Triesman proposed that there was an early filtering system and that in a situation in which there was a dichotic listening with different information projected to each ear then only changes in physical attributes e.g. changes of language could be detected in the "unattended ear" (early stage). Other theorists showed that the interpretation of the attended ear could be influenced by the unattended ear in a way that suggested the analysis of meaning (late stage). It is understood that differences between such studies were largely due to the requirements and the nature of the task. When the attended task (the particpant is asked to attend to one ear and disregard the other) contained difficult and demanding material, with a high perceptual load, then only physical changes were noted in the non-attended channel. In contrast in later studies a less demanding attended task was accompanied by more elaborate analysis of the unattended ear. In other words theories of early versus late selection were based more on attended ear task difficulty than any theory about the level of processing. The idea of physical analysis being earlier than semantic analysis rather than just salient is also controversial since such analysis may take place in parallel (see chapter on Language). Also, a second factor is likely to be important — the similarity of the material in the attended and non-attended ear. High similiarity is more likely to interefere and modify interpretation of the attended ear.

If the answer to the previous question is correct then the more difficult the attended information is the less spare capacity there will be for monitoring the unattended ear and consequently the less such information will distract us. This is indeed the case, although it may be that there are limits to this proposal. When we are overwhelmed by information as long as we have sufficient prior goals of attention we will seek out some information at the expense of other information. Information that has importance for us will distract us sometimes irrespective of the perceptual load placed upon us by the attended channel e.g. baby crying or our name being called. This is so even when the information to be attended to is hard to process and requires extra attentional demand. Selective attention is therefore a kind of competitition. Demanding information requires a full focus that leaves little spare attention for information that might potentially distract us. However, some information such as a mother's baby crying or our name being called at a cocktail party will be more likely to distract us because the stimulus has learned importance and personal relevance. This does not mean that we process everything and filter the incoming information. Rather it is more sensible that we have a readiness to perceive some information as if receptors are waiting for a fit with certain perceptual stimuli.

Understanding the two previous questions should allow you to answer this question and create both a high distraction and a low distraction experiment.

It would depend on the topic that you were intending to investigate. Factors might include:

1. Number of distractors.
2. The nature of the distractors in terms of the similarity with the target.
3. The importance of the information in terms of the familiarity of the information to the participant.
4. The degree of self-initiated selection required.
5. The spatial orietation required.

I am sure the student and certainly a researcher in this area are capable of thinking of further factors. All these factors might effect attention. However, if one of these factors is the focus of research then the other factors must remain consistent and controlled for across conditions, otherwise one would not be sure of what and why two experimental conditions showed a statistical difference.

There are a number of tests of everyday attention and questionnaires that may be used to test a variety of complaints e.g. "I can't go to social events because I cannot focus on what people are saying because of the other people who are talking around me". Think of a few more everyday examples and tests that might be useful. One would expect some discussion of tests sensitive to mild head injury with some reference to post-concussional syndrome.

This is a reference to perceptual neglect involving the inferior parietal cortex, allocentric neglect involving the temporal cortex and exploratory neglect involving the prefrontal cortex. The first is closer to the areas of the visual cortex and the what pathway. The second has been described as being a store of visual objects (the end point of the what pathway) and the third area directing attention search. This is a useful question if answered in a comprehensive way.

Larger lesions are likely to additionally involve subcortical areas that have been associated with neglect. The temporal parietal junction is seen as the hub of a network that serves attention and an occlusion to the middle cerebral artery at this point will additionally effect the dorsolateral prefrontal cortex. See the diagram of the cerebral arteries in Appendix 2. Large lesions may act to disconnect neural pathways that serve the three areas referred to in the previous question. This question can also be answered from a strictly functional perspectivee.g. allocentric neglect plus exploratory neglect might be seen as combining two types of neglect that exacerbate the disorder. If this question is more comprehensively answered this will enhance knowledge in this area.

TMS of the temporoparietal junction has been followed by neglect but damaged connections to other brain areas implicated in the processing will disrupt a nework that represents contribution to different areas that also contribute to attention in different ways. Damage to one centre may be compensated for by other centres but there is an emerging theory that this cannot occur if there is a disconnection between the damaged centre and the intact centre. It is as if connections provide information concerning the capacity of other centres. This is in some way substantiated by non-human animal research that has found disconnect between parietal and frontal centres causes more severe neglect than either centre on its own.

For these reasons the temporoparietal junction at the interface between the temporal and parietal lobe and near the border of the occipital lobe is a hub in that it is a centre for all attention pathways. A large lesion here which effects subcortical pathways will result in more severe neglect.

