A Primer on Priming

Priming refers to facilitated processing for a particular item based on a previous event. For example, if subjects are asked to rate the likeableness of the words "strawberry" "policeman" and "penguin," and are asked 10 minutes later to name a particular type of fruit, they are more likely to say "strawberry" than they would be otherwise. Or, if the task is to identify whether strawberry is a fruit, they are reliably faster than controls who weren't exposed to that word. Priming effects also occur when subjects are asked to identify briefly flashed stimuli, to complete word stem tasks, or to identify words or objects.

A couple of things differentiate priming effects from other memory phenomena. First, subjects are often unaware of the fact that they were primed. Second, a single presentation of an item is enough to facilitate processing of it and related items for an extremely long amount of time. Third, priming is related to decreased activation of relevant brain regions, as opposed to the increased activation typically seen in recall or recognition tasks. Finally, and most mysteriously, priming appears to be intact in amnesiacs - including patients with hippocampal and even more generalized medial temporal lobe damage.

What mechanism causes priming to occur? One old view is that abstract, long-term memory representations are activated after the presentation of an item. However, some research has shown that the magnitude of the priming effect is affected by changing specific features of the item, such as its font. To what degree is priming related by the semantic properties of an item as opposed to its specific perceptual components?

This question is the topic of a November 2004 Nature Reviews Neuroscience article by Schacter, Dobbins and Schnyer. According to their analysis, when the presented items are in the same modality as the response (aka 'within-modality priming'), occipitotemporal activity is significantly reduced. This reduction in activity suggests that within-modality priming may be a specifically perceptual effect.

In contrast, cross-modal priming results in increased anterior prefrontal cortex (BA10) activity. This area is involved in explicit retrieval tasks, indicating that there may be an explicit component to cross-modal priming effects, and providing some insight on the rather mixed evidence as to whether cross-modal priming is intact in amnesiacs.

One possible explanation of these conflicting results is that there may be two routes to cross-modal priming: the use of phonological areas (left remporoparietal) and/or use of explicit retrieval (anterior prefrontal) can both support priming effects.


Blogger LaVon said...

i think priming should be one of the "seven sins of memory." my gf told me that i had to buy her one of her favorite flowers because i was being stupid one weekend. i sort of embarrassed her at some bar. well, she likes lilies, white roses, and Hawaiian flowers (only know'm if i see'm). So, I leave and I'm running some arrands for a few hours. I come back with those turtle chocolates (minus one or two because I was hungry and I wanted some too) - and a giant sunflower. I'm not sure what went wrong, but priming hadn't worked then. i told her that it was because i wasnt showing decreased activation of relevant brain regions associated with priming. she then took the half-eaten chocolates and broke my giant sunflower. and now im by myself in her apartment while she's out partying with her friends.

4/05/2006 10:30:00 PM  
Blogger Shelley said...

A side note: in undergrad I used to study the primacy and recenncy effect in honeybees. I wanted to determine if this very well-conserved phenomenon was also present in invertebrates. Therefore, I arranged 5 targets with some drops of sucrose and introduced a bee to the first one (via a well-positioned matchbox and a drop of red nail polish). I recorded the sequence that the bee visited all the targets, and then waited for it to return to get more. Interestingly, there was a significant correlation---the 1st and last targets were visited about 3x as often as the others. The middle target was visited the least. This effect was the same when position, color, scent, etc was changed. So if a honeybee, that doesn't even have a hippocampus, shows this effect---it may be a much more simple and/or ancient brain structure than was previously thought.

4/06/2006 02:11:00 PM  
Blogger Chris Chatham said...

lavon, that's hilarious but sad. neuroscience is sufficiently advanced to get people in trouble (like in India's recent legal cases) but not far along to get us out of trouble with the fairer sex!

My fingers are crossed though.

Shelley - that fact about bees is quite interesting. I'd love to do a post on everything that Bees can do. Do you remember the recent study showing they are capable of recognizing human faces? There's been another one recently showing that they can actually teach each other too. THey certainly have a hugely advanced spatial memory. I don't remember enough of the details surrounding these studies to provided much informed comment, though.

4/09/2006 02:47:00 PM  

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