Visual Working Memory and Brain Stimulation
The topic of visual representation and visual memory first asks how much information we can take away with each eye fixation. The answer, surprisingly, is not much (the well known "change blindness" phenomenon). This is because we have a visual short-term memory (VSTM) that is very limited in capacity. The second question, then, is what kind of information are we storing if the short-term buffer is so limited? My research using the change detection paradigm has suggested that the gist can be captured with each fixation, but our conscious representations for objects do not build up fast enough to facilitate change detection over several fixations (Sampanes, Tseng, & Bridgeman, 2008). Therefore, effective top-down modulation of visual attention is a much-needed component if one is required to maintain precise visual representations beyond his or her memory capacity (Yang, Tseng, Huang, & Yeh, 2012), such as the case of an air traffic controller. This research has important implications for certain daily activities that require high levels of caution, such as driving, because detecting changes in the environment is crucial to road safety. Right now I am working closely with the Volkswagen group to study the impact of change blindness in driving situations and have one patent pending in the USA and Europe (Tseng, Lathrop, Sison, & Juarez, 2012).
Given people's poor performance in detecting changes in the environment, and how this may impact safety in many contexts (e.g., driving), one major question that follows this line of research is, well, how do we improve it? This is where my training in noninvasive brain stimulation comes in handy. Using event-related TMS (transcranial magnetic stimulation), my colleagues and I have identified the right posterior parietal cortex as a critical region in encoding information into VSTM (Tseng, Hsu, Muggleton, Tzeng, Hung, & Juan, 2010). Recently, we used positively-charged tDCS over the same region to artificially increase its neural activity level, and found that 15 minutes of electrical stimulation can indeed improve people's VSTM performance (at least temporarily), but only if these people's natural performance fell below average (Tseng et al., 2012). In other words, there seems to be an upper limit to human’s VSTM capacity, but the low-performers can at least reach their full potential via the help of electrical stimulation. This behavioral improvement is also supported by evidence from ERP (Tseng et al., 2012) and EEG (Hsu, Tseng, Liang, Cheng, & Juan, 2014), and we are currently conducting fMRI experiments and EEG time frequency analyses to better characterize the facilitating effect of tDCS (Hsu, Juan, & Tseng, 2016; Tseng, Chang, Liang, Chang, & Juan, 2016). I am also working very closely with neurologists to apply tDCS to improve patients' VSTM (Wu, Tseng, Chang, Pai, Hsu, Lin, & Juan, 2014).
To know more about this line of research, please take a look at our recent review paper in Current Directions in Psychological Science:
Juan, C.H., Tseng, P., Hsu, T.Y. (2017) Elucidating and modulating the neural correlates of visuospatial working memory via noninvasive brain stimulation. Current Directions in Psychological Science, 26(2), 165-173.
A complete list of our publications in this topic can be found here: http://medhuman1.tmu.edu.tw/philip/papers.html