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Cognitive Control

Theory - working memory, inhibition, task shifting and interference control with some clinical applications
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Marie-Claire Reville

on 12 October 2012

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Transcript of Cognitive Control

Cognitive Control Working Memory Working memory is a system for providing access to representations for complex cognition. Working memory has a limited capacity, is a system of domain-specific stores, and it provides access to representations for goal-directed processing (Oberauer, 09). A good model should be able to explain 1. Dynamic binding, 2. Selection mechanisms e.g. attentional selection contents, and selection of actions, 3. Reconfiguration and updating, 4. Interference control 5. Control long term memory transfer. Working memory is activated units of long term memories. Lots of things are activated in the long term memory via associations. Then the strongest activated memories are available in the region of direct access. Then the mind is able to pick the relevant information from this region of direct access. if information is unrelated, activation will be lower - less likely to be picked. Only elements activated in the region of direct access will be used in goal directed behaviour. Here we can bind information e.g. task rules to produce the right behaviour to be used - BINDING.
Declarative working memory:
-Activated long term memory
-Region of direct access (DA)
• Representations in region of DA can be manipulated and combined with other representations
• Main function is to make a (limited) number of elements directly accessible and integrate them in temporary structures (content-context bindings)
- by using schemata (e.g. agent-action-object)
- by binding to a position in a cognitive coordinate system
-Focus of attention Procedures compete with each other - the first response that reaches activation threshold will be activated. The more one is activated, the more it will suppress the other one - lateral inhibition. This is different to tip down inhibition (executive control / goal). Overcome competition by context-context bindings, increasing Region of DA threshold, and within DWM bias task sets within the bridge by goals. Declarative Procedural Working-memory capacity:

“WM capacity is not about individual differences in how many items can be stored per se but about differences in the ability to control attention to maintain information in an active, quickly retrievable state.” (Engle, 2002)
Oberauer (2009) produced a design for working memory, which explains these correlations (the details of this design are beyond the scope of this essay, however implications will be discussed). This theory suggests that executive control is only able to perform through the mode of working memory, and thus working memory is the common factor and relation between executive control functions. It may also suggest that without working memory, there can be no executive control. Research from Marcovitch, Boseovski, Knapp and Kane (2010) supports this, as 4-6 year olds with higher working memory capacity are more successful at carrying out goal maintenance. This insinuates that the more working memory capacity the more executive control can be executed.
According to Oberauer’s (2009) model of working memory improving working memory may improve executive control. A study on computer training working memory in children with ADHD showed that children improved on working memory, response inhibition and reasoning, with reduced ADHD symptoms as reported by parents (Klingberg, Fernell, Olesen, Johnson, Gustafsson, Dahlström et al., 2005). This insinuates that training working memory through computer tasks can improve ADHD symptoms. The findings of this study imply that Oberauer’s model (2009) does explain, to some extent, disorder symptoms, and therefore provides a better understanding of ADHD and is a ‘good’ theory of cognitive control. capacity Training Impact on Ageing Impact on Stopping For an efficient WM system we need to assume that at least some executive functions avail of a separate mechanism that enables them to run in parallel with primary processes, so that they can intervene in primary processes. This assumption is in agreement with theory and data on at least one executive process, stopping an action. Logan and Cowan (1984) analyzed the stop-signal paradigm, in which participants do a speeded choice task and are instructed to stop responding when they perceive a stop signal, which occurs on a minority of trials. Logan and Cowan successfully applied a race model to data from this paradigm in which the primary response- selection process and the stop process run in parallel. the bridge alows activation of two process in parallel then the bottleneck alows one to get through fist one two bottleneck wins. All require deliberately stopping a response that is relatively automatic, although the specific response that needs to be inhibited differs across tasks. Myaki Verbrugen &logan 08
