Thursday, 8 December 2011

Cognitive neuropsychology - Neuropsychological assessment

According to Martin (2006) neuropsychological assessment is a set of tests that are designed to measure the effects of brain damage on intellectual, motor or emotional functions. Generally if a neurologist suspects cognitive impairment in a patient they may be referred to a clinical psychologist for a series of assessment. This is essential as it helps to determine, identify and localise malfunction in the central nervous system (CNS) (Martin, 2006). Therefore neuropsychological assessment helps better direct clinicians to identify problems and see what functions are spared, and thus make the most effective treatment programmes. It may also help to identify which brain regions are responsible for certain neuropsychological problems. The aim for neuropsychological testing is to; aid the ability to diagnose, to be able to label cognitive deficits, and to study the change and the development of cognitive impairment problems over time. Barrett (1993) postulates that there are various reasons why a patient may have a malfunction of the central nervous system, these include; genetic and inherited disorders, infections, prenatal problems such as malnutrition and deprivation and also injuries caused from trauma (Barrett, 1993). When being neurologically tested the CNS malfunctions are likely to be 'low-order systems' such as sensory and motor deficits or 'higher-order systems' such as deficits in cognition and attention (Martin, 2006).

Monday, 28 November 2011

Cognitive neuropsychology - Week 9 - Memory

According to Martin, 2006 memory is one of the most difficult functions to master because it is an ongoing process and not merely a simple thing. Teng & Squire, (1999) suggest that the 'hippocampus is a part of a system of structures in the medial temporal lobe that are essential for memory'. The processes of memory include; encoding, retrieval, recall and recognition. Two main types of memory have been outlined by broadbent (1958) these are; Long term memory (LTM) which is prominent in the hippocampus. The excitatory neurotransmitter glutamate seems to be important for long-term memory. The second is short term memory (STM) he postulated that items from the STM would make their way via specific mechanisms to the LTM. Other dichotomies of memory have been proposed such as; procedural and declarative memory. Procedural memory is involved in automatic operations such as riding a bike. Declarative memory has been linked as similar to explicit memory and involves recall and recognition of items that are consciously available. Another dichotomy is episodic memory (memories that are personally meaningful) and semantic memory (memories based on knowledge of events, people or places). In addition to this, working memory allows a person to participate in one activity whilst contemplating another. It is clear that there are many factors involved in memory and that each involve specific systems and regions of the brain, consequently if these are damaged it can result in many different memory disorders; such as retrograde and anterograde amnesia.

Important information from the article - "Memory for places learned long ago is intact after hippocampal damage (Teng & Squire, 1999).

Teng & Squire (1999) state that the "hippocampus is a part of a system of structures in the medial temporal lobe that are essential for memory". It is suggested that the hippocampus plays a role in the acquisition & retrieval of spatial knowledge. The hippocampus is outlined as constructing and storing spatial maps and is important for learning and remembering places including places that were learned many years ago.
A patient E.P was tested who suffered from virtually complete bilateral damage to the hippocampus and also severe damage to surrounding structures situated in the medial temporal lobe. E. P was capable of describing the layout of roads and houses from where he grew up, but when asked to describe his current neighbourhood he had no knowledge, suggesting that he had antereograde amnesia. Results "support the view that the hippocampus and other structures in the medial temporal lobe are essential for the formation of long term declarative memories, both spatial & non spatial, but not for the retrieval of very remote memories, either spatial or non spatial.

Important notes from the lecture:

- Memory has evolutionary significance as it allows us to predict future outcomes on the basis of experience and be able to adapt to new situations.

Processes in Memory:
- Encoding - process used to store information in memory.
Storage - process used to maintain information in memory.
Retrieval - process used to get information back out of memory.

Types of memory:
-Sensory memory (iconic) - high capacity, very short lived-decays within seconds.
- Short term memory (STM) - Information currently held 'in mind'. Limited capacity. Miller (1956) 7+or-2. Chunks rather than words or syllables are stored.
- Working memory - Extension of STM, temporary storage & manipulation of info: central executive.
- Long-term memory (LTM) - Stored information, doesn’t need to be consciously accessed. Has unlimited capacity. Stored memories from hours, weeks and years ago.

