SAINT AUGUSTINE, FL, April 06, 2017 /24-7PressRelease/ -- Dr, Michael Gabriel has been included in Marquis Who's Who. As in all Marquis Who's Who biographical volumes, individuals profiled are selected on the basis of current reference value. Factors such as position, noteworthy accomplishments, visibility, and prominence in a field are all taken into account.
In pursuit of his passionate interest in brain function, Dr. Gabriel embarked on a journey that would change the field forever. He began as an assistant professor of Psychology at Pomona College, Claremont, California, from 1967 to 1970 and as a staff psychologist at Pacific State Hospital, Pomona, California, from 1968 to 1970. Dr. Gabriel spent the next three years as a National Institute of Mental Health Senior Postdoctoral Fellow in the Department of Psychobiology, University of California, Irvine. This fellowship paved the way for an appointment at the University of Texas at Austin, where Dr. Gabriel served as an assistant professor from 1973 to 1977 and as an associate professor from 1977 to 1982. Major research advances obtained at Texas led, in 1982, to an appointment as a Professor of Psychology at the University of Illinois at Urbana-Champaign. In 1988 Dr. Gabriel moved his laboratory from the Psychology building at Illinois to the newly constructed Beckman Institute for Advanced Science and Technology, where he served as leader of the Neuronal Pattern Analysis Group until his retirement in 2004.
Gabriel and his students provided extensive documentation of brain neuronal activity underlying behavioral learning and memory. In addition Gabriel served as Leader of a multidisciplinary project funded by the National Science Foundation, entitled "A database system for neuronal pattern analysis". This project sought to make available to neuroscientists increasingly powerful computational resources for handling huge data sets acquired by neuroscientists who study complex patterns of brain activity. Dr. Gabriel also served on the Neuroinformatics review panel of the National Institutes of Health.
Dr. Gabriel's pioneering research on the neuronal mediation of learning and memory involved multi-channel recording of the activity of many brain neurons simultaneously as animal subjects (rabbits) learned to discriminate between two sounds. Gabriel considered that a given neuron was involved in the learning process if: a) it "learned" to discriminate, i.e., to fire impulses specifically in response to a meaningful sound (one that predicted shock or reward), but not to a different, non-predictive sound, and; b) this neuronal discrimination reversed, when the initially predictive sound became non-predictive, and the initially non-predictive sound became predictive. Of course, the rabbits learned to discriminate and reverse by responding behaviorally to avoid shock, or, in different experiments, to gain reward. Gabriel's work also involved blocking, either permanently or temporarily, the activity of small collections of neurons, thus to promote understanding of how the neural impulses from a given set of neurons affect the activity of downstream neurons. Temporary lesions were achieved using intracerebral micro-injection of muscimol, which blocks neuronal activity in a small area for about 1.5 hours. This approach enabled Gabriel not only to observe the downstream effects of briefly disabling projecting neurons but also to observe the restoration of activity in the distal neurons as the temporary blockade "wore off".
These strategies led to the first comprehensive description of neuron activity in key learning-relevant circuitry of the brain. Gabriel and his students produced many breakthrough findings as this work progressed. For example, they provided the first demonstration of learning-relevant activity, i.e., discrimination and reversal of neuron activity elicited by the sounds used in his studies, as early as 15 - 30 milliseconds after sound onset, in the medial geniculate nucleus, a subcortical region believed, prior to Gabriel's research, to be involved only in acoustic processing but not learning. These results were published in the highly prestigious magazine, Science, in 1975.
As a postdoctoral researcher at Irvine, Gabriel studied neurons in the cingulate region of the cerebral cortex, a part of the brain's limbic system, often described as the "emotional brain". These neurons exhibited learning-relevant activity. Later work at Texas, also published in Science Magazine, showed that neurons in the deep layers (5 and 6) of the posterior cingulate cortex developed learning-relevant discriminative activity in the early stage of training, whereas the neurons in the upper cortical layers (1-4) discriminated only in the late stages of training, after the subjects had already shown behavioral learning. Clearly the late-discriminating neurons were not involved in the rabbits' original learning. Gabriel hypothesized that the late discriminative activity represented memory-related processing of the learned information.
Extensive additional work examined the effects of small, experimentally-induced permanent or temporary brain lesions on behavioral learning as well as learning-relevant neuronal activity. The small lesions were placed either in the posterior cingulate cortex itself or in various subdivisions of the anterior thalamus, a subcortical area which exhibits direct two-way communication with neurons in the posterior cingulate cortex. This work extended previous findings by demonstrating that neurons in the cortex and in various parts of the anterior thalamus exhibit maximal or "peak" learning-relevant activity during either initial, intermediate or in late stages of behavioral learning. Dr. Gabriel proposed a "nomadic engram" theory, i.e., the idea that the shifting anatomical focus of learning-relevant neuronal activity indicates that memories are "protected" by moving them to new brain regions as learning progresses, thereby preventing newer memories from interfering with older ones due to competition for "neuronal territory".
Dr. Gabriel had a long-standing interest in the key role played by contextual stimuli in the retrieval of memory. The impact of contextual factors on retrieval of memory is well-known from a vast literature demonstrating that human and animal memory suffers when the testing environment differs from the environment in which original learning occurred. Dr. Gabriel confirmed this finding in relation to avoidance learning of rabbits in several studies carried out at Pomona College from 1967 to 1970.
