Cognitive Psychology: Theory, Process, and Methodology - Dawn M. McBride, J. Cooper Cutting 2019

Cognitive Neuroscience

Questions to Consider

· How is the examination of brain activity involved in the study of cognition?

· How do case studies of individuals with cognitive deficits inform us about the connection between cognition and brain function?

· What can be learned about cognition through measurements of neuron activity in the brain?

· Can all behavior be explained in terms of brain activity?

Introduction: Knowledge From Cognitive Deficits

Imagine that you are a neurologist focusing on cognitive deficits in your patients. You see several patients in a day. One is an older woman who is having some memory problems. Another patient is a man who can identify which words on a page represent animals but cannot distinguish between an elephant and a horse or identify that a tiger is an animal that has stripes. Another patient is a veteran who lost a leg in the Iraq War but still feels pain where the leg should be. A fourth patient can understand and follow verbal instructions but cannot produce verbal speech.

As you further examine each one of these patients, you realize that they illustrate the connection between brain function and cognitive abilities. The first patient is tested with some cognitive tasks, including remembering words and numbers for a short time. She shows lower functioning on these tasks compared with typical scores of nonclinical individuals, and you conclude that she may be showing the first signs of Alzheimer’s disease. The second patient is one you have seen in your office several times before. He has Pick’s disease, a disorder where fine-grained conceptual knowledge is gradually lost due to deterioration of the neurons that help us retrieve general knowledge. The veteran is suffering from a condition known as phantom limb syndrome, where a patient has perceptions of feeling from a limb that has been removed. The last patient is suffering from Broca’s aphasia, a language disorder where comprehension abilities are spared but production abilities show a deficit.

What can we learn about the connection between brain activity and cognitive abilities from examining these patients? In fact, we can learn quite a lot. The first neuroscientists relied on such patients to learn about brain function and how it relates to different cognitive processes. When a patient showed a particular deficit, neuroscientists would identify the area of the brain that was damaged (either by learning about the patient’s disease or accident and/or by examining his or her brain after the patient’s death) to begin mapping out the functions of specific brain areas. From such studies, we were able to learn quite a lot about how the brain contributes to cognition. However, in more recent years, new brain recording techniques allow researchers to examine brain activity in cases where there is no deficit and to more precisely pinpoint the affected areas in cases where a patient shows a deficit. In this chapter, we consider how cognitive neuroscientists study brain function and review some of the important case studies of clinical patients that helped us learn about brain function. In upcoming chapters, we discuss more current studies in cognitive neuroscience that are contributing knowledge about brain function connected to attention, perception, memory, and language abilities.

Clinical Case Studies in Cognitive Neuroscience

As just described, neuroscientists have learned a lot about which brain areas contribute to different cognitive abilities through the examination of clinical patients. Such studies continue to contribute to our knowledge in this area. In this section we review some clinical case studies to show how these studies have contributed to the field of cognitive neuroscience and discuss the advantages and disadvantages of the case study.

One of the first clinical cases to contribute knowledge about brain function was that of Phineas Gage (Harlow, 1868/1993). Gage was a railroad foreman in the mid-1800s. While on the job, a blasting cap drove a metal rod into his left eye, up through the frontal lobe of his brain and out the top of his skull (see Figure 2.1). Gage survived the accident and lived for several more years, but his personality and cognitive abilities were altered from the way he was before the accident. He was less able to control his emotions, and his decision-making abilities suffered. He was no longer able to serve as a foreman because he lacked the cognitive control needed for this role. From this clinical case, we learned that the frontal lobe is important in emotional regulation and decision making.

Figure 2.1 Phineas Gage’s Brain

Source: Van Horn, J. D., Irimia, A., Torgerson, C. M., Chambers, M. C., Kikinis, R., & Toga, A. W. (2012). Mapping connectivity damage in the case of Phineas Gage. PLoS One, 7(5): e37454. doi:10.1371/journal.pone.0037454

Other clinical studies have helped researchers localize language functions in the frontal and temporal lobes of the brain (Rorden & Karnath, 2004). A patient named Tan was studied by Paul Broca in the late 1800s. Tan had been unable to speak for many years (“tan” was one of the only sounds he could produce). After Tan’s death, Broca examined Tan’s brain and found damage to the left frontal lobe, near the front of the temporal lobe (see Figure 2.2). This location was named Broca’s area, and damage to this area causes Broca’s aphasia, a disorder where a person has difficulty producing speech. Near this time, another important brain area for language was identified by Karl Wernicke. This area is in the left temporal lobe close to the front of the occipital lobe and is known as Wernicke’s area (see Figure 2.2). Damage to Wernicke’s area causes a deficit in language comprehension and meaningful language production. A person with Wernicke’s aphasia can speak, but his or her speech is meaningless. The person produces what is known as a “word salad,” where the speech is fluent but incomprehensible. For Broca and Wernicke, clinical case studies aided in their development of this early knowledge about the brain areas responsible for language abilities.

Figure 2.2 Broca’s and Wernicke’s Areas

A more recent case study illustrates the role of brain function in a more specific skill: object identification. Oliver Sacks (1990) described a patient he saw who had difficulty in distinguishing between living and nonliving objects. For example, the patient mistook parking meters for children and furniture for people. However, the patient was an academic in the field of music and had little difficulty with other cognitive abilities. He could even identify objects by touch and describe them in detail. His deficit only occurred in visual recognition of the objects. This condition is known as object agnosia, the inability to correctly recognize objects. Patients with object agnosia typically have damage in the inferior (lower) temporal cortex, suggesting that the deficit is related to language abilities.

