scholarly journals A neural signature of pattern separation in the monkey hippocampus

2018 ◽  
Author(s):  
John J. Sakon ◽  
Wendy A. Suzuki
Keyword(s):  
Dentate Gyrus ◽  
Neural Mechanisms ◽  
Pattern Separation ◽  
Visual Pattern ◽  
Complex Behavior ◽  
Firing Rates ◽  
Sensory Inputs ◽  
Neural Signature

AbstractThe CA3 and dentate gyrus (DG) regions of the hippocampus are considered key for disambiguating sensory inputs from similar experiences in memory, a process termed pattern separation. The neural mechanisms underlying pattern separation, however, have been difficult to compare across species: rodents offer robust recording methods with less human-centric tasks while humans provide complex behavior with less recording potential. To overcome these limitations, we trained monkeys to perform a visual pattern separation task similar to those used in humans while recording activity from single CA3/DG neurons. We find that when animals discriminate recently seen novel images from similar (lure) images, behavior indicative of pattern separation, CA3/DG neurons respond to lure images more like novel than repeat images. Using a population of these neurons, we are able to classify novel, lure, and repeat images from each other using this pattern of firing rates. Notably, one subpopulation of these neurons is more responsible for distinguishing lures and repeats—the key discrimination indicative of pattern separation.

scholarly journals A neural signature of pattern separation in the monkey hippocampus

2019 ◽  
Vol 116 (19) ◽  
pp. 9634-9643 ◽  
Author(s):  
John J. Sakon ◽  
Wendy A. Suzuki
Keyword(s):  
Dentate Gyrus ◽  
Neural Mechanisms ◽  
Pattern Separation ◽  
Visual Pattern ◽  
Complex Behavior ◽  
Firing Rates ◽  
Sensory Inputs ◽  
Neural Signature

The CA3 and dentate gyrus (DG) regions of the hippocampus are considered key for disambiguating sensory inputs from similar experiences in memory, a process termed pattern separation. The neural mechanisms underlying pattern separation, however, have been difficult to compare across species: rodents offer robust recording methods with less human-centric tasks, while humans provide complex behavior with less recording potential. To overcome these limitations, we trained monkeys to perform a visual pattern separation task similar to those used in humans while recording activity from single CA3/DG neurons. We find that, when animals discriminate recently seen novel images from similar (lure) images, behavior indicative of pattern separation, CA3/DG neurons respond to lure images more like novel than repeat images. Using a population of these neurons, we are able to classify novel, lure, and repeat images from each other using this pattern of firing rates. Notably, one subpopulation of these neurons is more responsible for distinguishing lures and repeats—the key discrimination indicative of pattern separation.

Reflections on the Structural-Functional Evolution of the Hippocampus: What Is the Big Deal about a Dentate Gyrus

2017 ◽  
Vol 90 (1) ◽  
pp. 53-61 ◽  
Author(s):  
Verner P. Bingman ◽  
Rubén N. Muzio
Keyword(s):  
Dentate Gyrus ◽  
Hippocampal Formation ◽  
Comparative Cognition ◽  
Pattern Separation ◽  
Sensory Inputs ◽  
Representation Of Space ◽  
Functional Consequences ◽  
Functional Equivalent ◽  
Structural Homologue ◽  
Broad Role

The vertebrate hippocampal formation has been central in discussions of comparative cognition, nurturing an interest in understanding the evolution of variation in hippocampal organization among vertebrate taxa and the functional consequences of that variation. Assuming some similarity between the medial pallium of extant amphibians and the hippocampus of stem tetrapods, we propose the hypothesis that the hippocampus of modern amniotes began with a medial pallium characterized by a relatively undifferentiated cytoarchitecture, more direct thalamic and olfactory sensory inputs, and a broad role in associative learning and memory processes that nonetheless included the map-like representation of space. From this modest beginning evolved the cognitively more specialized hippocampal formation of birds and the hippocampus of mammals with its confounding dentate gyrus. Much has been made of trying to identify a dentate homologue in birds, but there are compelling reasons to believe no such structural homologue/functional equivalent exists. The uniqueness of the mammalian dentate then raises the question of what might be the functional consequences of a hippocampus with a dentate compared to one without. One might be tempted to speculate that the presence of a dentate gyrus facilitates so-called pattern separation, but birds with their suspected dentate-less hippocampus display excellent hippocampal-dependent pattern separation relying on space. Perhaps one consequence of a dentate is a hippocampus better designed to process a broader array of stimuli beyond space to more robustly support episodic memory. What is clear is that any meaningful reconstruction of hippocampal evolution and the eventual identification of any subdivisional homologies will require more data on the neurobiological and functional properties of the nonmammalian hippocampus, particularly those of amphibians and reptiles.

