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Chapter: Chapter 1: Essay
Essay
1. Describe five distal stimuli and their associated proximal stimuli that one experiences in the
environment. No two stimuli should have the same perceptual dimension. For each of these distal
stimuli, discuss the top-down information used in perceiving it.
Ans: Answers should first relate sensory experience (visual, auditory, olfactory, etc.) to the
physical objects (or, distal stimuli) in the environment, and then show how knowledge and
expectations of an observer lead to perception of the stimuli.
2. Describe three activities in which one uses three different senses to detect small differences in
the intensity of sensory stimuli. What role does difference threshold play in each activity?
Ans: Cooking can be taken as an example here because one needs to adjust seasonings based on
the perception of taste. Similarly, proper functioning of a mechanical device (car, air conditioner,
etc.) can be detected based on the sound it makes. In the same way, an observer’s like or dislike
for a painting depends on his or her visual perception. The minimum difference between two
stimuli that allows an observer to perceive that the two stimuli are different is known as a
difference threshold. In all these cases, difference threshold helps an observer to differentiate
between any two given stimuli.
,3. Compare the advantages and disadvantages of the method of adjustment, the method of
constant stimuli, and the staircase method in determining absolute threshold.
Ans: The method of adjustment is the simplest method for estimating absolute thresholds. In this
method, a person observes the stimulus and manipulates a control that directly adjusts the
intensity of the stimulus. The results tend to vary quite a bit, even when the method is used
repeatedly with the same person. When compared with the method of adjustment, the method of
constant stimuli provides more reliable results. It isn’t very efficient because it involves repeated
presentations of stimuli that are already known to be well below or well above threshold. Hence,
presenting these stimuli doesn’t generate much useful data. The staircase method is a more
efficient version of the method of constant stimuli. It can be used to eliminate repeated
presentations of stimuli well below or above the threshold and to focus instead on presenting
stimuli near the threshold.
4. If the volume on an audio device is increased from one to two, how should the physical
intensity of the sound be changed so that the perceived intensity is doubled? Explain with the
help of Fechner’s law.
Ans: According to the text, when the physical intensity of a stimulus is low, doubling the
physical stimulus will double the perceived intensity of the stimulus. However, if the intensity of
the stimulus is much greater, there should be a considerable increase in the physical stimulus to
produce a noticeable difference in the perceived intensity.
5. What is the role of voltage-gated channels in the course of an action potential? Describe the
events in which they play their crucial role.
Ans: When a neuron receives a signal from another neuron, the receiving neuron undergoes an
abrupt change in membrane potential, which causes voltage-gated sodium channels to open at the
base of the axon, where it emerges from the cell body. This in turn allows extracellular sodium
ions (Na+) to flow into the axon. They move into the axon because the concentration of Na+ ions
is much greater outside the membrane than inside. The influx of positively charged Na+ ions
,causes the membrane potential to become more positive. This change in membrane potential is
called depolarization because the membrane potential is becoming less polarized—that is, less
extreme, moving from −70 mV toward 0. If the depolarization surpasses a threshold at about −45
mV, the inflow of Na+ ions continues rapidly until the difference in electric charge at the inner
and outer surfaces of the membrane is reversed, with the inside of the axon becoming more
positively charged than the outside, resulting in a membrane potential of about +30 mV at its
peak. Immediately after the sodium channels open, they close again, stemming the inflow of Na+
ions, and nearby potassium channels open (in response to the depolarization of the membrane),
allowing positively charged potassium ions (K+) to flow out of the axon, again driven by the
concentration difference. The outflow of K+ ions pushes the membrane potential back toward its
resting value of −70 mV, a process called repolarization. Like the sodium channels, the
potassium channels close again immediately after opening. The membrane potential briefly
exceeds the resting potential—this is termed hyperpolarization—before returning to the resting
potential.
6. How are neural signals transmitted across a synapse? How do the presynaptic membrane, the
postsynaptic membrane, the synaptic vesicles, and neurotransmitters react to an action potential?
Ans: A synapse is a tiny gap between the axon terminal of one neuron and the dendrite or cell
body of another neuron. Within an axon terminal, synaptic vesicles contain neurotransmitter
molecules. The arrival of an action potential causes the synaptic vesicles to merge with the
presynaptic membrane, which releases neurotransmitter molecules into the synapse. Some
neurotransmitter molecules drift across the synapse and bind to receptors on the postsynaptic
membrane (the neurotransmitter molecules fit into the receptors the way a key fits into a lock).
Binding causes ion channels to open on the postsynaptic membrane.