How do working memory and long-term memory contribute to successful stopping? Short-term memory might be necessary for maintaining task rules and action plans. Retrieval of short-term and long-term associations might also contribute to stop performance. After many repetitions, associations between stimuli and stopping might enable automatic response inhibition, which reduces the need for cognitive control processes [11]. Automatic inhibition is more likely to develop in the go/no-go paradigm, in which stimuli are consistently associated with going and stopping, than in the stop-signal paradigm, in which stimuli are inconsistently associated with going and stopping [11]. It will be useful to link the neural substrates of inhibition to the neural substrates of memory, and to explore the links between inhibition deficits and memory deficits. When people exert self-control they often rely heavily on executive functions such as inhibition (i.e., stopping an already initiated action such as reaching for a glass of beer) or working memory updating (i.e., keeping goal-relevant information such as personal drinking standards active in working memory, shield this information from distractors such as impulses, and adapt it if necessary in the specific context; Miyake, Friedman, Emerson, Witzki, & Howerter, 2000). Friese et al ‘11 conext bindings alow for goals to be specific to their context e.g do not drink on public transport Planning Inhibition Interference Control Task Switching ADHD Phineas Gage This theory of executive functions suggests ADHD patients have an inhibition deficit. To identify whether ADHD is a disinhibition disorder, Schachar and Logan (1990) compared length of time to respond in a stop signal task (which assesses ability to inhibit motor responses) of ADHD children, children with conduct disorder, ADHD and conduct disorder, learning disorder, and emotional disorder, with that of normal children. The ADHD group had significantly longer reaction times than the other groups, supporting that ADHD is a disinhibitory disorder. The finding that the ADHD and conduct disorder group had faster reaction times to the only ADHD group, suggests that the hyperactivity of children with conduct disorder may be due a psychosocial disturbance, rather than a cognitive disturbance (inhibitory deficits), which seems to be the reason for the ADHD hyperactivity. Attempting to further understand the causes of this disorder, Schachar, Tannock and Logan (1993) studied genetic vulnerability to ADHD and found that a sibling of someone with ADHD, had longer reaction times on the stop signal task than people with no siblings with ADHD. Therefore it seems that patients with ADHD are genetically predisposed to an inhibition deficit, this also implies that other factors might work in combination with the biological predispositions to cause someone to have ADHD. These behavioural findings appear to correspond at a neural level, Rubia, Smith, Brammer, Toone and Taylor (2005) carried out a functional magnetic resonance imaging study on ADHD medication-naïve adolescents, while carrying out a stop signal paradigm (to asses response inhibition). ADHD patients had abnormally reduced brain activation in the right interior frontal gyrus during successful motor response inhibition; this activation correlated with behavioural ADHD scores. This difference in normal and ADHD neuronal functioning, and strong theory that ADHD patients have a specific deficit in behaviour inhibition, implies that this specific area is involved in response inhibition. This develops knowledge of ADHD and neural response inhibition.
Advancements in neurochemical modulation of ADHD have been able to take place with the knowledge that ADHD is based on behavioural inhibition, rather than cognitive inhibition, and, that this occurs at a neurological level. Research focusing on the biological mechanisms of behavioural inhibition found that ADHD patients had lower levels of catecholamine metabolism, a brain chemical related to adrenalin and noradrenalin (Lubar, handout, as cited in Alhambra et al., 2004; Lubar, 1991). This led to the discovery that psycho stimulants such as methylphenidate are able to prevent re-uptake via transporter blockage and trigger release, thus increasing extracellular levels of noradrenaline and dopamine (Wilens, 2006). Methylphenidate has been shown to be effective for reducing symptoms in ADHD patients (Biederman, Mick, Surman, Doyle, Hammerness, Harpold et al., 2006). Therefore neurochemical research into specific inhibitory deficits developed our understanding of neurochemicals and biological mechanisms involved in cognitive control, and facilitated the development effective chemical treatments for ADHD (Chamberlain & Shahakian, 2007). Research presented suggests that each specific mechanism is completely separate from the others; however, they may in fact be related. Miyake and colleagues (2000) used scores on tasks, thought to measure executive functions to identify main executive functions (inhibition, updating, and shifting). They also carried out an exploratory and confirmatory factor analysis, which identified some correlation between the executive functions: 0.63 between inhibition and updating; 0.56 between updating and shifting and 0.42 between inhibition and shifting. These correlations are low, suggesting the functions are different, but that they are not completely independent of each other. Unity? biological aspects ADHD patients are able to execute functions to their goals, the level of their personal interest in tasks (Brown, 2006). Environmental of Genetic? when it says experiment 1 or experiment 2 does it mean the inhibition or task switching component of this experiment? MBCT aims to change what the mind is processing by training attention and building awareness (moving out of ‘automatic pilot’ and into ‘being’ mode), how the mind processes by being open, accepting, curious, and companionate, and perspective. It aims to do this mostly through the medium of meditation. Could it be working at a similar level to biofeedback training to change neural networks and behaviour?
