Specific Aims

A region of the cortex concerned with organizing motor control is termed the motor cortex. In Figure 4.33, a bizarre-looking figure is shown alongside the section of motor cortex. It represents the association between each part of the motor cortex and the part of the body over which it exerts some control. Imaging techniques can reveal the link between the activity of a given brain region and the region of body over which motor control is effected. Also, damage to a specific part of the motor cortex, as in a stroke, is associated with the corresponding disruption to motor control in particular regions of the body (e.g. loss of speech or use of the left arm). As you can see in Figure 4.33, the relative sensitivity of control of differentregions of cortex varies. The fingers have a disproportionately large area of cortex devoted to them, indicative of the ability to resolve fine details in motor control through the fingers.

Motor cortex The part of the cerebral cortex which is responsible for organizing motor control.

The autonomic nervous system
The autonomic nervous system (ANS) is involuntary and is responsible for effecting action within the body itself, but not on the external world see Figures 4.31 and 4.32). Again, the link between physiology and behaviour is two-way. Our emotions influence the physiology of the body and, in turn, emotions and moods depend upon feedback from the periphery of the body (e.g. activity by the immune system) (Damasio, 1996).

The ANS controls heart rate, the diameter of blood vessels throughout the body and the production of saliva, amongst other things. You do not have to make a conscious decision to accelerate your heart rate during an emergency or slow it down when you meditate, it happens automatically. Indeed, deliberately trying to target the ANS by voluntary control is extremely difficult. Try thinking of when you last blushed with embarrassment. Then think how futile or even counterproductive conscious attempts to counter this are. Blushing is caused by the dilation of blood vessels near to the surface of the skin of the face.

Autonomic nervous system Part of the nervous system which is responsible for exerting action on the internal environment, for example through smooth muscle.

Taken From: Mapping Psychology 1

This section shows how various sources of biological evidence can be brought together to give an integrated picture of influences on behaviour and how behaviour influences biology.

6.1 The control of behaviour
The present section considers the role of the brain in the control of behaviour, looking at both the external world and the internal physiologyof the body. Figure 4.31 exemplifies just two of the many features of such control. Signals that arise in the brain, are conveyed down the spinal cord (neurons 1 and 2) to the muscles that control the legs and to the heart (neurons 3, 4 and 5).

Imagine you are confronted with a runaway car. From adaptive considerations, it makes sense that your legs will be activated to move you as fast as possible. The legs require a large supply of blood in order to provide fuel to the muscles. This requires adaptive and coordinated internaladjustments of physiology, for example the heart beats faster and the internal ‘plumbing’ of the body is adjusted. Blood vessels at the muscles in the leg dilate to permit a larger flow of blood, and blood is diverted away from other body regions, such as the stomach, where the need is less acute. How are these actions effected? How is coordination between behaviour in the external world and the necessary internal adjustments achieved? Two branches of the nervous system are implicated – the somatic nervous system and the autonomic nervous system.

The somatic nervous system
As shown in Figure 4.32, the somatic nervous system (soma means body in Greek) is the part of the nervous system that is responsible for action exerted on the external world. It controls what are termed skeletal muscles, such as those in the arms and legs. Skeletal muscles are used to effect our voluntary behaviour under conscious control by the brain. Figure 4.31 shows one such route of action. Neurons with their cell bodies in a region of cortex project processes down the spinal cord and communicate with motor neurons. In turn, their activity causes contraction of the skeletal muscle. For convenience we often dichotomize between reflexes and voluntary behaviour. However, in reality, most behaviour is made up of a combination of both.

Somatic nervous system A division of the nervous system, which controls skeletal muscles.

Skeletal muscle A type of muscle attached to the skeleton, which is responsible for moving parts of the body such as the arm. Voluntary behaviour Behaviour that is under our conscious control.

Taken From: Mapping Psychology 1

What can a PET scan reveal? Brain regions can be scaled according to their activity level, as shown in Figure 4.30 where regions involved in auditory and motor functions are indicated. By recording images of brain activity while research participants perform different tasks, researchers are able to formulate a hypothesis about the relationship between brain functioning, the different regions involved and psychological phenomena. A participant can be asked to perform a specific response, such as clenching a fist, or the participant may be asked to imagine a scene. Brain regions which play a part in either of the two activities – the organization of motor control of the hands or the formation of visual images – will then be activated.

