UNIT 3 AOS 1: MIND, BRAIN & BODY

MIND, BRAIN & BODY On completion of this unit the student

should be able to explain the relationship between the brain, states of consciousness including sleep, and behaviour and describe the contribution of selected studies and brain research methods to the investigation of brain function.

THE INTERACTION BETWEEN COGNITIVE PROCESSES OF THE

BRAIN AND ITS STRUCTURE INCLUDING:

- Roles of the central nervous system, peripheral nervous system (somatic & autonomic), and autonomic nervous system (sympathetic & parasympathetic).

Activity:

1. Can you draw a flow chart of the NS?

2. What are the 2 main functions of the Peripheral NS?

3. What are the 2 main functions of the Somatic NS?

Video: The Nervous System

The Nervous SystemText: Oxford Psychology Units 3&4 Figure 7.3 Page 149

THE PERIPHERAL NERVOUS SYSTEM

- Has TWO main functions (Text Pg 150) - To communicate information from the

body’s organs, glands and muscles TO the CNS (including information about the outside world such as environmental temperature, and skin sensation, via the sensory neurons).

- To communicate information FROM the CNS to the body’s organs, glands and muscles, via motor neurons.

-

- Has 2 sub-divisions: the Somatic NS & the Autonomic NS

THE SOMATIC NERVOUS SYSTEM

S Sensory (senses information & communicates information TO the CNS)

A Afferent neurons

M Motor (receives & communicates information FROM the CNS)

E Efferent neurons

-Responsible for voluntary movement of the skeletal muscles- Text Pg 150

THE AUTONOMIC NERVOUS SYSTEM

Think Autonomic = Automatic (but don’t get them mixed up!)

Responsible for the regulation of automatic/involuntary operations concerned with internal bodily functions such as respiration & heart beat. Non-skeletal muscles. (Text Pg 151-153)

Also has 2 divisions. The Sympathetic & Parasympathetic Nervous systems which are responsible for the fight-or-flight response.

Key Terms: Do you know what these mean? Fight-or-flight response Arousal Physiological response Homeostasis

FIGHT-OR FLIGHT RESPONSE

SYMPATHETIC NERVOUS SYSTEM

Sympathetic NS. Stress = SurvivalBecomes active when the organism perceives itself to be in danger or in times of stress. It prepares the body to fight or flee.

PARASYMPATHETIC NERVOUS SYSTEM

Responsible for maintaining automatic day-to-day bodily functions such as digestion, breathing & heart rate.

When the fight-or-flight response is activated the Parasympathetic NS is responsible for restoring homeostasis, and restoring your body back to normal.

Just remember PARAsympathetic = a PARAchute bring you gently back down.

THE CENTRAL NERVOUS SYSTEM

All the information from the Peripheral Nervous System is sent to the Central Nervous System for processing.

The Central Nervous System is made up of the Brain & Spinal Cord

It has 2 main roles: To pass information along the

sensory neurons from the peripheral nervous system to the brain

To transmit information from the brain to the peripheral nervous system which activates motor neurons.

COMPARISON OF THE PNS & CNS

The role of the CNS is to integrate and co-ordinate all of the incoming neural information and to initiate neural messages to the rest of the body.

The role of the PNS is to carry information from the sensory and internal organs TO the CNS and carry information FROM the CNS to muscles, organs and glands.

ROLES OF THE FOUR LOBES OF THE CEREBRAL CORTEX IN THE CONTROL OF MOTOR,

SOMATOSENSORY, VISUAL AND AUDITORY PROCESSING IN HUMANS; PRIMARY CORTEX AND

ASSOCIATION AREAS

The brain is broken into two halves known as Cerebral Hemispheres.

The two halves are connected by the Corpus Callosum, which is a dense bundle of nerve fibres that allow the two hemispheres to communicate with each other.

The Cerebrum is covered by the Cerebral Cortex which is spongy grey matter approximately 3-4mm thick that protects the brain.

The surface of each area is highly convoluted (wrinkled) to increase the surface area

THE BRAIN

When labelling a picture of the brain, always look for the cerebellum so you know which way it is facing. The

Cerebellum is at the back of your head.

KEY FUNCTIONAL AREAS

EXAM QUESTIONS Sally is reading a story aloud to her son at bedtime. This

behaviour involves the coordinated activities of many parts of the cerebral cortex. Explain how the three cerebral areas of the brain (Broca’s area, Wernicke’s area and the Primary Visual Cortex) are involved in the process of reading aloud. 3 Marks

Tips: You must use the terms Broc’s area, Wernicke’s area and Primary Visual

Cortex. - You must use the terms, Sally, reading, aloud, pronunciation, fluent

speech, grammatical, understanding.

