Abstract
The goal of this study is to understand the relationship between feature binding and selective attention at the neural signal level. We recorded neurons with two microelectrodes inserted in macaque areas V1 or V2. The animal performed a delayed shape discrimination task that involved simultaneous processing of two edges of a trapezoid. The animal was cued to perform the task with one or the other of three simultaneously displayed figures. We studied the spike time correlations between neurons, comparing the conditions when two neurons respond to edges of the same figure (binding) versus edges of different figures, and when a figure is attended versus ignored. We analyzed the spike time cross correlation function and its power spectrum. In the ignore condition, we found a peak of correlation in the beta frequency range (~18Hz) when the neurons responded to the same figure (binding). When the neurons responded to different figures, this peak was absent. Attending to the common figure caused a two-fold increase of the peak, but did not affect correlation in the different-figures condition. Binding produced zero time lag spike synchrony across the population of pairs. Under attention, the synchrony was reduced after stimulus onset, but increased towards the end of the delay period. The emergence of correlation with binding and its increase with attention parallel our previous observations on the local field potentials (Martin and von der Heydt, Society for Neuroscience Abstracts 2010). Spike synchrony between widely separated neurons in cortex (3-10mm) indicates a common input. Thus, the emergence of synchrony with binding is consistent with feedback from grouping cells as postulated in Craft et al., J Neurophysiol (2007). The predominance of beta suggests feedback from parietal cortex. Our results show distinct mechanisms for binding and attention which interact because binding provides the structure for object-based attention.
Meeting abstract presented at VSS 2012