Youngson Cho, MD, PhD: Motivation improves working memory by shaping neural signals in the prefrontal and parietal cortex
December 01, 2020Information
Assistant Professor of Psychiatry; Assistant Director, NRTP
ID5938
To CiteDCA Citation Guide
- 00:00Hi, I'm young sunshine.
- 00:02I'm an assistant professor in
- 00:03the Yell Child Study Center and
- 00:06in the Department of Psychiatry.
- 00:08So my talk is entitled motivation
- 00:10improves working memory by
- 00:11shaping neural signals in the
- 00:12prefrontal and parietal cortex.
- 00:14And as you see,
- 00:15there's a pretty big carrot
- 00:16on the slide which I placed to
- 00:18symbolize incentives or those
- 00:19things broadly that motivate us.
- 00:21And my talk will focus on
- 00:23motivation and how motivation,
- 00:24effects cognition as a means of
- 00:27achieving goals.
- 00:27So to achieve goals,
- 00:28one must have both the
- 00:30desire to achieve a goal,
- 00:31which is the motivation and
- 00:33the means to achieve the goal,
- 00:34which here is the ability to
- 00:36draw on cognitive resources,
- 00:37and the overarching question in our work
- 00:39is how do these domains affect each other?
- 00:43So what is motivation?
- 00:44I think of it as a drive that helps
- 00:46organize our desires and efforts
- 00:48towards goal directed behaviors.
- 00:50And here we will specifically talk
- 00:52about incentive motivation or the
- 00:54motivation that is initiated by incentives.
- 00:56Theories of incentive motivation.
- 00:57By Kent Berridge and others suggest
- 01:00that two things have to come
- 01:01together for people to be motivated.
- 01:03External cues signaling incentives
- 01:04such as food or money,
- 01:05etc.
- 01:06And an internal physiological state that
- 01:07is conducive to integrating these cues,
- 01:09such as hunger or thirst.
- 01:11So as a concrete example,
- 01:12here's a child with ice cream in
- 01:14the ice cream Services Visual,
- 01:16an likely olfactory cue,
- 01:17and he said previous experiences with
- 01:20ice cream and just by seeing it can
- 01:22have an internal representation of
- 01:23ice cream and have an idea of what
- 01:25it would be like to taste in the near future.
- 01:29This creates a motivation
- 01:30to obtain the ice cream,
- 01:32or in his case,
- 01:33motivation to sit still and wait
- 01:35for the ice cream and motivation in
- 01:38the broadest sense is disrupted.
- 01:40In many psychiatric illnesses,
- 01:41including but not limited to schizophrenia,
- 01:43depression, substance use,
- 01:44and it's a challenge to know in
- 01:47which ways motivation is disrupted
- 01:48and exactly how this disruption
- 01:50relates to symptoms,
- 01:51which is a large part of our work.
- 01:55Motivation does not occur in isolation.
- 01:57By definition,
- 01:58motivation must affect other processes.
- 02:00So in our work we focus on
- 02:02how motivation affects the
- 02:04downstream process of cognition.
- 02:06We specifically focus on working memory,
- 02:08which is defined as the temporary
- 02:10maintenance and manipulation of
- 02:11information in the service of a goal.
- 02:13Working memory is important
- 02:14because it serves as a building
- 02:16block of higher order cognition.
- 02:18It's required for abstraction
- 02:20and problem solving.
- 02:21So examples of working memory
- 02:23include being verbally told,
- 02:24a phone number,
- 02:25and having to keep it in mind
- 02:27before being able to jot it down.
- 02:30Calculating a tip at a restaurant
- 02:32arithmetic requires working memory,
- 02:33keeping in mind a set of directions
- 02:35when traveling to a destination.
- 02:37Prior work has noted that working memory
- 02:39engages a number of prefrontal cortex
- 02:41and parietal cortex brain regions.
- 02:43Here shown in orange,
- 02:45red,
- 02:45and pink,
- 02:46including the dorsal
- 02:47lateral prefrontal cortex,
- 02:48the pre Motors cortex and
- 02:50areas the intraparietal sulcus.
- 02:51Working memory also improves
- 02:53throughout childhood and adolescence,
- 02:55likely paralleling the ongoing
- 02:57development of the prefrontal cortex.
- 02:59This ongoing development means that
- 03:01working memory is dynamic in development,
- 03:03but also vulnerable.
- 03:06So how do we achieve our task
- 03:08of understanding the effects of
- 03:10incentives on working memory?
- 03:11We drew from classic working memory
- 03:13tasks that have been critical for
- 03:15understanding of how individual
- 03:16neurons behave during working memory.
- 03:18However, these tests are typically
- 03:20used in nonhuman primates,
- 03:21so we translated this task to
- 03:23use it in human studies.
- 03:26The basic premise of this task involves
- 03:28an encoding period where spatial
- 03:29location is skewed by yellow circle.
- 03:31The delay period during which the
- 03:33yellow circle is disappeared and
- 03:35the participant has to maintain the
- 03:36location they previously saw the
- 03:38probe period in which a participant
- 03:39uses a joystick to move the Gray
- 03:42circle to indicate where they saw
- 03:43the yellow circle and what we care
- 03:45about is how closely they place
- 03:47that Gray probe circle to wear.
- 03:49The yellow circle was initially
- 03:50the closer the placement,
- 03:51the better the working memory,
- 03:53and here we call these working
- 03:55memory trials neutral trials.
- 03:56Since there's no incentive linked here.
