Saturday, April 2, 2016

Pay attention

I tried to read my school books despite the fact that my mind wandered a thousand miles away. I would come back to whatever I had been reading wondering to myself where I had been for the last five or ten minutes. It was not that I could not remember what I had read. Rather, I had never read the page I was staring at for that period of time. (Allan Schwartz, 2007)

This account of ADHD is something most people can identify with to some extent. Going over a lecture on attention for a neuroscience module at UCC, I'm thinking again about sustained attention. What can neuroscience tell us about how we focus our minds on a particular stream of information?

In studying sustained attention, a typical experimental task will ask participants to attend to a fairly boring set of stimuli for a prolonged time and produce a periodic response to an occasional target stimulus (e.g. a repetition of a number in a series of generally non-repeating numbers). Cognitive psychology giant Michael Posner and colleagues have suggested that the right cortex is key for this form of attention. However, other research has suggested that when a target is less salient (which made the task more difficult), activation was bilateral (i.e. activation occurred on both sides of the brain). It's a reminder that the nature of a task is key in the brain activity involved. Indeed, given that sustaining attention to such a task becomes more difficult as time goes by, the same task becomes a more difficult job over time within the same person. 

Isn't it almost redundant to say you need motivation to sustain attention on something? If something is interesting then it's inherently motivating to attend to it, but if it's boring you need something to threaten/entice you into attending to it. Given its influence on the reward system, it has been suggested that dopamine may influence sustained attention through its impact on motivation. Methylphenidate (often sold under brand name “Ritalin”) is used in the treatment of ADHD, and it is used to increase the extracellular level of dopamine. Speaking of dopamine-our familiar friend caffeine, which enhances dopamine, has been shown to enhance subjective alertness and improved sustained attention performance on a simulated driving task

However, as most people consume caffeine, experimental control is required to ensure that any effects are not due to withdrawal reversal. If you want to run a study on caffeine effects, you can ask people taking part to avoid caffeine for long enough before a study for any caffeine to have left the body. So now you can say that if you give 200mg of caffeine it's not being added to another 200mg the person drank an hour ago. However, long enough to get caffeine out of the system is not necessarily long enough for withdrawal symptoms to have passed. So there is a risk that the enhancing effects are only shown because you give a person caffeine when they are withdrawn. I should note that there has been some debate about the extent to which withdrawal reversal has confounded research on caffeine, including evidence to the contrary

Evidence for a role for noradrenalin comes from the spontaneously hypertensive rat (SHR). As the name suggests, it is prone to high blood pressure. However, it can also act as a model of ADHD-although it has its critics, this type of rat has been shown to demonstrate a number of traits associated ADHD (including impulsiveness as well as inattention). Noradrenalin has been implicated in the ADHD-like behavior of this rat by the alteration of such behavior by the noradrenergic drug Guanfacine. 

I can close with a quick tip on sustaining attention, as someone who has had his mind drift far away at many a lecture. When I decide I really need to focus on a talk, I try to think of a question as early on as possible in the talk. I then try to see if anything in the talk answers this question. Whether or not I will actually ask the speaker this question aloud, I imagine that I will have to ask it, and thus motivate myself not to look foolish by asking a question that has been answered by the content of the talk. I don't have any great solution for when one is sleep-deprived and heavily sleepy though-suggestions welcome!

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