Youngson Cho, MD, PhD: Motivation improves working memory by shaping neural signals in the prefrontal and parietal cortex

December 01, 2020

Information

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.