Cognitive neuroscience has identified a treatment for the impulsivity, inattention, and hyperactivity aspects of ADHD. This uses Electroencephalography (EEG) neurofeedback. EEG studies have shown that children with ADHD demonstrate increased theta activity (the EEG frequency referred to as slow brain wave activity, characterised by daydreaming) and lower beta activity (the EEG frequency known as fast wave activity associated with focused attention) ( Lansbergen, van Dongen-Boomsma, Buitelaar & Slaats-Willemse, 2011; Alhambra, Fowler & Alhambra, 2004; Lubar, 1991). During EEG neurofeedback training, children self-regulate ongoing neuronal oscillations by visual or auditory feedback, which rewards desired changes in neuronal oscillations (Lansbergen et al., 2011). This training attempts to reduce ADHD symptoms and thus improve cognitive functioning in patients’ lives (Gevensleben, Holl, Albrecht, Schlamp, Kratz, Studer, et al., 2009).
A meta-analysis by Arns, De Ridder, Strehl, Breteler and Coenen (2009) reported large clinical effect sizes of EEG neurofeedback training on inattention and impulsivity symptoms, and medium effect sizes for hyperactivity. These conclusions seem highly reliable as meta-analysis’ have a higher statistical power and are less influenced by local findings than single studies. Another study also showed evidence of long-term benefits (Gevensleben, Holl, Albrecht, Schlamp, Kratz, Studer et al., 2010). Although this standardised training seems useful, it has been suggested that not all children with ADHD have increased theta and decreased beta activity (van Dongen-Boomsma, Lansbergen, Bekker, Sandra Kooij, van der Molen, Kenemans et al., 2010). Thus it may be more effective to adjust training to specific children, this is currently applied in clinical practise, however, no studies have assessed its effectiveness as yet (Lansbergen et al., 2011). This treatment of impulsivity, inattention and hyperactivity symptoms of ADHD suggests the benefits of focusing on disorder specific symptoms rather than executive functioning as a whole, to better understand ADHD, cognitive control more generally, and develop effective treatments. Biofeedback Training Emotion overlap between brain areas? - emotion and inhibition thus use up resourses? faces become associated with negative/positive stimuli. participants asked to think, not think or nothing the faces more activation in control areas less activation in sensory and emotion areas. 1. attention
2. inhibition
3. distraction Chambres et al., '00
Drug users slower if background stimuli was drug related Substance Misues --- Gambling Substance misuse causes brain damage - difficult to see cause from result agressive and intellectual rumination - task switching Crews and Boettiger '09
Cirtical degeneration from alcohol misuse may increase impulsivity contributing to the development, persistence and severity of alcohol use disorders • Our environments can lead to “information overkill”
• Interference control:
- inhibit the processing of irrelevant information
- enhance processing if relevant information
- suppress automatic tendencies and habitual responses colour-naming Stroop task
Eriksen flanker task
Simon task
variants of the Stroop task see on left, respond on right HH S HH Nee et al., 07
Examining the combination of many tasks that involve resolution revealed that a network including the bilateral DLPFC, inferior frontal regions, the PPC and the ACC may underlie the resolution of conflict. We hypothesize that separating functions by the stage af processing at which conflict is resolved may provide a useful framework for understanding resolution. Bomyea & Amir '11
Inhibitory control over proactive interference, associated with intrusive thoughts

Individuals in the working memory condition demonstrated significantly greater WMC performance improvements from pre to post assessment relative to the control group. Individuals in the training group experienced fewer intrusions during a thought supression task. Improved inhibitory control through computerized traininng programmes may have clinical utility in disorders characterised by intrusive thoughts (depression, PTSD). list procedure (or mixed-blocks vs. single-blocks)
alternating runs (or predictable task switching)
task cuing (or unpredictable switching)
intermittent procedure
voluntary task switching Reconfiguration view:
- Task-switch cost reflects time to reconfigure the task set (e.g. Logan & Gordon, 2001; Rogers & Monsell, 1995) or to retrieve the task set from long-term memory (e.g. Mayr & Kliegl, 2000).
