Subcortical Mechanisms of Feature-Based Attention

Abstract

The degree to which spatial and feature-based attention are governed by similar control mechanisms is not clear. To explore this issue, I measured, during conditions of spatial or feature-based attention, activity in the human subcortical visual nuclei, which have precise retinotopic maps and are known to play important roles in the regulation of spatial attention but have limited selectivity of nonspatial features. Subjects attended to and detected changes in separate fields of moving or colored dots. When the fields were disjoint, spatially attending to one field enhanced hemodynamic responses in the superior colliculus (SC), lateral geniculate nucleus (LGN), and two retinotopic pulvinar nuclei. When the two dot fields were spatially overlapping, feature-based attention to the moving versus colored dots enhanced responses in the pulvinar nuclei and the majority of the LGN, including the magnocellular layers, and suppressed activity in some areas within the parvocellular layers; the SC was inconsistently modulated among subjects. The results demonstrate that featurebased attention operates throughout the visual system by prioritizing neurons encoding the attended information, including broadly tuned thalamic neurons. I conclude that spatial and feature-based attention operate via a common principle, but that spatial location is a special feature in that it is widely encoded in the brain, is used for overt orienting, and uses a specialized structure, the SC.

Pulvinar

“…42 Consistent with electrophysiologic recordings in experimental animals, functional neuroimaging also shows that initiation of saccades is associated with activation of the SC and pulvinar contralateral to the direction of the saccades. 43 Unilateral inactivation of the dorsal pulvinar in monkeys resulted in severely impaired visually guided behavior toward the contralateral space, including target selection in both manual and oculomotor tasks, limb usage, and spontaneous visual exploration.…”

Functional mapping of the magnocellular and parvocellular subdivisions of human LGN

“…Since fMRI is an excellent tool for the study of large-scale brain networks, M/P mapping of the LGN enables functional investigations of parallel thalamocortical processing pathways. Modulations of LGN activity have also been observed during selective visual attention (McAlonan et al, 2008; O'Connor et al, 2002; Schneider, 2011; Schneider and Kastner, 2009; Vanduffel et al, 2000) and perceptual fluctuations during binocular rivalry (Haynes et al, 2005; Wunderlich et al, 2005), supporting the idea that the human LGN may support higher-level aspects of vision, as opposed to operating as a simple sensory relay (Kastner et al, 2006). Indeed, reciprocal interactions between cortex and thalamus are increasingly recognized as central to sensory system function (Briggs and Usrey, 2008; Sherman and Guillery, 2002).…”

“…Previous studies have noninvasively measured activity in the human LGN using fMRI (Anderson et al, 2009; Chen and Zhu, 2001; Chen et al, 1999; D'Souza et al, 2011; Haynes et al, 2005; Kastner et al, 2004; Mullen et al, 2008; Mullen et al, 2010; O'Connor et al, 2002; Parkes et al, 2004; Schneider, 2011; Schneider and Kastner, 2009; Schneider et al, 2004; Uğurbil et al, 1999; Wunderlich et al, 2005), and there has been one attempt to localize the M and P subdivisions using fMRI (Schneider et al, 2004). In that study, stimulus contrast was manipulated (either 10% or 100% contrast-reversing checkerboard stimuli) to attempt to dissociate the M and P subdivisions.…”

The efference cascade, consciousness, and its self: naturalizing the first person pivot of action control

“…That exercise was conducted by directing attention alone, without eye or head movements, forwards and backwards from the egocenter lacuna, i.e., by covert attention in a full 360 degree egocentric space. The involvement of the superior colliculus in covert spatial attention is well established (Robinson and Kertzman, 1995; Cavanaugh and Wurtz, 2004; Ignashchenkova et al, 2004; Muller et al, 2005; Fecteau and Munoz, 2006; Lovejoy and Krauzlis, 2010; Schneider, 2011). Does it also host a full 360 degree directional compass, without which it could not have allowed us to move covert attention to the back of our head, and without which it cannot serve as central pivot or origin of a fully functional multimodal and egocentrically organized localization system (see Figure 1, and below)?…”