Ratcliff R, Hasegawa YT, Hasegawa RP, Smith PL, Segraves MA. Dual diffusion model for single-cell recording data from the superior colliculus in a brightness-discrimination task. J Neurophysiol 97: 1756Neurophysiol 97: -1774Neurophysiol 97: , 2007. First published November 22, 2006; doi:10.1152/jn.00393.2006. Monkeys made saccades to one of two peripheral targets based on the brightness of a central stimulus. Task difficulty was manipulated by varying the ratio of stimulus black-and-white pixels. Correct response probability for two monkeys varied directly with difficulty. Deep layer SC neurons exhibited robust presaccadic activity the magnitude of which was unaffected by task difficulty when the stimulus specified a saccade toward a target within the neuron's response field. Activity after stimuli specifying saccades to targets outside the response field was affected by task difficulty, increasing as the task became more difficult. A quantitative model derived from studies of human decision-making was fit to the behavioral data. The model assumes that information from the stimulus drives two independent diffusion processes. Simulated paths from the model were compared with neuron activity, assuming that firing rate is linearly related to position in the accumulation process. The firing rate data show delayed availability of discriminative information for fast, intermediate, and slow decisions when activity is aligned on the stimulus and very small differences in discriminative information when aligned on the saccade. The model produces exactly these patterns of results. The accumulation process is highly variable, allowing the process both to make errors, as is the case for the behavioral performance, and also to account for the firing rate results. Thus the dual diffusion model provides a quantitative account for both the behavior in a simple decision-making task as well as the patterns of activity in competing populations of neurons. I N T R O D U C T I O NResearch in neural decision making is at the point of identifying the mechanisms that implement simple decisions (Glimcher and Sparks 1992;Gold and Shadlen 2000;Hanes and Schall 1996; Newsome 1999, 2001;Kim and Shadlen 1999;Krauzlis and Dill 2002;McPeek and Keller 2002;Ratcliff et al. 2003a;Roitman and Shadlen 2002;Romo et al. 2002;Sparks 1999). In parallel to this work, psychology has produced a set of models that describe simple rapid two-choice decision making Townsend 1992, 1993;Diederich 1997;LaBerge 1994;Laming 1968;Link 1975;Link and Heath 1975; Pike 1966Pike , 1973Ratcliff 1978Ratcliff , 1981Ratcliff , 1988 Rouder 1998, 2000;Ratcliff and Smith 2004;Ratcliff et al. 1999;Roe et al. 2001;Smith 1995;Smith and Ratcliff 2004;Smith and Van Zandt 2000;Stone 1960;Townsend and Ashby 1983). We present a diffusion model that explicitly relates these two domains in the context of a single experiment. The model is applied to simple twochoice decisions and accounts for both behavioral data, namely, accuracy and correct and error response time (RT) distributi...

Simultaneous recordings were collected from between two and four buildup neurons from the left and right superior colliculi in rhesus monkeys in a simple two-choice brightness discrimination task. The monkeys were required to move their eyes to one of two response targets to indicate their decision. Neurons were identified whose receptive fields were centered on the response targets. The functional role of inhibition was examined by conditionalizing firing rate on a high versus low rate in target neurons 90 ms to 30 ms before the saccade and examining the firing rate in both contralateral and ipsilateral neurons. Two models with racing diffusion processes were fit to the behavioral data, and the same analysis was performed on simulated paths in the diffusion processes that have been found to represent firing rate. The results produce converging evidence for the lack of a functional role for inhibition between neural populations corresponding to the two decisions.

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Aim: Alcoholism is the most prevalent substance use disorder in Japan; the estimated number of patients and high-risk drinkers is in the millions. Although studies in the West have shown that cognitive behavioral therapy (CBT) is one of the most effective treatment strategies for alcoholic patients, there is a dearth of efficacy studies of CBT-based intervention for those patients in the non-Western setting. The aim of this study is to investigate the efficacy of a 12-session CBT-based relapse prevention program for Japanese alcoholic patients.Methods: Forty-eight alcoholic patients (M = 36, F = 12) who were admitted to an addiction treatment unit were randomly allocated either to a 12-session relapse prevention (RP) program (n = 24) or a 12-session psychoeducation (PE) program (n = 24). Both treatment programs were conducted in a group format once a week for 12 weeks.Other aspects of inpatient treatment (group meetings, etc) were the same in both groups. Self-rating scales, which measure behavioral and cognitive coping, coping response, self-efficacy, and cognition of drinking, were administered at pretreatment, mid-treatment, and posttreatment periods. The proportion of participants who relapsed at 3 and 6 months after discharge was evaluated.Results: Both RP and PE groups showed significant improvement in self-efficacy and cognition of drinking at posttreatment. However, there were no significant differences in the self-rating scales between both groups. In addition, there were no significant differences in relapse rate at 3 and 6 months after discharge between both groups. Conclusions:The 12-session CBT-based relapse prevention program and the psychoeducation program may be equally efficacious for alcoholic patients. Several factors that influenced the results are discussed.

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