7. What is diffuse optical tomography (DOT), and how is it advantageous over PET and fMRI?
Ans: Diffuse optical tomography (DOT), an emerging type of brain imaging, senses changes in
the blood oxygen level in the brain by using optical techniques. DOT employs an array of near-
infrared light sources and sensors placed on the head that measure changes in the light reflected
by the brain, caused by changes in blood flow. The method has some advantages over PET and
fMRI: it does not require the introduction of radioactive substances into the participant’s body
(as PET does), and it can be used with participants who have metal implanted in their body
(fMRI cannot be used with such participants because of the strong magnetic fields produced by
, that method). Also, DOT can be used in more naturalistic settings than PET and fMRI can be
used in because DOT equipment is relatively compact. DOT has similar temporal resolution to
fMRI but somewhat lower spatial resolution.
8. Explain how functional neuroimaging can be used to investigate areas in the brain that
perform specific functions.
Ans: Functional neuroimaging is an array of techniques that makes it possible for neuroscientists
to measure brain activity in healthy volunteers carrying out carefully designed perceptual and
cognitive tasks. Functional neuroimaging techniques can be divided into two broad types:
techniques for measuring the electrical or magnetic fields produced by populations of active
neurons (electroencephalography and magnetoencephalography) and techniques for measuring
the changes in blood flow and blood oxygenation that accompany brain activity (positron
emission tomography, functional magnetic resonance imaging, and diffuse optical tomography).
All of these techniques rely on the same assumptions of modularity and cognitive uniformity.
Electroencephalography (EEG) is a functional neuroimaging technique based on measurement of
the electrical fields associated with brain activity.
Magnetoencephalography (MEG) is a functional neuroimaging technique based on measurement
of the magnetic fields associated with brain activity. Positron emission tomography (PET) is a
functional neuroimaging technique based on measurement of the changes in blood flow
associated with brain activity; it relies on the introduction of a radioactive substance into the
blood. Functional magnetic resonance imaging (fMRI) is a functional neuroimaging technique
based on measurement of the changes in blood oxygenation associated with brain activity; it
relies on production of magnetic fields in the brain.
9. Explain the concept of modularity in cognitive neuropsychology with the help of an example.
Ans: Cognitive neuropsychology depends on the concept of modularity. Modularity is the idea
that the human mind and brain consist of a set of distinct modules, each of which carries out one
or more specific functions. Any complex task involves the coordinated activity of many
modules, each contributing its part—for example, the task of typing to spoken dictation engages
modules involved in audition, language, and finger movements, among others. A module
processes only specific types of information, such as information about faces or about speech—
that is, a module is domain specific.
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Multiple Keywords in Same Paragraph: No
Chapter: Chapter 1: Essay
Essay
1. Describe five distal stimuli and their associated proximal stimuli that one experiences in the
environment. No two stimuli should have the same perceptual dimension. For each of these distal
stimuli, discuss the top-down information used in perceiving it.
Ans: Answers should first relate sensory experience (visual, auditory, olfactory, etc.) to the
physical objects (or, distal stimuli) in the environment, and then show how knowledge and
expectations of an observer lead to perception of the stimuli.
2. Describe three activities in which one uses three different senses to detect small differences in
the intensity of sensory stimuli. What role does difference threshold play in each activity?
Ans: Cooking can be taken as an example here because one needs to adjust seasonings based on
the perception of taste. Similarly, proper functioning of a mechanical device (car, air conditioner,
etc.) can be detected based on the sound it makes. In the same way, an observer’s like or dislike
for a painting depends on his or her visual perception. The minimum difference between two
stimuli that allows an observer to perceive that the two stimuli are different is known as a
difference threshold. In all these cases, difference threshold helps an observer to differentiate
between any two given stimuli.
,3. Compare the advantages and disadvantages of the method of adjustment, the method of
constant stimuli, and the staircase method in determining absolute threshold.
Ans: The method of adjustment is the simplest method for estimating absolute thresholds. In this
method, a person observes the stimulus and manipulates a control that directly adjusts the
intensity of the stimulus. The results tend to vary quite a bit, even when the method is used
repeatedly with the same person. When compared with the method of adjustment, the method of
constant stimuli provides more reliable results. It isn’t very efficient because it involves repeated
presentations of stimuli that are already known to be well below or well above threshold. Hence,
presenting these stimuli doesn’t generate much useful data. The staircase method is a more
efficient version of the method of constant stimuli. It can be used to eliminate repeated
presentations of stimuli well below or above the threshold and to focus instead on presenting
stimuli near the threshold.
4. If the volume on an audio device is increased from one to two, how should the physical
intensity of the sound be changed so that the perceived intensity is doubled? Explain with the
help of Fechner’s law.
Ans: According to the text, when the physical intensity of a stimulus is low, doubling the
physical stimulus will double the perceived intensity of the stimulus. However, if the intensity of
the stimulus is much greater, there should be a considerable increase in the physical stimulus to
produce a noticeable difference in the perceived intensity.
