Search results for "hippokampus"

Rats bred for low intrinsic aerobic exercise capacity link obesity with brain inflammation and reduced structural plasticity of the hippocampus.

2021

Abstract BACKGROUND Increasing evidence shows obesity and poor metabolic health are associated with cognitive deficits, but the mechanistic connections have yet to be resolved. We studied rats selectively bred for low and high intrinsic aerobic capacity in order to test the association between low physical fitness, a genetic predisposition for obesity, and brain health. We hypothesized that low-capacity runner (LCR) rats with concurrently greater levels of adiposity would have increased hippocampal inflammation and reduced plasticity compared to the more physically fit high-capacity runner (HCR) rats. METHODS We examined markers for inflammation and brain plasticity in the hippocampi of LCR…

Rapid changes in bodily and neural states affect learning

2018

Declarative memories consist of the past events and factual information that can be recalled. One of the most popular experimental paradigms used in studying long-term memory formation is classical conditioning. Trace conditioning is a hippocampus-dependent task where two separate sensory stimuli are presented in contingency but with a temporal gap between. In trace eyeblink conditioning a conditioned stimulus, usually a tone, is presented with a short silent period followed by an airpuff to the eye. In the beginning of the learning process the behavioral response to the airpuff is naturally a blink of an eye. After repeated trials the subject learns to shut the eyelid after perceiving the …

Hippocampal theta phase-contingent memory retrieval in delay and trace eyeblink conditioning

2017

Hippocampal theta oscillations (3–12 Hz) play a prominent role in learning. It has been suggested that encoding and retrieval of memories are supported by different phases of the theta cycle. Our previous study on trace eyeblink conditioning in rabbits suggests that the timing of the conditioned stimulus (CS) in relation to theta phase affects encoding but not retrieval of the memory trace. Here, we directly tested the effects of hippocampal theta phase on memory retrieval in two experiments conducted on adult female New Zealand White rabbits. In Experiment 1, animals were trained in trace eyeblink conditioning followed by extinction, and memory retrieval was tested by presenting the CS at …

Learning to learn: Theta oscillations predict new learning, which enhances related learning and neurogenesis

2012

Animals in the natural world continuously encounter learning experiences of varying degrees of novelty. New neurons in the hippocampus are especially responsive to learning associations between novel events and more cells survive if a novel and challenging task is learned. One might wonder whether new neurons would be rescued from death upon each new learning experience or whether there is an internal control system that limits the number of cells that are retained as a function of learning. In this experiment, it was hypothesized that learning a task that was similar in content to one already learned previously would not increase cell survival. We further hypothesized that in situations in…

Hippocampal theta activity is selectively associated with contingency detection but not discrimination in rabbit discrimination-reversal eyeblink con…

2010

The relative power of the hippocampal theta-band (∼6 Hz) activity (theta ratio) is thought to reflect a distinct neural state and has been shown to affect learning rate in classical eyeblink conditioning in rabbits. We sought to determine if the theta ratio is mostly related to the detection of the contingency between the stimuli used in conditioning or also to the learning of more complex inhibitory associations when a highly demanding delay discrimination-reversal eyeblink conditioning paradigm is used. A high hippocampal theta ratio was not only associated with a fast increase in conditioned responding in general but also correlated with slow emergence of discriminative responding due to…

Mitochondrial function and sirtuin expression in hippocampus of young and old high- and low-capacity runner rats

2016

Introduction: Exercise and aerobic capacity are associated with improved learning in animals and humans. The hippocampus is a brain structure involved in learning and memory. High rates of neurogenesis have been shown to take place in the dental gyrus of hippocampus in response to physical exercise. It is not known whether mitochondrial dysfunction in the hippocampus is responsible for decline in cognitive function associated with low fitness level and aging, and whether intrinsic aerobic capacity is a risk factor for it. Methods: Mitochondrial function was investigated in the hippocampi of young and old highcapacity runner (HCR) and low-capacity runner (LCR) rats using high-performance res…

Effect of spontaneous activity at the old age on adult hippocampal neurogenesis in lrt and hrt rats

2018

Fyysinen aktiivisuus on hyväksi aivoterveydelle ja lisää aikuisiällä tapahtuvaa aivoturson eli hippokampuksen neurogeneesiä. Fyysisestä harjoittelusta saatavat vasteet riippuvat kuitenkin osittain geneettisistä tekijöistä ja siksi fyysisen harjoittelun vaikutukset ovat yksilöllisiä. Tämän tutkielman tarkoituksena on selvittää valikoivasti jalostettujen rottalinjojen spontaania fyysistä aktiivisuutta ja liikunnan vaikutuksia aivoterveydelle, kun fyysinen aktiivisuus on aloitettu myöhäisellä iällä pitkän inaktiivisuuden jälkeen. Tutkimuksessa käytettyjen rottien ikä vastaa noin 45 vuoden ihmisikää. Tutkimuksen rotat eroavat harjoitteluun reagoivuuden osalta ja omaavat joko korkean tai matalan…

Voimaharjoittelun vaikutus uusien hermosolujen säilymiseen hippokampuksessa aikuisilla nisäkkäillä

2016

Aerobinen harjoittelu vaikuttaa positiivisesti hippokampuksen uusien hermosolujen syntymiseen ja selviytymiseen. Lisääntyneen neurogeneesin on tutkittu vaikuttavan aivojen rakenteisiin ja toimintaan, muun muassa tehostamalla muistin ja oppimisen toimintoja. Tässä tutkimuksessa käytetyllä voimaharjoittelulla on myös tutkittu olevan positiivinen vaikutus kognitiivisiin toimintoihin. Nyt tutkittiin aikuisilla nisäkkäillä suoritetun progressiivisen voimaharjoittelun vaikutuksia hippokampuksen pykäläpoimun uusien hermosolujen säilymiseen. Lisäksi tutkittiin onko voimaharjoittelulla vaikutusta paikkamuistiin. Tutkimuksen koe-eläiminä käytettiin sukukypsiä Sprague-Dawley rottia (n = 20), jotka jae…

The role of the hippocampal theta activity in classical eyeblink conditioning in rabbits

2009

Disrupting neural activity related to awake-state sharp wave-ripple complexes prevents hippocampal learning

2012

Oscillations in hippocampal local-field potentials (LFPs) reflect the crucial involvement of the hippocampus in memory trace formation: theta (4–8 Hz) oscillations and ripples (~200 Hz) occurring during sharp waves are thought to mediate encoding and consolidation, respectively. During sharp wave-ripple complexes (SPW-Rs), hippocampal cell firing closely follows the pattern that took place during the initial experience, most likely reflecting replay of that event. Disrupting hippocampal ripples using electrical stimulation either during training in awake animals or during sleep after training retards spatial learning. Here, adult rabbits were trained in trace eyeblink conditioning, a hippoc…