Cognitive neuroscience
Chapter 1 – definitions, themes and approaches
Cognitive neuroscience is a relatively new discipline that has arisen from the recent marriage of
neuroscience and cognitive science.
Cognition means the faculty of knowing, but in practice it refers to the set of processes
(cognitive functions) that allow humans and many other animals to perceive external stimuli, to
extract key information and hold it in memory, and ultimately to generate thoughts and actions
that help reach desired goals. Cognition is sometimes described as processing carried out by
the mind. The phenomenology of cognition has always raised philosophical questions; how do
we perceive the world?
By the beginning of the 20th century there was a growing dissatisfaction with the lack of
systematic progress in the study of mental processes. Some parts of mental processes like
language seemed difficult to research and methods like introspection seemed imprecise. As a
result, psychology came to be dominated by an emphasis on controlled experiments and
measuring stimuli and behavior -> Behaviorism. This focus rejected the subjective work on
mental functions. The focus of behaviorists on learning from rewards has led them to ignore
other cognitive functions.
In the mid-20th century, a confluence of factors revived the legitimacy of psychological research
on cognitive functions. One factor was the advancement of computers and technology. Here,
the idea of the mind as a computer began. The computer model included symbolic
representations and hidden layers of meaning. Research on the processes of cognition has
since become a large and independent field of study. The term cognitive science unifies
research on mental processes regardless of the specific topic, experimental approach, method
or even discipline. Cognitive models, like the stimulus-response models created by behaviorists,
predict how sensory input leads to some behavior output. The elements of cognitive models are
sometimes called psychological constructs.
- Neuroscience
Nervous systems are found in all but the simplest animals. Early knowledge about nervous
system function came primarily from clinical cases and took a relatively holistic view of brain
function. By the early 19th century, physicians with a scientific bent had become particularly
interested in the functional properties of the cerebral cortex. The anatomist Franz Gall had long
suspected that differences among individuals in their cognitive functions and personality traits
were associated with different parts of the cerebral cortex, and he hypothesized that the size of
the cerebral cortex could be mapped by measuring bumps on the overlying skull. This
hypothesis led to a new approach to studying the brain called phrenology. After the second half
of the 19th century, phrenologists started to identify neurons. The neurotransmitters are now
known to be released by the terminals of neuronal axons at specialized contacts called
synapses, where the transmitters then bind to the receptor molecules on target neurons and
other cells, thus altering the membrane potential of the cell contacted. The signaling processes
of neurons require energy derived from oxygen and metabolites supplied by the vascular system.
Measurements of increased energy consumption and blood flow in active brain regions provide
the bases for the imaging methods essential to many brain studies.
- The neurobiological approach to cognition
,Cognitive neuroscience is defined by work at the intersection of cognitive science and
neuroscience. Thus, cognitive neuroscientists must have grounding in both of these domains.
This interdisciplinary nature of the field can cause problems; one common misconception is
that cognitive neuroscience simply maps the brain regions that are activated during a
psychological process, in what is sometimes called the search for neural correlates of
cognition. Much current research combines information about brain structure and function to
create neurobiologically grounded models of cognition.
The development of cognitive neuroscience models also has important practical applications,
like individual differences; understanding how and why people differ in their cognitive abilities
is a major area of research in psychology.
So, cognitive neuroscience seeks to create biologically grounded models of cognitive function.
Such models draw inspiration from prior work in cognitive science, while accommodating new
developments and findings in neuroscience. As a result, cognitive neuroscience models can
inform and constrain prior cognitive science models, and point out new directions for
neuroscience research.
- Methods: convergence and complementarity
By combining elements of cognitive science and neuroscience, cognitive neuroscience gains
access to a wealth of research techniques. The experimental and methodological diversity
allows cognitive neuroscientists to explore a given topic in many different ways – and it provides
many paths for beginning researchers to explore in their careers. Convergence describes the
approach of combining results from multiple experimental paradigms to illuminate a single
theoretical concept. This approach long predates cognitive neuroscience; how could
psychologists demonstrate the existence of internal mental states that could not be measured
directly, the answer was convergence. The diversity of cognitive processes engaged by even a
simple task seem like a fundamental limitation – and it does make it more difficult for cognitive
neuroscientists to apply results from a single experiment to real-world problems. Cognitive
neuroscience also benefits from the complementarity of its research methods, each of which
provides a different sort of information about brain function.
