Author
Edward G. Freedman
Other affiliations: Brown University, Cornell University, University of Pennsylvania ...read more
Bio: Edward G. Freedman is an academic researcher from University of Rochester. The author has contributed to research in topics: Saccadic masking & Psychology. The author has an hindex of 20, co-authored 49 publications receiving 2130 citations. Previous affiliations of Edward G. Freedman include Brown University & Cornell University.
Topics: Saccadic masking, Psychology, Saccade, Medicine, Gaze
Papers published on a yearly basis
Papers
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University of California, San Diego1, McGill University2, Oregon Health & Science University3, Florida International University4, Yale University5, Washington University in St. Louis6, Virginia Commonwealth University7, University of Vermont8, University of Michigan9, Medical University of South Carolina10, National Institutes of Health11, SRI International12, University of Southern California13, McGovern Institute for Brain Research14, Harvard University15, Medical College of Wisconsin16, University of California, Irvine17, University of California, Los Angeles18, University of California, San Francisco19, University of Colorado Boulder20, University of Florida21, University of Maryland, Baltimore22, University of Massachusetts Boston23, University of Minnesota24, University of Pittsburgh25, University of Rochester26, University of Tennessee27, University of Utah28, University of Wisconsin–Milwaukee29, Boston University30, United States Department of Veterans Affairs31
TL;DR: The baseline neuroimaging processing and subject-level analysis methods used by the Adolescent Brain Cognitive Development Study are described to be a resource of unprecedented scale and depth for studying typical and atypical development.
431 citations
TL;DR: Analysis of gaze shifts made by trained rhesus monkeys with completely unrestrained heads found that signals related to the initial positions of the eyes in the orbits and the direction of the gaze shift influence separate eye and head movement commands.
Abstract: Freedman, Edward G. and David L. Sparks. Eye-head coordination during head-unrestrained gaze shifts in rhesus monkeys. J. Neurophysiol. 77: 2328–2348, 1997. We analyzed gaze shifts made by trained ...
282 citations
University of California1, McGill University2, Oregon Health & Science University3, Florida International University4, Yale University5, University of Washington6, Virginia Commonwealth University7, University of Vermont8, University of Michigan9, Medical University of South Carolina10, National Institute on Drug Abuse11, SRI International12, Children's Hospital Los Angeles13, National Institutes of Health14, McGovern Institute for Brain Research15, Harvard University16, Medical College of Wisconsin17, University of Colorado Boulder18, University of Florida19, University of Maryland, Baltimore20, University of Massachusetts Amherst21, University of Minnesota22, University of Pittsburgh23, University of Rochester24, University of Tennessee25, University of Utah26, University of Wisconsin–Milwaukee27, Boston University28
TL;DR: The baseline neuroimaging processing and subject-level analysis methods used by the ABCD DAIC in the centralized processing and extraction of neuroanatomical and functional imaging phenotypes are described.
Abstract: The Adolescent Brain Cognitive Development (ABCD) Study is an ongoing, nationwide study of the effects of environmental influences on behavioral and brain development in adolescents. The ABCD Study is a collaborative effort, including a Coordinating Center, 21 data acquisition sites across the United States, and a Data Analysis and Informatics Center (DAIC). The main objective of the study is to recruit and assess over eleven thousand 9-10-year-olds and follow them over the course of 10 years to characterize normative brain and cognitive development, the many factors that influence brain development, and the effects of those factors on mental health and other outcomes. The study employs state-of-the-art multimodal brain imaging, cognitive and clinical assessments, bioassays, and careful assessment of substance use, environment, psychopathological symptoms, and social functioning. The data will provide a resource of unprecedented scale and depth for studying typical and atypical development. Here, we describe the baseline neuroimaging processing and subject-level analysis methods used by the ABCD DAIC in the centralized processing and extraction of neuroanatomical and functional imaging phenotypes. Neuroimaging processing and analyses include modality-specific corrections for distortions and motion, brain segmentation and cortical surface reconstruction derived from structural magnetic resonance imaging (sMRI), analysis of brain microstructure using diffusion MRI (dMRI), task-related analysis of functional MRI (fMRI), and functional connectivity analysis of resting-state fMRI.
276 citations
TL;DR: Stimulation of the primate SC can elicit high-velocity, combined, eye-head gaze shifts that are similar to visually guided gaze shifts of comparable amplitude and direction and there was a high correlation between the end of the stimulation train and the start of the evoked gaze shift for movements smaller than the site-specific maximal amplitude.
Abstract: 1. We electrically stimulated the intermediate and deep layers of the superior colliculus (SC) in two rhesus macaques free to move their heads both vertically and horizontally (head unrestrained). ...
245 citations
TL;DR: Microstimulation data, single-unit recording data, and behavioral data are consistent with the gaze displacement hypothesis of collicular function--the hypothesis that a gaze displacement signal is derived from the locus of activity within the motor map of the SC and subsequently is decomposed into separate eye and head displacement signals downstream from the colliculus.