Knowledge about localization of memory function has also been gained from clinical case studies. As discussed in the previous chapter, one of the most well known of these cases is that of H. M., a man who suffered from a form of amnesia where he could remember portions of his life before the damage occurred but could not remember episodes of his life that occurred after the damage (Hilts, 1996). H. M.’s brain lesion was caused by a surgical procedure he received early in his life to help diminish the severity of epileptic seizures from which he was suffering. During the surgery, a brain area known as the hippocampus was damaged. After the surgery, H. M. seemed to have lost the ability to form new memories. He would meet new people but would not remember them a few minutes later when they came back into his room. He did not remember world events that occurred after the time of his surgery. It seemed as if the timeline of his life stopped at the point of his surgery. From H. M.’s case, researchers learned about the importance of the role of the hippocampus in memory abilities, but they also learned that the hippocampus is not the only brain structure involved in forming and retrieving all types of memories. H. M. showed the ability to improve on tasks requiring motor skills, indicating that he could still retain new information and retrieve implicitly (i.e., without intention). Thus, H. M.’s case taught us that the hippocampus is not necessary for all types of memory formation and retrieval but is important for intentional retrieval of memories.

Stop and Think

· 2.1. Explain why controlled experiments cannot always be conducted to determine how different types of brain damage cause cognitive deficits.

· 2.2. Describe some of the limitations of using the clinical case study method in cognitive neuroscience.

Clinical case studies have revealed important connections between brain function and cognitive abilities. They provide clues to the brain areas most important for different types of cognitive tasks as we examine the damage areas in these patients. However, this points to the major disadvantage of using case studies in neuroscience—the researchers do not control the brain damage. If, for example, the damage is spread across multiple brain areas, it may be difficult for researchers to pinpoint the specific brain areas connected to the cognitive deficits seen in the patients. In addition, researchers are limited to studying those damaged brain areas in patients that are available for them to study. Current neuroscience brain recording techniques provide a means to more precisely identify the brain areas most active during different tasks and to examine the brain areas researchers are most interested in studying. Thus, these newer techniques have helped us overcome the disadvantages present in clinical case studies to further add to the knowledge gained in these studies. In the next sections, we describe some of the techniques cognitive neuroscientists have employed in recent research.

Structure of the Nervous System

Clinical case studies are still used as a method of study in cognitive neuroscience research. However, advances in technology have also allowed researchers to record the brain activity present in clinical and nonclinical subjects to test hypotheses about what kind of activity and where in the brain that activity should be located under different task conditions. The specifics of how these recording techniques work rely on some understanding of the brain and the nervous system, so we review the relevant physiology in this next section before we introduce the most common brain recording techniques used in cognitive neuroscience research.

The Neuron

The brain is composed of billions of microscopic neuron cells forming the basic structure seen in Figure 2.3. Neuron activity is both chemical and electrical. Chemicals called neurotransmitters are first brought into the cell by the dendrites at the top end of the neuron. These neurotransmitters provide signals to the cell that are either excitatory (i.e., more likely to fire) or inhibitory (i.e., less likely to fire). The cell body of the neuron takes in these chemical signals from the dendrites and determines if there is enough of an excitatory signal to allow the neuron to fire. If so, an action potential occurs that creates an electrical signal that travels down the neuron’s axon. This electrical signal is detected in some of the brain recording techniques used by researchers. Once the electrical signal reaches the end of the axon, the terminal buttons release neurotransmitters into the synapse to be collected by other neurons nearby. Then the process begins again.

Neuron: the basic cell of the brain

Dendrites: extensions from neurons that receive chemical messages (neurotransmitters) from other neurons

Axon: an extension from the neuron nucleus where an electrical impulse in the neuron occurs

Synapse: a space between neurons where neurotransmitters are released and received

Figure 2.3 A Neuron

The process of the action potential is what creates the electrical signal in the neuron when it fires. This activity occurs within the axon of the cell. Before the neuron fires, the inside of the axon contains a resting state negative charge due to the division of ions in the fluid inside and outside the cell (see Figure 2.4). The action potential redistributes these ions through channels in the axon’s membrane that control the flow of potassium (K⁺), sodium (Na⁺), and chlorine (Cl^-) ions in and out of the cell. When the excitatory signal comes down the axon from the cell body, the axon opens specific channels in the axon membrane to allow sodium to flow into the axon, producing a positive charge inside the cell. The channels open quickly in sequence from the top of the axon (at the axon hillock) near the cell body down to the end near the terminals that contain the neurotransmitter (see Figure 2.5). This positive charge can be detected and recorded by electrodes that are placed either inside the cell or on top of the scalp, as we see shortly in the discussion of brain recording techniques. Once the action potential is complete, other channels open in the axon membrane to allow potassium (K⁺) to flow out of the cell and the sodium channels close. This redistributes the ions back to the resting negative state inside the axon. The excitatory message then reaches the terminals and a neurotransmitter is released into the synapse (see Figure 2.6).

