ada leung phd, benson ng bsc department of occupational
Post on 05-Dec-2021
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Outline of the talk Neural mechanism of auditory working memory Neuroplasticity resulting from auditory working
memory – One case Cross-modal plasticity – Two cases
Working memory• Working memory refers to the ability to temporarily store
and manipulate information in a brief period of time.
• Dual-pathway model of auditory processing– Sound identity: ventral stream– Sound location: dorsal stream
Arnott et al., 2001
Auditory working memory1. Determine neural mechanisms of auditory working
memory
2. Any specific area(s) that is(are) responsible to location working memory load and category working memory load?
Participants 16 right handed, healthy young adults
9 women and 7 men
Mean age = 25.19 + 5.13 years
Normal hearing (pure-tone thresholds with normal limits for frequencies ranging from 250 and 8000 Hz)
Stimuli 0 degree
-90 degree (left)90 degree (right)
Humane.g.- Laugh- Cough- Cry
Musice.g.- Flute- Piano- Clarinet
Noisee.g.- Dog bark- Bird chirping- Door locking
• 1005ms duration, • digitally generated with a 16-bit resolution and a 12.21 kHz sampling rate,• passed through a digital-to-analog RP2 converter (Tucker-Davis Technology),• delivered at about 88dB via fMRI compatible headphone to suppress noise by 25 dB
Working memory task Location: 1-back, 2-back
RHuman
LNoise
LHuman
RHuman
LMusic
(1-back Target) (2-back Target)Instruction: L1 or L2 (10s)
Example of one block (20 stimuli)
Button press Button press
Working memory task Location: 1-back, 2-back
RHuman
LNoise
LHuman
RHuman
LMusic
(1-back Target) (2-back Target)
• Category: 1-back, 2-back
Instruction: L1 or L2 (10s)
Example of one block (20 stimuli)
RNoise
LNoise
LHuman
RMusic
RHuman
(1-back Target) (2-back Target)Instruction: C1 or C2
Example of one block (20 stimuli)
Button press Button press
Button pressButton press
Design (Pseudo-randomized)Block1 Block2 Block 3 Block 4 Block 5 Block 6
30s 30s 30s 30s 30s 30s
End of Scan464s(7m44s)
Begin scan
44s 40s 40s 40s 40s 40s 40s
•Four conditions:•location 1-back (L1)•location 2-back (L2)•category 1-back(C1) •category 2-back (C2)
•No. of blocks = 9
•Total no. of targets for each task = 45
Results - Behavioral
00.20.40.60.8
1
l1 l2 c1 c2
Hit
rate
00.020.040.060.08
0.10.12
l1 l2 c1 c2
Fals
e al
arm
rate
800850900950
100010501100
l1 l2 c1 c2
RT
for h
it ra
te
95010001050110011501200
l1 l2 c1 c2
RT
for f
a ra
te
Load: F(1,15)=56.30, p< 0.001 Load: F(1,15)=12.45, p< 0.005
Load: F(1,13)=5.71, p< 0.05Task: F(1,15)=11.32, p< 0.005Load: F(1,15)=11.83, p< 0.005
Results Main effects and interaction effects
All activations are significant at corrected p < 0.05 and > 196 µl.
Results Peak voxel activity at Right IPL
Discussion (Leung & Alain, 2011)
Frontal-parietal activation for auditory working memory
Two sub-regions in the parietal cortex are modulated differentially by working memory load:
Anterior ventromedial region – location load Posterior dorsolateral region – category load
Research questionsInvestigate the neural plastic changes in the “what”network after a course of auditory working memory training.
Training-induced neural activity on the “what”network – a case illustration
Mr. KB, male Age: 39 First stroke at March 19, 2011 Acute right subdural hematoma Multiple cortical infarcts, bilateral PCA, bilateral ACA.
Lesion involves right prefrontal and parietal cortices.
Cortical blindness Brain surgery: craniotomy
Demographic information Audiogram: less than 20 dB for 500 to 4000 Hz. WMS-II (Wechsler Memory Scale):
Letter-number sequencing: 5/21 Digit span forward: 9/16
Digit span backward: 6/14 Recognition memory (story): 15/30
MoCA (Montreal Cognitive Assessment): 10/22
The training 7 weeks of practice on auditory working memory tasks Stimuli are digits and letters Practice protocol:
5 days a week, 30 minutes a day. Only 1- and 2-back tasks in week 1. 1-, 2- and 3-back tasks in weeks 2 to 7 Total number of exposure to 1-, 2-, and 3- backs are the same.
