Abstract
Attention can be oriented in space covertly without the need of eye movements. We used multivariate pattern classification analyses (MVPA) to investigate whether the time course of the deployment of covert spatial attention leading up to the observer’s perceptual decision can be decoded from both EEG alpha power and raw activity traces. Decoding attention from these signals can help determine whether raw EEG signals and alpha power reflect the same or distinct features of attentional selection. Using a classical cueing task, we showed that the orientation of covert spatial attention can be decoded by both signals. However, raw activity and alpha power may reflect different features of spatial attention, with alpha power more associated with the orientation of covert attention in space and raw activity with the influence of attention on perceptual processes.
Highlights
The visual world conveys more information than observers can process (James, 1890; Moran and Desimone, 1985) and attention is the mechanism that allow us to select and prioritize visual information based on our goals (Carrasco, 2011)
The same test on RTs showed faster responses in the attention (M = 1.822 s; SD = 0.272 s) compared to the neutral condition (M = 1.983 s; SD = 0.254 s), p < 0.001. These reaction times corresponded to an average percentage of 51% of dots moving coherently in the attention condition and 56% in the neutral condition. This confirms that the cueing procedure we adopted successfully manipulated spatial attention: participants required less time in the attention condition to achieve the same level of performance as in the neutral condition
We decoded the temporal dynamics of covert spatial attention from both raw activity and alpha oscillations
Summary
The visual world conveys more information than observers can process (James, 1890; Moran and Desimone, 1985) and attention is the mechanism that allow us to select and prioritize visual information based on our goals (Carrasco, 2011). Attention is focused on our central vision and moves in tandem with our eye-movements. It can be oriented in space covertly without moving our eyes (Posner, 1980); we can “look out of the corner of our eye” as popular wisdom would say. Covert spatial attention has been extensively studied and one of the most popular methods used to manipulate it consists of cueing the Decoding Spatial Attention in Time location where a target stimulus will appear. Further studies have shown that covert attention does enhance processing time and increase contrast sensitivity (Ling and Carrasco, 2006)
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