With some patients there is anaesthesia of the paralysed limb. In other words they cannot feel the arm, so one might hypothesise that they would receive no somatosensory feedback that their arm is paralysed. However they can observe their own paralysis unless they additionally have neglect in which case they may ignore the paralysed state. While these additional symptoms might encourage anosognosia, anosognosia can occur without them.

A psychogenic problem would affect the left and right limb equally and would not be associated more with a right hemisphere lesion compared to a left. This is shown using the WADA technique when tested without confounding aphasia. There is a strong relationship between brain damage and anosognosia for hemiplegia. There is also a strong relationship between anosgnosia and other cognitive symptoms in the week following a stroke. Some elaboration of this answer is possible.

This theory is perhaps weakest in its explanation that stronger neglect is for the left side and although a subtle form of neglect for the right side may be assessed using special tests the Kinsbourne theory is better as a prediction of the style of performance of the patient with neglect rather than the dominance of the right hemisphere. One possibility might be to provide that when the left hemisphere is damaged subcortical structures such as the superior colliculus orients attention to the right. A special networked relationship between the right hemisphere and subcortical structures on the right would make such compensation more difficult. Further reading will find that the superior colliculus is important to orientation.

Such a speculative theory would still have to propose a dominant cortical role for attention but would argue that orientation would be an interaction between the dorsal pathway and the subcortical mechanism. Any theory would have the greatest success if orientation were found to be a separate mechanism that was nevertheless mainly dependent on a dominant right hemisphere system of attention. Further reading may help the student to think about this issue and propose their own model.

Neuroimaging studies of healthy persons argue that the dorsal attentional pathway is most associated with orientation and shifting of attention, yet unilateral neglect is most associated with a lesion within the dorsal attentional pathway. The second paradox is that the ventral pathways allow an attention to the left from the right and to the right from the left hemisphere. It is only the dorsal pathway that shows a right dominance i.e. the right hemisphere controlling shifts of attention both left and right while the left hemisphere showing only a right shift. In other words while the lesion evidence indicates that the ventral pathway is most vulnerable to neglect, strangely it is the dorsal pathway that potentially shows the features of neglect.

The evidence needs to be replicated and confirmed but the present state of play is that there are two systems that must be intimately linked within a network: one dorsal right dominant orientation system and the other ventral system which is described as a circuit breaker by Corbetta and Shulman, using a rather limited paradigm. If the circuit breaker analogy is correct then the ventral attention pathway would be important for a controlled attentional search while the dorsal pathway would be brought to play in an automatic search.

A solution to the paradox allows that within the controlled search the ventral pathway and the dorsal pathway areas are interdependent during shifts of attention. If the right ventral pathway is damaged then the dorsal pathway has no way to initiate a search for the target to the left or the right. However in the case of left ventral damage because the right ventral and dorsal pathways are intact the right and left may be searched (dorsal pathway) being guided by the goal of the search that is contributed by the intact right ventral pathway.

It could be predicted that if there is a lesion to the dorsal pathway on the right side there would be evidence of a failure to shift to the left. This is supported by the TMS studies. However one might expect that the target for attention is goal directed by the temporal parietal junction (TPJ) as an association area and part of the ventral system. The TPJ is well placed for the final encoding of incoming information (visual, auditory and somatosenory). If the ventral pathway is responsible for the meaningful analysis and setting up the goal of controlled search and it is undamaged the patient with dorsal pathway damage would still have the goal and the semantic understanding of what should be searched for: "I wish to find a bird with red feathers". Such a patient with a damaged right dorsal pathway would be inefficient in searching and shifting attention towards a bird located on the left side but would perceive the target if they located one by serendipitously looking in the correct direction to the left.

With a right ventral lesion (usual lesion for neglect) the dorsal pathway would not be activated to search to the left or right because it is dependent on the ventral pathway for the knowledge of what would be the goal of the search. If, however, the ventral pathway is damaged on the left the patient is unable to detect what is on the right because the left dorsal pathway can only search to the right and is dependent on goal-directed search of the left ventral pathway. However, in this same patient the undamaged right ventral system knows the target that should be the focus of attention even though the left is damaged, and can initiate the dorsal pathway to look to the right and thereby compensate for the failings of the left damaged ventral pathway (the right dorsal pathway can shift to both the right and left). A search to the right in this case will not be as efficient and will take a little longer, which is found in studies when there is left ventral damage and the target is to the right. This is because the natural and usual search space is to the contralateral visual space. There are other speculations as described earlier but the above seems to fit the findings so far. A book takes about a year to publish and therefore the student will hopefully find a review paper that confirms or provides another model for this process. The above may be hard to follow but when a drawing of the two systems is developed the explanation will be easier to understand.