Interference View Maybe overlapping systems e.g. monitoring! Ward, pos 2003?
Participants cant reconfigure the cog system in advance to prepare for the anticipated to be switched (RSI delayed).
Preparation or planning time and error rate increased witht he number of subgoal moves need to solve the puzzle - mental task switching not just behavioural. Logan 03
Task switch - alternation (memory - monitoring) alternating runs - still switch cost -> not just memory. Task-set inertia - proactive interference of task-set -> explains switching cost without EC Implications for depression

Mental (4.1)
Overgeneral autobiographical memory disorder is not an outcome of depression. More depression - less WM capacity, were related to over-rely on specific memories. WM capacity appears to be more a central factor than the associated clinical ailments for some phenomena RDA - unpacked (process in parallel because otherwise longer lists would take longer!), LTM packed - Oberauer '09 As a result of the threshold proactive intererence is limited in short term memory - Oberauer 09 Eagle '10
'stereotype threat' - told to perform badly - do! -> the effect of 'stereotype threat' was mediated by a reduction in WMC. Sleep deprivation and fatigue have similar effects (US air force pilots). Attention ignore 1 ear and pay attention to the other, if said name - 1/3 reported hearing it but no the other words (20% high WMC, 65% low WMC) - High WMC better at focusing attention
Goal Maintenance? Priming! homunculus? The first documented case of deficits in cognitive control was in the infamous (and perhaps exaggerated) case of Phinease Gage (Harlow, 1848). Phinease gage was a railway worker who survived a tamping rod through his frontal lobe. Following recovery from his injury Gage demonstrated remarkably intact performance on various well defined cognitive tasks from neuropsychological test batteries and IQ tests. However, his physician (Harlow) did notice personality changes. He seemed to be unable to organise his behaviour to attain goals. Similar patients seem to be impaired on Winconsin Card Sorting tests (need to adapt to rule changes to sort cards), and the Tower of Hanoi or London (need to plan how to move disks to get to goal whilst abiding by rules) Miyake. Although poor performance on these tasks may arise from a varied of reasons it was assumed to be a result of disco-ordination of cognitive processes, a lack of mental flexibility and planning. Oberauer (2009) produced a design for working memory (although the detail of this design is beyond the scope of this essay, the essential details will be described), which suggested that working memory is activated units of long term memories. Long term memories (declarative working memories) with high activation become available for direct access; these memories can be biased by goals (within procedural working memory) to enable goal directed behaviour. Then the focus of attention will help to choose from all the activated memories in the region of direct access, the appropriate information to produce a response Within the theory of task switching there is an interference point of view and a reconfiguration point of view, the later is described within this model. This has point of view has been supported by Monsell (2003)’s research which showed that the switch cost decreases when reconfiguration time increases, by presenting a delay between cue and stimulus to respond to. However, Wylie & Allport (200) produced data supporting the interference view. In their experiment participants performed a Stoop colour naming (in response to incongruent combinations of colour and distracter colour words) and word reading. The word-reading task was in response to both ‘Stroop’ and ‘neutral’ word stimuli. They found a large component of the ‘switch cost’ was due to earlier performance of the stroop colour naming task interfering with the execution of the current task (word reading). Thus suggesting interference is accounts for the ‘switch cost’ rather than time to reconfigure. Due to data supporting both attitudes, now a more hybrid account is a accepted whereby task switching is not a single control process (further fractionation the unity of cognitive control). In fact it is also accepted that other processes e.g. working memory capacity, novelty, task complexity, monetary value. Some of these other processes will be discussed in this essay. The combined approach was used within the ECTVA model (logan and Gordon, 2001), which describes executive control through the mod of working memory, organising task set parameters to enable the correct response to be made, and after response execution, executive control stops you from doing any more tasks. However, it has also been argued that task switching may not actually involve executive control Rumination is generally defined as a recurrent series of thoughts, and most often considered with depressed patients as it is a good predictor of depression. Whitmer and Banich '07 looked at the effect of different types of rumination on executive