- Amnesic patients who have normal digit span cannot acquire new information such as word lists.
- Impairments in short term phonological and long-term memory is associated with left parietal and media-temporal respectively.
-STM may represent the temporary activation of the LTM.

- To recall lists of items from STM, phonological similarity is needed.
- To recall lists of items from LTM requires semantic similarity.

- The central executive coordinates the slave systems by retrieving things from memory, specifying task goals, initiating and terminating cognitive routines.

Procedural memory
- This is a memory that is required for activities such as riding a bike. Basal ganglia are linked to this.

Perceptual representation systems
- This is needed for perceiving sounds, words and objects. Stores knowledge of the perceptual world and is capable of learning. Evidence for this comes from priming studies which suggest that information is easier to access if it has recently been encountered.

In an object recognition task only known objects showed priming effects suggesting that priming only tap a perceptual store of known objects.
- Priming involves brain regions that are involved in perception.

Semantic memory (autobiographical memory) - Knowledge about the world, places, & meaning of objects and words. Knowledge that is culturally shared.

Episodic memory - Autobiographical memory & specific events in one’s own life.

Retrograde amnesia = loss of memory for events that occurred before the trauma.
Antereograde amnesia - No memory for events that occur after the trauma and have difficulty in learning new information.

- Amnesia generally consists of severe impairments to anterograde memory with less impairment to retrograde memory.

Preserved & Impaired memory in amnesia:
- STM is spared.
- Episodic memory is impaired.
- Semantic memory is impaired (partially)
- Procedural and perceptual memory is spared

- Results from studies with amnesic patients support 'multiple memory systems' view of the brain in which episodic memory is partially affected.
-Episodic memory may be spared because they contain rich contextual detail. These contextual details may be linked by structures in the medial temporal lobe, including the hippocampus, and may gradually be consolidated over time.

Hippocampus and memory
- Contents of memory are stored in the neocortex but are unclear whether the hippocampus is needed for consolidation or even retrieval.
- Hippocampus - Is critical for integration and consolidation. Without the hippocampus only learning of skills and habits, simple conditioning and phenomenon of priming can occur.

Forgetting and encoding

- Information that is encoded semantically is more likely to be remembered than information that is processed perceptually.

Storage and retrieval
- Encoding specificity hypothesis = Contextual similarity between the retrieval attempt and the initial encoding phase predicts the likelihood of remembering versus forgetting.

Frontal lobes and LTM
- Damage to the lateral frontal lobes does not produce memory dysfunction, but disrupts cognitive control, which can produce false and incoherent memories.
- Ventro-lateral is activated during memory encoding and incidental learning not specific to LTM. It is also involved in maintaining and retrieving semantic memories.
- Dorso-lateral prefrontal region is associated with selecting from a range of alternatives that are not specific to memory tasks. Recognized for playing a role in memory retrieval.

Explicit memory tasks - Involves conscious recollection e.g. participants know that they are trying to retrieve information from their memory.
Implicit Memory - Requires participants to complete a task - the completion of a task indirectly indicates memory.

- Amnesia results support a multiple memory system view of the brain in which explicit memory is particularly affected.
-  Episodic memories may be special because they contain rich contextual detail
- Contextual details may be linked together by structures in the medial temporal lobe including; hippocampus, may be gradually consolidated over time.
- Newly learned semantic facts may initially be context dependent but become less so over time.

Monday, 21 November 2011

Cognitive Neuropsychology - Blog 8 - Frontal Lobes

As outlined by (Martin, 2006) the frontal lobes are the most recently developed out of the four lobes (Occipital lobe, temporal cortex, parietal cortex & the frontal lobes) and hold approximately 1/3 of the cerebral cortex. The frontal lobes are split into the 'orbito-frontal cortex' which is responsible for decision making and behavioural self regulation and the 'dorso-lateral region' which is responsible for cognitive & executive functioning, working memory and attention. The frontal lobes have been described as being the leader and are massively connected to other brain regions suggesting that the frontal lobes play a big part in the communication to the rest of the brain and support the notion that it is the master brain region. The frontal lobe is responsible for most types of our behaviour such as social behaviour, personality and motor movement and its roles include; engaging in abstract thought, planning and organisation, inhibiting inappropriate social and emotional responses. But more specifically the frontal lobes are involved in; working memory, encoding and retrieval of information, motor movement, attention and executive functions. Damage to the frontal lobes can destruct executive functioning which Banich (2009) said is vital to be able to live an independent life. A great example of this is the story of Phineas Gage who suffered major personality changes after a lateralization to his left frontal area (Damasio etal, 1994). Evidence shows that the frontal lobes play a crucial and perhaps master role in the brain, therefore damage to this area of the brain could consequently cause the inhibitoriest disorders. Many tests can be performed to test whether a patient has frontal lobe damage; the most frequently used test is the Wisconsin card sorting task where an examiner will change the rules without informing the patient and the patient will not adapt to this but will continue using the old and now inappropriate rule to sort out the cards.

