The pulvinar nucleus of the primate thalamus has been associated with selective visual attention. Especially, Saalmann et al. have shown that extensive cortico-pulvino-cortical loops modulate selective attention . However, the mechanism underlying these loops in modulating attention is still unknown.
By recording simultaneously from the pulvinar, V4, and IT regions of monkeys during a spatial attention task, Zhou et al. directly investigated how the pulvinar influences V4 and IT cortex . Their findings can be summarized into three main points:
- Attention significantly enhances spike-LFP synchrony within and across areas (pulvinar, V4, and IT).
The group investigated the spike-LFP coherence (as a measure of synchrony) within and across areas. Within V4, the group observed a significance increase in gamma spike-field coherence during “Attention In” trials (the visual stimulus in the receptive field of the recorded neurons was the target attended by the monkeys). This is nicely shown in Figure 3 (top left corner). In addition, gamma synchrony between the pulvinar and the V4 was significantly enhanced by attention (Figure 3 top right corner and bottom left corner). The IT cortex and V4 also demonstrated elevated gamma coherence during attention.
Figure 3 from .
- V4 influences the pulvinar and IT at gamma frequencies.
Because attention was found to enhance gamma synchrony within and across the three areas (above), Zhou et al. employed a Granger causality method to define the direction of influences in these areas. As shown in Figure 4 below, V4 was found to be influencing unidirectionally the pulvinar and IT during attention at gamma frequency ranges. This is shown in Figure 4A and 4C.
Figure 4 from .
- Deactivation of the pulvinar results in poor task performance and reduced visual responsiveness in V4.
To further probe the relationship between the pulvinar and V4, Zhou et al. deactivated (reversibly) the pulvinar with muscimol (GAGA-A agonist). This deactivation resulted in a significant decrease in the monkeys’ performance (shown in Figure 6A). The deactivation was also associated with lower mean firing rates in area V4 (Figure 6B and 6C).
Figure 6 from .
These three findings suggest that the pulvinar input to the cortex plays an important role in maintaining “the cortex in an active state” .
- Saalmann, Y. B., M. A. Pinsk, L. Wang, X. Li, and S. Kastner. “The Pulvinar Regulates Information Transmission Between Cortical Areas Based on Attention Demands.” Science6095 (2012): 753-56. Web.
- Zhou, Huihui, Robert John Schafer, and Robert Desimone. “Pulvinar-Cortex Interactions in Vision and Attention.”Neuron 1 (2016): 209-20. Web.
Robert Kim is a first-year graduate student in the neurosciences graduate program and a member of Dr. Terrence Sejnowski’s lab.