Abstract: When the head is free to move, microstimulation of the primate superior colliculus (SC) evokes coordinated movements of the eyes and head. The similarity between these stimulation-induced movements and visually guided movements indicates that the SC of the primate is involved in redirecting the line of sight (gaze). To determine how movement commands are represented by individual collicular neurons, we recorded the activity of single cells in the deeper layers of the superior colliculus of the rhesus monkey during coordinated eye-head gaze shifts. Two alternative hypotheses were tested. The "separate channel" hypothesis states that two displacement commands are generated by the SC: one signal specifying the amplitude and direction of eye movements and a second signal specifying the amplitude and direction of head movements. Alternatively, a single gaze displacement command could be generated by the SC ("gaze displacement" hypothesis). The activity of collicular neurons was examined during three behavioral dissociations of gaze, eye, and head movement amplitude and direction (metrics). Subsets of trials were selected in which the amplitude and direction of either gaze shifts or eye movements or head movements were relatively constant but the metrics of the other two varied over wide ranges. Under these conditions, the separate channel and gaze displacement hypotheses make differential predictions about the patterns of SC activity. We tested these differential predictions by comparing observed patterns with predicted patterns of neuronal activity. We obtained data consistent with the predictions of the gaze displacement hypothesis. The predictions of the separate channel hypothesis were not confirmed. Thus microstimulation data, single-unit recording data, and behavioral data are all consistent with the gaze displacement hypothesis of collicular function--the hypothesis that a gaze displacement signal is derived from the locus of activity within the motor map of the SC and subsequently is decomposed into separate eye and head displacement signals downstream from the colliculus.
206 citations
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TL;DR: Electrical microstimulation was used to study primary motor and premotor cortex in monkeys and it is suggested that these regions fit together into a single map of the workspace around the body.
874 citations
01 Nov 1994-Comparative Biochemistry and Physiology Part C: Pharmacology, Toxicology and Endocrinology
TL;DR: 11-Oxygenated androgens are generally more effective than T in stimulating secondary sexual characters, reproductive behaviour and spermatogenesis in teleost fishes but receptor-like binding has only reported for T and not for 11KT.
802 citations
TL;DR: Research carried out in the intervening years has made it possible to provide a detailed description of the saccadic command signals that are generated by motor neurons and the formation of these signals in premotor brainstem regions.
Abstract: The modern era of oculomotor research began with the advent of the chronic single-unit recording method in the late 1960s. Research carried out in the intervening years has made it possible to provide a detailed description of the saccadic command signals that are generated by motor neurons and the formation of these signals in premotor brainstem regions. These findings have been assimilated in control-systems models that simulate important behavioural features of saccades. Despite these great advances, key issues, such as the nature of the feedback signal and the location of the comparator, are unresolved and some of the factors that have impeded progress can be identified.
739 citations
TL;DR: This target article presents an information processing model for the control of these movements, with some close parallels to established physiological processes in the oculomotor system, for a number of well-established phenomena in target-elicited saccades.
Abstract: During active vision, the eyes continually scan the visual environment using saccadic scanning movements. This target article presents an information processing model for the control of these movements, with some close parallels to established physiological pro- cesses in the oculomotor system. Two separate pathways are concerned with the spatial and the temporal programming of the move- ment. In the temporal pathway there is spatially distributed coding and the saccade target is selected from a "salience map." Both path- ways descend through a hierarchy of levels, the lower ones operating automatically. Visual onsets have automatic access to the eye control system via the lower levels. Various centres in each pathway are interconnected via reciprocal inhibition. The model accounts for a num- ber of well-established phenomena in target-elicited saccades: the gap effect, express saccades, the remote distractor effect, and the global effect. High-level control of the pathways in tasks such as visual search and reading is discussed; it operates through spatial se- lection and search selection, which generally combine in an automated way. The model is examined in relation to data from patients with unilateral neglect.
739 citations
TL;DR: In this article , the authors used three of the largest neuroimaging datasets currently available, with a total sample size of around 50,000 individuals, to quantify brain-wide association studies effect sizes and reproducibility as a function of sample size.
Abstract: Magnetic resonance imaging (MRI) has transformed our understanding of the human brain through well-replicated mapping of abilities to specific structures (for example, lesion studies) and functions1-3 (for example, task functional MRI (fMRI)). Mental health research and care have yet to realize similar advances from MRI. A primary challenge has been replicating associations between inter-individual differences in brain structure or function and complex cognitive or mental health phenotypes (brain-wide association studies (BWAS)). Such BWAS have typically relied on sample sizes appropriate for classical brain mapping4 (the median neuroimaging study sample size is about 25), but potentially too small for capturing reproducible brain-behavioural phenotype associations5,6. Here we used three of the largest neuroimaging datasets currently available-with a total sample size of around 50,000 individuals-to quantify BWAS effect sizes and reproducibility as a function of sample size. BWAS associations were smaller than previously thought, resulting in statistically underpowered studies, inflated effect sizes and replication failures at typical sample sizes. As sample sizes grew into the thousands, replication rates began to improve and effect size inflation decreased. More robust BWAS effects were detected for functional MRI (versus structural), cognitive tests (versus mental health questionnaires) and multivariate methods (versus univariate). Smaller than expected brain-phenotype associations and variability across population subsamples can explain widespread BWAS replication failures. In contrast to non-BWAS approaches with larger effects (for example, lesions, interventions and within-person), BWAS reproducibility requires samples with thousands of individuals.
611 citations