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An Introduction to Consciousness and the Brain
Published in Max R. Bennett, The Idea of Consciousness, 2020
The CA3 neurons in turn project to the CA1 pyramidal neurons on which they synapse. These neurons also code for memories and their axons project to the region called the subiculum in the old paleocortex and from there to the neocortex. Thus the trisynaptic pathway is from the entorhinal cortex to the fascia dentata to the CA3 pyramids to the CA1 pyramids back to the cortex. There is another less specific input (on the left) necessary for the normal functioning of the hippocampus and that comes from the structure called the septum. These axons synapse on all neurons in the hippocampus. They are the first neurons to degenerate in the brain of people suffering from Alzheimer’s disease. This leads to the loss of memory formation that characterizes this disease. Surprisingly, these septal neurons are kept alive by Levi-Montalcini’s growth factor; that is, the growth factor which keeps autonomic neurons alive in the peripheral nervous system. So if a neurotrophic factor is discovered that saves a certain class of neurons in the periphery it may well work on a whole class of neurons in the brain.
Primary Stress Damage of the Heart
Published in Felix Z. Meerson, Alexander V. Galkin, Adaptive Protection of The Heart: Protecting Against Stress and Ischemic Damage, 2019
Felix Z. Meerson, Alexander V. Galkin
At present many circumstances concerning the mechanism of stress and its adaptive and damaging effects have become clear. As regards higher animals, it is now evident that emotions are decisive in the origin of stress. According to the information theory of emotions developed by Simonov4 they are brought about by the “conflict” between the actual needs of the organism (alimentary, sexual, self-preservation, self-assertion, domination) and the lack of sufficient information on whether or not these needs can be satisfied in the particular environment. This discrepancy between the need and the information necessary to fulfill it is perceived at the level of the brain neocortex and gives rise to descending cortical influences which activate the special neural apparatus of emotions: a system of nervous centers located in the area of hypothalamus, amygdaloid complex, and paleocortex. This system, according to numerous data, acts as a connecting link between the neocortex, which primarily senses the information deficiency, and the centers in the hypothalamus. Excitation of the latter centers is subjectively realized as emotions of fear, anxiety, rage, pleasure, etc. In our opinion, this actuates two interconnected regulatory mechanisms which together constitute the main content of the stress reaction.
The Neuropathology of Alzheimer’s Disease
Published in Zaven S. Khachaturian, Teresa S. Radebaugh, Alzheimer’s Disease, 2019
Suzanne S. Mirra, William R. Markesbery
Certain features seen grossly enable the neuropathologist to predict with reasonable certainty that the clinical diagnosis of AD was correct. Atrophy of the frontal, temporal, and parietal cortex manifested by narrowing of the gyri that form the convolutions of the brain, and widening of the spaces between them, or sulci, is common (Figure 1). Sections of the brain may additionally reveal narrowing of the entorhinal cortex, a part of the paleocortex, i.e., a portion of the cortex phyloge-netically older than the external neocortex as well as atrophy (shrinkage) of the hippocampus and amygdala, other key sites involved in memory.
Laterality in functional and metabolic state of the bulbectomised rat brain detected by ASL and 1H MRS: A pilot study
Published in The World Journal of Biological Psychiatry, 2023
Iveta Pavlova, Eva Drazanova, Lucie Kratka, Petra Amchova, Ondrej Macicek, Jana Starcukova, Zenon Starcuk, Jana Ruda-Kucerova
Spectroscopic voxels in the cortex contained a part of the cingulate cortex, the primary and secondary motor cortex, the frontal cortex, and a part of the primary somatosensory cortex (Paxinos and Watson 2006). All these regions belong to the paleocortex with emotional-driven and involuntary functions (Snyder et al. 2018). The thickness of voxels located in the cortex was only 1 mm; thus, the width and the length had to be higher to achieve a signal-to-noise ratio sufficient for quantitative analysis. Nevertheless, many of the spectroscopic data of these voxels had to be discarded from the post-processing because of the technical difficulty of shimming such a thin volume located near the skull. The lack of valuable data may explain that no significant metabolite ratio difference in the left and the right cortex between the groups was detected.
Amygdala structure and function in paediatric bipolar disorder and high-risk youth: A systematic review of magnetic resonance imaging findings
Published in The World Journal of Biological Psychiatry, 2022
Alessio Simonetti, Kirti Saxena, Alexia E. Koukopoulos, Delfina Janiri, Marijn Lijffijt, Alan C. Swann, Georgios D. Kotzalidis, Gabriele Sani
The amygdala is a heterogeneous complex of nuclei comprised in multiple networks modulating subprocesses related to social cognition, including evaluation, rule-based actions, emotional processes, attention, goal-directed behaviour, and memory (Salzman and Fusi 2010). In these networks, the main role of the amygdala is to encode the emotional valence and the motivational significance of certain stimuli (LeDoux 2007). The amygdala serves this role through (i) a broad input from associative sensory cortices and from areas involved in providing information about the internal state, such as the orbitofrontal cortex (Reiman et al. 1997; Arciniegas et al. 2013), and through (ii) projecting to a wide range of target structures, including PFC, striatum, sensory cortices, hippocampus, perirhinal and entorhinal cortices, and to subcortical structures responsible for physiological responses related to emotion, such as autonomic responses, hormonal responses, and startle (Davis 1992). In the field of affective neuroscience, great importance is given to the amygdala-PFC circuitry, because of its role in emotion generation and control, and the subsequent modulation of social behaviour. The amygdala is densely connected with the paleocortical, ventromedial regions of PFC, namely the orbitofrontal cortex, the mediodorsal PFC, and the rostral and subgenual anterior cingulate cortices (Phillips et al. 2008). These connections mediate the production and perception of emotional states, representation of reward value of a stimulus and the way in which this representation guides goal-directed behaviour (Rolls and Grabenhorst 2008). These areas are involved also in implicit (i.e. automatic) emotion regulation processes through the extinction of previously acquired behaviours, inhibition of stress response, regulation of emotional attentional resources, automatic behavioural monitoring, and rule learning (Phillips et al. 2008). Emotion regulation also occurs voluntarily through selective attention (Erk et al. 2007; Goldstein et al. 2007), emotion suppression and reinterpretation of the emotional content (Ochsner et al. 2013). Voluntary emotion suppression relies on the activation of ventrolateral and dorsolateral cortices, which are mainly involved in cognitive and higher-order executive functions, and deliver indirect connections to the amygdala via the paleocortex (Bickart et al. 2014).