Research Initiatives in the Lab

Spontaneous brain activity and perceptual decision making

Why does our perception of the same physical stimulus vary across repeated presentations? We have evidence [1,2] that incoming sensory information is processed differently depending on the state of ongoing neural oscillations when the stimulus arrives. We think that whether or not a stimulus is subjectively perceived [3], depends on stimulus properties as well as spontaneous brain activity. We aim to investigate the specific mechanisms by which different kinds of ongoing brain activity relate to different aspects of our perceptual experience.

Samaha, Gosseries, & Postle (2017) Journal of Neuroscience
Samaha, Switzky, & Postle (2019) Journal of Vision

Computational study of subjective reports of visual awareness

To understand what visual consciousness is good for and how it is related to brain activity, we argue that one must ensure that differences in brain activity or behavior under varying conditions of awareness do not simply reflect concomitant changes in attention or task performance [4]. Along with others, we have developed psychophysical paradigms and computational models [5,6] that can produce and explain dissociations between subjective measures of visual awareness (e.g., confidence, visibility) and objective task performance. Now we can ask, Does subjective awareness benefit other cognitive processes such as working memory or decision making?

Neural substrates of top-down control over sensory processing

Oscillations are a prominent feature of neural activity in sensory cortex. We have evidence that "top-down" factors such as spatial attention [7], temporal attention [8], expectations [9], and task demands [10] may influence perception by biasing oscillatory brain activity in the visual system in anticipation of stimulus processing.

Wutz, Melcher, & Samaha (2018) Proceedings of the National Academy of Sciences
Samaha & Postle (2015) Current Biology

Perceptual consequences of thalamocortical oscillations

Brain rhythms in the alpha range (8-13 Hz) emerge from interactions between the thalamus and visual cortex. Do these oscillations impact ongoing perceptual processing? We have found that alpha frequency may relate to the temporal resolution of our visual perception, such that individuals with a higher peak frequency have higher temporal resolution [11]. This could have consequences for our understanding of how perceptual processing is integrated across time. Do other properties of thalamocortical rhythms influence other aspects of perception?