Someone that has ever ignored the gorilla in the classic video in which basketball players are passing balls knows how visual attention plays a key role in our perception of the world.
Also using humans and monkeys, but in a slightly different way, Sabine Kastner, a professor at Princeton University, is interested in investigating how attentional selection is generated by the neural networks within our brains.
Dr. Kastner is a great example of someone who successfully switched between academic fields. She started to become interested in neuroscience during her undergraduate years as a philosophy student. The great questions related to brain-mind issues, particularly the basis of consciousness and self-awareness drove her to the amazing world of neurons. Then, she did her doctorate in Neurobiology at Max Planck Institute, and went to medical school, also in Germany, becoming gradually more interested in the neural mechanism of attention.
Recently, one of the main focuses of Dr. Kastner’s lab has been to investigate how the cortical networks interact with each other in order to process behaviorally relevant sensory information, under attentional selection. Applying electrophysiology and neural imaging techniques in monkeys subjected to a visual flanker task (see schematic figure below), Dr. Kastner’s lab was able to demonstrate that brain regions outside cortex are also involved in attention mechanisms (Saalmann et al. 2012).
In this work, Dr. Kastner’s research group showed that the pulvinar, a region of the thalamus, which is classically considered a passively relaying of sensory information to the cortex (Saalmann and Kastner 2011), also plays a crucial role in high cognitive functions, specifically coordinating the neural activity associated with attention.Flanker test in Salmaan et al. 2012. The monkey’s attention was drawn to the location of a variable cue, which signaled the location of the target in the subsequent array of six stimuli. To receive a juice reward, while maintaining fixation at the center spot, monkeys had to immediately release the lever after the onset of a barrel-shaped target or after the disappearance of the stimulus array for a bowtie-shaped target.
Models about selective attention predict that behaviorally relevant information is routed through cortical networks and that it depends on the degree of synchrony between these cortical areas. Based on previous findings and due to the pattern of connections of the thalamic pulvinar, which receives the majority of inputs from cortex, rather than sensory areas, and sends output back to cortex, creating cortico-pulvino-cortical loops, Dr. Kastner’s and colleagues hypothesized that this thalamic region would be a good candidate region to control the degree of synchrony between cortical areas.
Recording the activity from pulvinar neurons while the monkeys were performing the flanker task described above, Dr. Kastner’s research group showed that pulvinar neural activity was modulated by attention, comparing the neural activity when monkeys were attending to regions within the receptive fields of the recorded cells versus situations in which the attended spot is outside of the receptive field. This modulation was present during the period in which the monkey maintained spatial attention, from the cue-evoked response until after the array onset.
Then, Dr. Kastner’s research group performed simultaneous electrical recordings from pulvinar and two other high-order visual processing cortical areas, T4 and TEO. They showed that all areas presented higher levels of coherent activity when modulated by attention, especially in the 8 to 15 Hz range (alpha band). Moreover, they applied a statistical test called Granger causality in order to evaluate the influence that one area (e.g., the pulvinar) has on a second area (e.g., TEO), accounting for the influence of other areas (e.g., T4). In this way, they were able to show that the pulvinar causally influenced cortical synchrony even in the absence of visual stimulation (between the cue disappearance and the target onset).
Aiming to understand how the neural networks communicate with each other within the brain in order to modulate behavior and our perception of the world, Dr. Kastner hopes to shed light in the great questions about consciousness and self-awareness that originally attracted her attention to the field of neuroscience.
I am sure this awesome work caught your attention. So, please join us this Tuesday March 11, 2014 at 4:00PM at CNCB Large Conference Room to hear more about it from Dr. Sabine Kastner in her talk entitled “Neural network dynamics for attentional selection in the primate brain”.
Leonardo M. Cardozo is a first year student in the UCSD Neurosciences Graduate Program. He is currently rotating at Dr. Nicholas Spitzer’s lab, investigating the mechanism behind the match of neurotransmitters and neurotransmitter receptors during the process of neurotransmitter respecification.
Saalmann Y. & Kastner S. (2011). Cognitive and Perceptual Functions of the Visual Thalamus, Neuron, 71 (2) 209-223. DOI: 10.1016/j.neuron.2011.06.027
Saalmann Y.B., Pinsk M.A., Wang L., Li X. & Kastner S. (2012). The Pulvinar Regulates Information Transmission Between Cortical Areas Based on Attention Demands, Science, 337 (6095) 753-756. DOI: 10.1126/science.1223082