Brain Mechanisms for Directed Attention

Abstract

In his inaugural address of this series in 1957, Lord Adrian (Adrian 1957) elucidated the general conceptual approach used by Sherrington in his analysis of the function of the nervous system, and showed how in his long and productive scientific career Sherrington established the science of neurophysiology as we know it in the English-speaking world. Later lecturers (Denny-Brown 1962, Granit 1968, Whitteridge 1972 have illustrated through their own discoveries the continuing influence of Sherrington's ideas upon contemporary neuroscience. You will see from that which follows that I have taken a somewhat different approach in my research of recent years (Mountcastle et 0/. 1975, Mountcastle 1976, Lynch et 01. 1977. Nevertheless, I like to believe that Sherrington would have found something of interest in it.The experiments I shall describe have their conceptual origin in part in the studies of parietal lobe function in humans, particularly those studies of Holmes (1918Holmes ( , 1936, Critchley (1953) and Denny-Brown & Chambers (1958), and those of similarly perceptive neurologists who have followed them. Their clinical studies have led to the proposition that the parietal lobe of the cerebrum, together with its system connections, contains a neural apparatus which generates an internal neural image of the body position within the immediately surrounding behavioural space and the gravitational field, of the spatial relation between the body parts, of the direction of gaze and of visual attention, and of dynamic changes in these postural and attitudinal sets.It is the major theme of my lecture that this parietal lobe mechanism also receives signals concerning the internal state of the organism in terms of needs and interests, and from time to time generates commands for action, for selective and directed visual attention into the immediate behavioural surround, for the visual grasping of objects, and for skilled coordinated actions of hand and eye. On the afferent side this apparatus appears to be linked to the 'second' visual system, that which projects via the superior colliculus and pretectum to the dorsal thalamus and the parietal lobe, as well as to a relayed and convergent input from the geniculostriate system via the dorsal thalamus. This command apparatus of the parietal lobe appears to function less automatically than do more familiar ones linking input to output directly. It is conditional in nature, and depends for action upon the outcome of a matching function between the neural signals of the nature of objects -quality, location, novelty -and those of central drive states. AttentionThe human observer possesses a limited information processing capacity, yet he is immersed in a sea of signals which possess important implications and consequences for him -guides for.

Associations between prepulse inhibition and executive visual attention in children with the 22q11 deletion syndrome

“…47 While the Alerting network includes nuclei that participate in the primary startle/ startle inhibition circuit, the ANT Alerting index quantifies the benefit of a simple vs no cue condition, without the demand for resolution of conflicting visual stimuli, and thus a minimum of limbic loop influence. The Orienting network has been consistently associated with activity in posterior parietal lobe; [48][49][50] lateral pulvinar nucleus in the posterior thalamus; 50,51 and superior colliculus. 50,52,53 The superior colliculi are innervated primarily by a bundle of cholinergic (acetylcholine) neurons that originate in the brainstem and form an ascending fiber system.…”

3-D vision and figure-ground separation by visual cortex

“…The FCS, for example, enables visual search to be restricted to items of a particular color (Egeth, Virzi, & Garbart, 1984) or color-depth combination (Nakayama & Silverman, 1986). The motion BCS is suggested to operate via the magnocellular cortical processing stream (Figure 1), using mechanisms that are suggested to be closely related to apparent motion mechanisms (Grossberg, 1991, in press) and that may contribute to predictive eye tracking (Fischer, 1986;Mountcastle, 1978;Wurtz, Goldberg, & Robinson, 1982). These objectattention and spatial-attention processes thus model aspects of the What cortical stream through IT cortex, which subserves visual object recognition, and the Where cortical stream through parietal cortex, which subserves spatiallocalization & orientation (Goodale & Milner, 1992;Mishkin, Ungerleider, & Macko, 1983;Ungerleider & Mishkin, 1982).…”

Vigilance, alertness, or sustained attention: physiological basis and measurement

“…Thus, the aspect of vigilance distinct from arousal that requires a normally awake person to attend to a task for a prolonged period has not been as well-studied physiologicially. Attention usually refers to a more focused activation of cerebral cortex that enhances information processing (Mesulam, 1990;Mountcastle, 1978;Parasuraman, 1998;Posner and Petersen, 1990) but one aspect, sustained attention, is used synonymously with the most common usage of vigilance (Parasuraman, 1998b). While focused attention, divided attention, and shifting of attention, as well as executive control of attention, are all important, sustained attention is the aspect closely related to the alertness systems and the only attentional aspect that will be discussed in detail.…”