functioning, and found that in contrast to depressive rumination group, angry and intellectual rumination group had difficulties in switching to a new task, but not with inhibition of a prior task set. This suggests that emotion can affect task switching abilities, but rather than the level of emotion, but the specific type of emotion being ruminated on. Therefore it seems that emotion plays a part in regulating task switching abilities. It may be that this group had a task switching deficit which encouraged them to be aggressive and intellectual ruminators, whereas the depressive group originally had an inhibition deficit which encouraged depressive rumination. Thus rather than emotion mediating their deficit, a biological deficit in executive functions made them susceptible to different types of rumination. Although the direction of causality is unclear it does seem that task switching and emotion are related. Schizophrenia

Schizophrenia (a mental disorder in which patients experience delusions, with a .3-.7% prevalence rate) is associated with executive processing deficits. Wylie, et al., 2010 investiagated the abilities of schizophrenic patients with task switching tasks. They found that although patients and control showed similar switching costs (as consistent with prior literature) patients showed worse performance across conditions in the letter vs colour tasks. This suggests that the executive system regulates task switching slightly differently for different types of stimuli (letters or colours), and it is the specific switching process involved with letter stimuli which is affected in schizophrenic patients. Again this further fractionates the process of task switching. Lifespan
As is consistent with findings in other areas of executive control, ability in task switching abilities increase with age. Huizinga et al., 2006 shows that the task switching cost decreases, with age between 7-21, with the change being more dramatic in the early years than the later ones. Looking at the other end of the spectrum Kray and Linderberger (2000) looked at switching in 20-80 year olds. They concluded that age-associated increments in costs were significantly greater for general than for specific switching costs, suggesting that the ability to efficiently maintain and coordinate two alternative task sets in working memory instead of one is more negatively affected by advancing age than the ability to execute the task switch itself. The process of updating the bindings and region of direct access is a form of task switching. One of these main processes may be interference control. This is the ability to inhibit the processing of irrelevant information enhance processing of relevant information and suppress automatic tendencies and habitual responses. There is much debate within the literature about the differences in interference and inhibition. Within this essay the concept of interference control will be interpreted as how the mind deals with unnecessary information, and inhibition as restraint-related functions (Conway, 2006)
Nee et al 2007 hypothesised that by separating functions by the stage of processing at which conflict is resolved may provide a useful framework for understanding resolution. This essay will use this suggestion and discuss how executive control attempts to overcome interference at three main stages of processing. These are sensory input, working memory, and response activation. Sensory Input
Egner and Hirsch (2005) attempt to clarify whether inhibition or amplification enables us to stop irrelevant information from interfering with a task. To do this they carried out a variant of the stroop task (say colour of word which are congruent or incongruent with the colour), with faces of actors and congruent or incongruent names below them. Using brain imaging of the fusiform face area (FFA), an area of the brain activated by face stimuli to identify to what degree face stimuli is processed to relevant or irrelevant stimuli. The neural response of the FFA to faces varied with the degree of activation paid to the faces, but only when faces served as target stimuli and not when they served as distracting stimuli. The authors argue that the results show clear evidence for amplification of task-relevant information, but no evidence for inhibition of task irrelevant information. however we must be careful interpreting brain imaging data (Poldrack, ) and it may be that inhibition is working at a level before the FFA activation. They also found that this processes was mediated by the PFC (consistent with previous research on area of cognitive control). Thus it seems that the executive control amplifies relevant stimuli while processing perceptual stimuli to reduce interference of irrelevant stimuli. By only keeping relevant information for the task at hand within the region of direct access, it seems possible to limit the amount of interference. Specifically through the ability to increase the region of direct access threshold one can proactively limit interference in short term memory.
