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Projects we are actively working on at the moment.

Dissociating attentional allocation from evidence accumulation 

The lateral intraparietal area (LIP) contains spatially selective neurons that help guide attention and eye movements.  In addition, numerous studies have suggested that the same neurons accumulate sensory evidence in favor of one choice (e.g., look left) or another (look right).  These two functions, however, are not identical.  In order to dissociate them, and better understand the role of LIP, we designed a task that puts them in conflict, and trained two monkeys to perform it.  Using such task (an urgent version of the random-dot motion discrimination task), we found that while choice accuracy increased steeply with time, and thus with increasing sensory evidence, at the same time, the LIP selection signal became progressively weaker, as if it hindered performance.  The results were consistent with LIP activity regulating the spatial allocation of attention, and suggest that the ramping activity traditionally interpreted as evidence accumulation may correspond, instead, to a slow, post-decision shift of spatial attention from a central location (where the relevant stimulus is) to a peripheral one (where the saccade target is).  

We are currently extending this research to another prominent oculomotor area, the frontal eye field (FEF). We are also exploring the consequences of these findings to visuomotor behavior using human psychophysics.

The graph shows two curves as functions of processing time, which is the cue viewing time in each trial of the task. The black trace shows the combined performance of the two monkey subjects (percent correct), whereas the brown curve shows the differential activity in area LIP (SROC), which measures how strongly LIP neurons point to the location of the chosen saccade target. In this task, the performance of the monkeys increases with increasing sensory evidence while the spatial signal in LIP becomes weaker.

See a short slide show describing the main findings.

Or take a look at the full article.