Adult Hippocampal neurogenesis has often been associated with hippocampus-dependent learning memory. The whole process of neuron development is highly and differently susceptible to various factors and conditions that affect its survival, as well as functionality. Various prior researches have indicated that spatial training occurring 6-10 days after an injection of bromodeoxyuridine (BrdU), which is a DNA synthesis marker, increased the cell’s survival rate in male rats. However, sex differences has been reported in spatial cognition and hippocampal neurogenesis, hence developing difficulties in understanding whether spatial training would affect males and females hippocampal neurogenesis similarly.
Therefore, the article by Chow C et al (2012) examines the sex differences in hippocampal neurogenesis on following spatial training task. The study involved an examination of sex differences, where the male and the female rats were trained in a spatial and cued version of Morris water maze, where they were placed 6-10 days after an injection of (200mg/kg) of BrdU. Twenty days after the injection the animals under examination were put on a probe trial and perfused, in which the observations made showed that the males performed better than females in the spatial training. However, females performed better in cued version as compared to males. In addition, the spatial training increased the BrdU relatively as compared to cued training in males. However, the study showed that the both male and female indicated a greater activation of new cells after the spatial training as compared to the cued training (Chow, et al, 2012).
In addition, an observation that was made indicated that there was a positive correlation between cell activation in females during spatial training, but not in male. Therefore, the general observation in the study conducted by Chow et, al, (2012) indicates that, spatial training regulates hippocampal neurogenesis in males and females differentially. However, the study observes that there is similar response of the activity of new neurons to spatial memory retrieval. Therefore, this study is essential in providing various aspects of sex differences in neurogenesis, as well as the essentiality of sex in neural plasticity and cognition. Hippocampus region of the brain is among the most essential parts of the brains facilitating and regulating the complex emotional and cognitive responses.
Administration of BrdU to newborn male and female rats led to proliferation and increased differentiation of the male rats’ cells survival as compared to the female rats. There are sex differences in the rate at of cell genesis in the development of hippocampus based on the laboratory examination on rats. Various researches indicate that the male rats have a higher rate of cell genesis as compared to the female rats. This shows that there are widespread sex differences in the brain. These differences are brought about by the intensity and amount of excitatory and inhibitory synapses which are in particular parts of the brain.
Most of the neuroanatomical sex differences are found in the brain regions, which are directly involved in the reproduction, such as preoptic, hypothalamus and spinal cord regions. There are various essential behavioral and physiological functions, which are sub served by the hippocampus and are influenced by sex. These manifest themselves in the morphology of the hippocampus cells indicating subtle and identifiable sex differences in the development of hippocampus cells. These indicates differences in various hippocampal associated behaviors, which include spatial learning strategies, responsiveness to stress and impact of early negative life events in the long term. The differences in the development of the hippocampus are subtle but very complex and respond differently to various factors and conditions. Therefore, hormonally sex differences are centrally associated with sexual differentiation in various brain areas.
In various other studies examining the sex differences of hippocampal neurogenesis, where additional oestradiol treatment was included indicated differential sensitivity of adult males and females to oestradiol treatment. The studies indicate that due to differential in development of male and female parts of the hippocampus there may be sexual dimorphisms in the adult hippocampus. These differences contribute to the differential in sensitivity of the male and female brain hence differentials in development of the hippocampus.
There has been a high linkage between the adult hippocampal development and learning. However, the relationship between memory and neuronal development is yet to be established. For example, different studies show that the new neuron between the ages of 4 to 28 days at the time of spatial training is required for long term memory. However, the long term memory remains unaffected when the cued platform is used. The relationship between survival of new neurons and their proliferation on learning indicated some differences even though they were not significant. Therefore, adult neurogenesis plays an essential role in the consolidation of long term memories since the hippocampus is dependent on spatial memories.
According to Luu et al, (2012) adult neurogenesis in the dentate part of the hippocampus plays an essential role in learning and memory. However, studies have not been able to establish the contribution of new neurons to the functioning of the hippocampus. There have been various emerging studies, which suggest that, neurogenesis is essential for the separation of the pattern and mitigation of interferences when there are similar items, which are learned in different times. In their article, Luu, et al, (2012) wanted to establish the effect of cranial irradiation was consistent with their hypothesis that it would lead to reduction of neurogenesis within the dentate gyrus part of the hippocampus.
The studies established that focal cranial irradiation results were consistent with their results, which resulted to selective reduction of neurogenesis. This led to substantial inability to overcome interference during learning. In their study, they used a recent introduced olfactory memory task, which has various features. In the task, the rats were to be engaged in learning two highly interfering odor lists of pairs, which were to run one after the other in similar or different contexts. After focal cranial irradiation, ability of learning one single odor list remained unimpaired (Luu, et al, 2012). In addition, the studies were able to show that the focal cranial irradiation had no effect on learning in a hippocampal-dependent spatial alternating task.
The learning of different interfering odor remained unchanged and took place sequentially in different sessions. However, learning the interfering spatial locations took place concurrently in different sessions. Addition of new neurons provided a pattern of separation mechanism in the olfactory task, but not in the maze task. Therefore, the studies indicate that neurogenesis plays an essential role in resolving interference. In addition, the studies were consistent with other studies, which demonstrated that neurogenesis plays an essential role in pattern separation.
Adult neurogenesis plays an essential role in learning and memory as well as other functions related to hippocampal functions. For example, issues affecting an individual emotion and stress that result in drug addiction and regulations of such addictions. Therefore, adult neurogenesis emerges as an essential and integral process within the hippocampus due its role in learning and development. The studies conducted by Luu et al, (2012), demonstrate that new neurons play an essential role in pattern separation and reduction of interference. The studies found that mice with impaired or reduced neurogenesis are impaired in such tasks. The hippocampus neurogenesis is essential when the subject is to form two distinct memories, where there are highly interfering items since new neurons are involved in the encoding of different items.
In conclusion, the studies demonstrate that hippocampal neurogenesis plays an essential role in the learning and memory of an individual. The first article demonstrates the sex differences in development of hippocampal neurogenesis, where the studies demonstrate that male and female are differentially sensitive in neurogenesis development. The studies indicate that male rats have a higher rate of cell genesis as compared to that of female. The widespread differences are due to sex differences in the brains, which are often brought about by the number of excitatory and inhibitory synapses within various particular parts of the brain. The second article evaluates the role of new neurons in learning and memory, where the studies establish that there is a very close relationship between learning and memory and hippocampal neurogenesis. For example, the studies established that new neurons play an essential role in pattern separation as well as resolution of interferences.
References
Chow, C., Epp, J., Lieblich, S., Barha, C., & Galea, L. (2012). Sex differences in neurogenesis and activation of new neurons in response to spatial learning and memory. Psychoneuroendocrinology , 306-453.
Luu, P., Gao, L., Wojtowicz, J. M., Sill, O. C., Becker, S., & Smith, D. M. (2012). The Role of Adult Hippocampal Neurogenesis in Reducing Interference. Behavioral Neuroscience , 381-391.