Answer:

When reading aloud, Sally’s Primary Visual Cortex turns visual sensations into identifiable stimuli such as letters and words (1 Mark).

Her Wernicke’s area is involved with understanding the words and giving them meaning (1 Mark), whilst her Broca’s area assists with the pronunciation and articulation of grammatically correct speech controlling the muscles needed to produce fluent speech that matches the words on the page (1 Mark)

EXAM QUESTIONS

Elliot gets very nervous when he has to speak in public. However, his nervousness subsides as soon as he starts to speak.

After he is speaking for five minuets:

A. which branch of his autonomic nervous system is most active? (1 mark)

B. Elliot will experience physiological changes to his body. Describe two of these changes (2 Marks)

Tips:

Read the answer carefully. This question was commonly answered incorrectly due to being misread.

Answers:

A. Parasympathetic

B. Any two of the following: Heart rate returns to normal, breathing rate returns to normal/reduces, digestion of food is stimulated, pupils constrict, etc.

EXAM QUESTIONSA waiter brings Karen a coffee in a glass. Karen picks up the glass of coffee in her right hand. She decides that it is too hot to hold comfortable and puts it back down on the table after a few seconds.

Using psychological terms, explain the role of the sensory receptors and the brain in Karen’s action of putting the glass of hot coffee back down on the table (4 marks)

The sensory receptors in the fingers of the right hand relay the sensation of the temperature of the glass of coffee through the spinal cord to the primary somatosensory cortex in the left parietal lobe (1 mark). The decision that the coffee is to hot is made in the frontal lobe (association cortex) (1 Mark). The information is transmitted to the primary motor cortex in the left frontal lobe (1 mark) which sends neural impulses to the skeletal muscles in her right hand to put the hot coffee down (1 mark).

HEMISPHERIC SPECIALISATION: THE COGNITIVE AND BEHAVIOURAL FUNCTIONS OF THE RIGHT

AND LEFT HEMISPHERES OF THE CEREBRAL CORTEX, NON-VERBAL VERSUS VERBAL AND

ANALYTICAL FUNCTIONS

HEMISPHERIC SPECIALISATION Tips to remember: Read the questions carefully, look for the terms ‘left’ or

‘right’ visual field’ if they are discussing a severed/cut Corpus Callosum, as this means that it is only going to one hemisphere. If an image is shown to the entire eye/visual field it will got to both hemispheres.

Question: A picture of an apple is flashed into Mario’s left visual field.

A. In which hemisphere(s) (left, or right, or both) would this information first register? (1 Mark)

B. If Mario’s corpus callosum was completely severed, what would be the best way for him to demonstrate what he had seen? Why? (2 Marks)

Answer:

C. Right hemisphere (1 Mark)

D. Mario would be able to select by touch or visually point to the apple with his left hand, or, draw a picture of the apple with his left hand. (1 Mark)

E. The image in the left visual field would go to the right hemisphere which is responsible for non-verbal processing and motor control of the left side of the body, but cannot be transferred to the right hemisphere (due to the corpus callosum being cut) to allow for verbal processing or motor responses using the right side of the body. (1 Mark)

THE ROLE OF THE RETICULAR ACTIVATING SYSTEM IN SELECTIVE ATTENTION AND

WAKEFULNESS; ROLE OF THE THALAMUS IN DIRECTING ATTENTION AND SWITCHING SENSORY

INPUT ON AND OFF

The RAS: it is situated between the brain stem and the CNS. It is involved in the sleep/wake cycle ad damage can lead to permanent coma.

It helps mediate transitions from relaxed wakefulness to periods of high attention. There is increased blood flow in the RAS during tasks that require increased attention and alertness.

THE ROLE OF THE RETICULAR ACTIVATING SYSTEM IN SELECTIVE ATTENTION AND

WAKEFULNESS; ROLE OF THE THALAMUS IN DIRECTING ATTENTION AND SWITCHING SENSORY

INPUT ON AND OFF

The Thalamus is a symmetrical structure within the brain. Its role is to enable attention by receiving sensory input (except smell) and relay the information to the appropriate cortices.

It is considered a relay station for the brain shuttling information between the sensory neurons and the cerebral cortex.