P.1.i.053 Low behavioural pattern separation is linked to reduced dentate gyrus activation during fear generalisation

2015 ◽  
Vol 25 ◽  
pp. S330-S331
Author(s):  
I. Lange ◽  
L. Goossens ◽  
S. Lissek ◽  
T. Van Amelsvoort ◽  
K. Schruers
Keyword(s):  
Dentate Gyrus ◽  
Pattern Separation ◽  
Behavioural Pattern

scholarly journals Multi-domain cognitive assessment of male mice reveals whole body exposure to space radiation is not detrimental to high-level cognition and actually improves pattern separation

2019 ◽  
Author(s):  
Cody W. Whoolery ◽  
Sanghee Yun ◽  
Ryan P. Reynolds ◽  
Melanie J. Lucero ◽  
Ivan Soler ◽  
...  
Keyword(s):  
Dentate Gyrus ◽  
Fast Moving ◽  
Space Radiation ◽  
Pattern Separation ◽  
Whole Body ◽  
Cognitive Tasks ◽  
Male Mice ◽  
Functional Integrity ◽  
Brain Circuits ◽  
High Level

ABSTRACTAstronauts on interplanetary space missions - such as to Mars - will be exposed to space radiation, a spectrum of highly-charged, fast-moving particles that includes 56Fe and 28Si. Earth-based preclinical studies with mature, “astronaut-aged” rodents show space radiation decreases performance in low- and some high-level cognitive tasks. Given the prevalence of touchscreens in astronaut training and in-mission assessment, and the ability of rodent touchscreen tasks to assess the functional integrity of brain circuits and multiple cognitive domains in a non-aversive way, it is surprising the effect of space radiation on rodent touchscreen performance is unknown. To fill this knowledge gap, 6-month-old C57BL/6J male mice were exposed to whole-body space radiation and assessed on a touchscreen battery starting 1-month later. Relative to Sham, 56Fe irradiation did not overtly change performance on tasks of visual discrimination, reversal learning, rule-based, or object-spatial paired associates learning, suggesting preserved functional integrity of supporting brain circuits. Surprisingly, 56Fe irradiation led to better performance on a dentate gyrus-reliant task of pattern separation ability. Irradiated mice discriminated similar visual cues in ∼40% fewer days and ∼40% more accurately than control mice. Improved pattern separation was not touchscreen-, radiation-particle, or neurogenesis-dependent, as both 56Fe and 28Si irradiation led to faster context discrimination (e.g. Sham Block 5 vs. 56Fe Block 2) in a non-touchscreen task and 56Fe led to fewer new dentate gyrus neurons relative to Sham. These data urge revisitation of the broadly-held view that space radiation is detrimental to cognition.SIGNIFICANCE STATEMENTAstronauts on an interplanetary mission - such as to Mars - will be unavoidably exposed to galactic cosmic radiation, a spectrum of highly-charged, fast-moving particles. Rodent studies suggest space radiation is detrimental to cognition. However, here we show this is not universally true. Mature mice that received whole body exposure to Mars-relevant space radiation perform similarly to control mice on high-level cognitive tasks, reflecting the functional integrity of key neural circuits. Even more surprisingly, irradiated mice perform better than controls in both appetitive and aversive tests of pattern separation, a mission-critical task reliant on dentate gyrus integrity. Notably, improved pattern separation was not touchscreen-, radiation-particle-, or neurogenesis-dependent. Our work urges revisitation of the generally-accepted conclusion that space radiation is detrimental to cognition.

Mental Mechanisms

Mind-Society ◽  
2019 ◽  
pp. 22-47
Author(s):  
Paul Thagard
Keyword(s):  
Cognitive Appraisal ◽  
Mental Representations ◽  
Special Kind ◽  
Neural Mechanisms ◽  
Emotional Information ◽  
Sensory Inputs ◽  
The World ◽  
Sensory Motor ◽  
Human Thinking ◽  
High Level

Psychological explanations based on representations and procedures can be deepened by showing how they emerge from neural mechanisms. Neurons represent aspects of the world by collective patterns of firing. These patterns can be bound into more complicated patterns that can transcend the limitations of sensory inputs. Semantic pointers are a special kind of representation that operates by binding neural patterns encompassing sensory, motor, verbal, and emotional information. The semantic pointer theory applies not only to the ordinary operations of mental representations like concepts and rules but also to the most high-level kinds of human thinking, including language, creativity, and consciousness. Semantic pointers also encompass emotions, construed as bindings that combine cognitive appraisal with physiological perception.

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