Abstract
Persistent activity has been observed in the prefrontal cortex (PFC), in particular during the delay periods of visual attention tasks. Classical approaches based on the average activity over multiple trials have revealed that such an activity encodes the information about the attentional instruction provided in such tasks. However, single-trial approaches have shown that activity in this area is rather sparse than persistent and highly heterogeneous not only within the trials but also between the different trials. Thus, this observation raised the question of how persistent the actually persistent attention-related prefrontal activity is and how it contributes to spatial attention. In this paper, we review recent evidence of precisely deconstructing the persistence of the neural activity in the PFC in the context of attention orienting. The inclusion of machine-learning methods for decoding the information reveals that attention orienting is a highly dynamic process, possessing intrinsic oscillatory dynamics working at multiple timescales spanning from milliseconds to minutes. Dimensionality reduction methods further show that this persistent activity dynamically incorporates multiple sources of information. This novel framework reflects a high complexity in the neural representation of the attention-related information in the PFC, and how its computational organization predicts behavior.
Highlights
Numerous studies report an increase of spiking activity in different brain areas during the performance of visual delayed tasks [see Fuster and Alexander (1971), Goldman-Rakic (1995), Shafi et al (2007), Barak et al (2010), Watanabe and Funahashi (2014), Chaudhuri and Fiete (2016), Zylberberg and Strowbridge (2017), Manohar et al (2019), for a review]
Persistent activity has been described in other regions, including the regions where it is more prevalent compared to the FEF and LIP (Leavitt et al, 2017), we focus on neuronal activity in these two regions in the context of persistent activity during attention orienting
We have shown clear evidence that, at a singletrial level, the spiking activity of individual neurons is sparse and very heterogeneous across successive trials. We show that this applies to spatial attention, and that spatial attention is not attached to a specific cued location in space, but rather expresses intrinsic oscillatory dynamics covering the whole visual space in a rhythmic manner at approximately 8 Hz, impacting behavioral performance (Lakatos et al, 2008; Dugue and VanRullen, 2014; VanRullen, 2016; Fiebelkorn et al, 2018; Spyropoulos et al, 2018; Gaillard et al, 2020)
Summary
Numerous studies report an increase of spiking activity in different brain areas during the performance of visual delayed tasks [see Fuster and Alexander (1971), Goldman-Rakic (1995), Shafi et al (2007), Barak et al (2010), Watanabe and Funahashi (2014), Chaudhuri and Fiete (2016), Zylberberg and Strowbridge (2017), Manohar et al (2019), for a review]. The fact that FEF neurons explicitly encode the cue instruction suggests functional differences of how both the FEF and LIP represent a spatial orientation signal in the population level and sustain these representations in time.
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