Research Areas

Temporal integration windows in perception
Sensory input is continuous, as is our naïve impression of the world. In contrast, sensory systems must combine information over space and time in order to parse this input into meaningful units like moving objects, events and scenes. As part of the CoPeST project (link), we have been working to identify the different temporal integration windows underlying perception and uncover the brain mechanisms that underlie these processes.
Representative publications:
Drewes J, Zhu W, Melcher D (2015) Dense sampling reveals behavioral oscillations in rapid visual categorization. Scientific Reports, in press.
Wutz A, Shukla A, Bapi RS, Melcher D (2015), Expansion and Compression of Time Correlate with Information Processing in an Enumeration Task, PLoS One, Vol.10(8).
Drewes J, Zhu W, Melcher D (2014). Dissociation Between Spatial and Temporal Integration Mechanisms in Vernier Fusion. Vision Research.
Fairhall S.L., Albi A., Melcher D. (2014). Temporal Integration Windows for Naturalistic Visual Sequences. PLOS One.
Wutz A., Melcher D.P.(2014). The temporal window of individuation limits visual capacity. Perception Science in Frontiers in Psychology.
Wutz A., Weisz N., Braun C. & Melcher D. (2014). Temporal windows in visual processing: 'Pre-stimulus brain state' and 'post-stimulus phase reset' segregate visual transients on different temporal scales. Journal of Neuroscience, 34(4), 1554-65.

Visual stability

We make an average of 3 or 4 saccadic eye movements every second. Each eye movement creates motion across the retina and changes the retinal position of objects. One fundamental mystery of perception is how we keep track of the location, identity and properties of objects despite these dramatic changes to the visual input. Our group has been at the forefront of efforts to investigate the role of active mechanisms (predictive changes in way that visual input is turned into percepts that take into account eye movements) in visual stability. We are currently doing behavioral and neuroimaging studies to better elucidate the underlying mechanisms.

Representative publications:

Melcher, D. (2011) Visual stability. Philosophical Transactions of the Royal Society B., 366, 468-475.

De Pisapia, N., Kaunitz, L. & Melcher, D. (2010) Backward masking and unmasking across saccadic eye movements. Current Biology, 20, 613-7.

Melcher, D. & Colby, C.L. (2008) Trans-saccadic perception. Trends in Cognitive Sciences, 12, 466-73.

Melcher, D. (2007) Predictive re-mapping of visual features precedes saccadic eye movements. Nature Neuroscience, 10, 903-7.

Melcher, D. & Morrone, M.C. (2003) Spatiotopic temporal integration of visual motion across saccadic eye movements. Nature Neuroscience, 6, 877-881.

Melcher, D. (2001) Persistence of visual memory for scenes. Nature, 412, 401.

For a nice demonstration of stable perception of an object/event across a saccade, see:

Object individuation

In his seminal article, George Miller noted that there is a "magic number" of chunks which we can process at one time. When we look at a crowded scene, like a dinner table, the number of items which we can select as unique individuals is limited to about 3 to 5 items. Our goal is to explain the "magic number" for object individuation, with a biologically-plausible explanation rather than one that relies on "magic" or post hoc explanations. We have recently shown how capacity limits emerge naturally out of the spatial and temporal properties of object maps in parietal cortex.

Representative publications:

Knops A, Piazza M, Sengupta R, Eger E, Melcher D (2014). A shared, flexible neural map architecture reflects capacity limits in both visual short term memory and enumeration. Journal of Neuroscience, in press.

Wutz A., Weisz N., Braun C. & Melcher D. (2014). Temporal windows in visual processing: 'Pre-stimulus brain state' and 'post-stimulus phase reset' segregate visual transients on different temporal scales. Journal of Neuroscience, 34(4), 1554-65.

Wutz, A. & Melcher, D. (2013) Temporal buffering and visual capacity: the time course of object formation underlies capacity limits in visual cognition. Attention, Perception & Psychophysics, 75(5): 921-933.

Melcher, D. & Piazza, M. (2011) The role of attentional priority and saliency in determining capacity limits in enumeration and visual working memory. PLoS One, 6(12) : e29296

Piazza M, Fumarola A, Chinello A, Melcher D. (2011) Subitizing reflects visuo- spatial object individuation capacity. Cognition, 121(1):147-53.

Visual memory

What is the nature of what we remember while looking around complex, realistic scenes? We are studying memory for photographs and movies, to better understand where we look and what we remember.

Representative publications:

Subramanian R., Shankar D., Sebe N. & Melcher D. (2014) Emotion modulates eye movement patterns and subsequent memory for the gist and details of movie scenes. Journal of Vision, in press.

Melcher, D. (2010) Accumulating and remembering the details of neutral and emotional scenes. Perception, 39(8), 1011-1025.

Tatler, B. & Melcher, D. (2007) Pictures in mind: Initial encoding of object properties varies with the realism of the scene stimulus. Perception, 36, 1715-29.

Melcher, D. (2006) Accumulation and persistence of memory for natural scenes. Journal of Vision, 6, 8-17.

Melcher, D. (2001) Persistence of visual memory for scenes. Nature, 412, 401.

Melcher, D. & Kowler, E. (2001) Visual scene memory and the guidance of saccadic eye movements. Vision Research, 41, 3597-3611.

Attention and awareness

Paying attention to something-- selecting a particular object, location, feature or time period out of all the possible ones-- changes the way that we perceive the world. We are investigating the mechanisms of attention, the role of awareness in guiding behavior, and the interaction between attention and awareness. For more information, see also the ATTEND Project.

Representative publications:

Kaunitz, L., Fracasso, A., Lingnau, A. & Melcher D. (2013) Non-conscious processing of motion coherence can boost conscious access. PLoS One. 8(4):e60787.

Kaunitz, L.N., Fracasso, A. & Melcher, D. (2011) Unseen complex motion is modulated by attention and generates a visual aftereffect. Journal of Vision, 11(13), 10. DOI: 10.1167/11.13.10.

Alais, D. & Melcher, D. (2007) Strength and coherence of binocular rivalry depends on shared stimulus complexity. Vision Research, 47, 269-79.

Melcher, D. (2005) When the brain doesn’t see eye to eye. Trends in Cognitive Science, 9, 216-217.

Melcher, D., Papathomas, T.V. & Vidnyanszky, Z. (2005) Implicit attentional selection of bound visual features. Neuron, 46, 723-729.

Neuroscience and the Arts

This research interest has several aspects. One focus is to use an experimental approach to test claims by artists and critics about how a particular artefact influences the observer. Second, we are applying recent findings in cognitive neuroscience to classic problems in art history. Third, we are investigating the underpinnings of “aesthetic” responses to various types of stimuli.

Representative publications:

Bacci, F. and Melcher, D., Editors (2011) Art and the Senses, Oxford University Press. ISBN13: 9780199230600; ISBN10: 0199230609 (now in its second printing in a paperback edition)

Melcher, D. & Bacci F. (2013) Perception of emotion in abstract artworks: a multidisciplinary approach. Progress in Brain Research, 204:191-216.

Melcher, D. & Bacci, F. (2008) The visual system as a constraint on the survival and success of specific artworks. Spatial Vision (special issue on Vision and Art), 21, 347-62.

Melcher, D. & Wade, N. (2006) Cave art interpretation II. Perception, 35, 719-22. Wade, N. & Melcher, D. (2006) Cave art interpretation I. Perception, 35, 577-80.

Melcher, D. & Bacci, F. (2003) A moment’s monument: The central vision of Italian sculptor Medardo Rosso (1858-1928). Perception, 32, 1051-8.