The synapse is the small gap between neurons in the brain. Each neuron is connected to other neurons in an organized network that allows the pattern of firing in the network to translate into specific thoughts or behaviors. This is how information is processed and stored in the brain: through the pattern of firing across multiple neurons within the network (i.e., specific neurons being active or not active or firing at different rates) and types of connections (excitatory or inhibitory) across the neurons connected in each network.

The Brain

The brain is composed of the networks described in the previous section, which are organized according to their cognitive functions. This is known as localization of function. Many of the clinical cases reviewed in the previous section provided the initial information we have about localization and lateralization (i.e., the two hemispheres of the brain contribute to different types of tasks) of brain function through the deficits present in different areas of brain damage. Looking at the kind of task deficits these patients exhibited helped researchers to identify brain areas (i.e., the damaged areas) that were important for completing those tasks. These early studies suggested that different areas of the brain specialized in different functions. Figure 2.7 shows the four lobes of the brain and functions that are localized in those brain areas. Recent research in cognitive neuroscience has used the knowledge gained in early case studies to focus on different areas of the brain as researchers examine the functioning in different cognitive tasks. The newer brain recording techniques described in the next sections have allowed researchers to go beyond the basic knowledge of localization and lateralization of function to map out more specific brain areas and to piece together full neural systems (i.e., a collection of brain areas organized in pathways) that are involved in different tasks. We explore some of the most recent research in cognitive neuroscience throughout the subsequent chapters that cover different cognitive processes in further detail.

Figure 2.4 Distribution of Ions Inside and Outside the Resting Neuron

Figure 2.5 Ions’ Movement and Voltages During and After an Action Potential

Figure 2.6 Release of Neurotransmitter by the Presynaptic Neuron Into the Synapse

Recent brain research has suggested that despite the general feature of localization of function, many complex cognitive tasks (e.g., memory retrieval, object identification) are a function of distributed processing in the brain. In other words, brain areas work together in systems to process different kinds of information. This idea is supported by research in different areas of study. For example, a series of brain areas has been implicated in explicit memory retrieval (i.e., intentionally retrieving a memory). This system seems to be separate from more automatic or unintentional uses of memory, such as those relied on when we perform a skill or task we know how to do (Squire, 2004). Pulvermüller (2010a) also describes neural circuits for lexical and semantic processes underlying language abilities as “distributed neural assemblies reaching into sensory and motor systems of the cortex” (p. 167). In other words, the processing of spelling, grammar, and meaning of words is distributed across several areas of the brain. Thus, there is localization of function for cognitive processes, but for most functions multiple areas are organized into processing systems for different cognitive abilities.

Measures in Cognitive Neuroscience

In Chapter 1, we described the biological perspective on the study of cognition. Using this approach, researchers attempt to connect brain activity with cognitive processes they observe along with some of the other behavioral measures they observed (e.g., accuracy, reaction time). For example, cognitive neuroscientists have investigated how brain activity differs for accurate and false memories (e.g., Düzel, Yonelinas, Mangun, Heinz, & Tulving, 1997), which areas of the brain are involved in language production and comprehension (e.g., Gernsbacher & Kaschak, 2003), and whether visual areas of the brain are involved in imagery (e.g., Kosslyn et al., 1993).

Figure 2.7 Diagram of the Four Lobes of the Brain and Functions Localized in These Areas

iStockphoto.com/Ciawitaly

Advances in technology have allowed researchers to record different types of brain activity. Some techniques are considered too invasive and are typically only performed with laboratory animals (e.g., single-cell recordings), but many of the brain imaging techniques in use today are able to record brain activity in humans as they perform various cognitive tasks. However, all of the techniques rely on activity of the neuronal cells in the brain.

Single-Cell Recording

A technique available to record the electrical signals from neurons is single-cell recording. In this technique a tiny recording needle is inserted into a neuron in an area of the brain the researcher is interested in (see Figure 2.8). However, this technique requires surgical insertion of the needle and bonding to the head to keep the needle steady (see Figure 2.9). Thus, this technique is typically used only in research with laboratory animals. Such recordings have contributed important information about cognition. For example, using single-cell recordings from monkeys, Rizzolatti, Fadiga, Gallese, and Fogassi (1996) discovered a new type of neuron they called a mirror neuron. This neuron fired both when the monkeys picked up an object and when the monkeys were watching the researchers or other monkeys perform that action. In other words, these neurons were active when motor actions were performed and when the monkeys were just watching a motor action they knew how to perform. Since this discovery, researchers have suggested that mirror neurons may play a role in many sorts of social cognitions, including understanding others’ actions, imitation of others’ actions, and facilitation of language through gestures (Rizzolatti & Craighero, 2004). Other work using single-cell recordings has shown that neuronal cell responses can be extremely specific. For example, Quiroga, Reddy, Kreiman, Koch, and Fried (2005) found neurons in the hippocampus (known to be involved in memory functioning) that were selectively responsive to photos of celebrities such as Jennifer Aniston and Halle Berry (in recordings from epilepsy patients undergoing treatment). These results are consistent with the idea that neurons serve as feature detectors (see Chapter 3 for more discussion of feature detection); in this case, the features are specific faces. These neurons have been called “grandmother cells” (Gross, 2002), because they suggest that we might even have a neuron (or set of neurons) that selectively responds to the face of our grandmother (assuming we have met her before).

