23/07/54 ลักษณะของยาและสารเสพติด ‐Psychotomimetics, <strong>and</strong> some are Psychedelics ‐Euphoria, Ecstasy etc. ‐Reward <strong>and</strong> Reinforcement ‐Tolerance ‐Withdrawal syndromes <strong>and</strong> Dysphoria yp ‐Physical, psychological <strong>and</strong> behavioural dependence ‐Craving ‐Compulsive drug seeking behaviour ‐Relapse Brain Reward System Serotonin 5‐hydroxy tryptamine Raphe nucleus 26
23/07/54 415703 Cognitive Neuropsychology Week 3: Sensory ‐motor <strong>and</strong> cortical organization Naiphinich Kotchabhakdi, Ph.D. Director, Salaya Stem Cell R & D Project, Research Center for Neuroscience, Institute of Molecular Biosciences, Mahidol University Salaya Campus, 999 Phutthamonthol 4 Road, Salaya, Phutthamonthol, Nakornpathom 73170 Thail<strong>and</strong> Email: scnkc@mahidol.ac.th or naiphinich@gmail.com Web: www.neuroscience.mahidol.ac.th Main Objectives: 1. Sensory ‐ motor <strong>and</strong> cortical organization? 2. The sensory systems? 3. The Reticular formation, Sensory‐Motor Integration for states of Consciousness, Waking, Sleep <strong>and</strong> Dream. 4. The Motor System, Movements <strong>and</strong> Motor Controls 5. The Cerebral Cortex, <strong>and</strong> Cortical Columnar Organization, Concepts of functional localization <strong>and</strong> representation in the brain <strong>and</strong> brain mapping. 6. Brain Imaging <strong>and</strong> Functional Brain Imaging. sensory system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory receptors, neural pathways, <strong>and</strong> parts of the brain involved in sensory perception. Commonly recognized sensory systems are those for vision, hearing, somatic sensation (touch), taste <strong>and</strong> olfaction (smell). In short, senses are transducers from the physical world to the realm of the mind. The receptive field is the specific part of the world to which a receptor organ <strong>and</strong> receptor cells respond. For instance, the part of the world an eye can see, is its receptive field; the light that each rod or cone can see, is its receptive field. Receptive fields have been identified for the visual system, auditory system <strong>and</strong> somatosensory system, so far. Somatosensory system Dermatome Reticular Formation Ascending Reticular Activating System (ARAS) Regulation of States of Consciousness, e.g. waking, Sleep, Dream; attention; sensory‐motor integration Reticular formation is a part of the brain that is involved in actions such as awaking/sleeping cycle, <strong>and</strong> filtering incoming stimuli to discriminate irrelevant background stimuli. It is essential for governing some of the basic functions of higher organisms, <strong>and</strong> is one of the phylogenetically oldest portions of the brain. The reticular formation consists of more than 100 small neural networks, with varied functions including the following: 1. Somatic motor control ‐ Some motor neurons send their axons to the reticular formation nuclei, giving rise to the reticulospinal tracts of the spinal cord. These tracts function in maintaining tone, balance, <strong>and</strong> posture‐‐especially during body movements. The reticular formation also relays eye <strong>and</strong> ear signals to the cerebellum so that the cerebellum can integrate visual, auditory, <strong>and</strong> vestibular stimuli in motor coordination. Other motor nuclei include gaze centers, which enable the eyes to track <strong>and</strong> fixate objects, <strong>and</strong> central pattern generators, which produce rhythmic signals to the muscles of breathing <strong>and</strong> swallowing. 2. Cardiovascular control ‐ The reticular formation includes the cardiac <strong>and</strong> vasomotor centers of the medulla oblongata. 3. Pain modulation ‐ The reticular formation is one means by which pain signals from the lower body reach the cerebral cortex. It is also the origin of the descending analgesic pathways. Thenervefibersin these pathways act in the spinal cord to block the transmission of some pain signals to the brain. 4. Sleep <strong>and</strong> consciousness ‐ The reticular formation has projections to the thalamus <strong>and</strong> cerebral cortex that allow it to exert some control over which sensory signals reach the cerebrum <strong>and</strong> come to our conscious attention. It plays a central role in states of consciousness like alertness <strong>and</strong> sleep. Injury to the reticular formation can result in irreversible coma. 5. Habituation ‐ This is a process in which the brain learns to ignore repetitive, meaningless stimuli while remaining sensitive to others. A good example of this is when a person can sleep through loud traffic in a large city, but is awakened promptly due to the sound of an alarm or crying baby. Reticular formation nuclei that modulate activity of the cerebral cortex are called the reticular activating system or extrathalamic control modulatory system. 27
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