Notes from article - Executive function: The search for an integrated account.

- Brian damage can damage the frontal lobes which in turn can damage executive functioning which is said to be required to live an independent life.

Banich (2009) suggests that executive functioning is necessary to 'effortfully guide behaviour toward a goal' and is especially needed for nonroutine situations. Executive function is sad to be required for; prioritising, sequencing behaviour, inhibiting familiar or stereotyped behaviours, creating and maintaining an idea, switching between task goals, decision making and categorizing.

- Executive functioning covers a wide amount of skills so there is not one general test but many different ways to test executive functioning.

- The Wisconsin card sorting test is most frequently used. This involves the participant learning a rule and then the examiner will change the rule without telling the participant. Patients with frontal lobe damage will still try and sort the cards out using the old and inappropriate rule.

- Stroop task (Decisions made on task relevant information when faced with distracting information.) the task involves identifying a word's colour and ignoring the word. Executive functioning is needed here because word reading is automatic so it's needed to over-ride this automatic response and instead name the colour.

- Many psychiatric illnesses involve executive functioning these are; schizophrenia, bipolar disorder, depression and attention deficit hyperactivity disorder.

-There seems to be little knowledge about how the frontal lobes support executive functioning although it is clear that damage to the frontal lobes is associated with executive functioning. Therefore making this a hard problem to prevent or treat.

Notes from lecture

- Wisconsin card sorting task - needs a shift in strategy after an unexpected rule change. Patients with lateral prefrontal cortex damage show 'perseveration'

Frontal lobes function (tests)

- Error correction & trouble shooting (entails sorting cards by shape, colour or numbers and then changing the rules.

Executive functions of the frontal lobes

Divided attention, sustained attention, processing speed, initiation, sequencing, self-shifting, cognitive flexibility & planning.

-Important for planning & controlling behaviour.

-Frontal lobes are needed to enhance performance in situations that involve coordination between a series of cognitive processes.

- It is not domain specific but is more of a supervisory role to memory, perception and language.

- The frontal lobes are linked to prefrontal cortex.

- Five general situations that require the frontal lobes executive functions as stated by Norman & Shallice (1986) are;

- Planning or decision making
-Error correction or trouble shooting
-When responses are not well learned or contain novel sequences of actions
-Situations that are judged to be dangerous or technically difficult
- Also needed when overcoming a strong habitual response or resisting temptation.

What areas do what?

- Lateral prefrontal cortex = working memory.
- Ventromedial zone = emotions & decision making
- Anterior cingulate (ACC) = monitoring behaviour (conflict & error detection).

(ACC) Anterior cingulate cortex

- Is vital for reward, anticipation, decision-making, empathy and emotion.
- Dorsal ACC is related to rational cognition & ventral is related to emotional cognition.

- OCD sufferers have high ACC activation.

- Depression can be as a result from low ACC activity.

Friday, 18 November 2011

Cognitive Neuropsycholgy - Blog 7 - Hemispheric Lateralisation

The human brain is split into two parts, which appear to work individually and have separate roles; these are the 'right' and 'left' hemispheres. These two hemispheres are connected by a thick layer of nerves called the corpus callosum. Research has consistently shown that the left hemisphere is predominantly involved in language and logic and the right hemisphere is predominantly involved in aspects of visuospatial ability and creativity (Martin, 2006). Although research indicates that the right and left hemisphere have exclusive roles it has been shown that this is not entirely true e.g. the right hemisphere has some language capabilities and the left hemisphere has some visuospatial abilities. Vogel, Bowers & Vogel, 2003 suggest that a person can have a dominant hemisphere meaning that if a person holds a creative personality they will have a dominant right hemisphere. Lateralisation’s to either hemisphere consequently carries great consequences and can alter a person’s social and mental skills. In order for doctors to help patients affected by these deficits, research needs to address whether hemispheres are exclusively used for specific abilities, however only brains that are brain damaged are testable as obviously it is unethical to carry out such invasive research on healthy humans therefore it is causes ambiguity to which particular parts of the brain control what activities in a normal healthy working brain.
.............................................. END..................................................