As will be learned later in this chapter the ventral pathway is actually deactivated during the active search that is carried out by the dorsal pathway. However, this may still allow the ventral pathway to initiate the goal of the search within the dorsal pathway. Perhaps one should also keep in mind that this is usually referring to relative activity according to a secodndary indicator e.g. blood flow.

It should do. In an everyday situation there are contextual markers such as a tree or rock that would help orientation just through contextual memory e.g. the fish jumped near the rock, find the rock and I will know where the fish is.

The DLPFC with its facility to keep information in mind (working memory) may contribute to control the reflexive orientation associated with the collicular pathway especially in a situation in which a movement or other distraction causes a loss of crucial concentrated focus of attention. The strategy of such a controlled goal could be maintaind as part of a contribution by the DLPFC. Later there is a discussion concerning the role of the DLPFC and its likely influence on the parietal cortex. The role of the parietal cortex of locating the target in space suggests that the DLPFC may have a top-down role in the controlled attention towards a target. The superior colliculus is part of the network and therefore there is a possible mechanism for overriding the reflexive orienting of the collicular pathway.

Most obviously the posterior parietal cortex is involved in processing the location of an object. Also the prefrontal cortex may be involved in the discrimination of targets versus non-targets. As described above strategies of control may be maintained by the dorsal pathway. A retrieval of scenes from memory may be required so that expected distractions might be ignored more easily. Something should also be written when answering this question concerning the inhibitory roles of the right ventrolateral prefrontal system and related inhibitory systems.

This, like many of these study questions, may be as big or as small as you may wish to write. This is a brief pointer. The cholinergic system has a sub-system referred to as the nicotinic cholinergic system and it is easy to remember that nicotine is an agonist that helps smokers to concentrate but reduces attention below that of non-smokers when they are attempting to give up the habit. Dopamine 1 is an important neurotransmitter supporting the DLPFC in its controlling role of attention and as part of working memory.

The serotonergic system is associated with mood and depression and the role in attention is not clear, although depressed persons show general signs of slowed cognition. Selective Serotonin Reuptake Inhibitors (SSRI's) increase the amount of serotonin available in the system. Normally when a neurotransmitter is passed across the synaptic cleft between neurons it is broken down in readiness for the next transmission to reach threshold. Drugs aimed at reducing depression reduce the amount of neurotransmitter that is broken down and thereby lower the threshold for firing.

Norepinephrine is the term used in the USA and noradrenaline is used elsewhere. Drugs such as amphetamines act to increase arousal by encouraging (an agonist) the production within the norepinephrine/noradrenaline system that increases brain arousal. Amphetamines may also increase dopamine. Norepinephrine is produced under stress as a part of a flight and fight response. The amygdala, which is known to be active under conditions of social threat, has shown to be associated with increased activation associated with an increase in activity of norepinephrine.

Parkinson's disease is associated with a depletion of dopamine. The black recepter cells within the substantia nigra (part of the basal ganglia) die off in Parkinson's disease causing a number of effects. There are the effects of dopamine on cognitive function which may affect working memory but there may also be an effect on mood. There are two structures within the basal ganglia called the striatum that consist of the putamen (noted for effects on movement and motor function generally). There also effects on the caudate nucleus (noted for its ability to transmit frontal derived information to the rest of the brain). The ventral striatum is adjacent to the nucleus of the accumbens. This structure pays a role in feelings of elation and success and may be implicated in some addictive behaviours. Patients with excessive dopamine levels after treatment with el dopa i.e. Parkinson's patients may be involved in extreme rewarding behaviours such as gambling or excessive sexual activity presumably from too much activity within the nucleus of the accumbens. Further information may be gleaned from the text about Dopamine 2. See a more comprehensive description of motor disorders in the first edition.

This information may be obtained directly from the text but it should be acknowledged that this question is referring in some cases to active networks. In other words at the level of electrical brain activity this assesses the extent that brain activity might identify a network.

This is a straightforward question and the answer is supplied within the text.

When we move our heads to the left or right then the image of the external environment rushes over the retinal cells in the eyes. This should be seen as the world spinning around us but we perceive the process as the world standing still. Of course, when we go on a spinning wheel in a fairground we do see the world spinning around because we have not evolved to adapt for such an experience. Metaphorically, the brain cannot keep up and we may feel slightly ill into the bargain.