Pre- and post- fMRI testing 9 blocks of 1- and 2-back each 20 stimuli per block Stimuli are digits and letters
Behavioral results - fMRI
Hit Miss False alarm
1-back 37/46 (80%) 9/46 (20%) 1/134
2-back 30/46 (65%) 16/46 (35%) 6/134
Hit Miss False alarm
1-back 42/46 (91%) 4/46 (9%) 0/134
2-back 45/46 (98%) 1/46 (2%) 4/134
Pre-training scan
Post-training scan
Discussion (Leung et al., 2014)
Continuous practice of an auditory working memory task for 7 weeks as training induces:
Decrease of overall activation at the fronto-parietal network
Activities at adjacent regions are maintained Maintained neural activities at the precuneus
(posterior-lateral)
Activation decrease Increase in neural efficiency
Reflect sharpening of the response in a particular neural network so that fewer neurons now fire in response to a particular task or stimulus (Poldrack, 2000)
Typically observed in cognitive tasks N-back task (Hempel et al., 2004) Tower of London task (Beauchamp et al., 2003) Tests of verbal free recall (Andreasen et al., 1995)
Client 1 a 38 year-old man
Right CVA involving the MCA
Restricted diffusion to the right parietal lobe, superior right frontal lobe and the anterior portion of the anterior medial frontal lobe
Enlargement of the lateral ventricles
19 years prior to the study
Client 1 Completed a course of rehabilitative program for
improving his motor skills
Did not receive any training for cognitive remediation
Completed an undergraduate degree and was working full time in a business firm
Continues to report cognitive deficits that are noticeable during work and home life
Client 2
a 37 year-old woman
Right CVA involving the MCA three years ago
had an episode of cerebral infarction in the brain-stem during her hospitalized for her stroke
Client 2 Completed a course of cognitive training in an
outpatient clinic
Completed an undergraduate degree and was working full time in a private company
Feels fatigue easily
Continues to have difficulties with memory and concentration that affect her performance at work
Distribution of n-back tasksWeek 1 Week 2 Week 3 Week 4 Week 5 Week 6
1-Back 13 9 7 6 4 2
2-Back 5 7 7 7 7 6
3-Back 2 4 6 7 9 12
Neuropsychological test scoresClient 1 Client 2
Pre Post Pre Post
RAVLT a
Learning (trial 5 – 1) 5 5 6 7
Interference 5 6 4 8
Trial 6 6 10 13 14
Delayed recall 5 9 13 14
50-word recognition 11 14 14 15
SDMT b
Accuracy (correct – errors) 46 45 35 39
CFQ c 37 44 46 36
a Rey Auditory Verbal Learning Test b Symbol Digit Modalities Test c Cognitive Failure Questionnaire
Training effectsClient 1 Client 2
Auditory Visual Auditory Visual
1-b 2-b 1-b 2-b 1-b 2-b 1-b 2-b
Mean A1* 3.32 3.19 4.51 2.92 4.18 3.04 2.89 2.04
Mean A2* 3.43 3.05 3.64 4.24 4.23 3.90 4.03 3.88
Mean A2 – Mean A1* 0.11 -0.14 -0.87 1.32 0.05 0.86 1.14 1.84
SD A1* 0.42 0.62 0.85 0.49 0.79 0.11 0.74 0.48
Cohen’s d 0.27 -0.23 -1.02 2.68 0.06 7.90 1.54 3.83
Average Cohen’s d 0.02 0.83 3.98 2.69
Note: Mean A1 reflects the average of task performance in the pre-training testing and mean A2 reflects the average of task performance in the post-training measurement. Average Cohen’s d reflects the weighted mean of 1-back and 2-back task performance for the pre-training and post-training testing. 1-b = 1-back task; 2-b = 2-back task; all values represent d’.
Discussion (Leung & Ng, 2015)
Client 1 showed minimal improvement on auditory and visual n-back tasks and no improvement on SDMT, and CFQ.
Client 2 demonstrated substantial improvement on all n-back tasks and behaviourial tests.
Client 2 substantial activation in the frontal-parietal network before
training, which subsided after training
extensive activations in multiple cortices including the occipital and frontal-parietal regions in the untrained visual tasks during the post-training testing
Discussion Cross-modal plasticity
General pattern: Activation decrease in frontal and parietal regions in the post-training
testing
Consistent with previous working memory training studies on healthy young adults (e.g., Garaven et al., 2000)
Increased neural efficiency and the use of more precise neuronal and functional circuits (Kelly & Garaven, 2005; Takeuchi et al., 2010)
Specific pattern:
Intact frontal-parietal network for processing working memory
Promoted a favourable condition for cross-modal transfer to take place, which increased the client’s ability to succeed in other cognitive tests and perception of cognitive gains
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