5. What is the role of voltage-gated channels in the course of an action potential? Describe the
events in which they play their crucial role.
Ans: When a neuron receives a signal from another neuron, the receiving neuron undergoes an
abrupt change in membrane potential, which causes voltage-gated sodium channels to open at the
base of the axon, where it emerges from the cell body. This in turn allows extracellular sodium
ions (Na+) to flow into the axon. They move into the axon because the concentration of Na+ ions
is much greater outside the membrane than inside. The influx of positively charged Na+ ions
,causes the membrane potential to become more positive. This change in membrane potential is
called depolarization because the membrane potential is becoming less polarized—that is, less
extreme, moving from −70 mV toward 0. If the depolarization surpasses a threshold at about −45
mV, the inflow of Na+ ions continues rapidly until the difference in electric charge at the inner
and outer surfaces of the membrane is reversed, with the inside of the axon becoming more
positively charged than the outside, resulting in a membrane potential of about +30 mV at its
peak. Immediately after the sodium channels open, they close again, stemming the inflow of Na+
ions, and nearby potassium channels open (in response to the depolarization of the membrane),
allowing positively charged potassium ions (K+) to flow out of the axon, again driven by the
concentration difference. The outflow of K+ ions pushes the membrane potential back toward its
resting value of −70 mV, a process called repolarization. Like the sodium channels, the
potassium channels close again immediately after opening. The membrane potential briefly
exceeds the resting potential—this is termed hyperpolarization—before returning to the resting
potential.
6. How are neural signals transmitted across a synapse? How do the presynaptic membrane, the
postsynaptic membrane, the synaptic vesicles, and neurotransmitters react to an action potential?
Ans: A synapse is a tiny gap between the axon terminal of one neuron and the dendrite or cell
body of another neuron. Within an axon terminal, synaptic vesicles contain neurotransmitter
molecules. The arrival of an action potential causes the synaptic vesicles to merge with the
presynaptic membrane, which releases neurotransmitter molecules into the synapse. Some
neurotransmitter molecules drift across the synapse and bind to receptors on the postsynaptic
membrane (the neurotransmitter molecules fit into the receptors the way a key fits into a lock).
Binding causes ion channels to open on the postsynaptic membrane.
7. What is diffuse optical tomography (DOT), and how is it advantageous over PET and fMRI?
Ans: Diffuse optical tomography (DOT), an emerging type of brain imaging, senses changes in
the blood oxygen level in the brain by using optical techniques. DOT employs an array of near-
infrared light sources and sensors placed on the head that measure changes in the light reflected
by the brain, caused by changes in blood flow. The method has some advantages over PET and
fMRI: it does not require the introduction of radioactive substances into the participant’s body
(as PET does), and it can be used with participants who have metal implanted in their body
(fMRI cannot be used with such participants because of the strong magnetic fields produced by
, that method). Also, DOT can be used in more naturalistic settings than PET and fMRI can be
used in because DOT equipment is relatively compact. DOT has similar temporal resolution to
fMRI but somewhat lower spatial resolution.
8. Explain how functional neuroimaging can be used to investigate areas in the brain that
perform specific functions.
Ans: Functional neuroimaging is an array of techniques that makes it possible for neuroscientists
to measure brain activity in healthy volunteers carrying out carefully designed perceptual and
cognitive tasks. Functional neuroimaging techniques can be divided into two broad types:
techniques for measuring the electrical or magnetic fields produced by populations of active
neurons (electroencephalography and magnetoencephalography) and techniques for measuring
the changes in blood flow and blood oxygenation that accompany brain activity (positron
emission tomography, functional magnetic resonance imaging, and diffuse optical tomography).
All of these techniques rely on the same assumptions of modularity and cognitive uniformity.
Electroencephalography (EEG) is a functional neuroimaging technique based on measurement of
the electrical fields associated with brain activity.
Magnetoencephalography (MEG) is a functional neuroimaging technique based on measurement
of the magnetic fields associated with brain activity. Positron emission tomography (PET) is a
functional neuroimaging technique based on measurement of the changes in blood flow
associated with brain activity; it relies on the introduction of a radioactive substance into the
blood. Functional magnetic resonance imaging (fMRI) is a functional neuroimaging technique
based on measurement of the changes in blood oxygenation associated with brain activity; it
relies on production of magnetic fields in the brain.
9. Explain the concept of modularity in cognitive neuropsychology with the help of an example.
Ans: Cognitive neuropsychology depends on the concept of modularity. Modularity is the idea
that the human mind and brain consist of a set of distinct modules, each of which carries out one
or more specific functions. Any complex task involves the coordinated activity of many
modules, each contributing its part—for example, the task of typing to spoken dictation engages
modules involved in audition, language, and finger movements, among others. A module
processes only specific types of information, such as information about faces or about speech—
that is, a module is domain specific.