PET scans can also reveal regions of the brain that are functioning irregularly. A PET scan of an individual with brain injury may show lower brain activity levels(compared with a control group) in certain brain regions when asked to perform a range of tasks. By identifying the regions of the brain that are affected by the injury, therapy can be investigated. It is also possible to monitor any improvements in the individual by using PET scans to note increases in activity in the part of the brain affected by the injury.

The PET scans of violent criminals have been compared with scans of control participants to look for differences in brain activity levels. The question posed in this type of research was whether regions of the brain known normally to exert restraint on action (e.g. the frontal lobes) are under-active in violent criminals. There is some evidence that this is indeed the case (Raine, Buchsbaum and LaCasse, 1997).

You have now looked at the properties of individual neurons and neural systems as well as how to relate these to an understanding of the whole brain. Some links between neurons, the brain and psychology have been indicated. The next section continues in this direction, but does so within a broader context by returning to material introduced early in the chapter.

Summary Section 5
. The brain is divided into left and right hemispheres, and its outer layer is known as the cerebral cortex.

. Surgical lesions of the corpus callosum have been shown to disrupt communication between the two hemispheres.

. Techniques for studying the brain include looking at the effect of brain damage, electrical stimulation, and forming an image of brain activity using positron emission tomography (PET).

Taken From: Mapping Psychology 1

Non-invasive methods for s tudying the br a i n ’ s a c t i v i t y In Featured Method Box 4.1, we explored how invasive techniques enable us to study individual neurons. These types of invasive techniques are obviously limited since they cannot be applied to humans. But, it is possible to gain a general impression of the function of different brain regions by using brain imaging techniques. These techniques are called ‘non-invasive’, since the nervous system is not disrupted by them (or is only minimally and temporarily disturbed).

Positron emission tomography (PET) is a non-invasive imaging technique. PET allows an image to be formed of the activity of different regions of the brain. It is based on the fact that differences in activity between brain regions are associated with variations in the flow of blood to them and their utilization of fuel (glucose and oxygen). Blood flow to a region varies with the activity of the neurons in the region itself. This gives researchers a possible index of the magnitude of local information processing at the regions observed. Comparisons can be made (a) within a given individual, between different regions of the brain and at various times, and (b) by looking at the same brain region in different individuals.

To instigate the technique, a radioactively-labelled substance termed a tracer is introduced into the body, either by inhalation or by using an injection (Myers, Spinks, Luthra and Brooks, 1992). The presence and location of the tracer is then monitored. A range of cells, such as neurons, employ specific chemical fuels for their energy needs, a principal one being glucose, a type of sugar. One variety of PET exploits the properties of an artificial substance similar to glucose, termed 2- deoxyglucose (2-DG). After the substance is introduced into the body, it enters neurons in the same way that glucose does. However, rather than serving as a fuel, the substance accumulates in the neurons. The brain regions in whichneurons are most active accumulate most 2-DG. After a time, the radioactivelylabelled substance leaves the neurons and is lost from the body.

Positron emission tomography A technique for forming images of the activity of the brain.

Taken From: Mapping Psychology 1

In a controversial approach, applied to non-human animals, scientists have damaged selected parts of the brain to investigate what effect, if any, this has on the brain. In what is termed the ‘experimental group’, clearly defined parts of the brain have been lesioned and the effect observed. A ‘control group’ of the same sex and age receives what are termed ‘sham lesions’ and the results compared for the two groups. Sham lesions consist of control animals being subject to some of the same surgical procedure as the experimental group, such as anaesthesia and cutting the skin, but the brain itself is not lesioned. The animals are killed and the brain of the subjects in the experimental group can be analysed to confirm the exact site of the lesion.

Stop and consider the ethics of performing such experiments on animals. Is it justified to inflict damage to an animal’s brain if there is the possibility of gaining an insight into, for example, human psychiatric illnesses?

