Evidence to argue as whether the CE is homunculus Flashcards
Initially it was a homunculus (admitted by Baddeley) however with the adoption of the SAS and the more recent introduction of the episodic buffer the CE is less homunculus.
Homunculus Role of the CE Pre 2000 - To Focus Attention
Robbins (1996) -> Move selection of chess pieces was severely effected by random letter generation (known to need focused attention) other PL and VSSP tasks did not disrupt move selection to the same extent.
Homunculus Role of the CE Pre 2000 - To Divide Attention
Alzheimer patient study (Baddeley 1991) -> very clear tendency for dual task performance to deteriorate while single task performance is maintained.
Homunculus Role of the CE Pre 2000 - To Switch Attention
Baddeley et al (2001) → performance on a switching task under dual task conditions employing various articulatory suppression and central executive tasks → consistent but small role of the CE in attentional switching.
Final (controversial) Homunculus Role of the CE Pre 2000 - Ability to relate WM to LTM
Interface between the WM sub-systems and LTM has been subsequently transferred to the episodic buffer. However this can be discussed after
SAS - Supervisory Attentional System - Norman & Shallice - Frontal lobe patients.
Adopted by Baddeley in 1986 to account for the neurological substance of the CE. Via patient studys it was found those with frontal lobe damage continually failed to focus attention, responding to every environmental cue at hand (Utilisation Behaviour). Frontal lobe also seems to monitor behaviour, Baddeley found those with frontal lobe damage exhibited confabulation
Homunculus Role of the CE Pre 2000 - To Divide Attention (Alzheimers)
Baddeley 1991 - Alzheimers patients exhibited a marked deficit in dual tasking compared to elderly/young controls - This support the CE’s link with attention allocation/switching and the frontal lobe as Alzheimer’s patients are known to have frontal lobe damage.
Parkin 1998
the central executive becomes implicated in explaining task performance when neither of the operationally defined slave systems can be invoked in explaining data”
Non equipotentiality of frontal lobe (RIGHT example)
The frontal cortex is not a unitary system of the CE, it is divided up into a lot smaller parts .Bench 1993 -> fMRI supports the hypothesis that different parts of the frontal lobe are activated under different tasks.
Non equipotentiality of frontal lobe (LEFT example)
Fletcher 1995 - whereas tasks assessing encoding factors gives rise to left frontal activation. ➢ From the neuropsychological data, one can state unequivocally, that there is no evidence of a single brain region consistently associated with tasks assumed to ensure executive function
Baddeley 2000 saw holes in the CE’s role as a link between WM and LTM (Problem 1) - Episodic buffer
He introduced the episodic buffer in 2000. One of its main roles was to be used as a temporary store to chunk bits of info together. (Baddeley) Patient PV has a digit span of 2 but sentence span of 6 and can verify even lengthy meaningful sentences. Baddeley defines information that goes through the episodic buffer as any thing amnesiacs can’t do (implicit memory, conditioning still goes through)
Baddeley 2000 saw holes in the CE’s role as a link between the two slave systems (Problem 2) - Episodic buffer
There is a small but detectable visual similarity effect in verbal recall showing words are coded both phonemically and visually. Central ex on its own does not explain how this happens. Episodic buffer bridges this gap. – It is multimodal
Baddeley 2000 saw holes in the slave system’s ability to hold infomation (Problem 3) - Episodic buffer
Supraspan capacity is thought now to be held in the episodic buffer -manipulating it and utilising it over a time scale far beyond the normal capacity of slave systems.
Baddeley 2000 - The binding problem – how is information from various subsystems combined to form a temporary holistic representation that is available to consciousness?
How a sequence of words can be bound together in chunks - A demanding concurrent task impairs STM for shapes and colors bust does not disrupt the capacity to bind this information into colored objects - i.e. binding happens when slave systems and CE are disrupted = episodic buffer role
Conclusion - Both Baddeley & Parkin rights to some degree → it started as heinously homunculus → the introduction SAS and Episodic buffer has fleshed it out → not a single entity in the frontal lobe as S&N postulate → Recent neuropsychological and cognitive task evidence promotes a CE made of multi components.
- There has been support for the CE in it role described by Baddeley however it is not as simple a single entity (Nee et al 2013) Meta analysis of brain regions -> Results suggested that rather than dissociating into distinct functions, 2 separate frontal regions were recruited across diverse executive demands:1) Located dorsally in the caudal superior frontal sulcus = especially sensitive to spatial content
2) Located laterally in the midlateral prefrontal cortex = sensitivity to non-spatial content
