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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - CONTEXTVISION (Visual perception in Context)

Teaser

Summary

Everything occurs in a context. We see a car in the context of a street scene and a stove in the context of a kitchen. Context greatly helps the processing of individual objects. Surprisingly however, context hardly plays a role in most models of visual perception, which treat perception as a largely bottom-up categorization process.
In this research proposal, we examine how context changes the cortical computations that give rise to visual perception, focusing on contextual modulations in space and time. Moreover, we aim to translate this research to a clinical condition that is marked by aberrant context modulations in perception: Autism Spectrum Disorder (ASD). This integrative approach has the potential to significantly advance theoretical models of perception, based on underlying neurobiology, and underline the importance of context for understanding perception. Moreover, the knowledge gleaned can have significant clinical impact, helping us to better understand the pathophysiology of ASD.

Work performed

Team member Ekman has shown temporally precise and spatially specific prediction signals in the primary visual cortex (Ekman et al, Nat Comm 2017). The pre-stimulus nature of these prediction signals was verified in a separate study (Kok, Mostert, de Lange PNAS 2017). These predictions appear to attenuate neural activity for incoming information (Richter, Ekman, de Lange J Neurosci 2018).
Team member Fritsche has elucidated temporal context effects (Fritsche, Mostert, de Lange Curr Biol 2017), which can be opposite at different stages of the perceptual decision-making process.
Furthermore, we have found some support for the hypothesis stipulated in WP3 that predictions have distinct sensory consequences in individuals with ASD (Utzerath, Schmits, Buitelaar, de Lange Cortex 2018). Following a positive Ethics evaluation, Ella Bosch is currently examining similar prediction effects in temporal context. It is anticipated that data collection of this project will be finished by the end of 2018.
Alongside these core projects, team member Perez-Bellido has also assisted in two studies of multisensory contextual modulations of perception, culminating in two publications (Luettke et al 2016, Luettke, Perez-Bellido et al 2018).

Final results

The fMRI study of time-compressed preplay of anticipated events in human primary visual cortex (Ekman et al, Nat Comm 2017) employed a highly novel and unconventional use of fMRI imaging, employing ultra-high temporal resolution (TR=88 ms), alongside high spatial resolution in a restricted part of the brain. Usually fMRI measurements use TRs between 1500-3000 ms. This allowed us to temporally and spatially track anticipatory activity. This methodological innovation has generated a lot of interest within the field, and is being followed up on by several labs.
The MEG study of pre-stimulus templates (Kok et al, PNAS 2017) used innovative forward encoding models. All data and code have been made freely available, and the methods are being re-used by other researchers in the field.

There are still several exciting projects tof which the data are currently being collected or analyzed. Bosch is currently finalizing data acquistion on one of the WP3 projects, investigating possible alterations of temporal context in ASD. We also anticipate to examine the neural correlates of these alterations within the context of an MEG study. Ekman is following up on the temporal preplay activity, examining its probabilitistic characteristics. Furthermore, he is further examining the influence of task set on the contextual effects observed earlier.