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What are the genetic and neural components that support adaptive learning from positive and negative outcomes? Here, we show with genetic analyses that three independent dopaminergic mechanisms contribute to reward and avoidance learning in humans. A polymorphism in the DARPP-32 gene, associated with striatal dopamine function, predicted relatively better probabilistic reward learning. Conversely, the C957T polymorphism of the DRD2 gene, associated with striatal D2 receptor function, predicted the degree to which participants learned to avoid choices that had been probabilistically associated with negative outcomes. The Val/Met polymorphism of the COMT gene, associated with prefrontal cortical dopamine function, predicted participants' ability to rapidly adapt behavior on a trial-to-trial basis. These findings support a neurocomputational dissociation between striatal and prefrontal dopaminergic mechanisms in reinforcement learning. Computational maximum likelihood analyses reveal independent gene effects on three reinforcement learning parameters that can explain the observed dissociations.basal ganglia ͉ prefrontal cortex ͉ computational model

It is widely hypothesized that separate recollection and familiarity processes contribute to recognition memory, The present research measured event-related brain potentials (ERPs) from 128 head locations to identify patterns of brain activity related to recollection and familiarity, In two experiments, subjects performed a recognition memory task requiring discrimination between previously studied words, similar words that changed plurality between study and test, and new words (following Hintzman & Curran, 1994), The FN400 ERP component (300-500 msec) varied with the familiarity of words (new> studied = similar), The parietal component (400-800 msec) was associated with the recollection of plurality (studied> similar = new). Differences in the timing and spatial topography of the FN400 and parietal effects support the view that familiarity and recollection arise from distinct neurocognitive processes.Dual-process theories of memory posit that recognitionjudgments can be based on two different types of information: familiarity and recollection (Brainerd, Reyna, & Kneer, 1995;Hintzman & Curran, 1994;Jacoby, 1991;Mandler, 1980;Yonelinas, 1994). Familiarity is generally thought to reflect an assessment of the global similarity between studied and tested items (e.g., Clark & Gronlund, 1996;Gillund & Shiffrin, 1984; Hintzrnan, 1988;Humphreys, Bain, & Pike, 1989;Murdock, 1982). Recollection entails the retrieval of specific information about studied items, such as physical attributes (Chalfonte & Johnson, 1996;Hintzman & Caulton, 1997;Hintzman & Curran, 1994), associative/contextual information (Clark, 1992;Clark, Hori, & Callan, 1993;Gronlund & Ratcliff, 1989;Humphreys, 1978;Mandler, 1980;Yonelinas, 1997), or other source-specifying information (Hintzman, Caulton, & Levitin, 1998;Jacoby, 1991;M. K. Johnson, Hashtroudi, & Lindsay, 1993).Recognition memory research has addressed two major questions regarding dual-process theories. First, does recognition memory truly depend on more than one process? In some cases, single-process theories can' account for results that are commonly interpreted as requiring two processes (w. Donaldson, 1996;Hirshman & Master, 1997;McClelland & Chappell, 1998;Ratcliff, Van Zandt, & McKoon, 1995;Shiffrin & Steyvers, 1997 each process? Separating the distinct contributions ofrecollection and familiarity to recognition performance is difficult. Jacoby (1991) developed the process dissociation procedure for this purpose. Others have attempted to differentiate separate phenomenological states by asking subjects to introspectively differentiate "remembering" from "knowing" (reviewed by Gardiner & Java, 1993;Rajaram & Roediger, 1997). Others have used responsesignal, speed-accuracy tradeoff (SAT) procedures to separate fast familiarity from slower recollection processes (e.g., Hintzman & Caulton, 1997;Hintzman et al., 1998;Hintzman & Curran, 1994;McElree, Dolan, & Jacoby, 1999). The utility of these approaches has been debated elsewhere: process dissociation Graf, 1995;Graf & Komatsu, 1994;Jacob...

This research investigated the hypothesis that sequential patterns of behavior can be learned by 2 independent mechanisms. One requires attention to the relation between successive events, whereas the other operates independently of such attention. In 4 experiments, subjects learned visuospatial sequences in a serial reaction time task. The relation between attentional and nonattentional learning was explored by assessing the extent to which learning transferred between conditions with or without distraction. The results suggest that attentional and nonattentional learning operate independently, in parallel, do not share information, and represent sequential information in qualitatively different ways.A fundamental type of learning in which humans excel is the learning of sequential patterns of behavior. In four experiments, we investigated the hypothesis that humans exhibit two forms of sequential learning. One form of learning requires attention to the relation between successive events in the sequence, not only for acquisition but also for the expression of the learning in performance. We hypothesized that the other type of sequential learning did not require attention to these relations. Furthermore, these two forms of learning are independent of one another, with no communication or sharing of information between them. If subjects perform a series of behavioral acts that occur in a predictable order and under conditions relatively free of distraction, we suppose that attentionally based and nonattentionally based learning of the sequence occur in parallel. If distraction is added during learning, the attentional form is disabled, but the nonattentional one is unmodified.

Whether memories can be suppressed has been a controversial issue in psychology and cognitive neuroscience for decades. We found evidence that emotional memories are suppressed via two time-differentiated neural mechanisms: (i) an initial suppression by the right inferior frontal gyrus over regions supporting sensory components of the memory representation (visual cortex, thalamus), followed by (ii) right medial frontal gyrus control over regions supporting multimodal and emotional components of the memory representation (hippocampus, amygdala), both of which are influenced by fronto-polar regions. These results indicate that memory suppression does occur and, at least in nonpsychiatric populations, is under the control of prefrontal regions.