Struggling to remember faces? Forgetting how your favourite Backstreet Boys member looks? Help could be on its way in the form of the first non-invasive way of stimulating the brain that can boost visual memory: scull electrodes.
The technique uses transcranial direct current stimulation (tDCS), in which weak electrical currents are applied to the scalp using electrodes. The method can temporarily increase or decrease activity in a specific brain region and has already been shown to boost verbal and motor skills in volunteers.
Richard Chi, a PhD student at the Centre for the Mind, University of Sydney, and colleagues wanted to follow up on previous research showing that lesions in the left anterior temporal lobe (ATL), an area near the temple, can lead to improvements in visual memory and perceptual skills similar to the abilities exhibited by some people with autism. Chi's team wondered if inhibiting that area using tDCS might likewise improve memory.
To investigate, his team showed 36 volunteers a dozen "study" slides covered with shapes that varied in their number, arrangement, colour and size (see "Brain games"). The volunteers were then shown five "test" slides - two with patterns that appeared in the study slides, two with completely new patterns and one whose pattern looked similar to that on a study slide. Participants were asked to identify which of the test slides they had already seen, first performing the task without any brain stimulation.
Subjects then repeated the experiment 12 times, with one group receiving so-called anodal tDCS (which boosts activity) on their right ATL and cathodal tDCS (which inhibits activity) on their left. A second group received the opposite stimulation and a third group received a placebo treatment, which did not stimulate either side of the brain.
Those in the first group more than doubled their scores after receiving tDCS, experiencing a 110 per cent improvement in visual memory. Participants in the second and third groups showed no overall improvement in performance (Brain Research, DOI: 10.1016/j.brainres.2010.07.062).
The left ATL is known to be crucial for context processing, among other things, while the right ATL is associated with visual memory. Chi's team suggests that inhibiting activity in the left ATL cuts errors in visual memory by reducing the potentially confusing influence that context can have on recognition. This effect, combined with an increase in activity in the right ATL, allows someone to be more aware of the literal details of each pattern. Further studies in which the temporal lobes are stimulated individually may help to distinguish the underlying mechanisms involved.
A previous experiment using the same visual task, but without tDCS, showed that people with autism outperformed non-autistic individuals by roughly the same margin as the improvement seen in this experiment, says Chi.
In future, Chi says, it might eventually be possible to use tDCS to "develop a 'thinking cap' that enhances learning".
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