Single-cell recording: a brain activity recording technique that records activity from a single neuron or small group of neurons in the brain

Figure 2.8 Recording Electrical Activity in a Neuron

Photo at right courtesy of Bob Jacobs

Figure 2.9 Stereotaxic Instrument Used in Single-Cell Recordings

Photo 2.1 In recording an EEG, a scalp cap with electrodes in different locations on the head is worn by the participant.

iStockphoto.com/Latsalomao

Electroencephalography (EEG)

Another technique that records the electrical signals from neurons is electroencephalography or EEG. When recording an EEG, a set of electrodes is placed on the head (see Photo 2.1) to record the electrical signals from groups of neurons in different areas of the brain. Because the electrodes are recording from outside the skull, it is the activity of the neurons closest to the skull (primarily neurons in the outer cortex) that is being recorded. The activity is recorded over time to detect changes (positive or negative) in the electrical signals (see Figure 2.10). Researchers can use EEG recordings to examine an event-related potential (ERP), which is a change in activity related to a specific event like the presentation of a stimulus. In that way, they can determine if there is an effect of that stimulus presentation on neuron activity and in what general area of the brain the effect occurs. Electrical activity patterns can be overlaid onto a map of the brain to show the general location on the cortex of the different levels of electrical activity.

Electroencephalography (EEG): a brain recording technique that records the activity of large sections of neurons from different areas of the scalp

Figure 2.10 Sample EEG Recording

Source: From Hauri, P. (1982). Current concepts: The sleep disorders. Kalamazoo, MI: Upjohn.

Photo 2.2 A patient sits in a new brain scanner at the magnetoencephalography department of the Erasme hospital of Anderlecht on April 26, 2007, in Brussels, Belgium.

Mark Renders/Stringer/Getty Images Entertainment/Getty Images

An example of EEG/ERP research is provided by Düzel et al. (1997). These researchers recorded ERPs during recognition judgments for studied words. Although voltage for different scalp areas differed based on the type of judgment subjects made (i.e., did they “remember” having studied the word, or did they just “know” they had studied the word?), voltage recordings were similar for items the subjects correctly remembered and for items subjects falsely remembered having studied (i.e., items they recognized as studied in the memory test but that were not presented in the list). The electrical activity recorded in the ERP showed that similar activity occurs for true and false memories, but that the activity differs depending on the strength of the memory based on the type of response (“remember” or “know”) the subjects gave.

Magnetoencephalography (MEG)

Another newer technique that records electrical signals from neurons in the brain is magnetoencephalography (MEG). Instead of electrodes placed on the head as for an EEG, MEG involves placing the head in or near an electrical scanner that can detect electrical activity with better location accuracy than EEG. As with EEG recordings, MEG recordings can occur during a task such that changes in activity can be detected that correspond to the presentation of cognitive stimuli. However, as with EEG, MEG is limited to recordings on the outer cortex and cannot provide a good measure of activity occurring below the cortex.

Magnetoencephalography (MEG): a brain recording technique that records activity of large sections of neurons from different areas of the scalp using a large magnet that is placed over the head

Electrical Stimulation/Inhibition of Neurons

An even newer technique that also relies on the electrical activity in the brain involves transcranial magnetic stimulation (TMS). With TMS, researchers use a magnetic field to excite or inhibit neuron activity to investigate functioning in specific areas or processing systems of the brain. Like EEG and MEG, this technique is noninvasive, as it involves tracing a magnetic coil over the area of the brain the researcher wishes to study (see Figure 2.11). The electrical activity (an increase or decrease) can then be recorded using one of the brain imaging techniques discussed in the next section (e.g., magnetic resonance imaging). Studies (e.g., Sach et al., 2007) using TMS have shown that some cognitive tasks (e.g., making spatial judgments for visual stimuli) use a broader range of brain areas (e.g., frontal lobe) than what was previously thought using other brain recording techniques.

Transcranial magnetic stimulation (TMS): a method of temporarily stimulating or suppressing neurons using a magnetic field

A similar technique is transcranial direct current stimulation (tDCS). Like TMS, neuron activity can either be excited or inhibited using this technique. However, where TMS uses a magnetic field to create the electrical current, tDCS delivers a small electric current to the brain through electrodes attached to the scalp. Thus, it is also a noninvasive technique. tDCS is cheaper and easier to use than TMS but produces a weaker effect on neuron activity than TMS. Both of these techniques are becoming more popular for use in cognitive neuroscience research.

Transcranial direct current stimulation (tDCS): a method of temporarily stimulating or suppressing neurons using an electrical current

Figure 2.11 Transcranial Magnetic Stimulation (TMS)

Source: Courtesy of Eric Wassermann, M.D., Behavioral Neurology Unit, National Institute of Neurological Disorders and Stroke.

Brain Imaging Techniques

Magnetic Resonance Imaging (MRI)

Magnetic resonance imaging (MRI) is often used medically to gain clear images of interior structures of the body. Perhaps you or someone you know has gotten an MRI to examine an internal injury (e.g., a knee, hand, or foot). With the same technique, clear images of the brain can be gained. In an MRI scan, a magnetic field is generated to create an image using recordings of the signal coming from the positive hydrogen atoms within the cells of the body. An MRI of the brain can create a clear image of the different structures of the brain that allows comparison across individuals and identification of damage or the presence of tumors (see Photo 2.4).