Its other role is to filter out unnecessary information and determine which aspects of a stimulus require our attention

EXAM QUESTIONS

A person has suffered a major trauma (a stroke) which has affected the thalamus of the brain. The patient is experiencing a number of symptoms as a result of the injury. Indicate two possible symptoms a person might show if this part of the brain were damaged. (2 marks)

Tips: Consider that fact that the thalamus is on two sides of the body,

so only one hemisphere may be affected.

Answer: Anaesthesia to one side of the body opposite to the affected part

of the thalamus, painful burning or aching sensations on one side of the body, may be mute (unable to speak) or unable to move, may have visual tracking problems, or problems with any of the other senses (except smell). They may have trouble paying attention to any one stimulus or be unable to filter out unnecessary stimuli. (and of the above 2).

EXAM QUESTIONSList three important functions of the reticular activating system (3 marks).

Regulating sleep, alertness and waking cycles, assisting in the regulation or vital bodily functions such as heart beat, toileting, eating, focusing attention, physiological changes associated with states of consciousness, behavioural modification. (and of the above 3)

What is the main functions of the RAS and how does this influence selective attention? (4 Marks)

The RAS is a network of neurons extending in many directions from the reticular formation to different parts of the brain and spinal cord. (1 Mark)

Its main function is to regulate levels of arousal in the cerebral cortex. (1 Mark) When something happens that demands attention, the RAS will send an increased number of neural messages to specific cortical areas. (1 Mark) The RAS has the ability to focus on the most important neural information, directing attention towards potentially significant events. In doing so, it influences what we attend to – selective attention (1 Mark)

** When asked ‘What’ always describe it. EG, where it is, what it looks like, and what it does

If we had to add the thalamus in here, we would say that the RAS would have increased blood flow and neural messages to the Primary Visual Cortex (say because we are watching something intently). These neural messages would be relayed to and from the RAS to the PVC via the thalamus which would filter out all other unnecessary information such as touch or taste in order to pay more attention to the visual stimuli.

CONTRIBUTIONS OF STUDIES TO THE INVESTIGATION OF COGNITIVE PROCESSES OF THE BRAIN AND IMPLICATIONS FOR THE UNDERSTANDING OF CONSCIOUSNESS INCLUDING:STUDIES OF APHASIAS INCLUDING BROCA’S APHASIA AND WERNICKE'S APHASIA.

Tip:

- Associate the mouth both with speech production and being at the front.

- Associate an ear both with comprehending language and with being next to the temporal lobe.

EXAM QUESTIONS

CONTRIBUTIONS OF STUDIES TO THE INVESTIGATION OF COGNITIVE PROCESSES OF THE BRAIN AND IMPLICATIONS FOR THE UNDERSTANDING OF CONSCIOUSNESS INCLUDING:SPATIAL NEGLECT CAUSED BY STROKE OR BRAIN INJURY

Spatial Neglect is a common syndrome following a stroke, most commonly in the right hemisphere.

Patients demonstrate signs of contralesional (Describing the half of a patient's brain or body away from the site of a lesion) neglect.

For example, when searching through a visual scene patients with left neglect only tent to look at elements on the right side only. It can also involve ‘personal’ space with patients neglecting their own body.

Most importantly, most patients are completely unaware that they have these problems (anosognosia)

EXAM QUESTIONS

After a stroke that damaged the right parietal lobe of her brain, a 77 year old, ET, was diagnosed with spatial neglect. In order to understand more about the role of the brain in cognitive processes, ET was asked to participate in research which involved the researchers giving her a series of tasks. The findings of the research using ET were presented at a conference on the effects of brain damage.

What is spatial neglect? (2 marks) Describe one task involving cognitive processes that ET is

unlikely to do (2 marks)

No Answers to this questions (from VCAA 2011 Sample Paper) What can we come up with ourselves? Key words: right parietal lobe, cognitive processes.

CONTRIBUTIONS OF STUDIES TO THE INVESTIGATION OF COGNITIVE PROCESSES OF THE BRAIN AND IMPLICATIONS FOR THE UNDERSTANDING OF CONSCIOUSNESS INCLUDING:SPLIT-BRAIN STUDIES INCLUDING WORK OR ROGER SPERRY & MICHAEL GAZZANIGA

Sperry & Gazzaniga were the men who conducted research into split-brain studies without having to use brain damaged patients. This all relates back to the hemispheres.