The brain not only has to cope with steadying an apparently moving world but the eyes are also shifting back and forth and these are saccades. The process of coping with all this movement is called corollorary discharge. If you are having trouble with this question it is worth rereading this section. Broadly, one of the processes that helps to maintain a steady environment is the interaction between the colliculus, the frontal eyefields and the brain stem. The superior colliculus monitors the timing of saccadic shift of the eye with the brain stem, while the frontal eyefields register occular muscle movements. The image is registered briefly between shifts (saccades) and the frontal eyefields allow for the movement according to the muscle movements of the eye when a gaze is shifted. There should also be a discussion about the vestibular system and the compensation for relative movements. This is a specialised topic and a thorough understanding of this area is beyond the scope of this book. The brief overview is to draw attention to the presence of this advanced topic.

This question is asking for knowledge concerning the process of habituation. If our collicular pathway is metaphorically "crying wolf" then we must somehow cope with this or become exhausted by constantly orienting towards a non-threatening stimulus. The connections between the collicular system and the amygdala allow for the evaluation of the degree of threat there may be in the stimulus that is causing the reflexive orientation.

Endogenous orienting is when we know something about the direction or the nature of the to-be-presented stimulus while exogenous orienting is a response to unexpected external stimuli. There are a number of processes required in preparing for a shift of attention within endogenous responding. Broadly, in an experiment when we have foreknowledge of the impending stimulus or in an everyday situation we might be waiting for a bus or watching for a fish to take our line then we have a preparedness to shift our attention to a particular location. Three structures are active and associated with such preparedness — the superior colliculus, the frontal eyefields and the intraparietal sulcus. From general research in this area it can be assumed that the intraparietal sulcus within the parietal cortex is anticipating the upcoming location of the stimulus; the frontal eyefields are preparing for any required change of gaze, and the SC is preparing for a rapid reflexive shift in orientation.

Such endogenous orienting may be disappointed and a false alarm to an expected stimulus to a commonly occuring similar stimulus e.g. frequent buses that are of no use to the traveller will encourage an inhibition and some control of the endogenous response. Details of this inhibition e.g. the influence of structures such as the DLPFC, may be gauged by reading the preceding and other sections on habituation.

This is a somewhat controversial area at the present time. Unlike the other thalamic nuclei the pulvinar does not connect directly with primary sensory input areas therefore it is not a simple relay system. But this structure does have a big influence on the visual cortex (many more connections than the lateral geniculate nucleus — yes surprising) and so this area has a more important influence on attention within vision than was previously understood. In fact, further research may well show that given the proliferations of connections, the pulvinar has a very important role in modifying attention within visual perception. However, within the present discussion, the connections with the other structures that might be described as a collicular network are clearly structures that also modify orientation and endogenous search such as the intraparietal sulcus, the frontal eyefields and the dorsolateral prefrontal cortex (DLPFC). If you are having difficulty with this section it is worth having a second read because it appears that the pulvinar is important in allowing communication between cortical areas, and lesions in the area of the pulvinar using non-human models result in errors of search and binding (see perception) that one might expect from lesions to the individual brain areas it connects with.

At what level this occurs is uncertain but most obviously there are conditions in which the volume of one sensory system has to be metaphorically turned up compared to another. For example, someone who is temporarily blinded in an accident becomes more aware of alternative sensory systems. I will let you finish this question.

This is a question that refers to a model of what occurs over time within a continuous performance task. In such a test the participant waits for a long period for a particular stimulus embedded in other similar stimuli. It is a boring task which is similar to that required of radar watchers during the war waiting for a blip that could turn out to be an enemy aircraft or a rain storm.

Broadly it is speculated that in such a task there are two component systems. One keeps the participant from going into a daydream (default mode). This is a maintaining attention process, and another process for attention for the expected cued stimulus, and this includes the dorsolateral prefrontal cortex. Further reading within this chapter will focus on the attention required for an expected stimulus in terms of endogenous orienting.

The default mode is linked to a mode that switches to the external task at hand and is discussed in more detail in the chapter on Consciousness. This is described here as the cingulate-operculum stable attention network that is associated exclusively with the maintenance of set (see text). This area drives a state of consciousness that is aware of internal (introspection not on task) versus external environment (the task). However, for the purposes of a foray into this field it is important to note that these are two different networks that are likely to interact as part of the requirements of the CPT task.