Maartje C. de Jong - PhD thesis

Neural mechanisms underlying temporal modulation of visual perception.

In Dutch:
Neurale mechanismen die ten grondslag liggen aan temporele modulatie van visuele perceptie.


[read] PDF of the thesis

[read] Article about my PhD thesis
by Netherlands Organisation for Scientific Research
(in Dutch)

[read] Article about my PhD research by Kennislink (in Dutch)

Klik voor een korte samenvatting in het Nederlands.
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The thesis describes investigations into the way our brain interprets ambiguous visual information. I investigated this topic using a variety of techniques, including fMRI, scalp & intracranial EEG and psychophysics.
A [video] of my PhD research translated into a dance has won the AAAS Dance Your PhD contest 2010 in the category Biology (click here for article in Science magazine).

Published chapters of this PhD thesis:

M.C. de Jong, R.J.M. Hendriks, M.J. Vansteensel, M. Raemaekers, F.A.J. Verstraten, N.F. Ramsey, C.J. Erkelens, F.S.S. Leijten, R. van Ee. Intracranial recordings of occipital cortex responses to illusory visual events. [submitted]
Perception of a constant visual stimulus can change spontaneously in case the stimulus is ambiguous, creating the illusion that the stimulus changed. We investigate whether such spontaneous changes in visual perception involve occipital brain regions specialized for processing visual information, despite the absence of concomitant changes in stimulation. Spontaneous perceptual changes during binocular rivalry or ambiguous structure-from-motion were compared with stimulus-induced perceptual changes that occurred in response to an actual stimulus change. Intracranial recordings from human occipital cortex revealed that spontaneous and stimulus-induced perceptual changes were both associated with an early transient increase in high- frequency power that was more spatially confined than a later transient decrease in low- frequency power. We suggest that the observed high- and low-frequency modulations relate to initiation and maintenance of a percept, respectively. Our results are compatible with the idea that spontaneous changes in perception originate from competitive interactions within visual neural networks.

M.C. de Jong, J.W. Brascamp, C. Kemner, R. van Ee, F.A.J. Verstraten. Implicit perceptual memory modulates early visual processing of ambiguous images. Journal of Neuroscience (2014), 34(30): 9970-9981.   [link]   [PDF]
The way we perceive the present visual environment is influenced by past visual experiences. Here we investigated the neural basis of such experience-dependency. We repeatedly presented human observers with an ambiguous visual stimulus (structure- from-motion) that can give rise to two distinct perceptual interpretations. Past visual experience is known to influence the perception of such stimuli. We recorded fast dynamics of neural activity shortly after stimulus onset using event-related electro- encephalography. The number of previous occurrences of a certain percept modulated early posterior brain activity starting as early as 50 ms after stimulus onset. This modulation developed across hundreds of percept repetitions, reflecting several minutes of accumulating perceptual experience. Importantly, there was no such modulation when the mere number of previous stimulus presentations was considered regardless of how they were perceived. This indicates that the effect depended on prior perception rather than prior visual input. The short latency and posterior scalp location of the effect suggest that perceptual history modified bottom-up stimulus processing in early visual cortex. We propose that bottom-up neural responses to a given visual presentation are shaped, in part, by feedback modulation that occurred during previous presentations, thus allowing these responses to be biased in light of prior perceptual decisions.

M.C. de Jong, Z. Kourtzi, R. van Ee. Perceptual experience modulates cortical circuits involved in visual awareness. European Journal of Neuroscience (2012), 36(12):3718-3731.   [link]   [PDF]
Successful interactions with the environment entail interpreting ambiguous sensory information. To address this challenge it has been suggested that the brain optimizes performance through experience. Here we used functional magnetic resonance imaging (fMRI) to investigate whether perceptual experience modulates the cortical circuits involved in visual awareness. Using ambiguous visual stimuli (binocular rivalry or ambiguous structure-from-motion) we were able to disentangle the co-occurring influences of stimulus repetition and perceptual repetition. For both types of ambiguous stimuli we observed that the mere repetition of the stimulus evoked an entirely different pattern of activity modulations than the repetition of a particular perceptual interpretation of the stimulus. Regarding stimulus repetition, decreased fMRI responses were evident during binocular rivalry but weaker during 3D-motion rivalry. Perceptual repetition, on the other hand, entailed increased activity in stimulus-specific visual brain regions: for binocular rivalry in the early visual regions and for ambiguous structure- from-motion in both early as well as higher visual regions. This indicates that the repeated activation of a visual network mediating a particular percept facilitated its later re-activation. Perceptual repetition was also associated with a response change in the parietal cortex that was similar for both types of ambiguous stimuli, possibly relating to the temporal integration of perceptual information. We suggest that perceptual repetition was associated with a facilitation of neural activity within and between percept-specific visual networks and parietal networks involved in the temporal integration of perceptual information, thereby enhancing the stability of previously experienced percepts.

M.C. de Jong, T. Knapen, R. van Ee. Opposite influence of perceptual memory on initial and prolonged perception of sensory ambiguity. PLoS ONE (2012), 7(1):e30595.   [link]   [PDF]
Observers continually make unconscious inferences about the state of the world based on ambiguous sensory information. This process of perceptual decision-making may be optimized by learning from experience. We investigated the influence of previous perceptual experience on the interpretation of ambiguous visual information. Observers were pre-exposed to a perceptually stabilized sequence of an ambiguous structure- from-motion stimulus by means of intermittent presentation. At the subsequent re- appearance of the same ambiguous stimulus perception was initially biased toward the previously stabilized perceptual interpretation. However, prolonged viewing revealed a bias toward the alternative perceptual interpretation. The prevalence of the alternative percept during ongoing viewing was largely due to increased durations of this percept, as there was no reliable decrease in the durations of the pre-exposed percept. Moreover, the duration of the alternative percept was modulated by the specific characteristics of the pre-exposure, whereas the durations of the pre-exposed percept were not. The increase in duration of the alternative percept was larger when the pre-exposure had lasted longer and was larger after ambiguous pre-exposure than after unambiguous pre-exposure. Using a binocular rivalry stimulus we found analogous perceptual biases, while pre-exposure did not affect eye-bias. We conclude that previously perceived interpretations dominate at the onset of ambiguous sensory information, whereas alternative interpretations dominate prolonged viewing. Thus, at first instance ambiguous information seems to be judged using familiar percepts, while re-evaluation later on allows for alternative interpretations.