Experimenters do everything to minimize the discomfort of their subjects and there are strict laws on what can and cannot be done but the issue remains fraught.

Imaging the brain
In the last decades of the twentieth century, there were important advances in the techniques of forming images of the brain, both of its structure and the amount of blood flow to different regions. Advances in these techniques are continuing. Participants are studied as they engage in psychological tasks, which enables the activity of brain regions associated with the task to be measured.

Taken From: Mapping Psychology 1

Psychologists can also look at the circumstances under which the prefrontal cortex is most active in ‘normal’ participants. This method enables psychologists to construct theories on what this region does. The prefrontal cortex plays a role in, amongst other things, utilizing memories in the inhibition of behaviour, often in the face of competing tendencies to react to immediately present events. Following the accident, Gage showed a defect in his capacity to utilize emotional information concerning the more remote consequences of his actions (Damasio, 1996). Gage appeared to be emotionally in the ‘here-and now’, a victim of impulsivity.

A problem with basing our understanding of the brain on accidents is that they are ‘one-off’, uncontrolled phenomena. Damage is rarely to neat, circumscribed parts of the brain, and usually affects several areas simultaneously. Under ideal experimental conditions, scientists would employ a matched control group to analyse results and develop theories. In the case of human brain damage, there is no matched control group against which to compare the damaged brain.

There are additional difficulties in interpreting results when studying brain damage. For example, depending on the circumstances, other brain regions can take over some responsibility from the damaged region. The system might be fundamentally reorganized, and psychological function can be less disturbed than one might have first supposed. At a neural level, new communications between neurons can be formed. In some cases, such a process can offer hope to people suffering from brain damage.

If a part of the brain is damaged such that it is taken out of action, behaviour changes as a result. Strictly speaking, the working of the rest of the brain is revealed by the damage, and not the contribution or the role of the damaged part itself. An analogy can help to illustrate the problem (Gregory, 1966). Suppose that after removing a component from a radio, it emits a deafening howl. No one would assume that the normal function of the missing component is to suppress howling. When applied to interpreting the effects of brain damage, this analogy should encourage caution, but it does not negate the value of such evidence.

Taken From: Mapping Psychology 1

One major source of evidence on the relationship between brain and behaviour has been the study of damage to the brain, for example caused by gunshot wounds or tumours. Another cause of damage is the blocking of a blood vessel within the brain or the breaking of a vessel (known as a ‘stroke’), which results in a loss of the supply of fuel and oxygen to a part of the brain. Neurons in the location of the damage die and so any changes in behaviour suggest the contribution these regions usually make to normal functioning. A general term for damage to a region is lesion.

Lesion Damage to a region of the brain, for example in an accident or in surgery.

There have been some famous cases of lesions that have illuminated brain and behavioural science, none more so than that of an unfortunate man named Phineas Gage (see Box 4.2).

Phineas Gage was employed as foreman of a gang of railroad workers, who were constructing a new railway line in Vermont in 1848. This involved using explosives to blast rocks out of the way for the line. One day an explosion went wrong and a tamping iron, 3 cm in diameter, passed right through his brain. Amazingly Gage survived the accident. However, the missile caused extensive damage to his left frontal lobe and some damage to his right frontal lobe (Macmillan, 1986; Damasio, 1996). Damage was particularly to the front part of the frontal lobe, termed the prefrontal lobe.

Gage subsequently showed little in the way of intellectual or linguistic impairment. However, marked changes were noted in his personality. Quite out of character, he became obstinate, egocentric and capricious and started to use foul language. Reconsidering Gage in the light of more recent evidence on the role of the frontal lobes, suggests that the parts of the brain concerned with emotional expression were previously held in check by the frontal lobes. This source of inhibition was disrupted by the damage.

