1. Tonotopy during a Change Detection Task:
A Multi-Voxel Pattern Analysis Approach
Annika Linke
MRC Cognition and Brain Sciences Unit
MVPA Day
October 2009

2. Investigating Tonotopy
Tonotopy: low- to high frequency spatial gradient in anterolateral to posteromedial direction:
Aims:
Assessing tonotopy using fMRI:
possible but difficult due to low SNR
substantial inter-individual anatomical differences
Maintenance of auditory information?
frequency specific sustained firing in auditory cortex?

3. Task & Stimuli
Trial = sequence of two sounds – maintenance – sequence repeated
Task = same/different judgement
16 different pure tones (175 – 2794Hz)
Four frequency ranges comprising four tones each
Maintenance and ITI jittered (2/10s)

4. Methods high-resolution protocol (32 slices, TR=2150ms, 2.4x2.4x2.4mm)
continuous scanning
including temporal and parietal cortex,
sensorimotor regions, and parts of
ventrolateral prefrontal cortex
20 participants (12 completed two sessions)
3 blocks, 8 subblocks

5. Univariate Analysis FDR corrected at p<0.05 Encoding Maintenance
Response
FDR corrected at p<0.05
Activation
Deactivation

6. Univariate Analysis – Tonotopy
FWE corrected at p<0.005
encoding

7. MVPA Analysis
Correlation of patterns of activity across the four frequency ranges and stages of the STM task by extracting voxel-wise data from each ROI
unsmoothed data
Six ROIs
(superior temporal region representing auditory cortex, planum temporale, Heschel’s Gyrus, intraparietal sulcus (infIPS, supIPS, MD IPS))
Design Issues:
grouping of subblocks

8. Encoding – Auditory Cortex ROI
MVPA Analysis
Encoding – Auditory Cortex ROI
F F F F4 F1 F2 F3 F4

9. MVPA Analysis Auditory Cortex Heschel’s Gyrus Superior IPS “MD” IPS
Encoding
Maint.
Encoding
Maint.
Superior IPS
“MD” IPS
Encoding
Maint.
Adjust figure (no explanation, exchange left and right …)

10. Summary
Auditory cortex showed strong tonotopic organisation during the encoding phase of a change detection task
While sounds are maintained in short-term memory auditory cortex shows frequency specific suppression
Posterior parietal regions are involved in the encoding phase of ASTM