Thu, 21 Aug 2008 15:54:27 BST CiteULike: Group: Glimcher_Lab - Aron http://www.citeulike.org/group/70/author/Aron CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/group/70/article/1355835 <i>Hum Brain Mapp, Vol. 27, No. 4. (April 2006), pp. 306-313.</i><br /><br />A prominent theory in neuroscience suggests reward learning is driven by the discrepancy between a subject's expectation of an outcome and the actual outcome itself. Furthermore, it is postulated that midbrain dopamine neurons relay this mismatch to target regions including the ventral striatum. Using functional MRI (fMRI), we tested striatal responses to prediction errors for probabilistic classification learning with purely cognitive feedback. We used a version of the Rescorla-Wagner model to generate prediction errors for each subject and then entered these in a parametric analysis of fMRI activity. Activation in ventral striatum/nucleus-accumbens (Nacc) increased parametrically with prediction error for negative feedback. This result extends recent neuroimaging findings in reward learning by showing that learning with cognitive feedback also depends on the same circuitry and dopaminergic signaling mechanisms. Ventral-striatal/nucleus-accumbens sensitivity to prediction errors during classification learning. PF Rodriguez AR Aron RA Poldrack doi:10.1002/hbm.20186 Hum Brain Mapp, Vol. 27, No. 4. (April 2006), pp. 306-313. 2007-06-01T15:45:39-00:00 2006 Hum Brain Mapp 1065-9471 27 4 306 313 instrumental_conditioning nucleus_accumbens reinforcement_learning reward_prediction_error ventral_striatum http://www.citeulike.org/group/70/article/1355797 <i>J Neurosci, Vol. 27, No. 14. (4 April 2007), pp. 3743-3752.</i><br /><br />The ability to stop motor responses depends critically on the right inferior frontal cortex (IFC) and also engages a midbrain region consistent with the subthalamic nucleus (STN). Here we used diffusion-weighted imaging (DWI) tractography to show that the IFC and the STN region are connected via a white matter tract, which could underlie a "hyperdirect" pathway for basal ganglia control. Using a novel method of "triangulation" analysis of tractography data, we also found that both the IFC and the STN region are connected with the presupplementary motor area (preSMA). We hypothesized that the preSMA could play a conflict detection/resolution role within a network between the preSMA, the IFC, and the STN region. A second experiment tested this idea with functional magnetic resonance imaging (fMRI) using a conditional stop-signal paradigm, enabling examination of behavioral and neural signatures of conflict-induced slowing. The preSMA, IFC, and STN region were significantly activated the greater the conflict-induced slowing. Activation corresponded strongly with spatial foci predicted by the DWI tract analysis, as well as with foci activated by complete response inhibition. The results illustrate how tractography can reveal connections that are verifiable with fMRI. The results also demonstrate a three-way functional-anatomical network in the right hemisphere that could either brake or completely stop responses. Triangulating a cognitive control network using diffusion-weighted magnetic resonance imaging (MRI) and functional MRI. AR Aron TE Behrens S Smith MJ Frank RA Poldrack doi:10.1523/JNEUROSCI.0519-07.2007 J Neurosci, Vol. 27, No. 14. (4 April 2007), pp. 3743-3752. 2007-06-01T15:36:11-00:00 2007 J Neurosci 1529-2401 27 14 3743 3752 cognitive_control_network diffusion-weighted_imaging fmri