Extra notes;

  • Lesions in the left hemisphere affects language (aphasia).
  • It is suggested that the brain does not duplicate functions on both sides of the hemispheres, meaning that the two hemispheric sides are specalised for different functions.
  • The left hemisphere is more effective in language processing whereas the right hemisphere is more effective for visuospatial abilities.
  • The right hemisphere holds some linguistic ability but cannot perform phonological decoding.
  • In general the perceptual system first sees an object globally, it is reported that patients with a left-sided lesion are slow to identify local targets and that patients with right-sided lesions are slow to detect global targets.

Friday, 11 November 2011

Cognitive neuropsychology - Week 6 - Emotions

Emotions are fundamental in every aspect of a person’s life and can regulate behaviour either consciously or unconsciously. It has been reported that the orbito-frontal cortex and sub cortical structures such as the amygdala and hippocamal system are heavily involved in the expressing and recognition of emotions. There is much debate about the meaning of emotion and also the role of emotion but it seems clear that it is anything that in the short-term alters a person’s psychological state. Ekman (cited in Martin, 2006) suggest that there are six 'basic' emotions that are recognised the most across different cultures, these are; Happiness, sadness, anger, fear, disgust and surprise. Emotions are a key way to engage in social interaction and express feelings and can prepare for the fight or flight response. Ekman (1992) suggest that emotions have evolved to help deal with certain life events however some emotional responses can be inhibitory, e.g. if a person often experiences sadness then this would decrease arousal and motivational levels, so if faced with an aversive stimulus the body would have a slower emotive reaction. According to the oxford dictionary of psychology the amygdala's role is "controlling the experience and expression of emotion." (p31). It seems that different subcotical structures play a role and are activated more frequently in some emotions than others, for example the emotion fear has been linked with a high activation of the amgydala however overall these sub cortical structures all interlink and  implement the expressing and recognition of emotion.

Thursday, 27 October 2011

Week 5 - Movement Disorders

Among many neurological deficits, movement disorders seriously inhibit a person’s day to day life. Movement disorders are caused by damage to the central nervous system (CNS). This includes damage to neurons in subcortical structures or lesions to the cortex. Damage to the two subcortical structures causes the most harm to motor dysfunction. These are; the cerebellar loop, which controls the timings and trajectory of movement using sensory and motor information and; the basal ganglia loop, which controls the excitability of the frontal motor structures and will decide the likelihood of movement and the strength of the movement. The basal ganglia is a collection of nuclei which includes; the caudate, putamen and the globus pallidus. These nuclei are often involved in severe movement disorders such as Huntington’s disease and tourette syndrome, which is caused by excessive motor activity, and Parkinson’s disease which is caused by restricted movement.
This shows that the subcortical structures are extremely important for motor control because any damage or lesion affecting this area leads to some serious inhibitory movement problems.
Below I will discuss movement disorders (including Parkinson’s disease, Huntington disease and tourettes syndrome) and the methods used to treat these disorders.

Parkinson’s disease

The characteristics of Parkinson’s disease include akinesia (general loss of movement) rigidity and tremors when resting; Akinesia involves bradykinesia (a slowness of movement) and hypokinesia, which is a reduction in movement.
Age of onset - Is between 40 and 70 years of age.
Symptoms - Stooped posture, difficulty with speech and trouble turning their bodies, and also trouble with writing.
Treatment - L-dopa (penetrates the blood/brain barrier) Dopamine receptor agonists and MAO B inhibitors.

