Submitted on May 9, 2007
Accepted on September 6, 2007
Difficulty of Visual Search Modulates Neuronal Interactions and Response Variability in the Frontal Eye Field
Jeremiah Y. Cohen1, Pierre Pouget2, Geoffrey F. Woodman3, Chenchal R. Subraveti4, Jeffrey D Schall5, and Andrew F Rossi6*
1 Vanderbilt Brain Institute, Vanderbilt University, Nashville, Tennessee, United States
2 Department of Psychology, Vanderbilt University, Nashville, Tennessee, United States; Center for Integrative and Cognitive Neuroscience, Vanderbilt University, Nashville, Tennessee, United States; Vanderbilt Vision Research Center, Vanderbilt University, Nashville, Tennessee, United States
3 Department of Psychology, Vanderbilt University, Nashville, Tennessee, United States; Vanderbilt Univ., United States; Center for Integrative and Cognitive Neuroscience, Vanderbilt University, Nashville, Tennessee, United States; Vanderbilt Vision Research Center, Vanderbilt University, Nashville, Tennessee, United States
4 Department of Psychology, Vanderbilt University, Nashville, Tennessee, United States; Vanderbilt University, Nashville, Tennessee, United States
5 Department of Psychology, Vanderbilt University, Nashville, Tennessee, United States; Vanderbilt Brain Institute, Vanderbilt University, Nashville, Tennessee, United States; Psychology, Vanderbilt University, Nashville, Tennessee, United States; Center for Integrative and Cognitive Neuroscience, Vanderbilt University, Nashville, Tennessee, United States; Vanderbilt Vision Research Center, Vanderbilt University, Nashville, Tennessee, United States
6 Department of Psychology, Vanderbilt University, Nashville, Tennessee, United States; Vanderbilt Brain Institute, Vanderbilt University, Nashville, Tennessee, United States; Center for Integrative and Cognitive Neuroscience, Vanderbilt University, Nashville, Tennessee, United States; Vanderbilt Vision Research Center, Vanderbilt University, Nashville, Tennessee, United States
* To whom correspondence should be addressed. E-mail: andrew.rossi{at}vanderbilt.edu.
The frontal eye field (FEF) is involved in selecting visual targets for eye movements. To understand how populations of FEF neurons interact during target selection, we recorded activity from multiple neurons simultaneously while macaques performed two versions of a visual search task. We used a multivariate analysis in a point process statistical framework to estimate the instantaneous firing rate and compare interactions among neurons between tasks. We found that FEF neurons were engaged in more interactions during easier visual search tasks as compared to harder search tasks. In particular, eye-movement-related neurons were involved in more interactions than visual-related neurons. In addition, our analysis revealed a decrease in the variability of spiking activity in the FEF beginning about 100 ms prior to saccade onset. The minimum in response variability occurred about 20 ms earlier for the easier search task compared to the harder one. This difference is positively correlated with the difference in saccade reaction times for the two tasks. These findings demonstrate that a multivariate analysis can provide a measure of neuronal interactions and characterize the spiking activity of FEF neurons in the context of a population of neurons.