- 03:59And in our version of the task we also
- 04:01have a control condition in which
- 04:02there is no working memory required.
- 04:04We call this the motor condition and
- 04:06hear the yellow circle reappears during
- 04:08the probe phase and participants
- 04:10simply move the Gray circle on
- 04:11top of the yellow circle.
- 04:13We then manipulated the tasks
- 04:14such that on some trials you can
- 04:16win or lose money depending on
- 04:17your working memory performance,
- 04:19the better the working memory performance,
- 04:20the more money one and the worse
- 04:22the working memory performance,
- 04:23the more money lost.
- 04:24So in these types of trials there
- 04:27is feedback given about how much
- 04:29money is won or lost.
- 04:30And we named this task meant tag
- 04:32which stands for motivational
- 04:33interactions with cognition.
- 04:35We use this task with functional
- 04:37magnetic resonance imaging or fMRI,
- 04:38and in a group of healthy young
- 04:40adults and all imaging, acquisition,
- 04:42and processing was in line with
- 04:45pipelines from the Human Connectome Project.
- 04:48The first thing that we noted was that
- 04:50working memory improves when there
- 04:52is the possibility of monetary gain or loss,
- 04:54and throughout the talk the color
- 04:56red will indicate working memory
- 04:57trials with monetary loss.
- 04:59The color green will indicate working
- 05:00memory trials with monetary gain,
- 05:02and yellow or neutral working
- 05:03memory trials without any money
- 05:05at stake on the Y axis is the main
- 05:07angular difference between where
- 05:08the location was kyoudan where the
- 05:10probe circle was placed.
- 05:12In the smaller the distance,
- 05:13the better the working memory and
- 05:15we see that the gain and loss trials
- 05:18have better working memory performance
- 05:20compared to the neutral working
- 05:22memory condition shown in yellow.
- 05:23We next tested where in the brain
- 05:25integrates working memory with
- 05:27incentives and so that brain regions
- 05:28that are involved in both working memory,
- 05:30an incentivized working memory are located
- 05:32in prefrontal and parietal cortices,
- 05:34and when we look at the bold signal or
- 05:36the neural signal within these regions,
- 05:38we see that these regions have greater neural
- 05:40signal when working memory is incentivized.
- 05:42So this is true for both monetary
- 05:44reward which is shown in green and
- 05:46monetary loss which is shown in red.
- 05:48Each of these, the green lines and
- 05:50the green bars and the red lines
- 05:52in the red bars rides above the
- 05:54neutral working memory condition.
- 05:55And yellow, so these posterior parietal
- 05:58and prefrontal regions both support
- 06:01working memory and have greater bold
- 06:03signal during incentivized working memory.
- 06:06Next, we wondered whether greater
- 06:08neural signal could actually be linked
- 06:10to better working memory performance.
- 06:12And we observed areas shown in blue that
- 06:14specifically had greater neural signal when
- 06:16working memory performance was better.
- 06:17These were a subset of the regions we saw
- 06:20earlier in encompass specific regions of
- 06:22the prefrontal and parietal cortices.
- 06:23When we looked closely at the neural signal,
- 06:26we did see that trials with better
- 06:28working memory performance as shown
- 06:29on the X axis was associated with
- 06:31greater neural signals.
- 06:32This suggested that these regions are
- 06:34key to linking the brain effects for the
- 06:37observed improvement in working memory.
- 06:39Finally,
- 06:40we wanted to know what happens
- 06:42when participants win,
- 06:43lose or avoid losing money based on
- 06:45their working memory performance
- 06:46and what we saw suggested that the
- 06:48impact of this was emotionally felt.
- 06:50We saw that winning money more money
- 06:52was associated with greater neural
- 06:54signal in brain regions that process
- 06:56pleasure such as the ventral striatum
- 06:58or nucleus accumbens shown in green.
- 07:00Avoiding losing money was also
- 07:02associated with pleasure and here
- 07:03greater neural signal was also seen in
- 07:05the ventral striatum shown in purple.
- 07:07So there was some overlap here.
- 07:09However,
- 07:10greater amounts of money lost
- 07:11was associated with.
- 07:12Greater neural signal in regions
- 07:14that process pain and disappointment,
- 07:16including the habenula periaqueductal
- 07:17Gray in the insula, as shown in red.
- 07:21Overall,
- 07:22this suggested clear engagement of
- 07:24participants in our task and that
- 07:26completing a cognitive task that was
- 07:29incentivized affected internal emotions.
- 07:31So from this work we concluded that
- 07:34motivation improves working memory by
- 07:35shaping neural signals in the posterior
- 07:37prefrontal and parietal cortices.
- 07:39The amount of money won,
- 07:41lost or avoided in lost was encoded by
- 07:43brain regions that process feelings,
- 07:45such as pleasure, pain,
- 07:47and disappointment.
- 07:48And our future directions will include
- 07:50two related studies.
- 07:51In the first will test these effects
- 07:53in adolescents with depression
- 07:54using a longitudinal study design,
- 07:56and in the second will use a
- 07:58large publicly available data set
- 08:00to understand how cognitive and
- 08:01motivational abilities in children
- 08:03may affect developmental trajectories
- 08:05in risk for psychiatric illness.
- 08:07Thank you,
- 08:08thank you for watching this talk
- 08:10and thank you to all who helped
- 08:12and supported this study,
- 08:13especially the research participants
- 08:14in Teacher Bitch Lab.
- 08:16At the end, three division,
- 08:17the Department of Psychiatry
- 08:19and Yell Child Study Center.
- 08:20Thank you.