Objective assessment of the human visual attentional state

Abstract

Primary objective The purpose of this study was to develop an objective way to assess human visual attention using the alpha band component of the visual-evoked potential (VEP). Design and methods Six different attentional conditions were tested: eyes-open, eyes-closed, eyes-closed with backwards number counting, and three rapid serial visual presentation (RSVP) tasks. 18 visually-normal, young-adult subjects (ages 21 to 28 years) were tested binocularly at 1 meter for each condition on two separate days. The Diopsys™ NOVA-TR system was used to obtain the visual-evoked potential (VEP) and extracted alpha-wave and its related power spectrum. Additionally, the Visual Search and Attention Test (VSAT) was administered as a subjective measure of visual attention. Results Subjects exhibited significant decreases in power in the alpha band when comparing the eyes-closed to the eyes-open conditions, with power in the eyes-closed condition being, on average, twice as large. The response from the other four conditions did not reflect the differential attentional demands. The ratio of the power in the eyes-closed condition to the eyes open condition in the lower alpha frequencies (8–10 Hz) was found to be significantly correlated to the group’s performance on the VSAT, especially the 10 Hz component. Conclusions An individual’s ability to attenuate their alpha-component during visual processing may be a predictor of their visual attentional state. These findings solidify the role of the VEP alpha subcomponent as an objective electrophysiological correlate of visual attention, which may be useful in the diagnosis and treatment of human visual-attention disorders in the future.

Objective Assessment of Eye Dominance Using the VEP

“…30,31 The system consists of a 17·15 (horizontal·vertical) degree display monitor for stimulus presentation, a second monitor for use by the experimenter for data viewing, and a computer for stimulus generation, analysis, and graphical display. The Diopsys system is available commercially and is approved by the Food and Drug Administration for both research and clinical use.…”

Objective assessment of visual attention in mild traumatic brain injury (mTBI) using visual-evoked potentials (VEP)

“…This comparison is presented in Figure 1. More recent studies have demonstrated that the level of alpha band activity was correlated with different attentional states: eyes-closed as compared to the eyes-open condition [27][28][29], eyes closed with increased attentional demand as compared to the eyes-closed condition [28,30], visual imagery [31] and visual attention during reading [32]. These studies revealed that changes in neuronal activity occurred and were related to the different attentional states, thus producing predictable changes in the relative alpha band power contributions.…”

“…Recently, Willeford et al [28] used the above ideas and improved VEP hardware/software technology to assess normal human visual attention. They confirmed and extended Fuller's earlier findings in 18 visually-normal, young-adults.…”

“…The Willeford et al [28] results obtained in the laboratory serve as the normative database for the present study. In the Willeford et al [28] study, two different attenuation ratios (ARs) were calculated: the first was between the average alpha band power during the eyes-closed 'relaxed' attentional condition (EC) and the average alpha band power during the eyes-open condition (EO); and the second ratio was between the average alpha band power during the eyes-closed number counting condition (ECNC) and the average alpha band power during the eyes-closed 'relaxed' attentional condition (EC). The EC 7 EO AR was found to correlate with a standard subjective clinical visual attention test, namely the Visual Search and Attention Test (VSAT) [28,39].…”

“…In the Willeford et al [28] study, two different attenuation ratios (ARs) were calculated: the first was between the average alpha band power during the eyes-closed 'relaxed' attentional condition (EC) and the average alpha band power during the eyes-open condition (EO); and the second ratio was between the average alpha band power during the eyes-closed number counting condition (ECNC) and the average alpha band power during the eyes-closed 'relaxed' attentional condition (EC). The EC 7 EO AR was found to correlate with a standard subjective clinical visual attention test, namely the Visual Search and Attention Test (VSAT) [28,39]. In addition, Willeford et al [28] found the following: (1) alpha attenuation ratio (AR) (EC 7 EO) values of 2 or greater, which suggested presence of normal visual attention; (2) the objectively-based AR at 10 Hz was significantly correlated with the subjectively-derived VSAT percentile score; and (3) the second alpha AR (ECNC 7 EC) was less than 1, which was similar to Fuller's [30] normative value.…”