- Chapter 2: The methods of cognitive neuroscience
- Early brain mapping in humans
One of the earliest methods used to directly examine cognitive brain function in humans was
intracranial electrical stimulation in patients. Because there are no pain receptors in brain
tissue, such stimulation mapping can be performed on awake, responsive patients. One of the
first scientists to use electrical stimulation in this way was Wilder Penfield. He developed
procedures for treating patients with severe epilepsy by destroying the brain tissue in the regions
where the seizures originated. Before damaging any tissue, he used focal electrical stimulation
to functionally map the region as a way to better understand the functionality of the surrounding
area. Using this focal stimulation technique, Penfield was able to create maps of the sensory
and motor cortices of the brain. He found that the layout of these cortical representations
followed the general somatotopic relationships of the different parts of the body-> start of the
homunculus.
- Brain perturbations that elucidate cognitive functions
,Perturbations of the brain that impair or otherwise influence cognitive functions can come about
through a variety of mechanisms. Information from both of these ways by which normal brain
operations can be disrupted have greatly advanced our understanding of the neural
underpinning of cognitive functions.
- Perturbations imposed by stroke, trauma or disease
A major advantage of this approach is that if damage to a brain area or system disrupts a
cognitive function, it is likely that the damaged region is involved in some critical way in the
performance of that function. This approach was first accomplished by correlating a patient’s
signs, symptoms, and behavior during life with the location of brain lesions discovered upon
autopsy. A major limitation of clinical-pathological correlations in humans, however, is that the
brain damage is the result of many factors that are not under the control of the experimenter.
The distribution of brain regions supporting cognitive functions varies among individuals, making
it difficult to generalize results. The region of overlap among a group of patients more accurately
defines the part of the brain relevant to the cognitive function at issue. Another way researchers
have defined the relationship between brain damage and resulting deficits in cognitive functions
is by making restricted electrolytic or surgical lesions in experimental animals, including non-
human primates.
Lesion studies, whether in humans or in animals, also present problems of interpretation. If one
area of the brain is lesioned, other areas of the brain innervated by the damaged area may, from
the loss of input, also cease to function normally. Such effects, known as diaschisis, can lead to
wrongly attributing the loss and functionality to the lesioned area rather than to the downstream
area. Another possible misinterpretation of lesion findings is that damage to a cortical area can
also damage nearby fiber tracts, thereby disrupting the function of more distant areas.
- Pharmacological perturbations
Another way of perturbing cognitive function in the brain is via pharmacological manipulation.
Cognitive neuroscientists have taken advantage of psychoactive drugs such as caffeine,
cocaine, antidepressants, and a host of others to gain insight into the neuropharmacology of
these functions, both in humans and in experimental animals. Pharmacological studies in
humans have taken two main forms:
o The first approach is to examine the influence of chronic drug use or abuse on
cognitive processes, taking advantage of the unfortunate prevalence of these
social problems and the disorders they cause. Cocaine and other drugs of abuse
lead to specific changes in neurotransmission in the brain systems that underlie
these functions. Cocaine specifically activates dopamine receptors, altering the
physiology of the dopamine system, which is known to play a major role in
reward evaluation.
o More controlled pharmacological perturbation can be carried out in
experimental settings in which a drug is administered acutely and its effects are
monitored. It is possible to study the effects of nicotine, which affects
neurotransmission mediated by acetylcholine (mood, attention, memory). The
nicotine molecule binds to certain acetylcholine receptors and activates them
just as the neurotransmitter itself does. Drugs like nicotine that bind to and
activate receptors in a manner similar to a neurotransmitter are called agonists,
whereas drugs that bind to and block receptors are called antagonists. A
disadvantage of administering drugs systemically for studying cognitive
, processes is the relative lack of specificity of their effects; with systemic
administration, much of the brain is exposed to the drug, and sorting out the
effects of different brain systems can be difficult.
- Structural brain imaging techniques
The first technological breakthrough was the development of computerized tomography (CT). It
uses a movable X-ray tube that is rotated around the patient’s head. It is used to map the brain
structure like an MRI. Today, CT imaging for brain research purpose has been largely superseded
by magnetic resonance imaging (MRI), although CT remains important as it is faster and
cheaper, and can be used in situations in which MRI cannot, like patients with metal in their
heads. The characteristics of MRI:
1. Magnetic: when a person is inside an MRI scanner, protons in hydrogen atoms of the
brain become aligned with the strong main magnetic field of the scanner. Perturbations
with respect to this alignment provide a source signal that can be measured, analyzed
and used to construct an image.
