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Motor Neurological Examination of the Hand and Upper Limb
Published in J. Terrence Jose Jerome, Clinical Examination of the Hand, 2022
Coordinated movements are dependent on many individual but connected processes.Volition: This is the ability to initiate, maintain or stop an activity or motion. In other words, the voluntary control of the movements.Perception: This is very important to integrate motor impulses and the sensory feedback. If the patient is not able to perceive or feel where his joint is, he may not be able to perform the required movement. When proprioception is affected, it is usually compensated with visual feedback.Engram: This refers to a postulated physical or biochemical change in neural tissue that represents a memory. High repetitions of precise performance must be performed in order to develop an engram. This is seen in complicated dance movements, where repeated performance will ensure perfection.
The Stress System
Published in Len Wisneski, The Scientific Basis of Integrative Health, 2017
Therefore, if you are experiencing stress, you are secreting norepinephrine, which alerts the hippocampus to be incredibly vigilant to stimuli and the recording of memories. The amygdala receives the incoming sensory information and checks in with the hippocampus to see if there is what traditionally has been called an engram, that is, an engrained thought pattern, associated with a traumatic memory to which the hippocampus can respond. The amygdala is scouting around to see if there is a match. It is somewhat like doing an FBI computer search for a fingerprint. If the sensory data are close, you get a hit, and the sympathetic nervous system fastens onto the incoming information. The information locks into the amygdala and hippocampus in such a manner that you carry that engram with you until you find a way or receive help to erase it. Many individuals proceed through life accumulating engrams and, consequently, becoming generally more fearful as they age. It is my contention that engrams can be minimized, or even erased, through deep introspection or professional assistance.
Differential impairments of semantic cognition in progressive versus stroke-related aphasias
Published in Lars-Göran Nilsson, Nobuo Ohta, Dementia and Memory, 2013
Long before the term ‘semantic memory’ was introduced (Tulving, 1972), more than a century ago, Wernicke and Meynert (Eggert, 1977) considered how the brain forms and reactivates concepts – a process they referred to as ‘conceptualisation’. Unlike the language centres that Wernicke described in his work on aphasia, Meynert and Wernicke’s model of conceptualisation made the following assumptions: (a) that the building blocks of concepts were modality-specific engrams (stores of information) localised to the cortical areas responsible for the corresponding sensory, motor or verbal domain; (b) that these modality-specific engrams, in widespread brain regions, were fully interconnected; and (c) that this web of connections was the basis of conceptualisation – a specific concept being represented by the co-activation of all its associated engrams (see Figure 12.1, Panel A for a pictorial representation of this idea). For example, if you taste an apple (even with your eyes closed), the taste-specific engram will automatically activate all of the other associated modality-linked engrams, enabling your brain to retrieve other knowledge concerning the object: its visual form, likely colour, name, presence of seeds, how you would peel it, and so on. In this proposal, modality-specific engrams were located in specific yet different brain regions, but conceptualisation was not. Indeed, Wernicke-Meynert argued that – unlike forms of agnosia and aphasia – disorders of conceptualisation only occurred as a consequence of global brain damage (dementia) because only such widespread cortical damage would disrupt the neutrally distributed engram reactivation process.
Brain Surrogates—Empty or Full Makes the Difference
Published in The American Journal of Bioethics, 2021
In other words, “consciousness” is too ill-defined to be useful as a benchmark in determining the brain-likeness of brain surrogates. I suggest to use another feature instead, namely memory, as something that is specific for nervous systems and for which there is biological evidence, the mechanism of it can be rationally explained, and it is measurable. In a nutshell: neural systems can encode sensory input in so-called “engrams” at the level of neurons and synapses. Engrams are considered the basic units of memory. This means that memories have a biological (biophysical and biochemical) neural substrate (Josselyn and Tonegawa 2020). In laboratory experiments, it was demonstrated that in the intact live animal retrievable memories can even be artificially formed without sensory perception through direct optogenetic stimulation of brain areas (Vetere 2019).
Memory, Authenticity, and Optogenethics
Published in AJOB Neuroscience, 2021
Jan Christoph Bublitz, Dimitris Repantis
From the perspective of memory research, the case vignette on which the discussion of the article is based appears unlikely. We only note that optogenetic memory manipulations require rendering cells sensitive for light stimulation (“labelling”) at the moment of the experience; so far, it cannot be applied retrospectively. Accordingly, even if general obstacles of optogenetics in humans are overcome, it will likely not work in the way supposed by the article. Moreover, the rich autobiographic memories of the article may not have a distinct and discrete engram which can be activated directly via optogenetic light stimulation. While optogenetics has lend credibility to engram theories of memory (Tonegawa et al. 2015), current research concerns only specific parts of a memory such as contextual information, coded in specific regions of the hippocampus such as the dentate gyrus (Liu et al. 2012). That the other, much more comprehensive parts of an autobiographical memory are equally stored in such discrete engrams and locations is no more than speculation. According to the canonical view, such memories are stored in dynamic and plastic connections between cells as well as cell ensembles (Iriye and Jacques 2019), which are hard or impossible for optogenetics to track (Hardt and Nadel 2018).
NeuroEthics and the BRAIN Initiative: Where Are We? Where Are We Going?
Published in AJOB Neuroscience, 2020
Walter J. Koroshetz, Jackie Ward, Christine Grady
The neurotechnologies and scientific advances resulting from the BRAIN Initiative have brought us closer to understanding how information is processed in brain circuits. Scientist now have the tools to see the activity patterns in a million neurons in an awake mouse going about its regular mouse behaviors. Artificial Intelligence (AI) techniques can be applied to large data sets of neural activity to understand the patterns that give rise to behavior (Yuste et al. 2017). New methods have allowed scientists to identify the neurons in the mouse that are connected to form a memory, an entity called an “engram.” Neurotechnologies can be used to turn on such “engram” neurons to create a false memory of an event that did not happen, or the reverse, to turn off the cells to make the memory disappear (Josselyn and Tonegawa 2020). The networks underlying other forms of learning are under intense study. The core neuroethical issue in BRAIN revolves around the possibility that these technologies might deconstruct human thoughts, emotions, preferences, intentions, motor programs, learning and more into computational constructs of neural network states, some of which may even become detectable or modulatable (Yuste and Goering 2016). The derivative ethical concerns involve not only the appropriate development and use of such technologies but bleed into age-old philosophical questions about our nature as a species and as individuals. Coloring the societal discussion is the fact that technologies for brain monitoring and modulation have long captured the public imagination as “science fiction.” Those who report on the neurotechnologies developed in the BRAIN Initiative commonly make reference to science fiction books or movies in gathering attention to their stories.