Methods of examining functions of CNS


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Methods of examining functions of CNS

  2. 2. EXTIRPATION METHOD- Theextirpation method attempts to determinethe function of a given part of the brain byremoving or destroying it and observingthe resulting changes in the animalsbehavior A method for extirpation of thepineal gland in albino rats and otherrodents (e. g., ground squirrels) isproposed. Epiphysectomy is carried out byresection of a fragment of the bone with theunderlying pineal gland. Using thismethod, many animals can be operatedwithin a short period; the method isreliable and simple, which recommends itfor chronobiological studies.  . Pierre Flourens (1794-1867) was a professor of natural history at the College de France in Paris, who systematically destroyed parts of the brain and spinal cord in pigeons and observed the consequences of doing so. Flourens concluded that the cerebrum controls higher mental processes, parts of the midbrain control visual and auditory reflexes, the cerebellum controls coordination, and the medulla governs heartbeat, respiration, and other vital functions. Marshall Hall (1790-1857) Focused more on different parts of the brain and nervous system. He postulated that voluntary moveThe extirpation method attempts to determine the function of a given part of the brain by removing or destroying it and observing the resulting changes in the animals behaviorment depends on the cerebrum, reflex movement on the spinal cord, involuntary movement on direct stimulation of the muscles, and respiratory movement on the medulla
  3. 3. Section of various parts of CNS where extirpation can be done-1.SPINAL LEVEL-at the level of upper segments of spinal cord.2.BULBAR LEVEL-between Medulla Oblongata and Mesencephalon.3.MESENCEPHALIC LEVEL-section between mid brain and hind brain.4.DIENCEPHALIC LEVEL-section above diencephalon.Local Damage-1.Mechanical-Pricking with a needle or scalpel.2.ELECTRICAL-Inserting thin electrodes into the brain through which directcurrent is passed and produces destruction of tissues.3.FREEZING OR THERMAL COAGULATION4.INTENSE X RAY OR ULTRASONIC VIBRATION-portions of brain tissue canbe damaged.nerve pathways can be damaged by vibrations of intensity that doesnot effect the nerve cells.
  4. 4. 5.PROTON RADIATION -Non-invasive. inserts electrodes. does not destroy skin or bones. apparatus is applied on some portions of brain.
  5. 5. Stimulation- Electrical stimulation-applying a weak electrical stimulation to definite parts of CNS to produce different motor reactions. Used in neurosurgical operations on humans. Employed to examine the functions of brain stem and spinal cord. For this purpose,electrodes are implanted in different brain structures and attached to cranial bones. Non-invasive technique known as transcranial direct current stimulation (TDCS). TDCS involves stimulating specific regions of the brain with low-level electrical currents to enhance or reduce the activity of neurons. Over the last decade, the procedure has shown promise at improving brain. functioning in stroke victims as well as in people withParkinsons disease. But this is the first study to show that TDCS can help healthy individuals do better on math tests.
  6. 6. Chemical brain stimulation is the application of chemicals to brain tissue in orderto study aspects of neurochemistry , neuroanatomy andneurophysiology.Intoduction of different chemicals stimulate different parts of CNS.Uses the technique of electrophoresis.A small micro pipette filled with solution is introduced into nerve smallelectrode is inserted into mico pipette.another electrode is applied to the surface othe body.when a weak DC is passed through the electrodes,the solution from thepipette is introduced into the tissue. Electrophysiology is the study of the electrical properties of biological cells and tissues. It involves measurements of voltage change or electric current on a wide variety of scales from single ion channel proteins to whole organs like the heart. In neuroscience, it includes measurements of the electrical activity of neurons, and particularly action potential activity. Recordings of large-scale electric signals from the nervous system. Used in acute and chronic expts and neurosurgical operations.
  7. 7. Stereotactic surgery or stereotaxy is a minimally invasive form of surgical intervention which makes use of a three-dimensional coordinates system to locate small targets inside the body and to perform on them some action such as ablation (removal),biopsy, lesion, injection, stimulation, implantation, radiosurgery (SRS) etc.its applications have been limited to brain surgery The Horsley–Clarke apparatus they developed was used for animal experimentation and implemented a Cartesian (three-orthogonal axis) system. Improved designs of their original device came into use in the 1930s for animal experimentation and are still in wide use today in all animal neuroscience laboratories
  8. 8. Electroencephalography-EEG refers to the recording of the brains spontaneouselectrical activity over a short period of time, usually 20–40 minutes, as recordedfrom multiple electrodes placed on the scalp.In neurology, the main diagnostic applicationof EEG is in the case of epilepsy, as epilepticactivity can create clear abnormalities on astandard EEG study.[3] A secondary clinical use of EEG is in thediagnosis of coma, encephalopathies,and brain death. EEG used to be a first-line method for thediagnosis of tumors, stroke and other focalbrain disorders, but this use has decreasedwith the advent of anatomical imagingtechniques such as MRI and CT.
  9. 9. Wave patternsdelta waves.Delta is the frequency range up to 4 Hz. It tends to bethe highest in amplitude and the slowest waves. It isseen normally in adults in deep sleep. It is also seennormally in babies. It may occur focally with subcorticallesions and in general distribution with diffuse lesions,metabolic encephalopathy hydrocephalus or deepmidline lesions. It is usually most prominent frontally inadults (e.g. FIRDA - Frontal Intermittent RhythmicDelta) and posteriorly in children (e.g. OIRDA -Occipital Intermittent Rhythmic Delta).theta waves.Theta is the frequency range from 4 Hz to 7 Hz. Theta isseen normally in young children. It may be seen indrowsiness or arousal in older children and adults; itcan also be seen in meditation.[17] Excess theta for agerepresents abnormal activity. It can be seen as a focaldisturbance in focal subcortical lesions; it can be seen ingeneralized distribution in diffuse disorder or metabolicencephalopathy or deep midline disorders or someinstances of hydrocephalus. On the contrary this rangehas been associated with reports of relaxed, meditative,and creative states.
  10. 10. Alpha is the frequency range from 8 Hz to 12 Hz. Hans Berger named the firstrhythmic EEG activity he saw as the "alpha wave". This was the "posterior basicrhythm" (also called the "posterior dominant rhythm" or the "posterior alpharhythm"), seen in the posterior regions of the head on both sides, higher in amplitudeon the dominant side. It emerges with closing of the eyes and with relaxation, andattenuates with eye opening or mental exertion. The posterior basic rhythm isactually slower than 8 Hz in young children (therefore technically in the theta range).beta waves.Beta is the frequency range from 12 Hz to about 30 Hz. It is seen usually on bothsides in symmetrical distribution and is most evident frontally. Beta activity is closelylinked to motor behavior and is generally attenuated during activemovements.[20] Low amplitude beta with multiple and varying frequencies is oftenassociated with active, busy or anxious thinking and active concentration. Rhythmicbeta with a dominant set of frequencies is associated with various pathologies anddrug effects, especially benzodiazepines. It may be absent or reduced in areas ofcortical damage. It is the dominant rhythm in patients who are alert or anxious orwho have their eyes open.gamma waves.Gamma is the frequency range approximately 30–100 Hz. Gamma rhythms arethought to represent binding of different populations of neurons together into anetwork for the purpose of carrying out a certain cognitive or motor function.[2]