Neural networks provide the biological functionality that mediates consciousness. The neural network includes the peripheral nervous system as well as the central nervous system. A small dynamic subset of neurons, principally in the with temporal, parietal, and occipital cortices, where they receive higher-level visual, auditory, and somatosensory information. (Miller, Several frequency bands are often mentioned: Alpha frequencies, Delta frequencies, gamma frequencies, higher frequencies. can recall the appropriate memory from the network when provided with a fragment of one of the memories. This is called completion. (Rolls Joaquín Fuster has coined the term 'cognit' as a generic term for any representation of knowledge in the cerebral cortex. , which always stand ready to initiate movement. To effect a movement commanded by the motor cortex, an excitatory signal stimulates an inhibitory path that inhibits the quiescent inhibitory activity of the basal ganglia. The result is that body movement can respond quickly, is disproportionately larger in humans than other primates, which suggests a higher degree of connectivity in this part of the brain. (Gazzaniga, tend to have the greatest density of commissural projections, whereas fewer interhemispheric connections are present between primary sensory and motor cortices. (Miller, , allows radial communication of the thalamic nuclei with all aspects of the cortex. These cortical regions include the sensory, motor, and associational areas. These areas subserve a Thalamocortical system evolved to receive signals from sensory receptor sheets and give signals to voluntary muscles. Thalamocortical system is very fast in its responses (milliseconds to seconds), although its synaptic connections undergo some changes that last a lifetime. Cerebral cortex is arranged as a set of maps, which receive inputs via the thalamus. Most neurons in the thalamocortical system receive signals from other neurons, rather than directly from sensory inputs. (Edelman, In primary sensory cortical areas, the main extrinsic forward input is from the thalamus, and ends in layer 4, where synapses are formed onto spiny stellate cells. These in turn project heavily onto pyramidal cells in layers 3 and 2, which in turn send projections forward to the next cortical area. (Rolls The circuitry is more complex because the thalamic afferents also synapse onto the basal dendrites in or close to the layer 2 pyramidal cells, as well is onto layer 6 pyramidal cells and inhibitory interneurons. (Rolls Forward corto-cortical afferents to a cortical area sometimes have a columnar pattern to their distribution, with a column width 200-300 µ in diameter. (Rolls Orbitofrontal cortex, amygdala and hippocampus are stages of information processing at which the different sensory modalities (such as vision, hearing, touch, taste, and smell for the orbitofrontal cortex and amygdala) are brought together, so that correlations between inputs in different modalities can be detected in these regions, but not at prior cortical processing stages in each modality, as these cortical processing stages are mainly unimodal. (Rolls Brain can achieve the modification of body maps very rapidly, in the time scale of hundreds of milliseconds or less. (Damasio, Timescale for the brain to induce changes in the body-proper is seconds. It takes about one second for a long and often myelinated axon to convey signals to body parts. (Damasio, It takes a few seconds for a hormone to be released into the bloodstream and began to produce its cascade of subsequent effects. (Damasio, Columbus metaphor for growth cones. Don’t try to overextend this metaphor, just use it as a vague notion. In subsequent years, many other ships probed the lands. Only a few developed into active ports. Source.


Яндекс.Метрика Рейтинг@Mail.ru Free Web Counter
page counter
Last Modified: April 18, 2016 @ 6:09 pm