Movement and behavior analysis using neural spike signals in CA1 of rat hippocampus

The hippocampus which lies in the temporal lobe plays an important role in spatial navigation,learning and memory.Several studies have been made on the place cell activity,spatial memory,prediction of future locations and various learning paradigms.However,there are no attempts which have focused on finding whether neurons which contribute largely to both spatial memory and learning about the reward exist.This paper proposes that there are neurons that can simultaneously engage in forming place memory and reward learning in a rat hippocampus' s CA1 area.With a trained rat,a reward experiment was conducted in a modified 8-shaped maze with five stages,and utterance information was obtained from a CA1 neuron.The firing rate which is the count of spikes per unit time was calculated.The decoding was conducted with log-maximum likelihood estimation(Log-MLE) using Gaussian distribution model.Our outcomes provide evidence of neurons which play a part in spatial memory and learning regarding reward.     

Human navigation that requires calculating heading vectors recruits parietal cortex in a virtual and visually sparse water maze task in fMRI.

Spatial navigation in the real-world is a complex task that involves many functions, such as landmark identification, orientation, and the calculation of heading vectors. This study uses a 2 × 2 experimental design with fMRI to isolate mnemonic and navigational processes that accompany the calculation of heading vectors. The conditions are based on a working memory version of the Morris water maze task and navigation takes place in a visually austere virtual environment. In an allocentric condition, subjects navigate around a circular arena where there is one small red square on the wall. Each trial begins with an encoding phase in which subjects locate and navigate to a visible coin. Then, in a test phase, after being randomly repositioned, they retrieve the coin when it is invisible. In a control task, there are eight distinct cues around the arena that provide direct cue-place information. Results show significant interaction effects in bilateral posterior parietal cortex, which is compatible with evidence that parietal cortex helps translating between allocentric coordinates and egocentric directions. There was also greater activation for the allocentric task in right posterior hippocampus and left retrosplenial cortex, which could be related to self-localization and orientation. The findings are also compatible with the recent proposal by Kubie and Fenton (2009) that navigation primarily depends on heading vectors between salient places. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of aging on the neural correlates of successful item and source memory encoding.

To investigate the neural basis of age-related source memory (SM) deficits, young and older adults were scanned with fMRI while encoding faces, scenes, and face-scene pairs. Successful encoding activity was identified by comparing encoding activity for subsequently remembered versus forgotten items or pairs. Age deficits in successful encoding activity in hippocampal and prefrontal regions were more pronounced for SM (pairs) as compared with item memory (faces and scenes). Age-related reductions were also found in regions specialized in processing faces (fusiform face area) and scenes (parahippocampal place area), but these reductions were similar for item and SM. Functional connectivity between the hippocampus and the rest of the brain was also affected by aging; whereas connections with posterior cortices were weaker in older adults, connections with anterior cortices, including prefrontal regions, were stronger in older adults. Taken together, the results provide a link between SM deficits in older adults and reduced recruitment of hippocampal and prefrontal regions during encoding. The functional connectivity findings are consistent with a posterior-anterior shift with aging previously reported in several cognitive domains and linked to functional compensation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stem-cell-associated structural and functional plasticity in the aging hippocampus.

Aging frequently leads to a functional decline across multiple cognitive domains, often resulting in a severe reduction in life quality and also causing substantial care-related costs. Understanding age-associated structural and functional changes of neural circuitries within the brain is required to improve successful aging. In this review, the authors focus on age-dependent alterations of the hippocampus and the decline of hippocampal function, which are critically involved in processes underlying certain forms of learning and memory. Despite the dramatic reductions in hippocampus-dependent function that accompany advancing age, there is also striking evidence that even the aged brain retains a high level of plasticity. Thus, one promising avenue to reach the goal of successful aging might be to boost and recruit this plasticity, which is the interplay between neural structure, function, and experience, to prevent age-related cognitive decline and age-associated comorbidities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hippocampal lesions impair retention of discriminative responding based on energy state cues.