2. Resonance: refers to the ability of a system to absorb energy delivered at a particular
frequency. Protons in a strong magnetic field will efficiently absorb energy when the
energy is delivered at a particular resonant frequency. During a process called excitation,
the MRI scanner emits energy in the form of radio waves at precisely the resonant
frequency of protons. After a few milliseconds, the radio-wave energy is turned off,
whereupon the protons begin to release the energy they absorbed. This released energy
– MR signal – is measured by electromagnetic detectors around the head or other part of
the body.
3. Imaging: in order to create an image from the MR signal, electromagnetic coils in the
scanner can cause the local magnetic field to differ in strength along specific directions.
This complex variation in the signal emitted by the brain or other tissue is decoded by
sophisticated computer analysis to create an image that reflects the proton density, as
well as the distribution of other tissue characteristics, throughout the imaged volume.
The spatial resolution of MRI depends on the strength of the magnetic field, the strength of the
gradient coils and the types of images being collected. It should be apparent from this
description that MRI has a number of important features that make it an extraordinarily valuable
tool in cognitive neuroscience. Firstly, it is non-invasive; subjects are simply exposed to a strong
magnetic field and radio waves that are generally thought to be harmless to brain tissues.
Second, MRI of brain tissue are of extremely high resolution compared to those obtainable using
other techniques. Third, by varying the gradient and radio-frequency pulse parameters, MRI
scanners can be used to generate images that are sensitive to many different aspects of brain
structure. Because water tends to diffuse more along fiber tracts than across them, diffusion
tensor imaging (DTI) enables the imaging of fiber tracts at very high resolution.
- Perturbation by intracranial brain stimulation
A different way of perturbing brain function is direct electrical stimulation of a specific brain
region. Electrodes can be placed transiently or chronically for extended studies of the brain’s
electrical activity and responses to electrical stimulation. In experimental animals, chronically
implanted electrodes allow researchers to assess the function of individual neurons or groups of
neurons as the animal carries out a cognitive task. Although intracranial stimulation techniques
Chapter 1 – definitions, themes and approaches
Cognitive neuroscience is a relatively new discipline that has arisen from the recent marriage of
neuroscience and cognitive science.
Cognition means the faculty of knowing, but in practice it refers to the set of processes
(cognitive functions) that allow humans and many other animals to perceive external stimuli, to
extract key information and hold it in memory, and ultimately to generate thoughts and actions
that help reach desired goals. Cognition is sometimes described as processing carried out by
the mind. The phenomenology of cognition has always raised philosophical questions; how do
we perceive the world?
By the beginning of the 20th century there was a growing dissatisfaction with the lack of
systematic progress in the study of mental processes. Some parts of mental processes like
language seemed difficult to research and methods like introspection seemed imprecise. As a
result, psychology came to be dominated by an emphasis on controlled experiments and
measuring stimuli and behavior -> Behaviorism. This focus rejected the subjective work on
mental functions. The focus of behaviorists on learning from rewards has led them to ignore
other cognitive functions.
In the mid-20th century, a confluence of factors revived the legitimacy of psychological research
on cognitive functions. One factor was the advancement of computers and technology. Here,
the idea of the mind as a computer began. The computer model included symbolic
representations and hidden layers of meaning. Research on the processes of cognition has
since become a large and independent field of study. The term cognitive science unifies
research on mental processes regardless of the specific topic, experimental approach, method
or even discipline. Cognitive models, like the stimulus-response models created by behaviorists,
predict how sensory input leads to some behavior output. The elements of cognitive models are
sometimes called psychological constructs.
- Neuroscience
Nervous systems are found in all but the simplest animals. Early knowledge about nervous
system function came primarily from clinical cases and took a relatively holistic view of brain
function. By the early 19th century, physicians with a scientific bent had become particularly
interested in the functional properties of the cerebral cortex. The anatomist Franz Gall had long
suspected that differences among individuals in their cognitive functions and personality traits
were associated with different parts of the cerebral cortex, and he hypothesized that the size of
the cerebral cortex could be mapped by measuring bumps on the overlying skull. This
hypothesis led to a new approach to studying the brain called phrenology. After the second half
of the 19th century, phrenologists started to identify neurons. The neurotransmitters are now
known to be released by the terminals of neuronal axons at specialized contacts called
synapses, where the transmitters then bind to the receptor molecules on target neurons and
other cells, thus altering the membrane potential of the cell contacted. The signaling processes
of neurons require energy derived from oxygen and metabolites supplied by the vascular system.
