Neuronal and Neural-Population Mechanisms of Voluntary Visual-Spatial Attention

What neural mechanisms enable us to intentionally enhance visual perception at a specific location? Investigations using behavioral, neurophysiological, neuropharmacological, computational, neuroimaging, and electroencephalographic methods have revealed many ways in which visual processing is modulated by voluntary visual-spatial attention. Such modulatory effects include changes in single-neuron spike rates, specific neurotransmitter systems, normalization mechanisms, within-receptive-field input competition, fast-spiking inhibitory interneuron activity, and oscillations in neural excitability that facilitate synchronized neural responses. The goal of this chapter is to provide an integrative perspective on how these neural mechanisms work synergistically. Attention mechanisms concurrently operative at both neuronal and neural-population levels ultimately allow us to spatially highlight visual information under conditions ranging from low contrast to high contrast, small stimuli to large stimuli, and cluttered environments to sparse environments. Considering the neural mechanisms at many levels is key to developing a comprehensive understanding of attention and of its relation to perceptual awareness.