The brain is limited in its capacity to process all sensory stimuli present in the physical world at any point in time and relies instead on the cognitive process of attention to focus neural resources according to the contingencies of the moment. Attention can be categorized into two distinct functions: bottom-up attention, referring to attentional guidance purely by externally driven factors to stimuli that are salient because of their inherent properties relative to the background; and top-down attention, referring to internal guidance of attention based on prior knowledge, willful plans, and current goals. Over the past few years, insights on the neural circuits and mechanisms of bottom-up and top-down attention have been gained through neurophysiological experiments. Attention affects the mean neuronal firing rate as well as its variability and correlation across neurons. Although distinct processes mediate the guidance of attention based on bottom-up and top-down factors, a common neural apparatus, the frontoparietal network, is essential in both types of attentional processes.

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(02/02/2024, 12:10:20 ) *

Distinction top-down and bottom up

“Attention can be categorized into two distinct functions: bottom-up attention, referring to attentional guidance purely by externally driven factors to stimuli that are salient because of their inherent properties relative to the background; and top-down attention, referring to internal guidance of attention based on prior knowledge, willful plans, and current goals” (Katsuki and Constantinidis, 2014, p. 1)

“attention is allocated to the most salient stimulus, location, or feature”

“is that attention is allocated to the most salient stimulus, location, or feature that evokes the stronger neural activation than others in the visual field (Desimone and Duncan 1995; Koch and Ullman 1985; Wolfe 1994)” (Katsuki and Constantinidis, 2014, p. 2)

Relevance to goals impacts saliency

“The ability of stimuli to attract attention is determined not only by their inherent saliency but also by their relevance to current goals, an idea captured by early models of visual search (Wolfe, Jeremy 1994)” (Katsuki and Constantinidis, 2014, p. 2)

“priority map” (Katsuki and Constantinidis, 2014, p. 2)

Competition towards salient stimuli

“Stimuli that stand out from their background are selectively represented by neuronal activity throughout the visual system. Neurons are activated to a greater extent when salient stimuli appear in their receptive fields compared to activation elicited by background elements alone, and this phenomenon occurs from the earliest stages of visual cortical processing, including V1 (Knierim and van Essen 1992). This differential processing of salient stimuli suggests a competitive process in the selection of stimuli (Bichot and others 2005; Desimone and Duncan 1995)” (Katsuki and Constantinidis, 2014, p. 2)

[[Saliency Maps]]

“A related concept regarding the allocation of attention is that of a saliency map in which all types of feature information (e.g., shape, color, and orientation) in the visual field are pooled together (Koch and Ullman 1985; Niebur and Koch 1996), and attention is allocated to the location with the highest activity in this global map.” (Katsuki and Constantinidis, 2014, p. 3)

“Studies have suggested multiple brain areas that could serve as maps of saliency, including the frontal eye field (FEF) and area 46 of the PFC (Katsuki and Constantinidis 2012a; Schall and Hanes 1993; Thompson and others 1996), area 7a and the lateral intraparietal area (LIP) in the PPC (Constantinidis and Steinmetz 2001; Gottlieb and others 1998), the superior colliculus (McPeek and Keller 2002), and the substantia nigra (Basso and Wurtz 2002).” (Katsuki and Constantinidis, 2014, p. 3)

“Top-down visual attention is a voluntary process in which a particular location, feature, or object relevant to current behavioral goals is selected internally and focused upon or examined

(Connor and others 2004; Corbetta and Shulman 2002; Itti and Koch 2001). The main effect of top-down attention is that neural activity is enhanced for the particular location/feature/object of interest compared to behaviorally irrelevant stimuli (Fig. 5A)” (Katsuki and Constantinidis, 2014, p. 7)

Top-down and Bottom-up as distinction is criticized (CLA attention)

“In recent years, this interplay between top-down and bottom-up attention has come to the forefront, as it has become apparent that the same set of brain areas, particularly in the PPC and PFC, is engaged in both top-down and bottom-up attention. These areas can be thought as providing a priority map for the selection of stimuli based on both bottom-up and top-down factors (Fig. 6). Therefore, rather than the two attentional systems being separated processes, they should be better thought as intricately intertwined.” (Katsuki and Constantinidis, 2014, p. 10)