Magnetic resonance imaging (MRI): a technique to image the internal portions of the body using the magnetic fields present in the cells

Photo 2.3 A person undergoing transcranial magnetic stimulation.

Keith Bedford/The Boston Globe/Getty Images

Positron Emission Tomography (PET)

Using positron emission tomography (PET), researchers can measure the blood flow to different areas of the brain. Blood flows in greater volume to more active areas of the brain; thus, the measure of the blood flow will indicate the areas of the brain most active during a cognitive task. Blood flow is detected through the ingestion of a small amount of a radioactive substance. The radioactive substance is then absorbed into the blood and flows to the brain as blood is needed in active areas. The radioactivity in the blood is then measured in a PET scan to determine which areas of the brain are more active than others during a task. The recording of the radioactivity is then overlaid onto a map of the brain to examine which areas are the most and least active. In a PET scan, color indicates the level of activity occurring in different areas. Photo 2.5 shows PET scans for two individuals: one who has taken cocaine and one who has not. The most active areas of the brain are colored in red (followed by yellow and then green with the least amount of activity in blue). In this figure, it is clear that there is less activity globally for individuals who have cocaine in their system than for individuals who do not (control).

Positron emission tomography (PET): a technique that images neuron activity in the brain through radioactive markers in the bloodstream

Photo 2.4 Images from an MRI of the brain.

Thomas Northcut/Photodisc/Thinkstock

Functional Magnetic Resonance Imaging (fMRI)

A newer technique related to MRI is functional magnetic resonance imaging (fMRI). fMRI is a technique that records brain activity with a scan of the magnetic properties of the blood flowing through the brain. Similar to PET, fMRI shows blood flow activity to specific areas of the brain with more active areas shown in brighter colors on the scan. fMRI relies on a subtraction method, where activity recorded before the task (called the baseline recording, which is a control condition in this type of study) is subtracted from the activity recorded during the task. What is left is the activity present only during the tasks.

Functional magnetic resonance imaging (fMRI): an MRI technique that images brain activity during a task

Photo 2.5 PET scans. The areas in red are the most active; those in blue are least active.

NIDA. (2007, January 1). The Brain & the Actions of Cocaine, Opiates, and Marijuana, https://www.drugabuse.gov/brain-actions-cocaine-opiates-marijuana.

Like an MRI, an fMRI requires that the participant be placed in a magnetic scanner during the task. Typically, a mirror is positioned in the scanner for the participant to view the stimuli presented. fMRI is often preferred by researchers conducting brain scans because they are able to view brain activity during a task (unlike MRI) and there is no potentially harmful radioactive substance that needs to be ingested by the participant (unlike PET). Figure 2.12 shows images from fMRI scans for a participant performing different language tasks. As can be seen, different areas of the brain are most active during the various tasks.

Recording Activity in the Living Brain

Throughout this text, we discuss studies that have used the brain recording techniques described in this chapter to illustrate the connection between brain function and the cognitive processes discussed. Here we highlight two of these studies to illustrate the use of these techniques in cognitive neuroscience. In later chapters, we discuss some of the most recent cognitive neuroscience studies in perception, attention, memory, and language.

Figure 2.12 Images From PET Scans of the Brain Taken During the Different Language Tasks Identified in the Scan

Source: Adapted from Petersen, S. E., Fox, P. T., Posner, M. I., Mintun, M., & Raichle, M. E. (1988). Positron emission tomographic studies of the cortical anatomy of single-word processing. Nature, 333, 585—589.

Two categories of brain recording techniques were described earlier in this chapter: recordings of electrical activity of neurons (single neurons or larger groups of neurons) and brain imaging techniques. Each technique has contributed important knowledge about the connections between cognition and brain function. For example, many EEG studies have shown the areas of the cortex most active during specific tasks. When EEG recordings are connected to specific stimulus presentations, as in ERP, this activity can be examined across stimulus conditions to make comparisons as tests of theoretical hypotheses.

In an example of this type of study, Barron, Riby, Greer, and Smallwood (2011) used ERP recordings to examine the factors that contribute to mind wandering (i.e., thinking about things other than the current task you are working on). Do you ever start thinking about something going on in your life (e.g., an argument with your boyfriend, girlfriend, or spouse or an assignment that is due at the end of the week) while you are reading this text? If so, then you have experienced the type of mind wandering that Barron et al. studied. These researchers recorded EEGs during a task where subjects were asked to respond to a rare target event (a red circle appearing) that occurred in a series of presented stimuli (green and blue squares). However, the nontarget stimuli were presented in different proportions. Green squares were presented often and blue squares were presented as infrequently as the red circles. This type of stimulus presentation was used to see if the blue squares would capture the subjects’ attention even if they were not asked to respond to them (see Figure 2.13).

Figure 2.13 Stimuli Used in the Barron et al. (2011) Study

Past studies of this task have shown an increase in neuron activity in the parietal cortex about 300—500 milliseconds (ms) after the red circle is presented, which is believed to be related to maintenance of the stimulus in memory. Further, a similar increase in activity is shown in the frontal lobe if the blue square (that requires no response) is presented. The activity in the frontal lobe that occurs with this distracting rare event is believed to be due to attention being paid to this stimulus because it occurs infrequently in the trials (see Figure 2.14).

Stop and Think

· 2.3. What type of neuron activity is recorded in single-cell, EEG, and MEG recordings?

