Neurobiology of decision making

Decision making is ubiquitous in our everyday life, and plays a central role in transforming a vast and complex array of incoming sensory stimuli to a meaningful sequence of purposeful actions. Many of these decisions have important biological consequences, whereas others may appear to have more limited impact. Despite their distinct subjective qualities, both external and internal cues can be used to guide the selection of a single choice from many possible alternatives. Often, such decisions display features of optimally tuned systems. The neural mechanisms that underpin such decision making are currently the subject of intense investigation in the cognitive and behavioral neurosciences. Papers published in this special issue reflect several trends that have contributed to the recent surge of interest in the neural basis of decision making. First, neuroscientists have begun to realize the benefits of decision-making models developed by mathematical psychologists in order to understand the neural basis of discrimination and categorization (Mazurek, Roitman, Ditterich, & Shadlen, 2003). Often referred to as rise-to-threshold models or diffusion models, they make a simplifying assumption that an action is triggered when the process of evidence accumulation reaches a certain threshold. Second, the importance of reward and reward expectations as determinants of both decision making and neural activity is increasingly appreciated. In particular, reinforcement learning and economic theories have provided valuable insights into the function of many brain structures (Lee, 2006; Schultz, 2006). Third, network models of decision making have begun to reflect a detailed knowledge of the biophysical mechanisms involved in synaptic transmission and the generation of action potentials (Wang, 2002). These models have the potential to explain how complex behavior, such as decision making, can arise from the dynamics of cortical and subcortical networks. Fourth, advances in neuroimaging techniques have further facilitated neurobiological studies of decision making by making it possible to investigate the neural basis of complex decision making in humans (Montague, King-Casas, & Cohen, 2006). Accordingly, the neurobiological study of decision making has become an exciting area of interdisciplinary investigation and collaboration, as demonstrated by many of the papers included here. Sensory discrimination tasks employing visual motion and tactile stimuli have provided a wealth of information about the nature of neural circuitry necessary to perform such