Saccade Costs Fundamentally Drive Eye Movement Behavior

Core Concepts

Saccade costs, as measured by pupil size, critically determine where the eyes move, with affordable saccades being consistently preferred over costly ones.

Abstract

The study investigated whether the effort associated with making saccadic eye movements, referred to as "saccade costs", determines where the eyes move. The researchers first measured pupil size, a marker of noradrenaline release and mental effort, during the planning of saccades in different directions. They found that pupil size, and thus saccade costs, differed across saccade directions, with oblique saccades being more costly than cardinal saccades, and downward saccades being more costly than upward saccades. In a subsequent task, the same participants freely chose between two possible saccade targets. The researchers found that the saccade directions that were less costly, as indicated by smaller pupil sizes, were consistently preferred over the more costly directions. This relationship between saccade costs and preferences held even when participants made unconstrained eye movements during visual search in natural scenes. Furthermore, when cognitive demand was increased experimentally through an auditory dual task, participants made fewer saccades overall and especially reduced the number of costly saccades. This suggests that the eye movement system and other cognitive operations consume from a shared pool of resources, which are flexibly allocated based on the current cognitive demands. Together, the findings demonstrate that saccade costs fundamentally drive where the eyes move, even when other factors like physical salience, goals, and prior knowledge affect saccade selection. The brain appears to adaptively minimize saccade-inherent effort whenever possible.

Stats

Participants preferred cardinal over oblique saccade directions. Participants preferred upward over downward saccade directions. The more affordable saccade option was chosen above chance level across participants.

Quotes

"Saccade costs critically predict saccade preferences: affordable directions were preferred over costly directions." "Increasing cognitive demand via an additional auditory dual task led to a lower saccade frequency, and especially costly saccades were cut."

Key Insights Distilled From

Effort Drives Saccade Selection

by Koevoet,D., ... at www.biorxiv.org 02-07-2024

https://www.biorxiv.org/content/10.1101/2024.02.06.579052v2

Deeper Inquiries

How do saccade costs relate to the neural underpinnings of oculomotor control and decision-making?

Saccade costs are closely related to the neural underpinnings of oculomotor control and decision-making. The effort associated with planning and executing saccades, as reflected in pupil size, can be considered a form of cost that the brain needs to minimize. This effort is thought to be linked to the activity in the locus coeruleus (LC), which releases noradrenaline throughout the brain. Noradrenaline is known to modulate neural gain and coordinate communication within and between neural populations. Therefore, pupil size, as a marker of LC activity, can be used to quantify saccade costs. In terms of neural underpinnings, the brain areas involved in oculomotor control, such as the frontal eye fields (FEF), supplementary eye field, anterior cingulate cortex, superior colliculus (SC), and cerebellum, are also crucial for decision-making processes. These areas are not only responsible for controlling eye movements but are also involved in decision-making. The weighing of saccade costs during saccade selection is likely performed by this oculomotor-decision making network, along with other areas such as the orbitofrontal cortex.

How do saccade costs relate to the neural underpinnings of oculomotor control and decision-making?

Saccade costs are closely related to the neural underpinnings of oculomotor control and decision-making. The effort associated with planning and executing saccades, as reflected in pupil size, can be considered a form of cost that the brain needs to minimize. This effort is thought to be linked to the activity in the locus coeruleus (LC), which releases noradrenaline throughout the brain. Noradrenaline is known to modulate neural gain and coordinate communication within and between neural populations. Therefore, pupil size, as a marker of LC activity, can be used to quantify saccade costs. In terms of neural underpinnings, the brain areas involved in oculomotor control, such as the frontal eye fields (FEF), supplementary eye field, anterior cingulate cortex, superior colliculus (SC), and cerebellum, are also crucial for decision-making processes. These areas are not only responsible for controlling eye movements but are also involved in decision-making. The weighing of saccade costs during saccade selection is likely performed by this oculomotor-decision making network, along with other areas such as the orbitofrontal cortex.

How do saccade costs relate to the neural underpinnings of oculomotor control and decision-making?

Saccade costs are closely related to the neural underpinnings of oculomotor control and decision-making. The effort associated with planning and executing saccades, as reflected in pupil size, can be considered a form of cost that the brain needs to minimize. This effort is thought to be linked to the activity in the locus coeruleus (LC), which releases noradrenaline throughout the brain. Noradrenaline is known to modulate neural gain and coordinate communication within and between neural populations. Therefore, pupil size, as a marker of LC activity, can be used to quantify saccade costs. In terms of neural underpinnings, the brain areas involved in oculomotor control, such as the frontal eye fields (FEF), supplementary eye field, anterior cingulate cortex, superior colliculus (SC), and cerebellum, are also crucial for decision-making processes. These areas are not only responsible for controlling eye movements but are also involved in decision-making. The weighing of saccade costs during saccade selection is likely performed by this oculomotor-decision making network, along with other areas such as the orbitofrontal cortex.