Huntington’s disease

This is an inherited disease and causes a person to perform involuntary (dance-like) movements and causes dementia.
Age of onset - Is between 40 and 50 years of age.
Symptoms - Difficulty with speech and standing, changes to personality, clumsiness.
Treatment - No long term treatments. Dopamine antagonists relieve a small amount of symptoms for a temporary amount of time. Treatments aim is to restore balance to neurotransmitters in the basal ganglia but in the long run this is not enough to prevent the disease from progressing.

Tourettes syndrome

Has been proposed as the result of dysfunction between the basal ganglia and its connections to the orbito-frontal cortex.
Age of onset - Begins in childhood (typically before the age of 15)
Symptoms - Head jerking, shrugging of the shoulders and the most obvious is the repetition of words and swearing.
Treatment - A drug called haloperidal is administered to patients with tourettes syndrome.

Important revision notes from the article (week 5) - 'Abnormalities in the awareness of action'

- Researchers have proposed that the central nervous system (CNS) holds internal models that interact our own bodies and the external world in order to optimize motor control. The two internal models proposed are; 'The forward model' this predicts the sensory consequences of motor commands. The second model proposed is the 'inverse model' this provides the motor commands to achieve the desired outcome.

- Although we are aware of the goals underlying most of our movement it has been suggested that we are unlikely to have conscious access to all of our motor commands and adjustments that are made in order to carry out a command. This leads to the speculation that we do not have conscious access to the inverse model/motor commands. However this field of research is not conclusive.

- On the other hand the 'forward model' has been proposed as being available to awareness.
-The 'forward model' compares the actual outcome of motor commands to the desired outcome, all of which is made before a movement is made this allows for adjustments to be made before the action is carried out.

- The second job of the 'forward model' is to compare the prediction of the sensory consequences of movement to the actual feedback - this comparison is made after the movement is made. This allows for the body to compensate for the sensory effects of the movements being made.

  • An experiment took place to demonstrate that the motor system can function in the absence of awareness.
  • Goodale etal ran an experiment where participants were asked to point at a visual target. It was reported that during a saccade the target was displaced, this went unnoticed by the participants, however their arm moved in the correct direction.
  • Castiello etal found that participants were only aware of a target jump 200ms after the motor system had made appropriate adjustments.
  • An interesting study was ran by knoblich & Kircher. Participants were instructed to draw circles which they then saw reproduced by dots. The dots were slowly increased therefore making the circle bigger, participants were asked to lift their pen when they saw a change. Results found that participants compensated for the changes well before they were actually aware of the change. This shows that we are not conscious of all the fine adjustments made by the inverse model, and it's only when a change becomes so big that we notice any change. Overall so long as our desired intentions have been met, we are unaware of sensory feedback about the state of our motor systems.
Neurological abnormalities

Optic ataxia

- This is where patients have trouble with grasping objects that they can see before them. Although their actions are carried out in a clumsy manner the movement the patient is making matches their intention. The patient is aware of their problem in reaching and grasping. This condition is caused because the 'inverse model' is not properly tuned.

Anarchic hand sign

- This is where patient’s hands move of their own accord without the will of the patient. It seems that simply seeing an object is enough to trigger a movement. The patient clearly recognises a problem between desired actions and actions that do take place.

Utilization behaviour

- This is where a patient utilizes an object inappropriately, however in contrast to the 'anarchic hand sign' the patient does not see the discrepancy, this is because the patient will rationalize their movement by saying they thought someone wanted them to do it, their actions are involuntary however they feel like the movement was intended.

Phantom limbs

- This occurs after a patient has had a limb amputated, but still feels like they have still got the limb, and report feeling like they can move it or that it feels paralysed. An explanation put forward is that the estimated position of a limb is not entirely based on sensory information but also the stream of motor commands to the limb. The 'forward' model estimates the position of the limb before sensory information has been received. Therefore motor commands may be issued to the limb therefore making the phantom limb feel like its moving. In time the motor control system will adapt to changes therefore many patients report losing the ability to move their phantom limbs.