· 2.4. What type of brain activity is detected in PET and fMRI scans? Why is an fMRI scan preferred to a PET scan in most cases?

· 2.5. In general, what has been learned about the organization of brain activity using cognitive neuroscience techniques?

· 2.6. Does research connecting brain activity with cognitive task performance gain causal information or merely correlational information? Explain your answer.

In the Barron et al. (2011) study, subjects also completed a survey at the end of the trials to gauge the amount of mind wandering that occurred during the task. Subjects were separated into groups: high, medium, and low mind wandering. The study was designed to investigate different theories about how mind wandering occurs for those who reported off-task thoughts during the task (i.e., the high mind wandering group). For example, mind wandering might happen because something distracts the person from his or her main task. If so, subjects in the high group should show greater brain activity in the frontal cortex area when the distracting blue squares are presented. Alternatively, mind wandering might be due to subjects completely disengaging from the task and focusing attention on other thoughts. If so, subjects in the high group should show lower brain activity in both the frontal and parietal cortexes when the target and nontarget rare events (red circles and blue squares) are shown, because they are not attending well to any of the stimuli in the task. The results of the Barron et al. (2011) study showed that subjects with high levels of mind wandering had lower levels of brain activity in response to both the red circles and blue squares, supporting the idea that subjects were not attending to the task while their minds were wandering (see Figure 2.15). The researchers concluded from these data that suppression of the external events (i.e., not paying attention to the rare events, regardless of whether a response is required) contributes to mind wandering. This study shows how EEG/ERP studies can be used to test theories about cognitive processes.

Brain imaging techniques are also frequently used in cognitive neuroscience studies. An example of this type of study was done by Segaert, Menenti, Weber, Petersson, and Hagoort (2012) to investigate the link in processing between language production and comprehension. The similarities and differences between language comprehension and production have been a topic of interest in the past few decades within language research as researchers in this area develop and test theories of how these processes occur (see Chapter 9 for more discussion of language comprehension and production processes). Segaert et al. (2012) used fMRI recordings to test the idea that the same brain areas are active during syntactic processing (i.e., understanding how words fit together grammatically in sentences) in both language comprehension and production. Subjects were asked to complete a task of either comprehending a sentence or producing a sentence when a verb and a picture were presented. The color of the verb (green or gray) indicated whether a comprehension trial or a production trial was used. fMRI scans of the subjects’ brains were taken during the task. The researchers examined the change in brain activity when the same syntactic structure of sentences was repeated in the trials to see if adaptation to the structure (i.e., lowered brain activity) would be seen. They then compared the adaptation effects across the comprehension and production trials to see if adaptation was similar across speaking and listening trials. Results showed adaptation to the repeated syntactic structure of the sentences in both comprehension and production trials. In addition, the same level of adaptation was found in both speaking and listening trials. The researchers concluded that the same brain activity contributes to syntactic processing in both comprehension and production of language.

Figure 2.14 Graphs of Brain Activity From the Barron et al. (2011) Study

Source: Barron et al. (2011, figure 1).

The newest brain recording technologies have allowed cognitive neuroscientists to gain important knowledge about the connection between brain function and cognitive processes. As an example from language research suggests (Pulvermüller, 2010b), four key questions can be answered from cognitive neuroscience research: (1) where the brain activity occurs during specific cognitive tasks, (2) when the brain activity occurs during a task (e.g., at stimulus presentation or after a delay when processing has begun), (3) how the brain activity occurs (e.g., in specific networks of brain areas), and (4) why brain activity occurs (i.e., testing hypotheses about how the processing occurs in particular cognitive tasks). Thus, there is a great advantage in using brain recording techniques in cognitive neuroscience research to learn about these specific aspects of cognitive functioning. However, some disadvantages exist as well. One disadvantage is that not all cognitive tasks are easily adapted to the brain recording techniques. The neuroscientific study of insight (i.e., that “aha” moment when you suddenly realize how to solve a problem; see Chapter 11), for example, has been difficult to conduct because it is hard to predict when insight will occur for a specific problem. Luo and Knoblich (2007) describe the difficulties in using fMRI and EEG techniques to study the process of insight and some of their methods to adapt insight studies to brain recording techniques. Another disadvantage is the limited availability of brain scan technology. Because MRI machines are expensive and also serve as a medical tool, it can be difficult for researchers to obtain time available for use of these devices. EEG machines and technology are relatively cheaper and more readily available for research, but their use can be time-consuming for subject participation. Thus, although these recording techniques represent significant advances in our ability to connect cognitive function with brain activity, they are not without drawbacks.

Figure 2.15 Brain Activity Comparison Across Conditions in the Barron et al. (2011) Study

Source: Barron et al. (2011, figure 2).

Can All Mental Processes Be Explained in Terms of Brain Activity?

One question researchers have begun to ask is whether all behavior can be explained in terms of brain activity. Although we do not yet know the answer to this question, some interesting studies have begun to explore it. For example, Libet (1985) describes studies of EEG brain activity showing that about half a second before someone is aware that he or she will perform an intentional action (e.g., pressing a button in an experiment), the brain signals that it is preparing to perform that action. Libet argued this evidence suggests that our choices (at least simple ones like button presses) are determined unconsciously by the brain before we are consciously aware of making such choices. More recently, Schurger, Sitt, and Dehaene (2012) have argued that the activity seen in the brain before these choices are consciously made indicates readiness to make a choice rather than the actual choice itself. The debate on this question continues, but conscious choices are one area where researchers are investigating whether brain activity can define behavior.

