Parasympathetic and sympathetic nervous systems, which are part of the autonomic nervous system (ANS). The ANS maintains
homeostasis, or a balance of forces or equilibrium, for your entire body.
Among other functions, it controls the rate at which your heart beats, how fast you breathe, how much saliva your mouth is making, the rate of movement of material in your gut, your ability to initiate urination, how much you are perspiring, the size of your pupils, and the degree of visible sexual excitation you might experience.
Within the human brain are numerous acetylcholine pathways that infl uence the function of the cortex, hippocampus, and many other regions Within these various regions, the actions of acetylcholine allow you to learn and remember, to regulate your attention and mood, and to control how well you can move.
Thus, anything that affects the function of acetylcholine neurons has the potential to affect all of these brain and body functions. That “anything” could be a certain drug or a disease.
Sometimes we can learn much about the role of a particular neurotransmitter system by investigating what happens when it is injured or diseased.
In the brains of people with Alzheimer’s disease, for example, acetylcholine neurons that project into the hippocampus and cortex very slowly die.
The effects of this neuronal death have been the subject of research in my laboratory for more than 25years.
The loss of normal acetylcholine function in the cortex may be why patients with Alzheimer’s disease have difficulty paying attention to their environment.
The loss of acetylcholine projections to the amygdala, part of the brain’s limbic system, may underlie the emotional instability, such as irritability and paranoia, that is sometimes observed in these patients.
And the loss of acetylcholine projections into the hippocampus may underlie the profoundly debilitating memory loss that is the major hallmark of this disease.
Let me illustrate the effect of at least one of these losses by first describing the role of acetylcholine in the cortex of a normal brain (yours).
Imagine that, using an electroencephalogram or EEG, I have attached some electrodes to the front half of your head to record the electrical activity occurring inside your brain.
Next, I calmly inform you that as soon as I ring a bell (at the point in time shown by the number masked gunman will enter the room and start shooting. [You must also believe that I’m telling the truth for this to work.] Okay, now I ring the bell.
Take a look at the EEG recording labeled “ pre” in the figure. It shows that an electrical wave quickly appears within the frontal lobes of your brain that began as soon as I rang the bell.
The bell ringing causes those sharp spikes prior to the formation of the wave. This electrical pattern, also known as an EEG wave, will continue to live in your brain until one of two things happens: either someone runs into the room with a gun (at the point in time shown by the number 3) or the bell rings again and you decide nothing is going to happen after all.
At that point, the EEG wave will disappear. This prewave indicates that you were paying close attention to what you thought was about to happen. It is an expression of your brain experiencing anticipation.
Experiments in my laboratory and in others have demonstrated that the appearance of this wave of electrical activity requires the normal function of acetylcholine within your frontal cortex.
If the acetylcholine neurons that project into your frontal cortex are destroyed, then this wave cannot fully form and you will have great difficulty paying attention to important things, such as the impending appearance of a masked gunman.
An example of such a wave is labeled “ post” in the fi gure. In this case, the absence of acetylcholine does not allow the wave to fully develop.
This research has demonstrated that acetylcholine’s job is to instruct the neurons in your frontal cortex to pay attention to important information and be vigilant to impending danger.
If acetylcholine function is impaired, this ability is lost. These results provide valuable insight into why patients with Alzheimer’s disease have trouble paying attention to things that might be important, or even harmful, to them.
Indeed, during the later stages of their disease, when most of these acetylcholine neurons have disappeared, patients have difficulty paying attention to anything at all.
homeostasis, or a balance of forces or equilibrium, for your entire body.
Among other functions, it controls the rate at which your heart beats, how fast you breathe, how much saliva your mouth is making, the rate of movement of material in your gut, your ability to initiate urination, how much you are perspiring, the size of your pupils, and the degree of visible sexual excitation you might experience.
Within the human brain are numerous acetylcholine pathways that infl uence the function of the cortex, hippocampus, and many other regions Within these various regions, the actions of acetylcholine allow you to learn and remember, to regulate your attention and mood, and to control how well you can move.
Thus, anything that affects the function of acetylcholine neurons has the potential to affect all of these brain and body functions. That “anything” could be a certain drug or a disease.
Sometimes we can learn much about the role of a particular neurotransmitter system by investigating what happens when it is injured or diseased.
In the brains of people with Alzheimer’s disease, for example, acetylcholine neurons that project into the hippocampus and cortex very slowly die.
The effects of this neuronal death have been the subject of research in my laboratory for more than 25years.
The loss of normal acetylcholine function in the cortex may be why patients with Alzheimer’s disease have difficulty paying attention to their environment.
The loss of acetylcholine projections to the amygdala, part of the brain’s limbic system, may underlie the emotional instability, such as irritability and paranoia, that is sometimes observed in these patients.
And the loss of acetylcholine projections into the hippocampus may underlie the profoundly debilitating memory loss that is the major hallmark of this disease.
Let me illustrate the effect of at least one of these losses by first describing the role of acetylcholine in the cortex of a normal brain (yours).
Imagine that, using an electroencephalogram or EEG, I have attached some electrodes to the front half of your head to record the electrical activity occurring inside your brain.
Next, I calmly inform you that as soon as I ring a bell (at the point in time shown by the number masked gunman will enter the room and start shooting. [You must also believe that I’m telling the truth for this to work.] Okay, now I ring the bell.
Take a look at the EEG recording labeled “ pre” in the figure. It shows that an electrical wave quickly appears within the frontal lobes of your brain that began as soon as I rang the bell.
The bell ringing causes those sharp spikes prior to the formation of the wave. This electrical pattern, also known as an EEG wave, will continue to live in your brain until one of two things happens: either someone runs into the room with a gun (at the point in time shown by the number 3) or the bell rings again and you decide nothing is going to happen after all.
At that point, the EEG wave will disappear. This prewave indicates that you were paying close attention to what you thought was about to happen. It is an expression of your brain experiencing anticipation.
Experiments in my laboratory and in others have demonstrated that the appearance of this wave of electrical activity requires the normal function of acetylcholine within your frontal cortex.
If the acetylcholine neurons that project into your frontal cortex are destroyed, then this wave cannot fully form and you will have great difficulty paying attention to important things, such as the impending appearance of a masked gunman.
An example of such a wave is labeled “ post” in the fi gure. In this case, the absence of acetylcholine does not allow the wave to fully develop.
This research has demonstrated that acetylcholine’s job is to instruct the neurons in your frontal cortex to pay attention to important information and be vigilant to impending danger.
If acetylcholine function is impaired, this ability is lost. These results provide valuable insight into why patients with Alzheimer’s disease have trouble paying attention to things that might be important, or even harmful, to them.
Indeed, during the later stages of their disease, when most of these acetylcholine neurons have disappeared, patients have difficulty paying attention to anything at all.
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