The present research investigated the hypothesis that the hippocampus is involved with the control of appetitive behavior by interoceptive “hunger” and “satiety” signals. Rats were trained to solve a food deprivation intensity discrimination problem in which stimuli produced by 0-hr and 24-hr food deprivation served as discriminative cues for the delivery of sucrose pellets. For Group 0+, sucrose pellets were delivered at the conclusion of each 4-min session that took place under 0-hr food deprivation, whereas no pellets were delivered during sessions that took place when the rats had been food deprived for 24 hr. Group 24+ received the reverse discriminative contingency (i.e., they received sucrose pellets under 24-hr but not under 0-hr food deprivation). When asymptotic discrimination performance was achieved (indexed by greater incidence of food magazine approach behavior on reinforced compared with nonreinforced sessions), half of the rats in each group received hippocampal lesions, and the remaining rats in each group were designated as sham- or nonlesioned controls. Following recovery from surgery, food deprivation discrimination performance was compared for lesioned and control rats in both Groups 0+ and 24+. Discriminative responding was impaired for rats with hippocampal lesions relative to their controls. This impairment was based largely on elevated responding to nonreinforced food deprivation cues. In addition, hippocampal damage was associated with increased body weight under conditions of ad libitum feeding. The results suggest that the inhibition of appetitive behavior by energy state signals may depend, in part, on the hippocampus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cortical gray matter atrophy in healthy aging cannot be explained by undetected incipient cognitive disorders: A comment on Burgmans et al. (2009).

Burgmans, van Boxtel, Vuurman, et al. (2009) published an interesting study titled “The Prevalence of Cortical Gray Matter Atrophy May Be Overestimated in the Healthy Aging Brain” on how subclinical cognitive disorders may affect correlations between age and cortical volume. Correlations between cortical gray matter volume and age were found in 30 elderly with cognitive decline after 6 years, but not in 28 elderly without cognitive decline. This study is important, and demonstrates that preclinical cognitive disorders may affect cortical brain volumes before being detectable by neuropsychological tests. However, we are not convinced by the conclusions: “… gray matter atrophy… is to a lesser extent associated with the healthy aging process, but more likely with brain processes underlying significant cognitive decline” (p. 547) and “… cortical gray matter atrophy in the aging brain may be overestimated in a large number of studies on healthy aging” (p. 547). We analyzed the cross-sectional MR data (n = 1,037) as well as longitudinal data from a sample of very well-screened elderly followed by cognitive testing for 2 years. In the cross-sectional data, the correlations between age and brain volumes were generally not much reduced when the upper age limit was lowered. This would not be expected if age-related incipient cognitive disorders caused the correlations given that the incidence of cognitive decline increased with age. Longitudinally, 1-year atrophy was identified in all tested regions. It is likely that cortical brain atrophy is manifested in cognitively normal elderly without subclinical cognitive disorders. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

惊厥大鼠不同脑区突触体内5-HT及MDA含量的测定及其意义

目的探讨五羟色胺（5-HT）与惊厥的关系。方法选用wistar大鼠32只,采用硫代氨基脲腹腔注射（15 mg·kg^-1）,制作惊厥发作模型,分别取大脑皮层、海马、纹状体三个脑区的脑组织制备出突触小体,采用荧光分光度计及硫代巴比妥酸法测定上述各脑区组织突触小体不同时点的5-HT及丙二醛（MDA）的含量。结果惊厥发作各组中各脑区5-HT含量均明显低于对照组（P〈0.05或P〈0.01）,而MDA含量明显高于对照组（P〈0.05或P〈0.01）。结论 5-HT含量水平影响惊厥的敏感性,含量不足可降低惊厥发作阈,而诱发惊厥。     

Estradiol-induced enhancement of object memory consolidation involves NMDA receptors and protein kinase A in the dorsal hippocampus of female C57BL/6 mice.

This study examined the role of dorsal hippocampal NMDA receptors and PKA activation in 17β-estradiol (E?)-induced enhancement of object memory consolidation. Mice explored two identical objects during training, after which they immediately received intraperitoneal injections of 0.2 mg/kg E?, and bilateral dorsal hippocampal infusions of Vehicle, the NMDA receptor antagonist APV (2.5 μg/side), or the cAMP inhibitor Rp-cAMPS (18.0 μg/side). Retention was tested 48 hours later. The enhanced object memory and increased ERK phosphorylation observed with E? alone was reduced by APV and Rp-cAMPS, suggesting that estrogenic enhancement of object memory involves NMDA receptors and PKA activation within the dorsal hippocampus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bright light suppresses hyperactivity induced by excitotoxic dorsal hippocampus lesions in the rat.

The hippocampus has been implicated in anxiety, novelty detection, spatial- contextual processing, and hyperactivity. Accordingly, the authors contrasted the role of the dorsal hippocampus (DH) and the basolateral amygdala complex (BLA) in an open field task that presents the onset and termination of a bright light gradient. In the dark, DH rats demonstrated impaired habituation of locomotion behavior and hyperactivity, whereas in bright light their behaviors were normal. DH rats responded differentially to the onset and termination of the light stimulus, which indicates they have normal novelty detection. BLA lesion rats responded normally to bright light. These results demonstrate that a mild fear stimulus, such as bright light, can suppress DH lesion-evoked hyperactivity, and this hyperactivity results from impaired contextual processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)