Describe one finding or Sperry and Gazzaniga’s split brain studies and explain how it contributed to out understanding of the interaction between cognitive processes and the structure of the brain. (3 Marks)

Any of the following:

-Findings: Words presented on the right visual field are processed in the left hemisphere. Patients could read and report the words verbally.

Cognitive process/structure: left hemisphere can identify words and name them

- Words presented to the left visual field are processed in the right hemisphere. Patients are unable to report words verbally, could select item by touch behind screen but unable to say why they selected.

Cognitive process/structure: right hemisphere can identify words but not name them.

CONTRIBUTIONS OF STUDIES TO THE INVESTIGATION OF COGNITIVE PROCESSES OF THE BRAIN AND IMPLICATIONS FOR THE UNDERSTANDING OF CONSCIOUSNESS INCLUDING:PERCEPTUAL ANOMALIES INCLUDING MOTION-AFTER EFFECT, CHANGE BLINDNESS AND SYNAESTHESIA

Motion after-effect: A visual illusion experiences after viewing visual stimulus for a

time with stationary eyes and then fixating on a stationary stimulus. The stationary stimulus appears to be moving in the opposite direction.

- It is said to be the result of neural adaption and involves motion detector neurons .

Neural adaption is when the motion detector neurons adapt to the motion

Motion detector neurons: when motion is detected motion detector neurons detect movement in a particular direction and fire. After several seconds of continuous firing, they reduce their baseline activity in favour of perception in the opposite direction.

- The two most common motion after-effects are the waterfall and the spiral illusion

Motion after-effect clip

EXAM QUESTIONS

Question:

Although the exact cause of motion after-effect is unknown, many attribute the motion after-effect to neural adaption.

A. Explain the role of motion detector neurons in perceiving an object to be stationary.

B. What is neural adaption and when is it likely to occur?

Answers

A. There are a number of specific neurons designed to perceive motion in certain directions, known as motion detector neurons. Each of these specific motion detector neurons produces a stronger signal when there is motion in its specific direction and a weaker (but not zero) signal when it does not perceive motion in this direction. Our brain combines the input from these specific neurons in order to decide the direction of the movement. For example, to perceive an object as stationary, our motion detector neurons send signals that are balanced (an even amount from all directions). We do not perceive motion as long as all the motion detectors are in balance with each other.

B. Neural adaptation is when the neurons adapt to the motion.

CONTRIBUTIONS OF STUDIES TO THE INVESTIGATION OF COGNITIVE PROCESSES OF THE BRAIN AND IMPLICATIONS FOR THE UNDERSTANDING OF CONSCIOUSNESS INCLUDING:PERCEPTUAL ANOMALIES INCLUDING MOTION-AFTER EFFECT, CHANGE BLINDNESS AND SYNAESTHESIA

Change Blindness:

a phenomenon that occurs when a person viewing a visual scene apparently fails to detect changes in the scene.

Theories suggest that there has to be a brief disruption to visual continuity such as a Eye saccade (eye tremor) Screen flicker/blank screen/scene change Eye blink Mud splash Very slow change

The results of studies suggest that our internal representation of the world is much sparser than what we thought. An idea of ‘unintentional amnesia’ has been proposed whereby we see everything but forget most of it almost immediately. Only information that has been attended to will be transferred into the memory and available to access in order to detect change. Change blindness person swap Change Blindness breakdancing bear

EXAM QUESTIONS

Change blindness represents a potential problem for air traffic controllers. Air traffic controllers must monitor the movements and locations of multiple aircraft that are represented as intermittently flashing dots on the radar screen.

A. Define change blindness (1 Mark)

B. State when air traffic controllers would most likely experience change blindness (1 Mark)

Answers

C. Change blindness is the failure to notice large/significant change that occurs in full view in a visual scene.

D. Air traffic controllers would be most likely to experience change blindness when the change occurs simultaneously with a brief disruption in vision. The air traffic controller may blink continually, causing change blindness.

(Possible causes of the disruption include eye movements/saccades, eye blink, flicker or blank scree, mud splash, very slow change.)

CONTRIBUTIONS OF STUDIES TO THE INVESTIGATION OF COGNITIVE PROCESSES OF THE BRAIN AND IMPLICATIONS FOR THE UNDERSTANDING OF CONSCIOUSNESS INCLUDING:PERCEPTUAL ANOMALIES INCLUDING MOTION-AFTER EFFECT, CHANGE BLINDNESS AND SYNAESTHESIA

Synaesthesia:

It is a neurological condition in which the stimulation of one sensory or cognitive pathway leads to the automatic, involuntary experience in a second sensory or cognitive pathway.