Measurements of increased energy consumption and blood flow in active brain regions provide
the bases for the imaging methods essential to many brain studies.
- The neurobiological approach to cognition
,Cognitive neuroscience is defined by work at the intersection of cognitive science and
neuroscience. Thus, cognitive neuroscientists must have grounding in both of these domains.
This interdisciplinary nature of the field can cause problems; one common misconception is
that cognitive neuroscience simply maps the brain regions that are activated during a
psychological process, in what is sometimes called the search for neural correlates of
cognition. Much current research combines information about brain structure and function to
create neurobiologically grounded models of cognition.
The development of cognitive neuroscience models also has important practical applications,
like individual differences; understanding how and why people differ in their cognitive abilities
is a major area of research in psychology.
So, cognitive neuroscience seeks to create biologically grounded models of cognitive function.
Such models draw inspiration from prior work in cognitive science, while accommodating new
developments and findings in neuroscience. As a result, cognitive neuroscience models can
inform and constrain prior cognitive science models, and point out new directions for
neuroscience research.
- Methods: convergence and complementarity
By combining elements of cognitive science and neuroscience, cognitive neuroscience gains
access to a wealth of research techniques. The experimental and methodological diversity
allows cognitive neuroscientists to explore a given topic in many different ways – and it provides
many paths for beginning researchers to explore in their careers. Convergence describes the
approach of combining results from multiple experimental paradigms to illuminate a single
theoretical concept. This approach long predates cognitive neuroscience; how could
psychologists demonstrate the existence of internal mental states that could not be measured
directly, the answer was convergence. The diversity of cognitive processes engaged by even a
simple task seem like a fundamental limitation – and it does make it more difficult for cognitive
neuroscientists to apply results from a single experiment to real-world problems. Cognitive
neuroscience also benefits from the complementarity of its research methods, each of which
provides a different sort of information about brain function.
- Chapter 2: The methods of cognitive neuroscience
- Early brain mapping in humans
One of the earliest methods used to directly examine cognitive brain function in humans was
intracranial electrical stimulation in patients. Because there are no pain receptors in brain
tissue, such stimulation mapping can be performed on awake, responsive patients. One of the
first scientists to use electrical stimulation in this way was Wilder Penfield. He developed
procedures for treating patients with severe epilepsy by destroying the brain tissue in the regions
where the seizures originated. Before damaging any tissue, he used focal electrical stimulation
to functionally map the region as a way to better understand the functionality of the surrounding
area. Using this focal stimulation technique, Penfield was able to create maps of the sensory
and motor cortices of the brain. He found that the layout of these cortical representations
followed the general somatotopic relationships of the different parts of the body-> start of the
homunculus.
- Brain perturbations that elucidate cognitive functions
,Perturbations of the brain that impair or otherwise influence cognitive functions can come about
through a variety of mechanisms. Information from both of these ways by which normal brain
operations can be disrupted have greatly advanced our understanding of the neural
underpinning of cognitive functions.
- Perturbations imposed by stroke, trauma or disease
A major advantage of this approach is that if damage to a brain area or system disrupts a
cognitive function, it is likely that the damaged region is involved in some critical way in the
performance of that function. This approach was first accomplished by correlating a patient’s
signs, symptoms, and behavior during life with the location of brain lesions discovered upon
autopsy. A major limitation of clinical-pathological correlations in humans, however, is that the
brain damage is the result of many factors that are not under the control of the experimenter.
The distribution of brain regions supporting cognitive functions varies among individuals, making
it difficult to generalize results. The region of overlap among a group of patients more accurately
defines the part of the brain relevant to the cognitive function at issue. Another way researchers
have defined the relationship between brain damage and resulting deficits in cognitive functions
is by making restricted electrolytic or surgical lesions in experimental animals, including non-
human primates.
Lesion studies, whether in humans or in animals, also present problems of interpretation. If one
area of the brain is lesioned, other areas of the brain innervated by the damaged area may, from
the loss of input, also cease to function normally. Such effects, known as diaschisis, can lead to
wrongly attributing the loss and functionality to the lesioned area rather than to the downstream
area. Another possible misinterpretation of lesion findings is that damage to a cortical area can
also damage nearby fiber tracts, thereby disrupting the function of more distant areas.