Stop and Think

· 2.7. How has the use of brain recording techniques allowed researchers to test causal relationships between brain activity and cognitive functions?

· 2.8. Suppose that you were interested in learning about the brain areas involved in memory processing. You are specifically interested in testing whether the retrieval of accurate and false memories relies on the same underlying processes in brain function. Describe a study using one of the brain recording techniques described in this chapter that would test this question.

Another area where progress has been made in investigating how brain activity translates into specific behaviors is in patterns of activity related to identification of simple objects. For example, some studies have shown that a unique pattern of brain activity accompanies the identification of objects such as faces and houses (Grill-Spector, 2008). In fact, researcher Marcel Just and his colleagues (Mitchell et al., 2008) have been developing a “mind reading” program that can identify a word a person is looking at simply from the pattern of brain activity seen in an fMRI scan of the person’s brain.

The research highlighted here is promising in making specific connections between predictable brain activity and cognitive behavior. However, one criticism is that the behaviors being examined are too simple (e.g., choosing to press a button, looking at a word). It may be much more difficult, and maybe impossible, to make such precise connections between brain activity and more complex behaviors such as driving, having a conversation, and imagining yourself in a situation you have never been in. Thus, the question of whether all behavior can be connected to specific brain activity is as yet unanswered.

Stop and Think

· 2.9. Suppose research determined that specific brain activity is present when someone is lying and not present when the person is telling the truth. Do you think this knowledge could be used to develop a foolproof lie detector? Why or why not?

An alternate idea is that the mind and body (i.e., the brain) are separate and distinct entities. In other words, the mind exists and functions separately from the functioning of the brain. This idea has been debated by philosophers for over a century and is called the mind-body problem. Dualists believe that the mind exists separately from the brain—that the mind is our conscious self and is not reducible to brain function. In contrast is the view presented earlier—that the mind is defined by brain function and cannot be separated from brain activity. The research presented here represents some cognitive neuroscience support for this view, but this question is still typically discussed at a philosophical level, given the current state of the field.

Thinking About Research

As you read the following summary of a research study in psychology, think about the following questions:

1. Explain how this study used recordings of brain activity to test a theoretical description of a cognitive process.

2. What was the primary manipulated variable in this experiment? (Hint: Review the Research Methodologies section in Chapter 1 for help in answering this question.)

3. Do you think the researchers would have achieved similar results if they had used EEG instead of fMRI in this study? Why or why not?

4. Explain why it was important for the researchers to show that subjects were slower in performing the nonfocal than the focal prospective memory task.

Study Reference

McDaniel, M. A., LaMontagne, P., Beck, S. M., Scullin, M. K., & Braver, T. S. (2013). Dissociable neural routes to successful prospective memory. Psychological Science, 24, 1791—1800.

Purpose of the study: The researchers investigated brain activity associated with prospective memory, which is remembering to perform a future task (e.g., taking medicine after dinner, stopping at the store on the way home to buy milk). The researchers tested two theoretical perspectives used to describe how prospective memory operates. One perspective suggests that when there is a future task we are trying to remember, remembering the task always uses cognitive attentional resources. The other perspective suggests that in some cases, prospective memory can be performed after a spontaneous retrieval of the task that does not consume cognitive resources in the remembering period. To test these two perspectives, the researchers compared two prospective memory tasks, one that should consume cognitive resources to retrieve and one that (according to the second perspective) would not consume cognitive resources to retrieve because spontaneous retrieval could be used. If the second perspective on prospective memory is correct, different brain activity in the two types of tasks is predicted.

Method of the study: Subjects in the study performed one of two types of prospective memory tasks. The prospective memory tasks were given within the context of an ongoing task of category judgments (e.g., Is GREEN a COLOR? Is a GRAPE a type of FURNITURE?). All subjects completed the same ongoing task where an item appeared with a category on the computer screen, and subjects were asked to decide if the item belonged in the category given. However, different groups of subjects were given different prospective memory tasks to perform during the category task. One task, called a nonfocal task, has been shown in studies to require cognitive resources to retrieve (resulting in a slowing down in ongoing task performance). In this task, subjects were asked to respond if they saw the syllable tor in any of the category tasks. Looking for the syllable would require extra attention, because subjects do not need to notice the syllables of the words in order to complete the category task. The other type of prospective memory task, called a focal task, has been shown in studies to sometimes rely on spontaneous retrieval where no slowing down in ongoing task performance was seen. In this task subjects were asked to respond when they saw the word table in the category task. During the completion of the tasks, subjects’ brain activity was measured using fMRI scans.

Results of the study: The study results showed two important findings. First, subjects slowed down in the category task more when they completed the nonfocal prospective memory task than when they performed the focal prospective memory task, supporting previous findings that the nonfocal task requires more attentional resources than the focal task. The second primary finding was that brain activity differed in the two types of prospective memory tasks. In the nonfocal task, the researchers found activity in the prefrontal cortex area of the brain that was not present in the focal task. See Figure 2.16 for a comparison of the brain activity seen in the fMRI scans for the focal and nonfocal conditions.

