PseudoSloan: A perimetric-complexity and area-controlled font for vision and reading research.

Artificial orthographies have long been used in studies of verbal learning and reading. These orthographies, also known as pseudo or false fonts, are designed to match the letters of an existing alphabet on a range of visual features, isolating effects of orthography from those owing to lexical processing. In a parallel line of research, there has been much interest in the design of optotypes for measuring visual acuity that have good properties in terms of character complexity and graceful degradation under blur.

Distinct neural sources underlying visual word form processing as revealed by steady state visual evoked potentials (SSVEP).

EEG has been central to investigations of the time course of various neural functions underpinning visual word recognition. Recently the steady-state visual evoked potential (SSVEP) paradigm has been increasingly adopted for word recognition studies due to its high signal-to-noise ratio. Such studies, however, have been typically framed around a single source in the left ventral occipitotemporal cortex (vOT).

Aging of human alpha rhythm.

Alpha rhythm (AR) changes are the most pronounced electroencephalogram phenomenon in the aging brain. We analyzed them based on the inherent AR structure obtained by parallel factor analysis decomposition in the cortical source space. AR showed a stable multicomponent structure in 78% of sixty 20- to 81-year-old healthy adults.

Author Correction: Fine Structure of Posterior Alpha Rhythm in Human EEG: Frequency Components, Their Cortical Sources, and Temporal Behavior.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

Fine Structure of Posterior Alpha Rhythm in Human EEG: Frequency Components, Their Cortical Sources, and Temporal Behavior.

Heterogeneity of the posterior alpha rhythm (AR) is a widely assumed but rarely tested phenomenon. We decomposed the posterior AR in the cortical source space with a 3-way PARAFAC technique, taking into account the spatial, frequency, and temporal aspects of mid-density EEG. We found a multicomponent AR structure in 90% of a group of 29 healthy adults.

Figure-ground interaction in the human visual cortex.

Discontinuities in feature maps serve as important cues for the location of object boundaries. Here we used multi-input nonlinear analysis methods and EEG source imaging to assess the role of several different boundary cues in visual scene segmentation. Synthetic figure/ground displays portraying a circular figure region were defined solely by differences in the temporal frequency of the figure and background regions in the limiting case and by the addition of orientation or relative alignment cues in other cases.

Cue-invariant networks for figure and background processing in human visual cortex.

Lateral occipital cortical areas are involved in the perception of objects, but it is not clear how these areas interact with first tier visual areas. Using synthetic images portraying a simple texture-defined figure and an electrophysiological paradigm that allows us to monitor cortical responses to figure and background regions separately, we found distinct neuronal networks responsible for the processing of each region. The figure region of our displays was tagged with one temporal frequency (3.

Neural correlates of shape-from-shading.

Visual evoked potentials were recorded during presentation of a single stimulus that generated bi-stable perceptual alternation between two different three-dimensional percepts. One interpretation (asymmetric) changed depth structure from flat to corrugated in depth and the other (symmetric) had the appearance of a flat surface translating laterally behind a set of apertures. Responses during perception of the asymmetric three-dimensional structure contained larger negative components than did responses during perception of the symmetric three-dimensional structure.

Event-related potentials show configural specificity of global form processing.

Glass patterns are a type of moiré created when a random-dot field is overlaid with a rotated, translated or dilated copy. The overall form of the moiré cannot be detected using local processing mechanisms, and because of this, Glass patterns are useful probes of global form processing. Here, we use event-related potentials to show that certain global organizations (concentric structure created by rotation and radial structure produced by dilation) produce much larger brain responses than others (linear structure created by translation).

Temporal dynamics of the human response to symmetry.

Symmetry is a highly salient feature of animals, plants, and the constructed environment. Although the perceptual phenomenology of symmetry processing is well understood, little is known about the underlying neural mechanisms. Here we use visual evoked potentials to measure the time course of neural events associated with the extraction of symmetry in random dot fields.