06/01/2010 by admin.

ScienceDaily has an item on a paper in Dec Nature Neuroscience by reseachers at the Salk Institute. (here)

The work connects part of the brain stem that controls eye movements with control of mental attention. Mental attention is closely linked with consciousness.

Like a spotlight that illuminates an otherwise dark scene, attention brings to mind specific details of our environment while shutting others out. …

“Our ability to survive in the world depends critically on our ability to respond to relevant pieces of information and ignore others,” explains graduate student and first author Lee Lovejoy, who conducted the study together with Richard Krauzlis, Ph.D., an associate professor in the Salk’s Systems Neurobiology Laboratory. “Our work shows that the superior colliculus is involved in the selection of things we will respond to, either by looking at them or by thinking about them.”

As we focus on specific details in our environment, we usually shift our gaze along with our attention. “We often look directly at attended objects and the superior colliculus is a major component of the motor circuits that control how we orient our eyes and head toward something seen or heard,” says Krauzlis.

But humans and other primates are particularly adept at looking at one thing while paying attention to another. As social beings, they very often have to process visual information without looking directly at each other, which could be interpreted as a threat. This requires the ability to attend covertly.

It had been known that the superior colliculus plays a role in deciding how to orient the eyes and head to interesting objects in the environment. But it was not clear whether it also had a say in covert attention.

In their current study, the Salk researchers specifically asked whether the superior colliculus is necessary for covert attention. To tease out the superior colliculus’ role in covert attention, they designed a motion discrimination task that distinguished between control of gaze and control of attention.

The superior colliculus contains a topographic map of the visual space around us, just as conventional maps mirror geographical areas. Lovejoy and Krauzlis exploited this property to temporarily inactivate the part of the superior colliculus corresponding to the location of the cued stimulus on the computer screen. No longer aware of the relevant information right in front of them the subjects instead based all of their decision about the stimulus’ movement on irrelevant information found elsewhere on the screen.

“The result is very similar to what happens in patients with neglect syndrome,” explains Lovejoy, “Up to a half of acute right-hemisphere stroke patients demonstrate signs of spatial neglect, failing to be aware of objects or people to their left in extra-personal space.”

“Our results show that deciding what to attend to and what to ignore is not just accomplished with the neocortex and thalamus, but also depends on phylogenetically older structures in the brainstem,” says Krauzlis. “Understanding how these newer and older parts of the circuit interact may be crucial for understanding what goes wrong in disorders of attention.”

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16/06/2009 by admin.

An item in ScienceDaily (here) reports on research by R Desimone’s group at MIT into gamma waves associated with attention. The report uses an interesting analogy to describe the waves.

Just as our world buzzes with distractions — from phone calls to e-mails to tweets — the neurons in our brain are bombarded with messages. Research has shown that when we pay attention, some of these neurons begin firing in unison, like a chorus rising above the noise. Now, a study in the May 29 issue of Science reveals the likely brain center that serves as the conductor of this neural chorus. … neurons in the prefrontal cortex — the brain’s planning center — fire in unison and send signals to the visual cortex to do the same, generating high-frequency waves that oscillate between these distant brain regions like a vibrating spring. These waves, also known as gamma oscillations, have long been associated with cognitive states like attention, learning, and consciousness. …

To explain neural synchrony, Desimone uses the analogy of a crowded party with people talking in different rooms. If individuals raise their voices at random, the noise just becomes louder. But if a group of individuals in one room chant together in unison, the next room is more likely to hear the message. And if people in the next room chant in response, the two rooms can communicate. …

Desimone looked for patterns of neural synchrony in two “rooms” of the brain associated with attention — the frontal eye field (FEF) within the prefrontal cortex and the V4 region of the visual cortex. …

When the monkeys first paid attention to the appropriate object, neurons in both areas showed strong increases in activity. Then, as if connected by a spring, the oscillations in each area began to synchronize with one another. Desimone’s team analyzed the timing of the neural activity and found that the prefrontal cortex became engaged by attention first, followed by the visual cortex — as if the prefrontal cortex commanded the visual region to snap to attention. The delay between neural activity in these areas during each wave cycle reflected the speed at which signals travel from one region to the other — indicating that the two brain regions were talking to one another.

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17/04/2009 by admin.

Here is more from Psyblog (here) on attention. This time on the independence of eye direction and attention.

“Eye direction normally coincides with where attention is directed but it is such an important social signal that disguise is sometimes necessary. Take these for instance:
People in close proximity like rail commuters who can watch each other by adopting a fixed gaze and letting their attention wander around the visual field.
Parents keeping tabs on their children out of the corner of their eye while looking at their conversational partner.
Skilled sports people hiding their intended passes or moves by using their peripheral vision rather than looking directly…
Posner and others argued that it is our attention moving around the visual field, often remarkably independent of our actual gaze direction. Indeed even if we’re looking directly at something, and when we don’t expect to see it, we’re no more likely to notice it than if it appears on the edge of our vision…
It appears that attention can be likened to a spotlight roving across our vision like a virtual eye, just picking out the things in which it is interested; it’s not as attached to where we point our eyes as we might imagine. ”

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14/04/2009 by admin.

It is easy to confuse attention and consciousness. Attention seems even part of consciousness. Some articles in the blog Psyblog (here) make an interesting take on attention. In fact, what I found at this blog was so engaging that I intend to visit it regularly.
An article by M. Miller from Nature 2003 is cited by the blogger. It shows that visual attention can be divided between two things. Here is the abstract:

“By voluntarily directing attention to a specific region of a visual scene, we can improve our perception of stimuli at that location. This ability to focus attention upon specific zones of the visual field has been described metaphorically as a moveable spotlight or zoom lens that facilitates the processing of stimuli within its ‘beam. A long-standing controversy has centred on the question of whether the spotlight of spatial attention has a unitary beam or whether it can be divided flexibly to disparate locations. Evidence supporting the unitary spotlight view has come from numerous behavioural and electrophysiological studies. Recent experiments, however, indicate that the spotlight of spatial attention may be divided between non-contiguous zones of the visual field for very brief stimulus exposures (<100 ms). Here we use an electrophysiological measure of attentional allocation (the steady-state visual evoked potential) to show that the spotlight may be divided between spatially separated locations (excluding interposed locations) over more extended time periods. This spotlight division appears to be accomplished at an early stage of visual-cortical processing.”

This does seem to indicate that attention is a complex concept and not just another word for consciousness. If each sense mode has zero, one or more focuses of attention at any time, plus perhaps other things (non-sensory) being attended to, then attention may be a busy little area.

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