The neural correlates of visual search and target acquisition

Abstract

Visual target acquisition is performed during several daily tasks, often requmng time¬dependent behavioural responses towards stimuli. Information processing during such tasks is subject to bottom-up as well top-down influences, which results in an integrated processing mechanism. It follows that if the underlying neural mechanisms can be elucidated, behaviour towards visual stimuli will be better understood, allowing for the development of visual environments that facilitates desired behavioural response. The current study aimed to develop a systems-level approach according to which the mechanisms that underlie visual target acquisition can be understood, by interpreting psychophysical data in terms of the structural and functional organization of the visual system. Empirical work entailed psychophysical experiments and elaborated on previous studies regarding conspicuity areas around and response time towards visual targets. The rationale was that these two measures can be used as an indication of the conspicuity of a target within a specific background, which in turn can be related to the nature of information processing during a target acquisition task. Results showed that a proportional relationship exists between the size of the conspicuity area and a target's perceived conspicuity, with the most conspicuous targets being associated with the largest conspicuity areas. Response time trends showed that target detectability at different positions within the conspicuity area is equal, but that detection performance at positions outside the conspicuity area is greatly influenced by the nature of the background surrounding the target. Interpretation of the results points to the importance of visual attention during target acquisition, which in turn is supported by the structural and functional organization of the visual system. Findings from the psychophysical study presented here, along with the proposed framework of information processing, emphasise that behavioural outcome during visual target acquisition cannot be explained without considering the structural and functional organization of the visual system.