The influence of executive functions on spatial biases varies during the lifespan

Abstract

Many perceptual processes, such as language or face perception, are asymmetrically organised in the hemispheres already in childhood. These asymmetries induce behaviourally observable spatial biases in which the observer perceives stimuli in one of the hemispaces more efficiently or more frequently than in the other one. Another source for spatial biases is spatial attention which is also asymmetrically organised in the hemispheres. The bias induced by attention is directed towards the right side, which is clearly demonstrated by patients with neglect but also in lesser degree by healthy observers in cognitively loading situations. Recent findings indicate that children and older adults show stronger spatial biases than young adults. We discuss how the development of executive functions might contribute to the manifestation of spatial biases during the lifespan. We present a model in which the interaction between the asymmetrical perceptual processes, the age-related development of the lateralised spatial attention and the development of the executive functions influence spatial perceptual performance and in which the development and decline of the executive processes during the lifespan modify the spatial biases.

Keywords: Age; Attention; Executive functions; Hemispheric asymmetry; Laterality; Spatial perceptual bias.

Fig. 1

The efficiency of executive functions (EF) during a dichotic listening forced attention paradigm (Hugdahl et al., 2004, Takio et al., 2009) was calculated by subtracting the dichotic listening forced-left lateralisation index (FL LI) from the forced-right lateralisation index (FR LI) in each participant group. The difference score describes how efficiently the participants were able to modify the ear advantage under the forced-attention conditions in dichotic listening: the higher the different score is, the better the participant group was able to modify the ear advantage.

Fig. 2

Simplified schematic presentation of the underlying mechanisms (A) and of the age-related changes (B) in rightward spatial bias in situations with attentional load. In figure A, the mechanisms that induce the spatial rightward bias (language lateralised in the left hemisphere and attention lateralised in the right hemisphere) are presented. This rightward bias is modified by the executive functions located in the prefrontal areas. Black arrows denote a strong influence of the mechanism, narrow arrows denote a light influence. In figure B, the strength and the interactions of these mechanisms during the lifespan are summarised. The thickness of the arrows denotes the strength of the spatial bias. The darkness of the prefrontal areas denotes the efficiency of the executive functions. The E stands for executive functions, the L stands for language and the A stands for attention.