Conclusions of the study: From the recordings of brain activity seen in this study, the researchers concluded that some prospective memory tasks do not require cognitive resources to retrieve because no activity was seen in the prefrontal cortex area for the focal task, whereas this activity was present in the nonfocal task. The primary conclusion from this study was that brain activity supports the idea that prospective memory tasks do not always require additional attentional resources.

Figure 2.16 Activity Compared for the Focal and Nonfocal Prospective Memory Tasks From fMRI Scans in the McDaniel et al. (2013) Study

Source: McDaniel et al. (2013, figure 1).

Chapter Review

Summary

· How is the examination of brain activity involved in the study of cognition?

A number of brain activity recording techniques are used by cognitive neuroscientists to better understand how brain activity is tied to cognition. All rely in some way on neuron activity, with some (single-cell recordings, EEG) measuring the electrical signals from neurons and others (PET, fMRI) recording images of neuron activity in larger areas of the brain.

· How do case studies of individuals with cognitive deficits inform us about the connection between cognition and brain function?

Individuals who have suffered a brain lesion can help us connect cognitive deficits to specific areas of the brain. By examining the area(s) of the lesion and which cognitive deficits the individuals have, researchers can make hypotheses about the primary function of different areas of the brain. Much of the early knowledge of localization of function in the brain came from such clinical case studies.

· What can be learned about cognition through measurements of neuron activity in the brain?

Like clinical case studies, researchers can connect specific brain areas with cognitive abilities. However, measurements of brain activity also allow researchers to provide better tests of hypotheses about brain function because experiments can be conducted with brain activity as the dependent measures.

· Can all behavior be explained in terms of brain activity?

Some studies suggest that it can, at least for simple behaviors. However, the answer to this question is not yet known.

Chapter Quiz

1. Which brain recording technique(s) is (are) often limited to laboratory animals because it requires insertion of a recording needle into the brain?

1. PET scan

2. EEG/ERP

3. fMRI

4. single-cell recording

5. both (a) and (b)

2. Which brain recording technique(s) measures a change in blood flow to different areas of the brain?

1. PET scan

2. EEG/ERP

3. fMRI

4. single-cell recording

5. both (a) and (b)

3. What is meant by localization and lateralization of brain function?

4. Describe some disadvantages of using clinical case studies to connect brain function and cognition.

5. From Phineas Gage, researchers learned that the _____________ lobe of the brain is important for reasoning abilities and control of emotion.

1. frontal

2. parietal

3. temporal

4. occipital

6. In which lobe of the brain is visual information primarily processed?

1. frontal

2. parietal

3. temporal

4. occipital

7. In what ways is the single-cell recording technique different from other brain recording techniques?

8. How do brain recording techniques allow for experiments that cannot be done with clinical case study patients?

9. When EEG recordings are connected to the timing of the presentation of a stimulus, it is called _____________________.

10. The MEG technique provides better _____________ than EEG.

Key Terms

· Axon 27

· Dendrites 27

· Electroencephalography (EEG) 33

· Functional magnetic resonance imaging (fMRI) 36

· Magnetic resonance imaging (MRI) 35

· Magnetoencephalography (MEG) 34

· Neuron 27

· Positron emission tomography (PET) 36

· Single-cell recording 31

· Synapse 27

· Transcranial direct current stimulation (tDCS) 34

· Transcranial magnetic stimulation (TMS) 34

Stop and Think Answers

· 2.1. Explain why controlled experiments cannot always be conducted to determine how different types of brain damage cause cognitive deficits.

In order to conduct an experiment of this type, one would need control over the brain damage that occurs. This would be unethical in humans. However, animal models can provide some information about how brain damage affects behavior; thus, experiments are possible to conduct with animal subjects.

· 2.2. Describe some of the limitations of using the clinical case study method in cognitive neuroscience.

Because the brain damage is not controlled in these cases, it can be difficult to connect deficits with a specific brain region. It is also difficult to provide good tests of hypotheses about how brain function affects cognitive abilities.

· 2.3. What type of neuron activity is recorded in single-cell, EEG, and MEG recordings?

Electrical activity from a single neuron or multiple neurons is recorded with these techniques.

· 2.4. What type of brain activity is detected in PET and fMRI scans? Why is an fMRI scan preferred to a PET scan in most cases?

Blood flow to active regions of the brain is recorded in these techniques. fMRI scans are typically preferred because they are less invasive than PET scans. The subject or patient does not need to ingest anything to conduct an fMRI scan.

· 2.5. In general, what has been learned about the organization of brain activity using cognitive neuroscience techniques?

Research has uncovered the localization of function in the brain, and how different areas are specialized for different tasks.

· 2.6. Does research connecting brain activity with cognitive task performance gain causal information or merely correlational information? Explain your answer.

This knowledge is primarily correlational due to measurement of the relationship between two measured variables (brain activity and cognitive performance on a task). However, some causal information can be gained by manipulating the cognitive task the subject performs to examine how this affects the brain activity being measured.

· 2.7. How has the use of brain recording techniques allowed researchers to test causal relationships between brain activity and cognitive functions?

Brain recording techniques allow for the measurement of brain activity during the manipulation of cognitive tasks.

Answers will vary, but the key is to measure brain activity during the retrieval of accurate and false memories to compare these situations. Chapter 7 provides some discussion of how false memories can be created experimentally for such studies.

Answers will vary.

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