 |
| Learning about the Brain |
Learning about the Brain
There are a number of sources of information about the structure and operation of the brain.
Brain injuries
Whenever someone experiences a damaging head wound and survives, there is an opportunity to compare any resulting disability with the damaged region of the brain.
Historically, the advent of high-speed bullets in the 19th century led to many nonfatal head wounds. Survivors had characteristic impairments when specific parts of the brain were injured.
Animal experiments
While there are recognized ethical constraints that limit neural experiments on humans, there are as yet few constraints limiting experiments on animals. And since there are many parallels between the structures of human and animal brains, much has been learned from animal studies about how our brains function. Continued experiments on animals reflect our basic ignorance of subtle biological processes.
Brain surgery
The techniques and procedures for performing successful operations on human brains evolved rapidly during the 20th century. There are no pain sensors in the brain itself and patients are normally restrained but awake during brain surgery. Surgeons can then talk to patients during an operation to confirm that incisions are having the intended effect.
During operations to treat patients with severe epilepsy, Wilder Penfield discovered that stimulating specific regions of the brain produced physical sensations. During the early 1950’s, he demonstrated that the sense of touch for each part of the body’s surface is represented on the parietal lobe (see section 1.1.4), and that adjacent parts of the body are represented on adjacent parts of the brain. Penfield also found that the more important and sensitive body regions have proportionally greater parts of the brain assigned to them. He discovered, as well, that stimulation of other regions could elicit particular memories in a patient.
In the 1960’s, a new operation was designed to ease the symptoms of severe epilepsy. In this operation the main connection (corpus callosum) between the left and right cerebral hemispheres of the forebrain is severed to prevent future epileptic seizures from spreading across the whole brain. While the operation limited the damage of epileptic seizures, it also led to characteristic deficiencies. Roger Sperry won the Nobel Prize in 1981 for his studies of the subsequent behavioural characteristics of these patients.
Brain scans
Non-invasive scanning techniques allow the human brain to be studied in action. A variety of scanning techniques have been developed since 1920, when the German physiologist, Hans Berger, first used electroencephalography to study the human brain. Newer techniques can detect activity in smaller regions of the brain over shorter time periods.
Here are brief descriptions of some of the common scanning techniques: 1. EEG – Electroencephalography – measures the electrical activity of the brain as detected by electrodes on the surface of the head.
2. MEG – Magnetoencephalography – similar to EEG but it measures magnetic signals.
3. MRI – Magnetic Resonance Imaging – uses strong magnetic fields and radio waves to analyze soft tissue. It can be used on any part of the body, including the brain.
4. CT – Computerized Tomography (or CAT – Computerized Axial Tomography) – converts the information from a MRI into a three dimensional image.
5. fMRI – functional MRI – a newer version of MRI that is much faster (and much more expensive).
6. PET – Positron Emission Topography – requires the injection of a radioactive substance into a patient’s bloodstream. The patient is given a specific mental task to perform and the most active areas of the brain then absorb the most radioactive material.
7. NIRS – Near-Infra-Red Spectroscopy – can be used to assess brain function by detecting changes in blood hemoglobin concentrations that are associated with neural activity.
There are a number of sources of information about the structure and operation of the brain.
Brain injuries
Whenever someone experiences a damaging head wound and survives, there is an opportunity to compare any resulting disability with the damaged region of the brain.
Historically, the advent of high-speed bullets in the 19th century led to many nonfatal head wounds. Survivors had characteristic impairments when specific parts of the brain were injured.
Animal experiments
While there are recognized ethical constraints that limit neural experiments on humans, there are as yet few constraints limiting experiments on animals. And since there are many parallels between the structures of human and animal brains, much has been learned from animal studies about how our brains function. Continued experiments on animals reflect our basic ignorance of subtle biological processes.
Brain surgery
The techniques and procedures for performing successful operations on human brains evolved rapidly during the 20th century. There are no pain sensors in the brain itself and patients are normally restrained but awake during brain surgery. Surgeons can then talk to patients during an operation to confirm that incisions are having the intended effect.
During operations to treat patients with severe epilepsy, Wilder Penfield discovered that stimulating specific regions of the brain produced physical sensations. During the early 1950’s, he demonstrated that the sense of touch for each part of the body’s surface is represented on the parietal lobe (see section 1.1.4), and that adjacent parts of the body are represented on adjacent parts of the brain. Penfield also found that the more important and sensitive body regions have proportionally greater parts of the brain assigned to them. He discovered, as well, that stimulation of other regions could elicit particular memories in a patient.
In the 1960’s, a new operation was designed to ease the symptoms of severe epilepsy. In this operation the main connection (corpus callosum) between the left and right cerebral hemispheres of the forebrain is severed to prevent future epileptic seizures from spreading across the whole brain. While the operation limited the damage of epileptic seizures, it also led to characteristic deficiencies. Roger Sperry won the Nobel Prize in 1981 for his studies of the subsequent behavioural characteristics of these patients.
Brain scans
Non-invasive scanning techniques allow the human brain to be studied in action. A variety of scanning techniques have been developed since 1920, when the German physiologist, Hans Berger, first used electroencephalography to study the human brain. Newer techniques can detect activity in smaller regions of the brain over shorter time periods.
Here are brief descriptions of some of the common scanning techniques: 1. EEG – Electroencephalography – measures the electrical activity of the brain as detected by electrodes on the surface of the head.
2. MEG – Magnetoencephalography – similar to EEG but it measures magnetic signals.
3. MRI – Magnetic Resonance Imaging – uses strong magnetic fields and radio waves to analyze soft tissue. It can be used on any part of the body, including the brain.
4. CT – Computerized Tomography (or CAT – Computerized Axial Tomography) – converts the information from a MRI into a three dimensional image.
5. fMRI – functional MRI – a newer version of MRI that is much faster (and much more expensive).
6. PET – Positron Emission Topography – requires the injection of a radioactive substance into a patient’s bloodstream. The patient is given a specific mental task to perform and the most active areas of the brain then absorb the most radioactive material.
7. NIRS – Near-Infra-Red Spectroscopy – can be used to assess brain function by detecting changes in blood hemoglobin concentrations that are associated with neural activity.
