[Probcogsci] Fwd: [Neuro-faculty-L] Special Seminar: Anne Churchland, June 12th

[Angela Yu]

Begin forwarded message:

> From: Anirvan Ghosh <aghosh at ucsd.edu>
> Date: June 5, 2009 2:30:22 PM PDT
> To: Neuro GradStudents <neuro-students-l at ucsd.edu>, Neuro Faculty <neuro-faculty-l at ucsd.edu 
> >
> Cc: Libby Weber <e1weber at ucsd.edu>
> Subject: [Neuro-faculty-L]  Special Seminar: Anne Churchland, June  
> 12th
>
> Special Seminar
>
> Anne Churchland, University of Washington
> Mechanisms for understanding decisions of increasing complexity
>
> Friday, June 12th, 12:00 pm
> NSB auditorium
>
> Hosts: David Kleinfeld and Anirvan Ghosh
>
> _____
> Abstract
>
>             Simple perceptual tasks have provided a preliminary  
> foundation for understanding the neurobiology of decision-making. In  
> these experiments, human or monkey subjects report the direction of  
> a random dot motion stimulus with a saccade. Physiology experiments  
> have suggested that the accumulation of sensory evidence is  
> reflected in firing rates in the lateral intraparietal area (LIP).  
> The decision process ends when the accumulated evidence reaches a  
> threshold level or bound: the option corresponding to that bound is  
> taken as the choice. This class of mechanisms has helped connect the  
> physiology with the monkeys’ speed and accuracy for very simple  
> decisions. However, it is not known whether the same mechanisms will  
> be relevant for understanding more complex decisions.
>
>             As a first step towards extending our understanding of  
> decision-making, we examined behavior, physiology and the effects of  
> microstimulation on a 2- and 4-choice decision task. We observed  
> differences in monkeys’ speed and accuracy on the 2- and 4-choice  
> tasks and considered two hypotheses about the neural mechanism  
> underlying the differences.  First, we asked whether behavioral  
> differences were due to changes in the conversion of sensory inputs  
> from the middle temporal area (MT) into evidence in LIP. We found  
> that changes in motion strength had the same effect on the build up  
> of firing rate in LIP for the 2- and 4-choice tasks.  Further,  
> microstimulation in MT biased the monkeys’ choices similarly on the  
> 2- and 4-choice tasks. Taken together, these observations suggest  
> that the conversion of sensory inputs into evidence was similar on  
> the 2- and 4-choice tasks.  Next, we asked whether behavioral  
> differences were due to changes in the monkeys’ threshold for making  
> a choice.  Interestingly, the rules for terminating decisions  
> appeared to be rather different on the 2 and 4-choice tasks.  
> Specifically, evidence accumulation began at a lower firing rate for  
> the 4-choice task, but reached a common level at the end of the  
> decision process. The larger firing rate excursion suggests that  
> decision-making mechanisms required more evidence before committing  
> to a choice. Importantly, these changes appear to explain  
> differences in speed and accuracy on the two tasks. The  
> physiological adjustments constitute an effective strategy for  
> handling increased difficulty on the 4-choice task.
>
>   
> _________________________________________________________________________________________________________________
>
> Anirvan Ghosh
> Chair, Neurobiology Section, MC0366
> Director, Neurosciences Graduate Program
> University of California San Diego
> La Jolla, CA 92093-0366
>
> 858-822-4142 (ph)
> 858-822-4144 (FAX)
> http://www.ghoshlab.org
>
>
>

---------------------------------------------------------
Angela J. Yu
Assistant Professor
Department of Cognitive Science
UCSD, Mail Code 0515
9500 Gilman Drive
La Jolla, CA 92093-0515

Email: ajyu at cogsci.ucsd.edu
Phone: 858-822-3317
Fax: 858-534-1128
Website: www.cogsci.ucsd.edu/~ajyu
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