Significant Breakthroughs in Neurology
Significant breakthroughs in the discipline of neurology have resulted in modifications in the methods employed by neuroscientists to carry out their jobs. Initially, neurologists used the lesion approach extensively in procedures. This procedure sought to ascertain the association between a specific brain area and the occurrence of the current behavior. The advancement of techniques employed in the examination of brain architecture resulted in the development of Computed Axial Tomography (CAT), a procedure that required the coordination of multiple X-ray pictures using a computer in the generation of cross-sectional views of the human body. "Magnetic resonance imaging (MRI) and Functional Magnetic Resonance (fMRI)" are neuroscience developments where the process of imaging is done basing on the Nuclear Magnetic Resonance (NMR) (Hodos & Bonbright, 1974). Another notable development in the methods used by a neurologist is called Positron Emission Tomography (PET), and here examination is done involving the acquisition of physiologic image basing on the detection of radiation from the emission.
Changes in Brain Activity Modeling
Other significant changes in the techniques used in modeling the activity of the brain involve the use of optogenetics in brain procedures. The Transcranial magnetic stimulation (TMS) is one of the significant methods of brain modulation where the electromagnetic induction where isolation of brain region is done. Transcranial Direct Current Stimulation (tDCS) is a method which works in fixing of two electrodes on the brain. Furthermore, there are behavioral methods that are significant in the analysis of behavior in attempts to gain insight on cognition. The behavioral methods focus on the overt behavior of a test person (Ramirez et al., 2013).
Summary of Liu et al. Article
The purpose of the study was to evaluate the output of elicit the behavior of a particular memory through having a direct activation of neuron populations which were active in the process of learning. The study aimed at finding out if the "optogenetic reactivation of hippocampal neurons activated during fear conditioning is sufficient to induce freezing behavior" (Liu et al., 2012). The method of study involved labeling the population of neurons of hippocampal dentate gyrus neurons that were under a direct activation when in fear learning with "channelrhodopsin-2 (ChR2)7, 8" (Liu et al., 2012). The study used mice as test subjects. After that, optically reactivation of these neurons in a variety of context was done.
The result stipulated indicated that the mice depicted an increase in freezing when the stimulation light that indicated light induced fear memory recall. However, the freeze was not evident in not-fear conditioned mice cell that expressed ChR2 in the same proportion of cells. The results were similar to those mice that were labeled with EYFP instead of ChR2. Additionally, cell activation labeled in a context that is not associated with fear did not provoke freezing in the mice which were initially conditioned with fear in a different context. This result suggested that the light induced memory fear recall in a specific context. The study also indicated that the activating of a "sparse but specific ensemble of hippocampal neurons that contribute to a memory engram is sufficient for the recall of that memory" (Liu et al., 2012). The experiment is significance in offering a typical method of mapping the cellular population that bears memory engrams. The study is also significant in the field of neuroscience as it enables the neuroscientist to understand the concept of optogenetic stimulation of a hippocampal engram in activated fear memory and impact in recalling. A logical follow-up study would be to carry out a study to identify manipulation of optogenetic in memory engrams to test for the adequacy of engrams in memory recalling.
References
Hodos, W., & Bonbright, J. (1974). Intensity difference thresholds in pigeons after lesions of the tectofugal and thalamofugal visual pathways. Journal Of Comparative And Physiological Psychology, 87(6), 1013-1031. http://dx.doi.org/10.1037/h0037586
Liu, X., Ramirez, S., Pang, P., Puryear, C., Govindarajan, A., Deisseroth, K., & Tonegawa, S. (2012). Optogenetic stimulation of a hippocampal engram activates fear memory recall. Nature. http://dx.doi.org/10.1038/nature11028
Ramirez, S., Liu, X., Lin, P., Suh, J., Pignatelli, M., & Redondo, R. et al. (2013). Creating a False Memory in the Hippocampus. Science, 341(6144), 387-391. http://dx.doi.org/10.1126/science.1239073
