Distinguishing the "updating" component of working memory

A memory system must be able to serve at least two functions, to hold information over time, and to change the information that is being held. While several studies have identified a vast cortical network to be involved in working memory, little work has tried to distinguish the two different functions.

In 2008 I came into contact with Patrick Sörqvist, then a PhD student from an applied psychology lab in Gävle, Sweden, who was interested in practical implications of memory systems. He wanted to run an fMRI study of the number updating task, which can distinguish the points in time when working memory content is being updated, as opposed to when the content being held constant while ignoring new information. I helped out with experiment design, programming, fMRI analysis and write-up. We found some cortical regions to be more activated for memory updating than when not updating, and other regions to be activated in the inverse condition.

Sörqvist & Sætrevik (2010) The neural basis of updating: Distinguishing substitution processes from other concurrent processes - Scandinavian Journal of Psychology

We probably used the wrong heatmap shading for the fMRI activations shown in Figure 1 and 2, as they did not come out well in the black and white print. They were supposed to look more like this:

Figure 1: Areas more activated when updating.

Figure 2: Areas more activated when not updating.

Here are the same activations shown in an animated glass brain. Areas more activated when updating are shown in "hot", areas more activated when not activated are shown in "cold" (t-values 6-16 are shown).

The study had quite few participants, but we later supported the main finding in another study with more participants (currently under review).

Introductory lecture on language and thought

The second introductory lecture was on language and thought. I tried to hold the two concepts up against each other, to contrast them and discuss whether they had any overlap.



The final 20 minutes of the two-hour lecture I briefly talked about the concept of intelligence and how it can be measured: http://prezi.com/pznxc5ihzxd3/psyk100-intelligens/

Introductory lecture on "memory"

When I began working at the Department for psychosocial science, I was persuaded to give two lectures in cognitive psychology to the first year students. There were between 200 and 300 students at each lecture, and this was their first introduction to the topic.

The first of these lectures was on the topic of memory. I planned the lecture around the Atkinson and Shiffrin model of three memory stores, so I used this as a visual structure for the presentation, and placed all theories and findings in relation to this model.

The presentation (Norwegian only) is included below. Note that the lecture is supposed to run over 2x45 minutes, so if you click through it in 3 minutes it may induce motion sickness.

Transient activation of speech areas following language task

My fMRI study of primed dichotic listening from 2009 showed that stimulus conflict increased medial prefrontal activation, and response conflict increased left dorsolateral activation. That went some way in terms of figuring out which mechanisms are involved in the task, and we accounted for it in terms of the Desimone and Duncan's biased competition model and/or Botvinick's model of interaction between cognitive conflict and control.

After publishing this work, I started thinking whether the data could also be used to understand how the mechanisms interacted. Some recent studies have indicated that high cognitive conflict on one trial leads to  increased cognitive control on the following trial. The increased control is typically seen as faster and more accurate performance, and increased activation in cortical areas assumed to hold the task set instructions. Could I do something similar with my task? Given that I had formally left the neurocognitive research group at this time, I was perhaps also motivated to get the most out of my already collected fMRI data.

The 2009 analysis had analysed according to what the current stimuli and the current response was. The new analysis restructured the data file according to whether the previous and the current trial was high (prime repeated in targets) or low conflict (no prime-target repetition). This yielded four different categories (previous trial - current trial):

1. High - high
2. Low - high
3. High - low
4. Low - low

From this we could run two different analyses: In the first contrast, we compared sequence 1+2 with sequence 3+4, i.e. examined what the effect of the current trial was, regardless of what happened on the previous trial. As expected, this yielded much the same result as the 2009 analysis, showing that task conflict activates medial and dorsolateral prefrontal areas. The second contrast compared sequence 1+3 with sequence 2+4, i.e. examined what the effect of the previous trial was, regardless of the current trial. This showed that following a stimulus conflict, activation increased in temporal areas, more on left than on right side. No behavioural after effect of conflict was seen, perhaps since there is no defined correct answer in the prime dichotic listening task (both syllables are correct, and error rates are low), and response times were not measured. 

In line with current models for how cognitive conflict modulates cognitive control, we interpreted the effect as challenging task leading to more resources being dedicated to the type of processing involved in the task, in this case discriminating verbal stimuli. The fact that sequential effects showed temporal rather than e.g. dorsolateral activation, may indicate that conflict did not lead to increased task or instruction focus, as has been seen in e.g. sequential effects of Stroop tasks, perhaps as the task is rather simple. 

  

My by then former college Karsten Specht helped me with the analyses and the manuscript, and we published this in "Brain and Cognition" in 2012. A lab meeting presentation of this study can be found here. 

Cognitive conflict in a syllable identification task causes transient activation of speech perception area of speech perception area - Brain and Cognition

Lab meeting: Transient activation of speech areas

In December 2012 I was asked to give a 20 minutes presentation of some of my research at our department's research seminar. I was relatively fresh in the field of work and organizational psychology at that time, so I presented a re-analysis of some previous fMRI work. Although I tried to simplify the work and focus on the gist of it, I'm afraid most of my audience had a hard time to following the unfamiliar topic and methodology. Looking back at it now, I think I may also have overused the prezi features somewhat...

The work I presented had just been accepted into Brain and Cognition the same day as my presentation was due, so I make a note of this at the end.