The distributed human neural system for face perception

Face perception, perhaps the most highly developed visual skill in humans, is mediated by a distributed neural system in humans that is comprised of multiple, bilateral regions. We propose a model for the organization of this system that emphasizes a distinction between the representation of invariant and changeable aspects of faces. The representation of invariant aspects of faces underlies the recognition of individuals, whereas the representation of changeable aspects of faces, such as eye gaze, expression, and lip movement, underlies the perception of information that facilitates social communication. The model is also hierarchical insofar as it is divided into a core system and an extended system. The core system is comprised of occipitotemporal regions in extrastriate visual cortex that mediate the visual analysis of faces. In the core system, the representation of invariant aspects is mediated more by the face-responsive region in the fusiform gyrus, whereas the representation of changeable aspects is mediated more by the face-responsive region in the superior temporal sulcus. The extended system is comprised of regions from neural systems for other cognitive functions that can be recruited to act in concert with the regions in the core system to extract meaning from faces.     

SuperLab: General-purpose Macintosh software for human experimental psychology and psychological testing

SuperLab is a general-purpose psychology testing package for the Macintosh. SuperLab presents static visual and auditory stimuli in blocks of trials, each trial consisting of a user-specified sequence of stimuli. Responses can be recorded from the keyboard or from switches connected to an I/O board. Stimuli can be contingent on subjects’ responses, allowing feedback based on response accuracy. Timing uses Time Manager routines from the Macintosh Toolbox. Data are recorded in a text format with tabs delimiting fields, allowing analysis and presentation by other Macintosh spreadsheet, statistics, and graph-making applications. SuperLab has a Macintosh user interface for developing experiments. Psychological tasks can also be designed and modified with any application that generates a text format file.     

Beyond mind-reading: multi-voxel pattern analysis of fMRI data

A key challenge for cognitive neuroscience is determining how mental representations map onto patterns of neural activity. Recently, researchers have started to address this question by applying sophisticated pattern-classification algorithms to distributed (multi-voxel) patterns of functional MRI data, with the goal of decoding the information that is represented in the subject's brain at a particular point in time. This multi-voxel pattern analysis (MVPA) approach has led to several impressive feats of mind reading. More importantly, MVPA methods constitute a useful new tool for advancing our understanding of neural information processing. We review how researchers are using MVPA methods to characterize neural coding and information processing in domains ranging from visual perception to memory search.     

Relations among age, visual memory, and resting cerebral metabolism in 40 healthy men

Visual memory, as measured by the Benton Visual Retention Test (BVRT), and resting regional cerebral metabolic rates for glucose (rCMRglc), as measured by positron emission tomography (PET) and [18-F]fluorodeoxyglucose, were examined in 40 very healthy men, aged 21 to 83 years. Age-related differences in visual memory were found but were significantly smaller than differences reported in the general population. This discrepancy is attributable to our rigorous health screening. The age-related differences found in this sample are estimates of the lower limit of population differences unconfounded by disease. Age-related differences on undistracted delayed visual memory were greater than differences on immediate visual memory, suggesting age-related differences in spontaneous elaborative visual information processing. No relation between visual memory and resting rCMRglc was found, supporting the hypothesis that mental abilities are unrelated to resting brain metabolism unless both functions are influenced by disease.     

Learning conditional frequencies in a probability learning task

The study was prompted by a theoretical discussion of probability learning by Estes (1976). In three separate experiments, subjects were presented with frequency information in the form of wins and losses among 3 teams, and later predicted future wins and losses. Frequencies were devised so that conditional win frequencies for a pair of teams were either inconsistent or consistent with marginal win frequencies for each team. In experiment 1, when subjects predicted future events on the basis of known past frequencies, predictions were generally based on conditional frequencies. In experiment 2 six blocks of observations were presented, with predictions following each block. What little learning did occur was in the direction of the conditional frequencies. Subjects in experiment 3 were able to learn conditional frequencies when given explicit instructions to do so. Results were discussed in terms of a two-stage hypothesis generation model that might operate within the framework of an associative theory of probability learning.