Thursday, 20 October 2011

Week 4 revision blog - Visual perception

Lesions to the parietal cortex results in a deficit to a person’s spatial perception abilities. Neglect after stroke appears to have high consequences, an example of this is when a patient has a right hemisphere stroke they lose awareness of any left side stimulus when there is a competing right stimulus. It is reported that patients are only aware of half of the world. This disorder causes difficulties in most everyday life events, e.g. difficulty dressing one side of the body, reading things on only one side of the page, and often only eating from one side of their plate. Some patients are unaware that they are neglecting information on one hemifield, this is called 'anosagnosia' this is obviously detrimental to the recovery of the patient. Spatial neglect can be simply tested using a task that involves copying a drawing. A person with spatial neglect will only copy one half of a drawing. Blindsight is another sensory impairment, this is caused by damage to the striate cortex and involves the ability to locate an unseen object, even though reporting they could not see the object itself. Riddoch (1917) reported that patients with blindsight could tell the direction an object was moving, but could not actually see the object. Research has hypothesised that this happens due to 'extraocular scatter' which is when light reflects off of the stimuli therefore allowing it to be picked up by the visual system. The subcortical pathway that carries information from the retina to the superior colliculus could help explain blindsight, as this neural pathway only provides rough information at a quick pace, therefore the patient picks up rough movement, but cannot distinguish any fine detail.

Revision material from the article (week 4) – ‘Implicit face perception in a patient with visual agnosia? Evidence from behavioural and eye-tracking analyses’.

Le. S & Raufaste. E etal (2002)
investigate whether a patient with a face perception deficit can recognise faces in the absence of their awareness. Prosopagnosia is the inability to recognise faces that the person previously knew. It has been suggested that although prosopagnosia patients report not feeling familiarity when viewing a face it has been shown that the processing of familiar faces can still happen without the patients awareness (this has been shown by skin conductance test).
It has been shown that
object recognition and face recognition activate different loci in the same cortical area therefore although one type of recognition may stay intact, the other becomes severely damaged. The article puts forward two hypotheses to explain why a patient with visual agnosia and prosopagnosia was still capable of some visual processing. The two hypothesis are; 'The spared hypothesis' this suggest that the patients abilities are due to spared modules of implicit face processing. The second hypothesis is the 'general strategy hypothesis' this suggests the patient’s ability was due to compensatory strategies. Experiment one saw the patient along with control participants having to distinguish if the picture being shown to them was a face or a vegetable and experiment two saw the patient and control participants having to state whether the picture they were being shown was a face or not. Results showed that the patient was not aware of faces, however it showed that he processed them differently to non-faces. Eye tracking shows that facial features were processed similarly to the control participants, therefore it was discussed that the results rejected the 'general compensatory strategy hypothesis' therefore supporting the 'spared module hypothesis'. These results suggest that a patient with severe deficits to visual perception can recognise faces without conscious awareness.

Important info from lecture

- Lesions of the parietal cortex lead to spatial deficits.
-When a patient has had a right hemisphere stroke they lose awareness of any left stimulus when there is a competing right stimulus.

Neglect is a directional bias modulated by competing stimuli not a lack of awareness of one half of space.

- Patients with right parietal lesions have impaired detection on their right side and often revisit locations on the right side because they cannot remember where they have looked before.
- Neglect patients also show deficits on non-spatial tasks, therefore sustained attention & selective attention are impaired.

- The optic nerves from each eye meet at the optic chiasm - Information from the left part of the visual field goes to the right side of the brain & information from the right part of the visual field goes to the left side of the brain.

Homonymous hemianopia

- This is a loss of vision on the corresponding area of visual field in both eyes.


This includes; a loss of half of the field of vision and can detect/discriminate visual stimuli in their blind field e.g. colour, motion etc.

- The visual pathway is fast and unconscious and provides only rough information about the location and identity of stimuli not fine detail - this could explain why the patient can detect colour and motion but not actually able to fully detect/see the stimuli.

- Some researchers found that after training homonymous hemianopia patients with visual search everyday for a month the patients improved and became faster at finding targets - eye tracking also revealed that patients more effectively made allocation of fixations after training, therefore suggesting that this visual problem can be improved with visual training.

-Milner & goodale (1995) suggest that there are two vision systems; visual perception and visuomotor control only the first is involved in conscious awareness. Blindsight has been suggested as dissociation between fast motor reactions and conscious perception.

What and where

What = Bilateral lesion of the temporal lobe leads to a deficit in the discrimination of objects.
Where = Bilateral lesion of the parietal lobe leads to a deficit in the discrimination of locations.