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Nociception is the sensory nervous system's process of encoding noxious stimuli. In nociception, intense chemical, mechanical, or thermal stimulation of sensory nerve cells called nociceptors produces a signal that travels along a chain of nerve fibers via the spinal cord to the brain. Nociception triggers a variety of physiological and behavioral responses and usually results in a subjective experience, or perception, of pain in sentient beings.
Pain is a distressing feeling often caused by intense or damaging stimuli. The International Association for the Study of Pain defines pain as "an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage." In medical diagnosis, pain is regarded as a symptom of an underlying condition.
The visual cortex of the brain is the area of the cerebral cortex that processes visual information. It is located in the occipital lobe. Sensory input originating from the eyes travels through the lateral geniculate nucleus in the thalamus and then reaches the visual cortex. The area of the visual cortex that receives the sensory input from the lateral geniculate nucleus is the primary visual cortex, also known as visual area 1 (V1), Brodmann area 17, or the striate cortex. The extrastriate areas consist of visual areas 2, 3, 4, and 5.
A free nerve ending (FNE) or bare nerve ending, is an unspecialized, afferent nerve fiber sending its signal to a sensory neuron. Afferent in this case means bringing information from the body's periphery toward the brain. They function as cutaneous nociceptors and are essentially used by vertebrates to detect noxious stimuli that often result in pain.
A nociceptor is a sensory neuron that responds to damaging or potentially damaging stimuli by sending “possible threat” signals to the spinal cord and the brain. If the brain perceives the threat as credible, it creates the sensation of pain to direct attention to the body part, so the threat can hopefully be mitigated; this process is called nociception.
The pretectal area, or pretectum, is a midbrain structure composed of seven nuclei and comprises part of the subcortical visual system. Through reciprocal bilateral projections from the retina, it is involved primarily in mediating behavioral responses to acute changes in ambient light such as the pupillary light reflex, the optokinetic reflex, and temporary changes to the circadian rhythm. In addition to the pretectum's role in the visual system, the anterior pretectal nucleus has been found to mediate somatosensory and nociceptive information.
Neuralgia is pain in the distribution of a nerve or nerves, as in intercostal neuralgia, trigeminal neuralgia, and glossopharyngeal neuralgia.
Thalamocortical radiations are the fibers between the thalamus and the cerebral cortex.
In the scientific study of vision, smooth pursuit describes a type of eye movement in which the eyes remain fixated on a moving object. It is one of two ways that visual animals can voluntarily shift gaze, the other being saccadic eye movements. Pursuit differs from the vestibulo-ocular reflex, which only occurs during movements of the head and serves to stabilize gaze on a stationary object. Most people are unable to initiate pursuit without a moving visual signal. The pursuit of targets moving with velocities of greater than 30°/s tends to require catch-up saccades. Smooth pursuit is asymmetric: most humans and primates tend to be better at horizontal than vertical smooth pursuit, as defined by their ability to pursue smoothly without making catch-up saccades. Most humans are also better at downward than upward pursuit. Pursuit is modified by ongoing visual feedback.
The gate control theory of pain asserts that non-painful input closes the nerve "gates" to painful input, which prevents pain sensation from traveling to the central nervous system.
In cognitive neuroscience, visual modularity is an organizational concept concerning how vision works. The way in which the primate visual system operates is currently under intense scientific scrutiny. One dominant thesis is that different properties of the visual world require different computational solutions which are implemented in anatomically/functionally distinct regions that operate independently – that is, in a modular fashion.
Group C nerve fibers are one of three classes of nerve fiber in the central nervous system (CNS) and peripheral nervous system (PNS). The C group fibers are unmyelinated and have a small diameter and low conduction velocity, whereas Groups A and B are myelinated. Group C fibers include postganglionic fibers in the autonomic nervous system (ANS), and nerve fibers at the dorsal roots. These fibers carry sensory information.
Nav1.8 is a sodium ion channel subtype that in humans is encoded by the SCN10A gene.
In neuroscience, the N100 or N1 is a large, negative-going evoked potential measured by electroencephalography ; it peaks in adults between 80 and 120 milliseconds after the onset of a stimulus, and is distributed mostly over the fronto-central region of the scalp. It is elicited by any unpredictable stimulus in the absence of task demands. It is often referred to with the following P200 evoked potential as the "N100-P200" or "N1-P2" complex. While most research focuses on auditory stimuli, the N100 also occurs for visual, olfactory, heat, pain, balance, respiration blocking, and somatosensory stimuli.
