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=Mortimer Mishkin= Mortimer Mishkin is an American cognitive neuroscientist and Chief of the National Institute of Mental Health (NIMH)’s Section on Cognitive Neuroscience in the Laboratory of Neuropsychology. He is also a visiting professor at University College London's Institute of Child Health. His areas of primary expertise in cognitive science and neuroscience include neural pathways in perception and attention, recognition and recall, emotion and motivation, and volition and movement, as well as brain mechanisms of learning and memory. Mishkin discovered the spatial and visual processing property or the “’’where’’ vs. ‘’what’’” distinction of the dorsal and ventral streams first described by David Milner and Melvyn A. Goodale. He received the National Medal of Science in 2010.

Academic History
Mishkin received a Bachelor of Arts degree from Dartmouth College in 1946. His master’s thesis completed in 1949 was supervised by Donald O. Hebb at Yale University. There he began his career as a research assistant in the Physiology and Psychiatry departments. His doctoral thesis completed in 1951 in the areas of visual perception in primates was supervised by H.E. Rosvold and Karl H. Pribram. After Mishkin completed his postdoctoral fellowship in 1955, he conducted research at a primate neurobehavioral research laboratory at the Institute of Living in Hartford, Connecticut and at New York University's Bellevue Medical Center.

Career
Mishkin served as President of American Psychological Association Division 6 in 1968-69. He also served as president of the Society for Neuroscience. Furthermore, he has been elected to the National Academy of Science, Institute of Medicine, and Society of Experimental Psychologists. Mishkin chaired the psychology sections of both the National Academy of Science and the American Association for the Advancement of Science. Mishkin became Chief of the Section on Cerebral Mechanisms at the NIMH in 1989. A year later, he became Chief of the Laboratory of Neuropsychology at the NIMH. Then in 1994, he became Associate Director of Basic Research at the NIMH.

Major Contributions to Cognitive Science
Mishkin's research studies contributed to the scientific understanding of the pathways for vision, hearing and touch as well as learning and memory.

The Where vs. What Distinction of the Dorsal and Ventral Stream
In the 1980s, Mishkin and Leslie G. Ungerleider identified the function of two cortical pathways later described by David Milner and Melvyn A. Goodale as the dorsal and ventral stream. The dorsal and ventral stream was described as part of the two-streams hypothesis.

Mishkin and Ungerleider proposed the notion that two processing streams for visual perception emanate from the dorsal stream leading to the visual cortex of the parietal lobe and the ventral stream leading to the visual areas of the temporal lobe. The dorsal stream provides the parietal lobe with the information needed for visual location or the “where” of objects, whereas the ventral stream provides the temporal lobe with the information needed for visual identification or the “what” of objects. This was discovered with brain lesion studies on monkeys.

Distinguishing Neurobiological Mechanisms of Memory vs. Habits
Mishkin’s work with nonhuman primates led to the discovery that the brain uses divergent pathways to process two types of memory: cognitive memory and behavioural memory. Cognitive memory is memory for new events and information, whereas behavioural memory is memory for skills and habits. Further, the two types of memory involve different brain circuits stimulated by cortical sensory streams in each modality. Cognitive memory is processed by the limbic structures which is also known as the cortico-limbic circuit, while behavioural memory is processed by the basal ganglia which is also known as the cortico-striatal circuit.

The Combined Role of the Hippocampus and Amygdala
Mishkin found that monkeys with either just the amygdala or hippocampus removed do not experience semantic memory loss. However, when both the monkeys' amygdala and hippocampus removed, semantic memory loss results.

Research Approach
Mishkin applies a multidisciplinary approach with monkeys to understand the brain and behavior relationships underlying learning and memory in primates. Metabolic mapping techniques, including both autoradiography and neuroimaging, are utilized to map the cerebral areas belonging to a targeted functional neural system. Lesion studies in combination with learning and memory tasks in various sensory modalities help separate and identify different mnemonic functions as well as to localize their key neural substrates. Anatomical tracing techniques are used to reveal the organization of various substrates as components of a neural system or circuit in a functional family. In addition, the electrophysiological activity is recorded within identified substrates to determine the nature of the information the neurons receive and transmit at various stages of learning. Lastly, pharmacological agents are injected into the substrates studied with anatomical tracing techniques to relate the learning-dependent changes in behavioural and neuronal activity to the underlying cellular and synaptic mechanisms. The learning and memory mechanisms uncovered with monkeys serve as the basis for localizing homologous mechanisms in brain-damaged patients using both neuropsychological and quantitative magnetic resonance techniques.

Visual Learning and Memory
Mishkin researches the visual memory system related to the limbic structures with normal and brain damaged children, as well as nonhuman primates. His studies aim to address the following questions:
 * 1) Is there is a distinction between a visuo-perirhinal object memory circuit and a visuo-posterior parahippocampal spatial memory circuit? (This distinction may aid in understanding memory impairments in aging and many psychiatric or neurologic illnesses such as schizophrenia, depression and Alzheimer’s disease.)
 * 2) Does a hierarchical organization of familiarity-based and recollection-based memory exist?
 * 3) Do the synaptic changes that occur during learning and memory in the visuo-limbic and visuo-striatal circuits depend disproportionately on the neuromodulators – acetylcholine and dopamine?
 * 4) Do the synaptic changes in the two systems have different temporal properties paralleling the differences between memories and habits?(Memories are formed all at once but readily forgotten, and habits are formed only gradually but hardly ever forgotten)

Auditory Learning and Memory
Mishkin’s research investigates short-term auditory memory in monkeys. One of his studies with monkeys explores whether oral language is unique to humans because it depends on not only articulate speech but on the long-term storage of auditory stimulus representations. Another one of his studies investigates how auditory stimuli are processed in the cerebral cortex. More specific, he is interested in how auditory stimuli are processed in the divisions of the auditory cortex beyond the early auditory areas. As well, his research examines whether an acoustic cortico-striatal system supports the formation of auditory discrimination habits similar to the way the visuo-striatal system mediates the formation of the visual discrimination habits.

Criticism of Mishkin’s Research
Gaffan criticized Mishkin’s hippocampal lesion studies in monkey. He argued that Mishkin’s findings of object recognition memory loss with hippocampal or fornix lesions in monkeys should not be generalized to memory impairment patterns in densely amnesic patients. The reason for his argument is that hippocampal lesions in monkeys may leave object recognition memory intact in some cases.

Future Research Directions
Mishkin underscored the need to understand at a molecular level of how information is transmitted in the brain. He thought there is a need for more refined tools to visualize in real time what is happening through the brain as an event transpires that we are experiencing.

Awards
Mishkin was awarded with the National Medal of Science in 2010. He is the first NIMH intramural scientist to receive the medal.