The most common form is sound to colour.

Brain scans on synathetes have shown that when they hear a sound both their primary visual and primary auditory cortex light up. Normal people only show activity in the auditory cortex.

Synaesthesia Clip Part 1

Synaesthesia Clip Part 2

THE APPLICATION AND USE OF BRAIN RESEARCH METHODS IN INVESTIGATING THE RELATIONSHIP BETWEEN BIOLOGICAL

AND COGNITIVE FACTORS OF HUMAN BEHAVIOURS INCLUDING:

DIRECT BRAIN STIMULATION (DBS) AND TRANSCRANIAL MAGNETIC STIMULATION (TMS)

Direct Brain Stimulation (also know as electrical brain stimulation). A small electrode is placed on or inserted into the brain in order to stimulate or inhibit electrical activity in order to determine specific locations of brain function.

Advantages: Enables ‘mapping’ of brain function and is quite accurate and specific to the individual and can be used prior to surgery.

Limitations: Only relevant for patients about to undergo surgery as it is invasive. Can’t really generalise to the public.

Transcranial Magnetic Stimulation (TMS). Induces a flow of electrical current within neurons by the external application of a magnetic field.

Advantages: Non-invasive, can stimulate or deactivate areas of the brain

Limitations: Limited knowledge of the side effects, results can be ambiguous, can cause seizures. Only penetrates to a depth of 2cm.

THE APPLICATION AND USE OF BRAIN RESEARCH METHODS IN INVESTIGATING THE RELATIONSHIP BETWEEN BIOLOGICAL

AND COGNITIVE FACTORS OF HUMAN BEHAVIOURS INCLUDING:

BRAIN RECORDING AND IMAGING TECHNIQUES: COMPUTERISED TOMOGRAPHY (CT) POSITRON EMISSION

TOMOGRAPHY (PET)

Computerised Tomography (CT): Patient is injected with a dye to increase the contrast, patient lies on a bed and x-rays are passed through the body to produce an image.

Advantage: Provides a detailed image of the structure of the brain. Can be constructed into a 3D image. Can be used to locate precise locations of damage/tumours etc.

Limitations: No information about function. Images are only in black and white, expose to x-rays (which emit radiation) so frequent use is not recommended.

Positron Emission Tomography (PET): Scan indicate brain function by assuming that increased blood flow to an area indicates an increase in activity. A small radioactive isotope is injected into the patient which emits signals that are detected by gamma rays.

Advantages: Can be used on normal and brain damaged patients. Can be used to track disease deterioration such as Alzheimer's.

Limitations: Scanner is expensive, needs highly trained staff, requires radioactive material so cannot be used frequently or on pregnant women.

THE APPLICATION AND USE OF BRAIN RESEARCH METHODS IN INVESTIGATING THE RELATIONSHIP BETWEEN BIOLOGICAL

AND COGNITIVE FACTORS OF HUMAN BEHAVIOURS INCLUDING:

SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY (SPECT), MAGNETIC RESONANCE IMAGING (MRI)

Single Photon Emission Computed Tomography (SPECT): A radioactive tracer is injected into the bloodstream and is detected by a gamma camera. Enables doctors to track function.

Advantages: Cheaper than a PET scan. Provides a 3D image of the brain. More widely available than PET

Limitations: Images not as detailed as PET (poorer resolution), takes longer to complete. Radioactive tracer used.

Magnetic Resonance Imaging (MRI): Uses magnetic fields and radio waves to produce a computer-enhanced image of brain structure.

Advantages: Produces a 3D computer-enhanced colour picture. Uses harmless magnetic filed. Provides a clear and detailed image.

Limitations: Is expensive and not as commonly available as CT. Cannot be used on people with metal devices such as pins and pacemakers. Chamber can be too mall for patients and they can find it claustrophobic. Highly susceptible to ghosting.

THE APPLICATION AND USE OF BRAIN RESEARCH METHODS IN INVESTIGATING THE RELATIONSHIP BETWEEN BIOLOGICAL

AND COGNITIVE FACTORS OF HUMAN BEHAVIOURS INCLUDING:

FUNCTIONAL MAGNETIC RESONANCE IMAGING (FMRI)

Functional Magnetic Resonance Imaging (fMRI): Advantages: Produces high resolution 3D images to a 1mm

accuracy. Shows structure and function of the brain and is more detailed than PET and CT scans. Can show continuous changes in brain activity and does not require any exposure to radiation.

