rewards, a region of the MPFC preferentially tracks rewarding outcomes.

  View details for DOI 10.1016/S1053-8119(02)00057-5

  View details for Web of Science ID 000181182500007

  View details for PubMedID 12595181

• A region of mesial prefrontal cortex tracks monetarily rewarding outcomes: characterization with rapid event-related fMRI NEUROIMAGE Knutson, B., Fong, G. W., Bennett, S. M., Adams, C. M., Homme, D. 2003; 18 (2): 263-272

  Abstract

  The function of the mesial prefrontal cortex (MPFC: including Brodman areas 10/12/32) remains an enigma. Current theories suggest a role in representing internal information, including emotional introspection, autonomic control, and a "default state" of semantic processing. Recent evidence also suggests that parts of this region may also play a role in processing reward outcomes. In this study, we investigated the possibility that a region of the MPFC would be preferentially recruited by monetary reward outcomes using a parametric monetary incentive delay (MID) task. Twelve healthy volunteers participated in functional magnetic resonance scans while playing the MID task. Group analyses indicated that while the ventral striatum was recruited by anticipation of monetary reward, a region of the MPFC instead responded to rewarding monetary outcomes. Specifically, volume-of-interest analyses indicated that when volunteers received $5.00 after anticipating a $5.00 win, MPFC activity increased, whereas when volunteers did not receive $5.00 after anticipating a $5.00 win, MPFC activity decreased, relative to outcomes with no incentive value. These findings suggest that in the context of processing monetary rewards, a region of the MPFC preferentially tracks rewarding outcomes.

  View details for DOI 10.1016/S1053-8119(02)00057-5

  View details for Web of Science ID 000181182500007

  View details for PubMedID 12595181

• Amygdalar recruitment during anticipation of monetary rewards - An event-related fMRI study Hommer, D. W., Knutson, B., Fong, G. W., Bennett, S., Adams, C. M., Varner, J. L. edited by ShinnickGallagher, P., Pitkanen, A., Shekhar, A., Cahill, L. NEW YORK ACAD SCIENCES. 2003: 476-478

  View details for Web of Science ID 000182918800037

  View details for PubMedID 12724180

• Dissociation of reward anticipation and outcome with event-related fMRI NEUROREPORT Knutson, B., Fong, G. W., Adams, C. M., Varner, J. L., Hommer, D. 2001; 12 (17): 3683-3687

  Abstract

  Reward processing involves both appetitive and consummatory phases. We sought to examine whether reward anticipation vs outcomes would recruit different regions of ventral forebrain circuitry using event-related fMRI. Nine healthy volunteers participated in a monetary incentive delays task in which they either responded to a cued target for monetary reward, responded to a cued target for no reward, or did not respond to a cued target during scanning. Multiple regression analyses indicated that while anticipation of reward vs non-reward activated foci in the ventral striatum, reward vs non-reward outcomes activated foci in the ventromedial frontal cortex. These findings suggest that reward anticipation and outcomes may differentially recruit distinct regions that lie along the trajectory of ascending dopamine projections.

  View details for DOI 10.1097/00001756-200112040-00016

  View details for Web of Science ID 000172397000012

  View details for PubMedID 11726774