Recent studies of interference on working memory have shown single PFC region (BA 45) more active for interference trials (Jonides et al., 1998) and that this activation is greater for interference trials only at the time of probe (D’Esposito et al., 1999). This suggests the existence of reactive control mechanisms that resolve interference. Burgess and Braver (2010) argued that two types exist. They found that interference effects on WM are modulated by expectancy, with differential use of proactive control mechanisms in high expectancy blocks, and differential use of reactive control mechanisms in low expectancy blocks. They also found interference effects dependent on individual differences (fluid intelligence) when utilizing proactive control. Thus it seems that both proactive and reactive techniques are used to control WM interference, depending on the situation.
Oberaures 2009 theory of WM suggests that executive control is only able to be performed through the mode of working memory, and thus it may suggest that without WM there can be no executive control. Research from Marcoritch et al 2010 supports this as they suggest that4-6 year olds with higher WM capacity are more successful at carrying out goal maintenance. Thus perhaps by improving working memory one can improve executive control. Bomyea and Amir 11 found that individuals who experienced WM training demonstrated greater WMC performance form pre to post relative to controls. They also experienced fewer intrusive thoughts during a thought suppression task. The authors argue that training WM enables better inhibitory control over proactive interference associated with intrusive thoughts, Thus here it seems inhibitory and interference control processes are able to work together to reduce intrusive thoughts. Response activation
One of the tasks of interference control is to suppress automatic tendencies and habitual responses. This seems very similar to the restraint-related function of inhibition. This ability seems most often defined as behavioural inhibition throughout the literature. The stop signal paradigm (Logan and Cowan 1984) seems to be the most appropriate to analyse this ability as it allows for a more detailed understanding. Within this task, the stop signal appears after the go stimulus, and the stop-signal reaction time is the time between this signal and stopping. Boucher et al 2007 put forward a race model to explain this behaviour, it seems that when the go and stop stimuli are presented they start a process and the first one to reach the activation threshold will be executed and it seems most people make a strategic decision to slow down when they expect these stop signals so that this process is more likely to be successful (Verbuggen & Logan 2009). This strategic decision could be interpreted as a interference control strategy. Although it was previously thought that executive control was purely top down biasing of bottom up (stimulus driven) activation (Miller and Cohen, 2001). This biasing allowed voluntary behaviour, which was goal directed, and could co-ordinate control processes. The first documented deficits in cognitive control was in the infamous (and perhaps exaggerated) case of Phineas Gage (Harlow, 1848). After damage to his prefrontal cortex his performance on well defined cognitive tasks from neuropsychological test batteries and IQ tests was intact, however, his physician (Harlow) noticed a personality change, and an inability to organise behaviour to goals. From this point it was thought that cognitive control was a unitary process which occurs within the PFC. However, since, there has been much evidence (this details of which are beyond the scope of this essay) suggesting that this is not in fact a unitary process, and in fact contains main processes, which although being carried out separately may also overlap.
One of these processes identified by Miyake and colleagues (2000)’s exploratory and confirmatory factor analysis was inhibition. Inhibition is most often used to describe restraint-related functions (Conway, 2007). Some investigators also use the term to describe processes involved with deleting unnecessary information from attention and working memory, and controlling access to the attentional focus (Lustig, Hasher & Zacks, 2007). These differences in meaning throughout the literature, cause some uncertainty of whether tasks used to identify inhibition are process pure, and complicate the findings of studies (Lustig et al., 2007). Still, most researchers focus on the restraint-related functions, and so conclusions can generally be interpreted as associated with this ability (Conway, 2006).
Nigg (2001)’s research into ADHD investigated Although whether ADHD patients have difficulty with all aspects of inhibition by comparing studies of ADHD effects on different types of inhibitory processes. This study only found clear effects for behavioural inhibition. This suggests that ADHD participants have a specific deficit in behavioural inhibition. This also implies inhibition can be unpacked to specific processes, with behavioural inhibition acting independently from the others. Working memory
Miyake and colleagues (2000) also identified some correlation between the executive functions: 0.63 between inhibition and updating; 0.56 between updating and shifting and 0.42 between inhibition and shifting. These correlations are low, suggesting the functions are different, but that they are not completely independent of each other. This essay will focus on the function of inhibition. Oberauer (2009) produced a design for working memory, which may explain these (the details of this design are beyond the scope of this essay, however implications will be discussed). This theory suggests that executive control is only able to perform through the mode of working memory, and thus working memory is the common factor and relation between executive control functions. It may also suggest that without working memory, there can be no executive control. Research from Marcovitch, Boseovski, Knapp and Kane (2010) supports this, as 4-6 year olds with higher working memory capacity are more successful at carrying out goal maintenance. This insinuates that the more working memory capacity the more executive control can be executed.
