INTRODUCTION

Posterior cortical atrophy (PCA) is a neurodegenerative syndrome marked by progressive visuospatial and perceptual impairments (Goldstein et. al., 2018). While resting-state studies have reported oscillatory alterations in PCA, less is known about how event-related oscillatory responses are affected during sensory processing. Auditory and visual oddball paradigms offer a robust framework for examining oscillatory activity related to attention and stimulus evaluation. This study compared oscillatory power and phase-locking responses between PCA patients and healthy controls (HC) to identify frequency-specific differences across auditory and visual modalities.

METHOD

Demographically-matched 14 PCApatients and 14 HC

EEG was recorded on Brain VisionRecorder

Auditory and Visual oddball tasks(40target/80nontarget)

Mental counting for target

Event-related spectral power (ERSP)and inter-trial coherence (ITC) 

Included electrodes:F3,Fz,F4,C3,Cz,C4,P3,Pz,P4,O1,Oz,O2

1.5-15 Hz frequency

−3000 to 3000ms time window, 

Cluster-Based Permutation Test(Fieldtrip)

Delta (1,5-4 Hz,0-1000ms), Theta(4-7 Hz,0-600ms), Alpha (8-13Hz,0-500ms) 

RESULTS

There was a significant cluster in delta ITC in 146-776ms timewindow, including posterior electrodes(P3,Pz,P4,O1,Oz,O2) at1.5-3.33Hz frequency band (p=.041). Another significant cluster in 0-108ms time range was found inAlpha ITC (p=.049). The cluster included F3, Fz, F4, C3, Cz, C4,P3, Pz, P4 in 10.33-13Hz. There were significant main group effects in visual delta and alpha power. The PCA group showed reduced visual delta total power in 250-536ms, whilst visual alpha total power increased in 272-500ms at frontal, central, parietal, and occipital sites.

CONCLUSION

This is the first study to show that modality-specific differences in phase locking of delta and alpha frequency bands during auditory and visual oddball processing are reduced in posterior cortical atrophy.