Auditory spatial attention gradients and cognitive control as a function of vigilance

Abstract

Selection and effort are central to attention, yet it is unclear whether they draw on a common pool of cognitive resources, and if so, whether there are differences for early versus later stages of cognitive processing. This study assessed effort by quantifying the vigilance decrement, and spatial processing at early and later stages as a function of time-on-task. Participants performed an auditory spatial attention task, with occasional "catch" trials requiring no response. Psychophysiological measures included bilateral cerebral blood flow (transcranial Doppler), pupil dilation, and blink rate. The shape of attention gradients using reaction time indexed early processing, and did not significantly vary over time. Later stimulus-response conflict was comparable over time, except for a reduction to left hemispace stimuli. Target and catch trial accuracy decreased with time, with a more abrupt decrease for catch versus target trials. Diffusion decision modeling found progressive decreases in information accumulation rate and non-decision time, and the adoption of more liberal response criteria. Cerebral blood flow increased from baseline and then decreased over time, particularly in the left hemisphere. Blink rate steadily increased over time, while pupil dilation increased only at the beginning and then returned towards baseline. The findings suggest dissociations between resources for selectivity and effort. Measures of high subjective effort and temporal declines in catch trial accuracy and cerebral blood flow velocity suggest a standard vigilance decrement was evident in parallel with preserved selection. Different attentional systems and classes of computations that may account for dissociations between selectivity versus effort are discussed.

Keywords: DDM; Simon effect; attention capture; diffusion decision model; eye tracking; sustained attention; transcranial Doppler; vigilance decrement.

Figure 1:

Behavioral measures as a function of stimulus location. A) Reaction time as a function of watch period (1&2, 3&4, 5&6) and sound location. B) Mean reaction time across all 6 watch periods. Data for shift trials are collapsed over the four lateral shift locations. C) Accuracy as a function of watch period and sound location. D) Accuracy to targets at the standard location, shift trials collapsed across the four shift locations, and no-go catch trials, also collapsed across locations. Error bars = SE.

Figure 2:

Results from diffusion modeling analysis. Parameters of drift rate (A), boundaries (B), and non-decision time (C) are plotted against watch period. Results show that drift rate, boundaries, and non-decision time all progressively declined over watch periods. Data were collapsed across shift locations for each adjacent pair of watch periods. Error bars = SE.

Figure 3:

Simon effect results. Difference in left-right A) reaction time and C) accuracy as a function of stimulus location. The Simon effect is indicated by faster reaction times and accuracy by the left hand to sounds on the left side of space, and vice versa for right hand responses to sounds on the right. Reaction times and accuracy were comparable for both hands to sounds at the midline. B) The Simon effect (non-corresponding minus corresponding) over watch periods, collapsed across lateral locations on the left (−45°, −90°) and right (+45°, +90°). There was a significant watch x hemispace interaction (p<.02), due to a reduction in the Simon effect on the left side in watch periods 5&6 (p<.005). Error bars = SE.

Figure 4:

Psychophysiological measures across watch periods. A) Transcranial Doppler measures of blood flow velocity (% of 1 min baseline). Blood flow significantly increased from baseline to watch period 1 in both hemispheres, and then returned to baseline (right hemisphere) or continued to decrease over the remaining watch periods (left hemisphere). B). Eye tracking measures as a function of watch period. Pupil dilation response (PDR) increased for the first watch relative to baseline, and then decreased towards baseline. Blink rate progressively increased over watch periods.