Limitations: Very expensive and requires highly trained staff. Cannot be used on people with metal devices such as pins and pacemakers. Chamber can be too mall for patients and they can find it claustrophobic. Highly susceptible to ghosting.

THE APPLICATION AND USE OF BRAIN RESEARCH METHODS IN INVESTIGATING THE RELATIONSHIP BETWEEN BIOLOGICAL

AND COGNITIVE FACTORS OF HUMAN BEHAVIOURS INCLUDING: DBS, TMS, CT, PET, SPECT, MRI, FMRI

Investigating the relationship between biological and cognitive factors of human behaviour:

Today the availability of DBS and imaging techniques enable a range a medical, psychological and research professionals to investigate the relationship between biological and cognitive factors of human behaviours.

In the past, most knowledge about the brain and its relationship with cognitive functions was through

Case studies such as Phineas Gage Autopsy such as Broca Operations

EXAM QUESTIONS Dr Aslop was a neuropsychologist who worked at a head injury

clinic. Dr Aslop needed to determine whether one of his patients suffered from Broca’s aphasia or Wernicke’s aphasia.

A. What is aphasia? (1 Mark)

B. Explain how functional Magnetic Resonance Imaging (fMRI) could distinguish Broca’s aphasia from Wernicke’s aphasia. (2 Marks)

Answer:

A. Aphasia is an impairment of language as a result to damage to the brain.

(students needed to mention both language impairment and brain damage)

B. Functional Magnetic Resonance (fMRI) would shoe the area of the brain that is/is not functioning and sites of structural damage to the brain. Broca's aphasia is the lack of functioning or damage to the left frontal lobe near the primary motor cortex. Wernicke’s areas would be functioning. Wernicke's aphasia is the lack of functioning or damage in the left temporal lobe near the primary auditory cortex. Broca’s area would be functioning.

(Students were required to identify properties of fMRI (showing structure and brain function) and the specific location of wither Wernicke’s or Broca's area. Many students described symptoms that would differentiate Broca’s and Wernicke’s aphasia

EXAM QUESTIONS People who suffer from spatial neglect do not usually

acknowledge the existence of the left half of their body and environment.

A. According to the results of a CT or MRI scan, in which lobe and hemisphere would you expect to see significant change and damage? (1 Mark)

B. B. Compared to a MRI, what is a limitation of a CT scan? (1 Mark)

Answers:

A. Parietal lobe of the right hemisphere

B. Any of the following: The CT image is not as detailed or clear as an MRI image The CT scan is in black and white and the MRI scan is in colour,

there is better contrast in the MRI. The CT scan uses powerful x-rays and cannot be repeated regularly

as there is a risk of damage The CT scan requires an injections of iodine to provide contrast. An

invasive technique.

EXAM QUESTIONS

Explain how electrical stimulation may be used to locate which parts of the primary somatosensory cortex are responsible for sensation in the hands (3 marks)

Electrodes deliver an electrical current to the precise are of the brain (the somatosensory cortex). The patients reports where they are feeling a tingling sensation. When they report a tingling sensation in the hand, the researcher can conclude that the part of the brain being stimulated is responsible.

(Many students referred to motor functions, however, this was not an appropriate response to the question)

Describe on benefit of functional Magnetic Resonance Imaging (fMRI) compared to DBS (ESB) for conducting research on intact living brains (1 Mark).

An fMRI can be used on all patients (unless that patient has a pacemaker or internal metallic device) whereas DBS can only be used on patients already undergoing brain surgery.

A detailed picture can be taken from an fMRI but not a DBS

fMRI is non-intrusive

fMRI can be used on normally functioning brains, whereas DBS is normally conducted on abnormal brains, making it difficult to generalise the results.

EXAM QUESTIONS A patient experiencing speech difficulties was treated for

a brain tumour. A doctor wishes to check that treatment of the patient's tumour has been successful. He conducts both a positron emission tomography (PET) scan and a computerised tomography (CT) scan of the patients brain. Why might the doctor order both scans? (2 marks)

Answer: A CT scan gives a clear image of the structure of the brain but not

its function. A PET scan gives information about the functioning of different parts of the brain (but not its structure). The doctor would need to measure both structure and function to ensure that the operation had been successful.