According to Oberauer’s (2009) model of working memory improving working memory may improve executive control. A study on computer training working memory in children with ADHD showed that children improved on working memory, response inhibition and reasoning, with reduced ADHD symptoms as reported by parents (Klingberg, Fernell, Olesen, Johnson, Gustafsson, Dahlström et al., 2005). This insinuates that training working memory through computer tasks can improve ADHD symptoms such as response inhibition. The findings of this study imply that Oberauer’s model (2009) does explain, to some extent, disorder symptoms, and therefore provides a better understanding of ADHD and is a ‘good’ theory of cognitive control. Emotion
Response inhibition is often tested using the stop signal paradigm (Logan and Cowan, 1984). This paradigm allows for a more detailed understanding as it can measure (or attempt to because it actually seems that people proactively adjust their response strategies) the stop reaction time from the presentation of the stop signal. Boucher et al., (2007) put forward a race model to explain this behaviour, it seems that when the go and stop stimuli are presented they start separate processes, and the first one to reach the activation threshold will be executed. Vergruggen and De Houwer, 2007 used this paradigm to study the effect of positive and negative stimuli on reaction times, and stop signal reaction times, they found that positive and negative as opposed to neutral images dramatically increased reaction and stop signal reaction times. However there did not seem to be much difference in the valence of the images, thus suggesting that arousal affected their inhibition ability. Thus suggests that perhaps there is an overlap of brain areas, with emotion processing and inhibition processing using the same resources, and thus arousal is able to effect inhibition processing. This overlap may be attention Pessoa (2009) argues that high threat stimuli grasps out attention and uses much of the executive system, as these are of the highest priority for survival, we must first identify whether it is safe to continue doing the activity. It may also be that this is not just for high threat information, but for highly arousing stimuli (as this requires a quick reaction for survival (possible partner, or possible threat)). This attention conclusion may also explain why drug users show slower responses when background stimuli is drug related (chambers et al., 00).
A study (Dunn et al 2006) showed that after ventro medial prefrontal cortex damage patients were more likely to choose risky (high reward, and high los) card decks than less risky ones. Further research into their skin response showed no change during tasks as opposed to control who sweated. Thus suggesting that they were less responsive to the risky situation as they did not experience the emotional response. Therefore it seems that to some extend emotions may increase motivation for less risky behaviour. Verbruggen et al (in press) then looked at the effect of controlling motor responses (response inhibition) and risky behaviour. This study suggested that stopping-induced cautiousness, which transferred to a monetary choice task.
Thus it seems that as well as high arousing stimuli have a negative effect on response inhibition abilities, practicing stopping can reduce risk taking in a different type of monetary choice task. Depressive Rumination
Depression is a specific type of emotion consisting of extreme low mood. Rumination is generally defined as a recurrent series of thoughts, and most often considered with depressed patients as it is a good predictor of depression. Whitmer and Banich '07 researched the effect of types of rumination on executive control and found that participants who scored high on depressive rumination, also did not seem to be that much faster (compared to controls) on a cba sequence to an aba sequence, which would be thought to be the case as it is harder to overcome backward inhibition effect. Thus suggesting that they are not inhibiting the previous a as much as controls. Aggressive, and intellectual ruminators on the other hand showed more of a switching deficit. It seems that depressive rumination is associated with an inhibition deficit. However, rather than emotion mediating their deficit, a biological deficit in executive functions may have made them susceptible to different types of rumination. Although the direction of causality is unclear it does seem that inhibition and depression are related. more activation in control areas less activation in sensory and emotion areas.
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