The pioneering work of Professor Brenda Milner at McGill University provided thorough documentation of the impaired memory exhibited by patient H.M., who had undergone bilateral surgical removal of his hippocampal formation in treatment for epilepsy. Milner's studies established the important role in human memory of the brain's hippocampal formation. Hippocampal formation neurons send impulses to many places in the brain, including a direct projection to the posterior cingulate cortex, a major region of interest in the studies of Dr. Gabriel.
Following his discovery of the nomadic engram in the posterior cingulate cortex, Dr. Gabriel and his students examined role of hippocampal influences on activity in the posterior cingulate cortex and on discriminative avoidance learning in rabbits. As shown in Gabriel's earlier studies at Pomona, post-learning alteration of background environmental (contextual) stimuli of the training environment impaired rabbits' performance of previously learned avoidance responses. Remarkably, lesions induced in the hippocampal formation before learning eliminated the controlling influence of contextual stimuli. Rabbits' with hippocampal lesions did not exhibit the slightest loss of performance in response to the contextual alterations. Therefore, although hippocampal activity does not contribute to avoidance learning per se, it does clearly modulate behavioral performance in response to contextual changes.
These studies yielded an additional and very important finding. Learning-relevant discriminative neuronal activity in rabbits with hippocampal lesions developed at full magnitude in early training stages and remained so throughout the course of training, uniformly in all layers and regions of posterior cingulate cortex. No training-stage-specific peaks of activity were found. On the basis of these findings Dr. Gabriel proposed that: a) hippocampal influences in the posterior cingulate cortex establish the training-stage specific peaks of neuronal activity, and; b) that the stage-specific peaks represent a restriction of the neuronal territory that is devoted to habit processing in particular training stages. This allows the coding of multiple habits in separate cortical domains, thus insuring that inputs to the system do not simultaneously activate multiple memories and behaviors willy-nilly, regardless of the environmental context occupied by the subject. This account constitutes what is to date the most detailed neurological account of the functional role of key components of the brain's memory circuitry. Dr. Gabriel's work advances the findings of Milner and her colleagues in indicating what is the key role of the hippocampal formation in memory processing, that is, the utilization of contextual stimuli to achieve context-appropriate memory retrieval and behavioral responding.
Dr. Gabriel also employed his approach in a series collaborative studies with scientists engaged in an effort funded by the National Institute of Drug Abuse (NIDA) to understand changes in brain structure and function produced by exposure to cocaine in utero. Dr. Gabriel's work demonstrated that exposure to cocaine in utero in rabbits was associated with a specific avoidance learning deficit in the earliest stages of training, as well as altered task-related activity of anterior cingulate cortical neurons.
Dr. Gabriel was: co-editor with Dr. Brent A. Vogt the comprehensive volume entitled "Neurobiology of Cingulate Cortex and Limbic Thalamus"; co-editor with Dr. John Moore in 1989, of a volume entitled "Learning and Computational Neuroscience: Foundations of Adaptive Networks"; editorial board member of the scientific journals Neural Plasticity and Neurobiology of Learning and Memory.
As a testament to Dr. Gabriel's knowledge, abilities and hard work, he was honored with a variety of accolades, including features in numerous editions each of Who's Who in the World, Who's Who in America, Who's Who in Medicine and Healthcare, Who's Who in the South and Southwest and Who's Who in the Midwest. He was also a grantee of the National Science Foundation from 1992 to 2003, the National Institutes of Health from 1988 to 2003, NIDA from 1996 to 2001, National Institute of Mental Health (NIMH) from 1978 to 1988, and the Air Force Office of Scientific Research from 1988 to 1991. He attributes much of his success to his education, which includes a Bachelor of Arts in Psychology from St. Joseph's College (Philadelphia PA, 1958-1962), Master of Arts and Ph.D. degrees in Psychology from the University of Wisconsin (1962-1967), and an NIMH Senior Postdoctoral Fellowship in the Department of Psychobiology at the University of California, Irvine (1970-1973).
During his lifetime Dr. Gabriel performed as a jazz musician. He learned first to play the trumpet in grade school, then the slide trombone, followed by valve trombone. In June of 1962 while living at home with his parents in Philadelphia, he received a telephone invitation to join the Woody Herman band for a summer tour of Russia. This call arrived on the very same day in which his acceptance to the graduate program in Psychology at the University of Wisconsin, arrived in the mail. Gabriel played in an ever-widening circle of musicians during his high school and college years in Philadelphia. Some of his musician friends (now Facebook friends) went on to become jazz icons. During his academic career Gabriel played jazz with many musicians in Madison, Wisconsin (1962-1967), Los Angeles/Orange County, CA (1967-1973), Austin, Texas (1973-1982) and Champaign IL (1982-2003). In Champaign, Gabriel co-founded the Boneyard Jazz Quintet with trombonist Morgan Powell. During post-retirement summers in Massachusetts, Dr. Gabriel played with Lou Columbo and his band at the Roadhouse Restaurant in Hyannis, MA. Dr. Gabriel and his wife Sonda live in St. Augustine, Florida where Dr. Gabriel plays with various area groups. His music can be heard on ReverbNation.com/gabriel's horn.
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