Research - Other
In addition to the ERC project on naturalistic vision, we actively pursue two further research lines, one investigating category specificity in the ventral stream, and the other investigating factors determining object visibility. There are obviously many links between all three projects. For example, objects that are selectively represented in ventral temporal cortex, such as bodies and faces, are detected more quickly. Similarly, real-world spatial regularities contribute to the efficiency of naturalistic vision partly by facilitating stimulus visibility. Finally, understanding responses in scene-selective cortex is relevant both for natural scene perception and for principles of ventral stream organization.
Research line: Category specificity in the ventral stream
Evidence for category specificity in the organization of human perception and cognition, and in the organization of the ventral stream, stretches back to the beginnings of modern cognitive neuroscience. Classic neuropsychological patient studies revealed striking dissociations in the performance of patients on judgments about living and non-living objects, as well as more selective deficits relating to specific categories such as human body parts.
The advent of functional neuroimaging built on these findings by exploring the topography and properties of visual object representations in healthy participants. Large-scale patterns of activity that span the ventral temporal cortex distinguish inanimate from animate categories. Several focal regions exhibit strong and highly selective responses to more-specific categories, such as scenes, faces, tools, body parts and words. Numerous fMRI studies have established the regular and consistent arrangement of such regions, which collectively span the ventral and lateral posterior surface of the brain and extend from the occipital cortex deep into the medial temporal cortex. The selectivity and functional significance of some of these regions has been further demonstrated by brain stimulation methods (such as transcranial magnetic stimulation) that reveal selective behavioral impairments - for example in making judgments about faces, objects, bodies, scenes or tools - when normal neural activity is disrupted.
That these regions respond selectively to their preferred category, relative to items of other kinds, is widely accepted; however, debates continue over nearly every other conceivable basic question about these regions. How do they contribute to behaviour? Why do they consistently fall in the same cortical territory across individuals? How are they connected? How do they develop? Ongoing work in the lab addresses these questions. In particular, we study what these regions represent about their preferred category, and how these representations contribute - as parts of broader domain-specific networks (figure below) - to achieving real-world goals such as navigation, reading, recognizing conspecifics, using tools, and understanding others’ actions and emotions.
Examples of recent research:
- Thorat S, Proklova D, Peelen MV (2019). The nature of the animacy organization in human ventral temporal cortex. eLife 8:e47142
- Proklova D, Kaiser D, Peelen MV (2019). MEG sensor patterns reflect perceptual but not categorical similarity of animate and inanimate objects. NeuroImage 193:167-177
- Bracci S, Caramazza A, Peelen MV (2018). View-invariant representation of hand postures in the human lateral occipitotemporal cortex. NeuroImage 181:446-452
- Kaiser D, Azzalini DC, Peelen MV (2016). Shape-independent object category responses revealed by MEG and fMRI decoding. J Neurophysiol 115:2246-2250
- Proklova D, Kaiser D, Peelen MV (2016). Disentangling representations of object shape and object category in human visual cortex: the animate-inanimate distinction. J Cogn Neurosci
- Bracci S, Caramazza A, Peelen MV (2015). Representational similarity of body parts in human occipitotemporal cortex. J Neurosci 35:12977-12985
- Peelen MV, Bracci S, Lu X, He C, Caramazza A, Bi Y (2013). Tool selectivity in left occipitotemporal cortex develops without vision. J Cogn Neurosci 25:1225-1234
- Bracci S, Peelen MV (2013). Body and object effectors: the organization of object representations in high-level visual cortex reflects body-object interactions. J Neurosci 33:18247-258
For reviews, see:
- Peelen MV, Downing PE (2017). Category selectivity in human visual cortex: Beyond visual object recognition. Neuropsychologia 105:177-183
- Downing PE, Peelen MV (2016). Body selectivity in occipitotemporal cortex: causal evidence. Neuropsychologia 83:138-148
Research line: Factors determining object visibility
What determines how quickly we become aware of the presence of an object in our environment? While the visibility (or detectability) of a visual stimulus is primarily determined by its physical characteristics, such as its luminance contrast relative to other elements in the visual field (bottom-up saliency), several other factors also play a role. In our research, we investigate how expectation, attention, knowledge, and experience influence how quickly observers detect or localize objects. For example, we found that the simple detection of an object (on a uniform background) is influenced by the observer’s expectations and attentional set (Stein & Peelen, 2015). Extensive visual experience with object configurations (e.g., lamp above table; Stein et al., 2015) and object categories (e.g., faces and bodies; Stein et al., 2012; 2016) also influences how quickly participants become aware of an object. Emotional faces, and objects associated with rewarding outcomes, also have an advantage in being noticed (Peelen et al., 2009; Hickey et al., 2015), though great care is needed to distinguish between high-level aspects, such as social or emotional significance, and co-varying low-level visual properties (Gayet et al., 2019; Stein et al., 2018).
Beyond revealing factors that influence detectability, we are also interested in determining what drives these differences; specifically, do differences in detectability reflect differences in unconscious processing? To address this question, in collaboration with Timo Stein, we use behavioural paradigms, such as continuous flash suppression and backward masking, in combination with tasks probing detection and awareness of stimulus manipulations.
Examples of recent research:
- Gayet S, Stein T, Peelen MV (2019). The danger of interpreting detection differences between image categories. Emotion 19:928-932
- Stein T, Awad D, Gayet S, Peelen MV (2018). Unconscious processing of facial dominance: The role of low-level factors in access to awareness. J Exp Psychol Gen. 147:e1-e13
- Stein T, Reeder RR, Peelen MV (2016). Privileged access to awareness for faces and objects of expertise. J Exp Psychol Hum Percept Perform 42:788-98
- Stein T, Peelen MV (2015). Content-specific expectations enhance stimulus detectability by increasing perceptual sensitivity. J Exp Psychol Gen 144:1089-104
- Hickey C, Kaiser D, Peelen MV (2015). Reward guides attention to object categories in real-world scenes. J Exp Psychol Gen 144:264-73
- Stein T, Kaiser D, Peelen MV (2015). Interobject grouping facilitates visual awareness. J Vis 15:10
- Stein T, Sterzer P, Peelen MV (2012). Privileged detection of conspecifics: evidence from inversion effects during continuous flash suppression. Cognition 125:64-79
For reviews, see:
- Kaiser D, Quek GL, Cichy RM, Peelen MV (2019). Object Vision in a Structured World. Trends Cogn Sci 23:672-685
- Battistoni E, Stein T, Peelen MV (2017). Preparatory attention in visual cortex. Ann N Y Acad Sci 1396:92-107