- Pharmacological perturbations
Another way of perturbing cognitive function in the brain is via pharmacological manipulation.
Cognitive neuroscientists have taken advantage of psychoactive drugs such as caffeine,
cocaine, antidepressants, and a host of others to gain insight into the neuropharmacology of
these functions, both in humans and in experimental animals. Pharmacological studies in
humans have taken two main forms:
o The first approach is to examine the influence of chronic drug use or abuse on
cognitive processes, taking advantage of the unfortunate prevalence of these
social problems and the disorders they cause. Cocaine and other drugs of abuse
lead to specific changes in neurotransmission in the brain systems that underlie
these functions. Cocaine specifically activates dopamine receptors, altering the
physiology of the dopamine system, which is known to play a major role in
reward evaluation.
o More controlled pharmacological perturbation can be carried out in
experimental settings in which a drug is administered acutely and its effects are
monitored. It is possible to study the effects of nicotine, which affects
neurotransmission mediated by acetylcholine (mood, attention, memory). The
nicotine molecule binds to certain acetylcholine receptors and activates them
just as the neurotransmitter itself does. Drugs like nicotine that bind to and
activate receptors in a manner similar to a neurotransmitter are called agonists,
whereas drugs that bind to and block receptors are called antagonists. A
disadvantage of administering drugs systemically for studying cognitive
, processes is the relative lack of specificity of their effects; with systemic
administration, much of the brain is exposed to the drug, and sorting out the
effects of different brain systems can be difficult.
- Structural brain imaging techniques
The first technological breakthrough was the development of computerized tomography (CT). It
uses a movable X-ray tube that is rotated around the patient’s head. It is used to map the brain
structure like an MRI. Today, CT imaging for brain research purpose has been largely superseded
by magnetic resonance imaging (MRI), although CT remains important as it is faster and
cheaper, and can be used in situations in which MRI cannot, like patients with metal in their
heads. The characteristics of MRI:
1. Magnetic: when a person is inside an MRI scanner, protons in hydrogen atoms of the
brain become aligned with the strong main magnetic field of the scanner. Perturbations
with respect to this alignment provide a source signal that can be measured, analyzed
and used to construct an image.
2. Resonance: refers to the ability of a system to absorb energy delivered at a particular
frequency. Protons in a strong magnetic field will efficiently absorb energy when the
energy is delivered at a particular resonant frequency. During a process called excitation,
the MRI scanner emits energy in the form of radio waves at precisely the resonant
frequency of protons. After a few milliseconds, the radio-wave energy is turned off,
whereupon the protons begin to release the energy they absorbed. This released energy
– MR signal – is measured by electromagnetic detectors around the head or other part of
the body.
3. Imaging: in order to create an image from the MR signal, electromagnetic coils in the
scanner can cause the local magnetic field to differ in strength along specific directions.
This complex variation in the signal emitted by the brain or other tissue is decoded by
sophisticated computer analysis to create an image that reflects the proton density, as
well as the distribution of other tissue characteristics, throughout the imaged volume.
The spatial resolution of MRI depends on the strength of the magnetic field, the strength of the
gradient coils and the types of images being collected. It should be apparent from this
description that MRI has a number of important features that make it an extraordinarily valuable
tool in cognitive neuroscience. Firstly, it is non-invasive; subjects are simply exposed to a strong
magnetic field and radio waves that are generally thought to be harmless to brain tissues.
Second, MRI of brain tissue are of extremely high resolution compared to those obtainable using
other techniques. Third, by varying the gradient and radio-frequency pulse parameters, MRI
scanners can be used to generate images that are sensitive to many different aspects of brain
structure. Because water tends to diffuse more along fiber tracts than across them, diffusion
tensor imaging (DTI) enables the imaging of fiber tracts at very high resolution.
- Perturbation by intracranial brain stimulation
A different way of perturbing brain function is direct electrical stimulation of a specific brain
region. Electrodes can be placed transiently or chronically for extended studies of the brain’s
electrical activity and responses to electrical stimulation. In experimental animals, chronically
implanted electrodes allow researchers to assess the function of individual neurons or groups of
neurons as the animal carries out a cognitive task. Although intracranial stimulation techniques