Figure 4.29 The accident of Phineas Gage (left, tamping iron and skull drawn to scale; top right, the skull; bottom right, the brain showing damage to the left frontal lobe)

Taken From: Mapping Psychology 1

The surgery did however have some consequences. By targeting visual information to only one hemisphere, experimenters found a way of training the individuals on one task using just one hemisphere. On testing them, it was found that this learning was unavailable to the other hemisphere. One bit of information can be selectively presented to one hemisphere and different information to another. Each hemisphere could assimilate conflicting pieces of information. For example, a green light on a button would signal reward as far as the left hemisphere was concerned (and a red light would signal an absence of reward), but this information would be unavailable to the right hemisphere. Indeed, as far as the right hemisphere was concerned, a red light could be used to signal reward. On being set such tasks, patients were sometimes in conflict as to what to do, though whether their consciousness had been split remains a formidable problem.

Brain surgery can be performed on conscious humans since cutting the tissues of the brain does not evoke pain (there are no tips of neurons sensitive to tissue damage in the brain). In a classic study by Penfield and Rasmussen (1968), humans undergoing brain surgery for the removal of diseased tissue received electrical stimulation to different regions of their brains. Patients were asked to give reports on the conscious sensations evoked. For example, electrical stimulation of regions of the temporal lobe evoked vivid memories of incidents earlier in life. Such evidence enables theories on the biological bases of memory to be produced (and we will return to these in more detail in Chapter 8).

In some cases, for patients in chronic pain, electrodes are permanently implanted with their tips in regions associated with emotion. Patients can control stimulation of these electrodes and a decrease of pain is sometimes experienced. It is assumed that the stimulation alters the pattern of electrical activity within certain neural systems. It increases the electrical activity in neural systems associated with positive emotions and reduces activity in those associated with pain.

Taken From: Mapping Psychology 1

This section examines some of the techniques used to investigate how the brain works and how its activity links with psychological phenomena.

Human brain surgery and electrical stimulation
In some cases, surgery has to be performed on the human brain, for example, to remove cancerous tissue. The behaviour of patients (e.g. performance on memory tasks) can then be compared before and after surgery. One particularly interesting surgical intervention for severe epilepsy was pioneered by Roger Sperry and his associates in California (Sperry, 1969). The basis of epilepsy is chaotic electrical activity amongst the neurons found in a particular part of the brain.

The two halves of the brain communicate through several routes, a principal one being the corpus callosum. Figure 4.28 shows a section through the midline of the brain, a slice through the corpus callosum.

Corpus callosum A bundle of processes of neurons which connect one hemisphere with another.

Communication between the hemispheres is needed to integrate information throughout the brain. Unfortunately, epilepsy focused in one half of the brain also tends to influence the other half electrically, acting via the corpus callosum. The radical and daring surgery by Sperry consisted of cutting through the corpus callosum. The surgery did indeed restrain the epilepsy but what effect did it have on the rest of the mental and physical life of the individual? After the operation, the patients’ epilepsy was muchimproved, but otherwise they appeared to be remarkably unchanged in their everyday behaviour, relative to that shown prior to surgery.

Taken From: Mapping Psychology 1

Figure 4.18 showed the retina and the ganglion cells that project information from the eye to the brain. This section briefly relates an understanding at the level of individual neurons to their location in the
brain.

As represented in Figure 4.26, the processes of ganglion cells (forming the optic nerve) terminate at the brain structure known as the lateral geniculate nucleus (LGN). Anatomists have devised a very rich vocabulary for describing the brain. Let’s dissect the expression ‘lateral geniculate nucleus’. The term ‘nucleus’ is used with reference to sites throughout the brain and refers to a collection of the cell bodies of neurons at a particular location. The expression ‘lateral’ refers to a given location being away from the midline of the brain relative to another location (see Figure 4.27). By comparison, the medial geniculate nucleus (which, incidentally, processes auditory information from the ears) is nearer to the centre of the brain. Finally, the term ‘geniculate’, derives from the Latin name for knee, which is genu. Early anatomists felt that the LGN looked something like a knee.

Lateral geniculate nucleus A part of the visual system that is a collection of cell bodies of neurons.

The neurons whose cell bodies are located in the LGN project processes to the visual cortex (see Figure 4.26), located at the occipital lobe, where further analysis of the visual world is performed.

Taken From: Mapping Psychology 1