Inhibitory component of externally controlled covert orienting in visual space.

Abstract

Four experiments are reported that investigate an inhibitory effect associated with externally controlled orienting and first identified by Posner and Cohen (1980, 1984). The effect takes the form of an inability to respond quickly to a stimulus appearing in the same location in the visual periphery as a previous one that produced covert orienting. Several characteristics of the effect are revealed that eliminate possible explanations in terms of response inhibition, masking, and sensory habituation. The inhibitory component of orienting occurs whether or not the first stimulus requires a response (Experiment 1), lasts at least a second (Experiments 1, 2, and 3), affects not only the originally stimulated location but also nearby locations (Experiment 2), is determined by environmental coordinates (Experiment 3), and occurs both in the periphery and at the fovea (Experiment 4). It is concluded that inhibition may act together with an early facilitatory component (Posner & Cohen, 1984) in directing the attention and eye movement systems in order to maintain efficient spatial sampling.

Variability of response times as a marker of diverted attention

“…To summarise, neglect patients had slower RTs than controls. Controls showed an advantage of valid over invalid trials at 150-ms SOA; for longer SOAs, this advantage turned into a cost, as predicted by the notion of inhibition of return [20,26,27,29]. Neglect patients showed a disproportionate cost for left targets preceded by right (invalid) cues; this cost was maximal at the shortest SOA, consistent with the idea of a biased exogenous orienting in neglect.…”

Prioritization in visual search: Visual marking is not dependent on a mnemonic search

“…This is important, since such an attentional scan should optimize memory for, or inhibition of return at, the old locations (Chun & Jiang, 1998;Klein, 1988;Logan, 1988;Maylor & Hockey, 1985;Müller & von Muhlenen, 2000;Posner & Cohen, 1984;Takeda & Yagi, 2000).…”

“…The idea is that, when searching for a target object, the observer somehow needs to memorize which objects (or locations) have already been inspected. Klein (1988) argued that the visual system might accomplish this by assigning inhibitory tags to previously attended locations-a mechanism known as inhibition of return (Maylor & Hockey, 1985;Posner & Cohen, 1984). Consistent with this idea, Klein (1988) found that probe dots presented at searched locations were more difficult to detect than probe dots at other locations.…”

Orienting of attention in left unilateral neglect

“…In addition, the fact that IOR seems to be a phenomenon exclusive of exogenous orienting [25] further suggests that this form of orienting is particularly impaired in left unilateral neglect.…”

“…Interestingly, the posterior bank of the intraparietal ®ssure is one of the main sources of cortical projection to the intermediate and deeper layers of the superior colliculus [148,149], a subcortical structure involved in programming saccades to visual targets. Another phenomenon related to exogenous orienting [25] is IOR. The role of extrageniculate visual pathways, and particularly of the superior colliculus, in mediating this phenomenon is well known [27,150].…”