Whether fish feel pain similar to humans or differently is a contentious issue. Pain is a complex mental state, with a distinct perceptual quality but also associated with suffering, which is an emotional state. Because of this complexity, the presence of pain in an animal, or another human for that matter, cannot be determined unambiguously using observational methods, but the conclusion that animals experience pain is often inferred on the basis of likely presence of phenomenal consciousness which is deduced from comparative brain physiology as well as physical and behavioural reactions.
Peter John Snow, Dr. is an Australian neuroscientist and author.
Pain in invertebrates is a contentious issue. Although there are numerous definitions of pain, almost all involve two key components. First, nociception is required. This is the ability to detect noxious stimuli which evokes a reflex response that moves the entire animal, or the affected part of its body, away from the source of the stimulus. The concept of nociception does not necessarily imply any adverse, subjective feeling; it is a reflex action. The second component is the experience of "pain" itself, or suffering—i.e., the internal, emotional interpretation of the nociceptive experience. Pain is therefore a private, emotional experience. Pain cannot be directly measured in other animals, including other humans; responses to putatively painful stimuli can be measured, but not the experience itself. To address this problem when assessing the capacity of other species to experience pain, argument-by-analogy is used. This is based on the principle that if a non-human animal's responses to stimuli are similar to those of humans, it is likely to have had an analogous experience. It has been argued that if a pin is stuck in a chimpanzee's finger and they rapidly withdraw their hand, then argument-by-analogy implies that like humans, they felt pain. It has been questioned why the inference does not then follow that a cockroach experiences pain when it writhes after being stuck with a pin. This argument-by-analogy approach to the concept of pain in invertebrates has been followed by others.
As long as humans have experienced pain, they have given explanations for its existence and sought soothing agents to dull or cease the painful sensation. Archaeologists have uncovered clay tablets dating back as far as 5,000 BC which reference the cultivation and use of the opium poppy to bring joy and cease pain. In 800 BC, the Greek writer Homer wrote in his epic, The Odyssey, of Telemachus, a man who used opium to soothe his pain and forget his worries. While some cultures researched analgesics and allowed or encouraged their use, others perceived pain to be a necessary, integral sensation. Physicians of the 19th century used pain as a diagnostic tool, theorizing that a greater amount of personally perceived pain was correlated to a greater internal vitality, and as a treatment in and of itself, inflicting pain on their patients to rid the patient of evil and unbalanced humors. This article focuses both on the history of how pain has been perceived across time and culture, but also how malleable an individual's perception of pain can be due to factors like situation, their visual perception of the pain, and previous history with pain.
Robert H. Wurtz is an American neuroscientist working as a NIH Distinguished Scientist and Chief of the Section on Visuomotor Integration at the National Eye Institute. He is a member of the US National Academy of Sciences and the American Academy of Arts and Sciences. He is recognised for developing methods for studying the visual system in 'awake-behaving' primates, a technique now widely used for the study of higher brain functions. He pioneered the study of the neuronal basis of vision and its relation with cognitive functions.
Eberhard Erich Fetz is an American neuroscientist, academic and researcher. He is a Professor of Physiology and Biophysics and DXARTS at the University of Washington.
References
- ↑ "Trove". trove.nla.gov.au.
- 1 2 "Loop | Kenneth L Casey". loop.frontiersin.org.
- ↑ W. Edward Craighead; Charles B. Nemeroff (11 November 2002). The Corsini Encyclopedia of Psychology and Behavioral Science. John Wiley and Sons. p. 937. ISBN 978-0-471-27082-9 . Retrieved 15 May 2011.
- ↑ Melzack, R; Casey, KL (1968). "Sensory, motivational and central control determinants of chronic pain: A new conceptual model". In Kenshalo, DR. The Skin Senses. Springfield, Illinois: Thomas. p. 432.
- ↑ Casey, Kenneth (1966). "Unit analysis of nociceptive mechanisms in the thalamus of the awake squirrel monkey". Journal of Neurophysiology. 29 (4): 727–750. doi:10.1152/jn.1966.29.4.727. PMID 4961088.
- ↑ Casey, Kenneth; Minoshima, S.; Berger, K.L.; Koeppe, R.A.; Morrow, T.J.; Frey,K.A. (1994). "Positron emission tomographic analysis of cerebral structures activated specifically by repetitive noxious heat stimuli". Journal of Neurophysiology. 71 (2): 802–807. doi:10.1152/jn.1994.71.2.802. PMID 8176441.
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